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Warp Drive Might Be Less Impossible Than Previously Thought

runner_one writes "Harold 'Sonny' White of NASA's Johnson Space Center said Friday (Sept. 14) at the 100 Year Starship Symposium that warp drive might be easier to achieve than earlier thought. The first concept for a real-life warp drive was suggested in 1994 by Mexican physicist Miguel Alcubierre, however subsequent calculations found that such a device would require prohibitive amounts of energy, studies estimated the warp drive would require a minimum amount of energy about equal to the mass-energy of the planet Jupiter. But recent calculations showed that if the shape of the ring encircling the spacecraft was adjusted into more of a rounded donut, as opposed to a flat ring the warp drive could be powered by the energy of a mass as small as 500 kg. Furthermore, if the intensity of the space warps can be oscillated over time, the energy required is reduced even more."

603 of 867 comments (clear)

  1. But then, a slight solar wind... by TorrentFox · · Score: 5, Funny

    Eject the core!

    1. Re:But then, a slight solar wind... by RyuuzakiTetsuya · · Score: 1

      We're fresh out of warp cores!

      --
      Non impediti ratione cogitationus.
    2. Re:But then, a slight solar wind... by Drishmung · · Score: 5, Funny

      Eject the core!

      Frog Blast The Vent Core!

      --
      Protoplasm. Quiet Protoplasm. I like quiet protoplasm.
    3. Re:But then, a slight solar wind... by sortius_nod · · Score: 4, Interesting

      It's amusing, because the shape they have come to is essentially the same shape as the warp field on the Enterprise.

    4. Re:But then, a slight solar wind... by rubycodez · · Score: 5, Funny

      maybe not a coincidence, this Harold "Sonny" White who came up with the shape is part of the 100 year starship project, I'm suspecting he was a trekkie who tried out the warp field shape just to see what would happen. but he's too embarrased to admit it!

    5. Re:But then, a slight solar wind... by kilodelta · · Score: 5, Insightful

      It's funny how Sci-Fi becomes reality on a relatively short time scale. Think about the stuff on Star Trek that is reality today, granted not exactly like ST, but damnably close. The MRI is in my opinion the preeminent scanning technology now. And cell phones and hand held radios - they're all essentially SDR's now. My little Yaesu VX-7r is a quad band radio, and I remember back in 1992 my Kenwood TH-28 was only a dual band and didn't have a general coverage receiver on it like my little Yaesu.

    6. Re:But then, a slight solar wind... by Gilmoure · · Score: 1

      I'm not assimilated!

      --
      I drank what? -- Socrates
    7. Re:But then, a slight solar wind... by youn · · Score: 1

      I believe they call that going to the bathroom nowadays :p

      --
      Never antropomorphize computers, they do not like that :p
    8. Re:But then, a slight solar wind... by otterpop81 · · Score: 1

      I remember back in 1992 my Kenwood TH-28 was only a dual band and didn't have a general coverage receiver on it like my little Yaesu.

      I have one of those (TH-28A) on the desk behind me right now. The 28 is dual-band receive, transmit on 2m only. I think it was a great radio then, and still is now. Sure there's stuff better, but what I love about radio (as opposed to phones and computers) is that the one I bought in the 90s still works just as well now as it did then. While there are better radios now, the goalpost is in the same position as it was back then (hitting the repeater, talking on the same modes, etc).

    9. Re:But then, a slight solar wind... by kilodelta · · Score: 1

      That's right - thanks for jogging the memory. Haven't had the TH-28 for almost twenty years now. I also had a Yaesu FT-2500 - the one built like a tank. Then I had a Yaesu FT-5100 but it got stolen.

    10. Re:But then, a slight solar wind... by stepho-wrs · · Score: 1

      So many Star Trek comments and nobody picked up "the warp drive could be powered by a mass about the size of a spacecraft like the Voyager 1 probe".
      V'ger was Voyager 6 but even so...

    11. Re:But then, a slight solar wind... by oPless · · Score: 1

      I'm really sick of this misinformation cropping up over and over again.

      The original TOS devices were wedge clipboard type things, nothing like the iPad of today.

      The TNG PADD devices and those in Undiscovered Country didn't show until 1987 / 1991

      Microsoft Tablet PC was announced in around 2001, GridPad in 1989

      2001 a space odyssey 1968 http://www.youtube.com/watch?v=ZKt9ZyDmA44

      A rip off? Maybe, the source correct? No

      Apple had this kind of thing on their bluesky "roadmap" advert back in 1987
      http://www.youtube.com/watch?v=JIE8xk6Rl1w

    12. Re:But then, a slight solar wind... by Anonymous Coward · · Score: 1

      Holy shit. Calm down, dude.

    13. Re:But then, a slight solar wind... by mcgrew · · Score: 1

      I don't wish the Vulcans or Klingons on us

      What do you have against Vulcans? Spock was my favorite ST character!

    14. Re:But then, a slight solar wind... by Winkkin · · Score: 1

      How about the screens on our phones and tablets. Straight out of the show. I'm a believer in StarTrek and what mankind is capable of. After all its out dream

    15. Re:But then, a slight solar wind... by Marxist+Hacker+42 · · Score: 1

      As a rule, science fiction becomes science fact in three human generations.

      --
      SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
    16. Re:But then, a slight solar wind... by wdef · · Score: 1

      It's funny how Sci-Fi becomes reality on a relatively short time scale.

      That is because we can only imagine most novel developments in technology a limited time ahead of a working invention. Most technology builds on previous technology. Then there's outright magical tech that right now we have scant justification will ever exist because the basic science doesn't yet (eg immortality, time travel in the Dr Who sense, warp drives). There is no "exotic matter" as yet.

    17. Re:But then, a slight solar wind... by Asmodae · · Score: 1

      It wouldn't be unheard of for the field metrics to be named after either whoever discovers them, or the fictional character Cochrane, if the discover has a sense of humor. :)

    18. Re:But then, a slight solar wind... by Marxist+Hacker+42 · · Score: 1

      Look out for the High Command- they're the Vulcan equivalent of Nazis!

      --
      SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
    19. Re:But then, a slight solar wind... by quintus_horatius · · Score: 1

      So we can expect the first shipment of spice in how many years?

    20. Re:But then, a slight solar wind... by kilodelta · · Score: 1

      Actually it takes less than 2/3's of a human lifespan for sci-fi to become reality.

    21. Re:But then, a slight solar wind... by C0R1D4N · · Score: 1

      They coulda done a much better job avoiding the continuity errors (especially from TOS to TNG, really you go from NX-2000 to the NCC-50000s in 80 years?)

    22. Re:But then, a slight solar wind... by Pfhorrest · · Score: 1

      Thank God It's You!

      --
      -Forrest Cameranesi, Geek of all Trades
      "I am Sam. Sam I am. I do not like trolls, flames, or spam."
    23. Re:But then, a slight solar wind... by Marxist+Hacker+42 · · Score: 1

      It's already out on the streets. It's highly illegal, but it exists.

      --
      SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
    24. Re:But then, a slight solar wind... by Marxist+Hacker+42 · · Score: 1

      Given a potential human lifespan of more than 60 years (really now average 73+), and the normal "generation" being only 20, I'd say we're both right

      --
      SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
    25. Re:But then, a slight solar wind... by kilodelta · · Score: 1

      The thing is, those extended lifespans have been due to improved sanitation and health care. Think about it, what do we have that they didn't have about 100 years ago. I'll tell you, widespread electricity and refrigeration as well as gas and oil services, though electricity is the best of all.

      Plus medical science is learning how to put the human body back together again. In fact regenerative medicine could prove to be our salvation. And again, life extension gets more than passing mention in a lot of science fiction, and it's looking remarkably like it's all starting to come true now.

    26. Re:But then, a slight solar wind... by Marxist+Hacker+42 · · Score: 1

      I'm Darth Vader at night myself: http://www.cpapplus.com/ so I know about the advances happening in life extension. In a previous century, I'd be at serious risk for congestive heart failure within the next 5 years- and I'm only 41. My father is the oldest man ever in my genetic ancestry at 70.

      But my point is that 40 years from mentioned in popular science fiction, to becoming reasonable science fact is pretty darn common these days. Market viability of said product may vary however. Certainly the incredibly dangerous flying motorcycle seems to be going nowhere.

      --
      SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
    27. Re:But then, a slight solar wind... by toddestan · · Score: 1

      No one would care if it wasn't for Apple running around suing anyone who dares to make a tablet computer with rounded corners.

    28. Re:But then, a slight solar wind... by toddestan · · Score: 1

      While I've never figured out Starfleet's numbering system, I've gathered it's not just a simple sequential system. Given how many vessels have been numbered some form of 1701 should tell you that :)

    29. Re:But then, a slight solar wind... by oPless · · Score: 1

      This is true. So very true. :(

  2. What did I tell you? by Cyphase · · Score: 5, Funny

    To all those anti-warp drive downers.. HAHAHAHA!!!!

    --
    by Cyphase ( 907627 )
    1. Re:What did I tell you? by Anonymous Coward · · Score: 5, Informative

      The energy argument was completely secondary. The main objection (which is barely touched on in the article) is that there are some fairly strong proofs that you need exotic matter in order to actually implement the drive. My understanding is that the space-time configuration necessary for the warp drive has been shown to be impossible to create without exotic matter.

      Exotic matter, by definition, requires violations of the known laws of physics. In other words, the currently accepted laws of physics indicate that you need to break the laws of physics to make the drive work. This means that while the results in this article might have alleviated some secondary concerns, the main problem with this type of warp drive is still completely unaddressed.

      Of course, there are some people who will waive their hands and say "abracadabra - QUANTUM MECHANICS" to try and get around the exotic matter problem. But you are now trying to combine general relativity with quantum effects, so there isn't any firm foundation to base your arguments on.

    2. Re:What did I tell you? by Anonymous Coward · · Score: 5, Funny

      there are some people who will waive their hands

      This I have to see.

    3. Re:What did I tell you? by Anonymous Coward · · Score: 3, Interesting

      The negative mass (energy) required is not expressly forbidden. We've just never seen anything with such a property and the existence of it would raise some interesting questions. But you could say that about a lot of things that have come out of particle physics....

    4. Re:What did I tell you? by AK+Marc · · Score: 1

      Next you'll be telling me that nothing can go faster than the speed of light. The "rule" is that nothing can accelerate past the speed of light, which says nothing of things which do travel faster than the speed of light, other than implying they (if they exist) can't interact with our universe.

    5. Re:What did I tell you? by Anonymous Coward · · Score: 5, Interesting

      We have seen this effect, just not in regular solid matter; we can see it in certain configurations of regular matter, such as the Casimir effect. So it's not *real* exotic matter, but it does show that negative energy is technically an observable thing. How exactly we can make use of that to do the necessary space-folding is still unknown. It's an incredibly hard, potentially impossible engineering problem, but impossible engineering problems have a tendency to become trivial given enough time and motivation.

    6. Re:What did I tell you? by Anonymous Coward · · Score: 1

      Waived hands are one of the sources of exotic matter--They loose their quantum spin

    7. Re:What did I tell you? by Splodgey · · Score: 5, Funny

      A spelling mistake in a reply to a spelling mistake is probably exotic enough to power a small unicycle. -> They lose their quantum spin

      --
      Sigs are for losers....oh wait...damnit
    8. Re:What did I tell you? by nine-times · · Score: 4, Interesting

      In fairness, the claim that it "might be less impossible than previously thought" may be accurate. It could be less impossible and still be pretty much impossible. And I don't think anyone believed that a warp drive could be built without violating some of our current laws of physics.

    9. Re:What did I tell you? by erice · · Score: 5, Interesting

      Exotic matter, by definition, requires violations of the known laws of physics.

      That's a very peculiar definition of exotic mater you have there. Elsewhere, "exotic matter" generally refers to matter of a type neither observed nor predicted by current theory. No violation of known physics is implied. It is just that we haven't seen any and there is no particular reason to believe that it exists.

      The particular flavor of exotic matter needed for the warp drive is "negative" matter. Negative matter has negative energy. Unlike antimatter where antimatter + matter = lots of energy, negative matter + matter = nothing.

      'Last I heard, running the usual math through with negative matter results in some situations that don't make a lot of sense. They aren't necessarily wrong or forbidden, we just don't know what they mean. Math is like that sometimes.

    10. Re:What did I tell you? by Anonymous Coward · · Score: 1

      If you'd read the Alcubierre's theory you knew it doesn't violate the general relativity law. There nothing travlling faster than light ONTO the space-time texture, it is the space-time itself to contract and stretch, it's not the ship that's moving, it's the space-time itself, and in this case the not-faster-than-light rule doesn't apply.

    11. Re:What did I tell you? by Nyrath+the+nearly+wi · · Score: 4, Informative

      No, nothing can go faster than the speed of light because it will violate causality. Which is more or less forbidden by the entirety of physics.

      The only way to avoid this is by some magic-juju like Parallel Universes, Consistency Protection, Restricted Space-Time Areas, or Special Frames (with Special Frames forbidden by Relativity). All of which look like desperate hand-waving, if you examine them closely.

      http://www.projectrho.com/public_html/rocket/fasterlight.php#id--Causality

    12. Re:What did I tell you? by hoggoth · · Score: 4, Informative

      No pictures, but its true. There are some people who have waived their hands:

      http://www.thedailybeast.com/newsweek/2008/05/28/cutting-desire.html

      --
      - For the complete works of Shakespeare: cat /dev/random (may take some time)
    13. Re:What did I tell you? by Anonymous Coward · · Score: 1

      Sorry but there can be no strings attached.

    14. Re:What did I tell you? by VanessaE · · Score: 5, Funny

      So what you're saying is, it never occurred to him to think of space as the thing that was moving?

    15. Re:What did I tell you? by Cyberax · · Score: 5, Informative

      There are no proofs that it's impossible to create a warp drive without exotic matter. It's just that we know several configurations of exotic matter that can produce warp drives.

    16. Re:What did I tell you? by mrsquid0 · · Score: 2

      I would happily waive my hands in exchange for a working (and practical) warp drive.

      --
      Just because you are paranoid does not mean that no-one is out to get you.
    17. Re:What did I tell you? by mark-t · · Score: 4, Interesting

      It is more correct to say that "exotic matter" refers to some substance that has never been observed to exist and possesses one or more properties that are so radically distinct from properties you would find more conventionally that it might as well be magic.

      Examples: A frictionless pulley; a shield against gravity; an invulnerable metal.

    18. Re:What did I tell you? by rubycodez · · Score: 1

      I would say nonsense, this drive is a means outside of special relativity whereby we CAN violate casualty. special relativity doesn't cover the types of situations that man may be able to fabricate.

    19. Re:What did I tell you? by rubycodez · · Score: 1, Interesting

      indeed, the recent (nearly confirmed) discovery of dark matter is one example of exotic matter outside of known physics until the last two decades.

    20. Re:What did I tell you? by dietdew7 · · Score: 1

      Those are mere details for the engineers to solve. The scientists have done the heavy lifting by proving it's not impossible.

    21. Re:What did I tell you? by jd2112 · · Score: 4, Funny

      We have seen this effect, just not in regular solid matter; we can see it in certain configurations of regular matter, such as the Casimir effect.

      Oh let the sun beat down upon my face, stars to fill my dream
      I am a traveler of both time and space, to be where I have been...

      --
      Any insufficiently advanced magic is indistinguishable from technology.
    22. Re:What did I tell you? by slick7 · · Score: 1

      There are no proofs that it's impossible to create a warp drive without exotic matter. It's just that we know several configurations of exotic matter that can produce warp drives.

      Platonic solid geometry and Cermet. The only exotic matter necessary is the human brain, well of course, a little imagination goes a long way.

      --
      The mind conceives, the body achieves, the spirit manifests.
    23. Re:What did I tell you? by Jane+Q.+Public · · Score: 3, Informative

      "Exotic matter, by definition, requires violations of the known laws of physics."

      No, it doesn't. Antimatter is one valid type of "exotic matter", and it has been manufactured in labs in various (small) amounts for many decades now, without a physics violation in sight.

      Further, there is nothing theoretically preventing us from manufacturing it in fairly large quantities, as long as it can be kept in magnetic containment.

    24. Re:What did I tell you? by Greyfox · · Score: 3, Funny

      The universe will protect itself from having causality violated by destroying itself in a massive explosion when one of these drives is activated. Perhaps the residents of the universe borne of this explosion will be more sensible about violating the constraints of the thing they live in.

      --

      I'm trying to teach myself to set people on fire with my mind... Is it hot in here?

    25. Re:What did I tell you? by EGSonikku · · Score: 1

      "These aren't the equations you're looking for. You may go about your business."

      --
      - "Scientia non habet inimicum nisp ignorantem"
    26. Re:What did I tell you? by Black+Parrot · · Score: 2

      In other words, the currently accepted laws of physics indicate that you need to break the laws of physics to make the drive work.

      Ah, I was wondering what the summary meant by "less impossible".

      --
      Sheesh, evil *and* a jerk. -- Jade
    27. Re:What did I tell you? by Jane+Q.+Public · · Score: 4, Informative

      "... we can see it in certain configurations of regular matter, such as the Casimir effect."

      What does the Casimir effect have to do with it? That is merely a demonstration of so-called "zero point" fluctuations. It isn't "negative energy", except to the extent that you have particles and their counter-particles spontaneously arising at the same time. Even so, in the case of the Casimir effect it exerts a net positive energy on the affected mass.

    28. Re:What did I tell you? by Howitzer86 · · Score: 1

      Does negative matter have negative gravity?

      In any gravity simulator, placing a repeller next to a normal source of gravity creates a kind of odd acceleration feedback loop. The object falling into the positive gravity well is also the object repelling it with a negative gravity well. The result looks a lot like that image, with a ship along for the ride somewhere in between.

    29. Re:What did I tell you? by F34nor · · Score: 1

      I thought the new objection was that the field would gather the radiation it passed through on the journey and bake the destination to a glowing mass on deceleration.

    30. Re:What did I tell you? by F34nor · · Score: 5, Insightful

      I would happily throw 90% of the human race under a bus for a working warp drive.

    31. Re:What did I tell you? by Jane+Q.+Public · · Score: 5, Interesting

      "No, nothing can go faster than the speed of light because it will violate causality. Which is more or less forbidden by the entirety of physics."

      Incorrect. There is nothing we know of that actually works to prevent the violation of causality. There are a number of ways it can theoretically be done.

      See Tipler, "Rotating Cylinders and the Possibility of Global Causality Violation".

      All rhetoric (like the post at that link) aside, all we really have about it is guesses. The fact that we have never observed anything, so far, that would violate causality says absolutely nothing about the possibility. Further, it is not necessarily true that limited instances of causality violation would render the entirety of physics invalid, any more than relativistic situations render Newton "invalid". They are "special cases". That is all.

    32. Re:What did I tell you? by mysidia · · Score: 2

      Next you'll be telling me that nothing can go faster than the speed of light. The "rule" is that nothing can accelerate past the speed of light

      Maybe they do, and maybe they don't.... one thing is for sure, we won't be able to observe things accelerating past the speed of light as they do, because it's actually light that carries to us the details required to make our observation.

      If something did accelerate past the speed of light, the limited speed of light, would restrict our ability to observe its acceleration.

    33. Re:What did I tell you? by colinrichardday · · Score: 3, Insightful

      No, nothing can go faster than the speed of light because it will violate causality. Which is more or less forbidden by the entirety of physics.

      It is true that faster-than-light travel would mean that we have causal sequences whose order is frame dependent, but would that be a violation of causality?

    34. Re:What did I tell you? by mysidia · · Score: 1

      Negative energy does not exist.

      The word used to describe the negative energy term is Dark Energy

    35. Re:What did I tell you? by MidnightBrewer · · Score: 1

      Actually, by definition, exotic matter can be any number of things which, while rare, can exist within the known laws of physics. Dark matter, Bose-Einstein condensates, exotic baryons, etc., are all examples of things that either may exist or could be created under the right circumstances.

      Also, if you read the article you'll see that they've already started experimenting with micro-warp fields using a mundane laser. We're getting closer.

      --
      "Give a man fire, and he'll be warm for a day; set a man on fire, and he'll be warm for the rest of his life
    36. Re:What did I tell you? by IndustrialComplex · · Score: 1

      Congratulations. Here is your warp drive. Unfortunately, you tossed the guy who knew how to maintain it under a bus.

      --
      Out of modpoints but really liked a post? 1BDkF6TtmmeZ3yqXbz9yhdYVqRYnwFoXDj
    37. Re:What did I tell you? by tqk · · Score: 1

      Of course, there are some people who will waive their hands and say "abracadabra - QUANTUM MECHANICS" ...

      I don't know if you realize it, but that's actually a not bad paraphrase of Richard Feynman. "No, it doesn't make any sense, but that's how it works."

      We have smart people all over the place these days postulating Dark Matter, Dark Energy, and infinitesimal^N Superstrings, FFS.

      Hand waving appears to have quite an audience these days.

      --
      "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
    38. Re:What did I tell you? by Genda · · Score: 1

      Dude, we're still talking about wielding 500kg converted into energy or about 4.5 x 10^19 Joules! Let me put this another way... this is approximately equal to a 10 Gigaton nuclear device. The actual yield of the largest hydrogen bomb ever detonated was between 2-4% of this? So I realize the exotic matter problem is like WOO WOO! But the handling of that much raw power in a confined space to make space and time warp... uh... that's pretty WOO WOO too, or am I missing something?

      Let's reframe this, not to Mock Star Trek, but if one of these nacelles blows, you don't wanna just be outside the same zipcode, hell, you wanna be outside the same parsec! Repeat after me... "Boom! Big BaddaBoom!"

    39. Re:What did I tell you? by tqk · · Score: 1

      I think you're well deserving of a whoosh right back. Either lose or loose make perfect sense in the GP.

      "They loose their quantum spin"
      "They lose their quantum spin"

      Try to keep up, or at least buy better Scotch. :-)

      --
      "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
    40. Re:What did I tell you? by Mr.+Slippery · · Score: 1

      No, nothing can go faster than the speed of light because it will violate causality. Which is more or less forbidden by the entirety of physics.

      Causality-as-we-know-it is an assumption, not a result, of physics. It may be that our everyday notion of cause-and-effect is just wrong in the big picture.

      --
      Tom Swiss | the infamous tms | my blog
      You cannot wash away blood with blood
    41. Re:What did I tell you? by tqk · · Score: 1

      Congratulations. Here is your warp drive. Unfortunately, you tossed the guy who knew how to maintain it under a bus.

      Ptheh. "apt-get install warpdrive-doc"

      Yes, I have been pushed under a bus by colleagues, and prevailed in the end. "xman -notopbox -bothshown &", then click on warpdrive (it's likely in the "Sys. Administration" section).

      --
      "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
    42. Re:What did I tell you? by Genda · · Score: 1

      Excuse me for cutting in, but inflation says that the newly born universe expand profoundly faster than the speed of light. Space-time isn't a "Thing" like the things in the space-time. The space-time can move infinitely fast as long as you're willing to manipulate it with it with infinite force and energy. Look at the black holes, light does not escape because the space-time inside the Schwartzschild radius is collapsing faster than the speed of light.

      The particles in the universe must obey the laws of the universe, the universe itself... not so much.

    43. Re:What did I tell you? by khayman80 · · Score: 5, Informative

      "Exotic matter, by definition, requires violations of the known laws of physics."

      No, it doesn't. Antimatter is one valid type of "exotic matter", and it has been manufactured in labs in various (small) amounts for many decades now, without a physics violation in sight.

      Antimatter certainly isn't common, but it's not "exotic matter". Stable wormholes and the Alcubierre drive require using exotic matter that has negative mass-energy, which would violate the weak energy condition.

      "... we can see it in certain configurations of regular matter, such as the Casimir effect."

      What does the Casimir effect have to do with it? That is merely a demonstration of so-called "zero point" fluctuations. It isn't "negative energy", except to the extent that you have particles and their counter-particles spontaneously arising at the same time. Even so, in the case of the Casimir effect it exerts a net positive energy on the affected mass.

      The Casimir effect is the best known example of negative energy:

      Morris, Thorne and Yurtsever[4] pointed out that the quantum mechanics of the Casimir effect can be used to produce a locally mass-negative region of space-time. In this article, and subsequent work by others, they showed that negative matter could be used to stabilize a wormhole.

    44. Re:What did I tell you? by Genda · · Score: 1

      Though we are still looking for gravity waves and gravitons and if they in fact are tachions, and move faster than the speed of light, then we will know for certain that the universe doesn't give a hoot either way about our pretty ideas like causality.

    45. Re:What did I tell you? by Genda · · Score: 1

      Oh! Oh! I call Clarke's Second Law!!!

      Do I get a prize?

    46. Re:What did I tell you? by Genda · · Score: 1

      You should read the Wikipedia FTL article, its very enlightening. The point is that there are two areas that could yield interesting results, messing with the Higgs field (effectively eliminating inertial mass), and surrounding a craft with a powerful EM field has perhaps altering its dimensionality... The wild hairs are having a ball coming up with interesting ideas.

    47. Re:What did I tell you? by Cyberax · · Score: 4, Informative

      Nope. He has shown that that one configuration requires exotic matter. He hasn't proved that in the general case as that's incredibly hard to do it - the equations of the general relativity do not impose a lot of boundary conditions.

      Moreover, even the Alcubierre drive might be possible with only positive matter if one uses a dynamic metric. I've seen a paper about it a few years ago, but I can't find it.

    48. Re:What did I tell you? by Cyberax · · Score: 1

      "Warp drive" in this case is a region of space that's moving faster-than-light in some frame of reference.

    49. Re:What did I tell you? by isorox · · Score: 1

      I would happily throw 90% of the human race under a bus for a working warp drive.

      That would have to be a big bus

    50. Re:What did I tell you? by metacell · · Score: 1

      It is true that faster-than-light travel would mean that we have causal sequences whose order is frame dependent, but would that be a violation of causality?

      Yes. You could send a signal to the object travelling faster than light, which could then wait a moment, send it back, and it would arrive earlier than it was sent.

    51. Re:What did I tell you? by locofungus · · Score: 1

      I've not tried to look into it in detail (and I'm pretty sure I wouldn't understand the maths even if I did) but I think the whole point about the Alcubierre warp drive idea is that it doesn't violate causality. Instead it changes the shape of space or, alternatively, changes the speed of light. I think what Alcubierre did was to show that that distortion doesn't have to be global, it can be local, and still not violate causality.

      The fundamental problem is that, other than via general relativity, nobody has any idea how to change the shape of space even in the tiniest way. There isn't even any hints about how we might do this.

      Tim.

      --
      God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
    52. Re:What did I tell you? by Man+Eating+Duck · · Score: 1

      http://www.projectrho.com/public_html/rocket/fasterlight.php#id--Causality

      THANK YOU for reintroducing me to that site. Since stumbling across it a couple of years ago I've been looking for it on occasion (I haven't been able to find it through Google). The whole thing should be required reading for any budding science fiction author out there, that way they're at least aware of the principles they're breaking :)

      --
      Are you a grammar Nazi? I'm trying to improve my English; please correct my errors! :)
    53. Re:What did I tell you? by fahrbot-bot · · Score: 1

      Exotic matter, by definition, requires violations of the known laws of physics. ... the currently accepted laws of physics indicate that you need to break the laws of physics to make the drive work.

      Yes it sounds improbable, perhaps infinitly improbable, but all we need is some calculations as to exactly how improbable, a finite improbability generator, and a fresh cup of really hot tea.

      --
      It must have been something you assimilated. . . .
    54. Re:What did I tell you? by fahrbot-bot · · Score: 1

      nothing can go faster than the speed of light because it will violate causality.

      Apparently this restriction doesn't apply to space itself, which is how this drive would operate - stretching and contracting space-time around an area of normal space-time to propel that area FTL. There's no causality concerns within the area of normal space-time.

      --
      It must have been something you assimilated. . . .
    55. Re:What did I tell you? by pmontra · · Score: 1

      A sends a signal S. Later on B leaves A travelling faster than light. B catches up with S and sends S back to A. A receives S after A sent it and S travelled at the speed of light all the time. A would receive S later than it sent it even if B was already travelling (towards A, not leaving A of course) and comes back faster than light to deliver S in person. Probably you were thinking about a different setup. I can't think of it but I'd love to know it.

    56. Re:What did I tell you? by hherb · · Score: 4, Interesting

      Traveling faster than light does not necessarily violate causality.
      If I could travel instantly from place A to place B which is 1 light year away, I would arrive at B long before the light arrives. However, the "absolute" time at place B is exactly the same as at place A, the fact that an observer depending on optical information via photons lazily traveling at the speed of light from B to A would only be able to see me arriving there a year later has nothing to do with causality. If I instantly travel back to A, I am still not arriving any earlier than I departed, and hence have not moved in time, only in space - and once again I cannot violate causality.

    57. Re:What did I tell you? by Guignol · · Score: 1

      I agree with you Nyrath, also, we could get rid of a lot of these nonsense theories if only we were able to directly prove that Causality can not be violated

    58. Re:What did I tell you? by Alex+Belits · · Score: 1

      Because!

      --
      Contrary to the popular belief, there indeed is no God.
    59. Re:What did I tell you? by khayman80 · · Score: 4, Informative

      What does the Casimir effect have to do with it? That is merely a demonstration of so-called "zero point" fluctuations. It isn't "negative energy", except to the extent that you have particles and their counter-particles spontaneously arising at the same time. Even so, in the case of the Casimir effect it exerts a net positive energy on the affected mass.

      The AC is terse but correct. The Casimir effect occurs because vacuum fluctuations are suppressed between two parallel conducting plates that are placed very close together. Maxwell's equations force E=0 inside perfect conductors, which means that vacuum fluctuations with a half-wavelength longer than the separation between the plates can't exist between the plates. Because they exist in the vacuum outside the plates (which is defined to have zero energy), the energy inside the plates is actually negative. The attractive force implies negative energy between the plates because force is the negative gradient of potential energy.

    60. Re:What did I tell you? by arth1 · · Score: 2

      If you'd read the Alcubierre's theory you knew it doesn't violate the general relativity law. There nothing travlling faster than light ONTO the space-time texture, it is the space-time itself to contract and stretch, it's not the ship that's moving, it's the space-time itself, and in this case the not-faster-than-light rule doesn't apply.

      It still allows violation of causality and thus time travel. So where are all the time travellers?

    61. Re:What did I tell you? by Ost99 · · Score: 1

      Short answer: yes

      Long answer: no

      --
      ---- Sig. gone.
    62. Re:What did I tell you? by Geeky · · Score: 1

      Keep the telephone sanitisers.

      --
      Sigs are so 1990s. No way would I be seen dead with one.
    63. Re:What did I tell you? by bev_tech_rob · · Score: 1

      In fairness, the claim that it "might be less impossible than previously thought" may be accurate. It could be less impossible and still be pretty much impossible. And I don't think anyone believed that a warp drive could be built without violating some of our current laws of physics.

      All someone needs to do is hurry up and invent verterium cortenide and everything else will fall into place....

      --
      You're messin' with my Zen Thing, man.....
    64. Re:What did I tell you? by TedRiot · · Score: 1

      This exotic matter that you speak of is of course melange?

    65. Re:What did I tell you? by V+for+Vendetta · · Score: 1

      Consider flying. In 1683 (1 century before the Montgolfier brothers) flying was impossible. The technology wasn't far enough. However it was clearly not absolutely impossible, since it was done a century later.

      Flyging was possible, even in 1683 (and earlier). Birds and insects already did it for a long time. It just was not practicable for humans back then. (Although someone might object with the fact that jumping from a cliff would have led to some kind of "flight" - as short as it might have lasted - even for a human)

      There's a huge difference between impossible and impracticable.

    66. Re:What did I tell you? by leonardluen · · Score: 1

      and see Casimir Effect for experimental results proving the existence of Negative Energy.

    67. Re:What did I tell you? by Jamu · · Score: 1

      If you mean instantly from your frame of reference, then you'd arrive at the same time as the light. There's no such thing as absolute time: Two different places get two different times. It would be two years later. The year you took to get there (instantly from your point of view), and the year it took to see you. If you instantly travel back (according to you), you'll arrive at the same time A sees you arrive at B. There is no absolute time. You left A, arrived at B, departed and came back to A, at the same time in your frame of reference. But to A and B you've not violated the speed of light, and it's taken you two years.

      --
      Who ordered that?
    68. Re:What did I tell you? by Splodgey · · Score: 1

      Fair comment :-)

      I'll return my copy Physics for Pedants tomorrow.

      --
      Sigs are for losers....oh wait...damnit
    69. Re:What did I tell you? by mcgrew · · Score: 1

      Cry havok, and loose the quantum spin of the dilithium bosuns!

      Know what a warp drive sounds like? WOOOOSH!!!

    70. Re:What did I tell you? by leonardluen · · Score: 1

      Now you know the source of the Gamma Ray Bursts

    71. Re:What did I tell you? by amRadioHed · · Score: 1

      Not impossible based on our current understanding, just as accelerating past the speed of light wasn't impossible based on Newton's understanding. Just because it's not yet known to be impossible doesn't mean it's possible.

      --
      We hope your rules and wisdom choke you / Now we are one in everlasting peace
    72. Re:What did I tell you? by Iniamyen · · Score: 1

      Quantum mechanics!

      /waves hands

    73. Re:What did I tell you? by Paradise+Pete · · Score: 1

      Here is your warp drive. Unfortunately, you tossed the guy who knew how to maintain it under a bus.

      Dude, you don't put it under a bus, it goes in a starship. Sheesh Man, do some research.

    74. Re:What did I tell you? by die+standing · · Score: 1

      The speed of light is not the upper speed limit of the universe; nothing can travel slower than light. We are all traveling faster than light, always. Everything is.

      Didn't you get the memo?

    75. Re:What did I tell you? by TheRaven64 · · Score: 1

      That amount of energy is huge, but it's an amount that it is conceivable to produce. We can produce antimatter in small quantities, and so it's not implausible to assume that within 100 years we'd have the ability to use a fusion power plant to generate enough that we could power something like this, if we could build it. In contrast, earlier models showed that it would take more than the energy output of a star. This is the difference between 'we don't have any way of building this with current technology' and 'we probably can't ever build this'.

      --
      I am TheRaven on Soylent News
    76. Re:What did I tell you? by omnichad · · Score: 1

      That's for actual FTL travel. A warp drive isn't technically FTL (just effectively) since warps the space around it.

    77. Re:What did I tell you? by wdef · · Score: 1

      Think of the children! They have every right to go under buses, too!

    78. Re:What did I tell you? by mark-t · · Score: 1

      Yes, "exotic matter" does include matter that has been theorized to exist based on already understood laws, but has never been discovered. However, such hypothetical matter often goes by another name (such as non-barionic dark matter, as you mentioned). The only practical reason to ever call matter "exotic" if its existence has not yet been theorized in a manner consistent with known laws of physics, and it does not have a better name yet , and calling it "unobtanium" isn't practical for whatever reason.

    79. Re:What did I tell you? by wdef · · Score: 1

      No, it's a *fundamental physics* problem. No engineering without physics.

    80. Re:What did I tell you? by TJNoffy · · Score: 1

      Isn't less impossible like being less pregnant? It's either impossible or it's not.

    81. Re:What did I tell you? by nine-times · · Score: 1

      Yes, that's the joke. Congratulations on identifying it.

    82. Re:What did I tell you? by TJNoffy · · Score: 1

      I clearly missed the laugh track.

    83. Re:What did I tell you? by mark-t · · Score: 1

      I never once said that exotic matter was impossible... only that its properties might as well be magic*, given what we know right now.

      *See Clarke's Third Law.

    84. Re:What did I tell you? by Prune · · Score: 1

      What an incredibly callous comment!

      --
      "Politicians and diapers must be changed often, and for the same reason."
    85. Re:What did I tell you? by Prune · · Score: 1, Insightful

      Yes, it does. Someone will observe you traveling faster than light, going from point A to point B faster than light would travel the same distance. If nobody sees you traveling faster than light, then how can you say you did so at all? And the whole point of relativity is that the laws of physics have to hold everywhere. That observer, depending on their own velocity in space-time, potentially see you arrive at your destination before you left, violating causality according to them. Given a few such warp ships, you could even arrange it so that that person would receive a message they had written and sent with you before they had actually written it. And then causality is broken for everyone.

      --
      "Politicians and diapers must be changed often, and for the same reason."
    86. Re:What did I tell you? by WaffleMonster · · Score: 1

      Yes, it does. Someone will observe you traveling faster than light, going from point A to point B faster than light would travel the same distance. If nobody sees you traveling faster than light, then how can you say you did so at all?

      So what? We observe stars and shit moving hundreds to thousands of times faster than light realitive to ourselves all the time.

      And the whole point of relativity is that the laws of physics have to hold everywhere. That observer, depending on their own velocity in space-time, potentially see you arrive at your destination before you left, violating causality according to them

      It is HOW you get there that matters. At no point is there any contradiction or apparent violation of causality. See twin paradox for an example of why "how" matters.

      The speed limit is on the act of *propogation*... if you stretch space your actual distance traveled is shorter. It is no different than traveling thru a "wormhole".

    87. Re:What did I tell you? by putzin · · Score: 1
      Hubert Farnsworth wins again!

      The ship does not actually move itself, but, using the Dark Matter Accelerator, it moves the universe around it as stated by Professor Farnsworth, and later realized by Cubert Farnsworth.

      http://futurama.wikia.com/wiki/Planet_Express_ship

      --
      Bah
    88. Re:What did I tell you? by Greyfox · · Score: 1

      Yes. Thank you for explaining the plot to my short science fiction story :-P

      --

      I'm trying to teach myself to set people on fire with my mind... Is it hot in here?

    89. Re:What did I tell you? by mdmkolbe · · Score: 1

      However, the "absolute" time at place B is exactly the same as at place A

      Special relativity says this statement is false. It's call the relativity of simultaneity and has nothing to do with the amount of time necessary for light to travel from A to B (i.e., it holds even once you cancel out that effect from the observations). In special relativity, speed doesn't actually compress or expand time, it applies a skew transform to the space and time axises of your local reference frame.

    90. Re:What did I tell you? by DamnStupidElf · · Score: 1

      I would happily throw 90% of the human race under a bus for a working warp drive.

      Including yourself?

    91. Re:What did I tell you? by Aryden · · Score: 1

      The reality is, our current understanding of the laws of physics as well as the laws themselves, can and will be updated/changed/reworked as we experiment and find the breaks. If we went by the logic that the laws of physics are set in stone and can never be altered, then throughout history, we would never have made any real scientific advances. 2000 years ago, scientists believed man couldn't fly, we fly now.

    92. Re:What did I tell you? by zachie · · Score: 1

      Please ellaborate. I can't understand why traveling instantly from place A to place B means you can deliver a message before it was been written. I can't quite follow the causality here.

    93. Re:What did I tell you? by platypusfriend · · Score: 1

      I would happily throw 90% of the human race under a bus for a working warp drive.

      :) I want to see what the people look like who modded your comment 'Insightful'.

    94. Re:What did I tell you? by Holladon · · Score: 1

      I'm less familiar with the last three than with the first, so I'll focus on that one: why is the multiverse "desperate hand-waving"? It seems to me that it's a theoretical possibility that may become testable if we ever achieve the ability to travel (or communicate) at speeds exceeding the speed of light. Of course it's subject to misinterpretation and over-dramatization -- but that's true of anything sufficiently new, shiny, and/or untested. The problem as I take it isn't that faster-than-light travel has been proven to be *actually* impossible; it's that it is *theoretically* impossible because our current understanding of reality tells us that (1) causality is essential to existence and (2) FTL travel will weaken or destroy causality.

      Why is it more scientific to presume that FTL, something that does not yet exist, will necessarily act in a particular way, thereby rendering it impossible (isn't this its own kind of intellectual paradox? Something that doesn't exist can't exist because if it existed it would destroy everything including itself? Seems circular, at least, if not paradoxical), than is it to hypothesize that, *IF* FTL travel were possible, that possibility could be explained by something that, *under current conditions*, is for now unfalsifiable? Doesn't that basically amount to arguing that it's more scientific to presume we'll never be able to test something we think is theoretically impossible than it is to discuss hypothetical models that neither contradict current scientific theories nor foreclose the eventual possibility of testing? Why isn't it equally unscientific to roll your eyes at the theory out-of-hand when, technically, it's as good a possibility as any? It may not be *practical* (yet), but it strikes me as unreasonably dismissive to write it off as "desperate."

    95. Re:What did I tell you? by alexo · · Score: 1

      I would happily throw 90% of the human race under a bus for a working warp drive.

      Calculating the required dimensions, mass and velocity of the bus is left as an exercise to the reader.

    96. Re:What did I tell you? by mcswell · · Score: 1

      I already told you next week that I'm here.

    97. Re:What did I tell you? by colinrichardday · · Score: 1

      Arrive earlier than it was sent with respect to what frame of reference?

    98. Re:What did I tell you? by colinrichardday · · Score: 1

      But the author assumes that direction of signal propagation is relativistically invariant.. With respect to Carol/Dave's frame of reference, the signal went from Bob to Alice, and the top arrow should be pointing to the left. With respect to Alice/Bob's frame of reference, the signal went from Dave to Carol, and the arrow of the diagonal side should point to the upper right. Is there a single reference frame with respect to which the arrows point as the author has them?

    99. Re:What did I tell you? by metacell · · Score: 1

      So what? We observe stars and shit moving hundreds to thousands of times faster than light realitive to ourselves all the time.

      Actually, we don't. Only the expansion of the universe causes galaxies to recede from us faster than the speed of light - and they're unobservable for that very reason.

    100. Re:What did I tell you? by metacell · · Score: 1

      Different observers (reference frames) have different ideas of what events are simultaneous. For an observer R who moves relative to A and B, the "instant" message may arrive before or after it is sent, depending on which direction R moves in.

      To actually send messages back in time, A and B can use R as a relay station. A sends an instant message to R, who then relays it instantly to B. But what is instant delivery in R's message frame, may actually mean the message is delivered before it is sent in A's and B's reference frames.

    101. Re:What did I tell you? by alexo · · Score: 1

      I was under the impression that "impossibility" was a Boolean state.

    102. Re:What did I tell you? by WaffleMonster · · Score: 1

      So what? We observe stars and shit moving hundreds to thousands of times faster than light realitive to ourselves all the time.

      Actually, we don't. Only the expansion of the universe causes galaxies to recede from us faster than the speed of light - and they're unobservable for that very reason.

      This is a common misunderstanding. We are able to see further than the hubble sphere because scale is changing in flight.

        If I remember correctly speeds of thousands of times the speed of light have been observed as measured by red shift.

    103. Re:What did I tell you? by Jane+Q.+Public · · Score: 1
      This is going to be one of my rare responses to your posts. Prepare to be ignored for the most part, from here on in.

      "Antimatter certainly isn't common, but it's not "exotic matter". "

      Okay, I will concede that point, although it is about a Wikipedia entry. If you really want to argue about those...

      But my point is still valid, since Bose-Einstein condensates of macro-size have been manufactured in laboratories since 1998. Thus, "exotic matter" IS being manufactured, in significant quantities, right here in the real world, for 14 years now with no physics violations in sight. ("Exotic Matter", according to your own citation.)

      "The Casimir effect is the best known example of negative energy:"

      Get a clue. If you are seriously using that link as a citation, then you lose. You did not properly comprehend what it said. The Casimir effect can be modeled mathematically as a negative-mass region; Hawking showed that negative energy is necessary for negative matter to have certain effect on WORMHOLES, in conjunction with just such a negative mass. But that does not establish a direct relationship between the two. It is a very FAR cry from equating negative energy with the Casimir effect.

      Dude. I know you are a scientist. But do you even really know what the Casimir effect is? Of course I expect you will by the time you answer (if you do). And if you do answer, I probably won't reply. But at this very moment, at the time you first read this, from what you have already stated, I suspect that you really don't know what it is.

    104. Re:What did I tell you? by Jane+Q.+Public · · Score: 1
      Correction.

      "Hawking showed that negative energy is necessary for negative matter to have certain effect on WORMHOLES, in conjunction with just such a negative mass. "

      should have read:

      "Hawking showed that negative energy is necessary for certain effects on WORMHOLES to take place in conjunction with such a negative mass. But he did not claim that the negative energy was supplied by it."

    105. Re:What did I tell you? by Jane+Q.+Public · · Score: 1

      Apologies. I did not see your additional reply until I had already answered. It appears that you do, in fact, know what the Casimir effect is. But I will have to look at it more closely before I will make a judgment about it.

      Nevertheless, Hawking's findings did not point at Casimir effect as a source of negative energy; they merely indicated that negative energy was necessary for the negative mass to have the calculated effect. Not the same thing.

    106. Re:What did I tell you? by Jane+Q.+Public · · Score: 1

      "Because they exist in the vacuum outside the plates (which is defined to have zero energy), the energy inside the plates is actually negative."

      You're trying to get my goat. Haha. That isn't what it says. According to the article, the force is negative, in relation to the chosen physical framework, which (as it clearly says in the article) merely implies that the energy is lowered when the physical substrates come together. The same phenomenon can be demonstrated with magnets. No "negative energy" is implied.

      By your logic, I could demonstrate "negative energy" with a child on a playground swing. All I have to do is choose my coordinates appropriately.

    107. Re:What did I tell you? by Jane+Q.+Public · · Score: 1

      I will clarify my point a bit, because it has become obvious to me that we do not think much alike; what I think is a straightforward application of logic often does not seem to be so to you, while at the same time, I have often though that you have been taking leaps more of faith than logic. Maybe you feel the same; regardless, we have often not communicated well. I was going to put it in less polite terms, but I am controlling myself.

      A force being applied in the context of the Casimir effect is definitely a vector. It has direction. Neither a positive or negative vector implies "negative energy": it simply defines the physical direction in which the energy is directed. The coordinates are arbitrary according to vector calculus.

      There are circumstances in which energy can also be considered a vector, but this is not one of them. The Casimir effect is definitely a measurable vector in a particular direction, and he clear implication then is positive energy.

      Again, granted: Hawking showed that negative energy might be required for negative mass effects in relation to wormholes. But I have never seen any science indicating that this negative energy is actually related to or a result of the Casimir effect. That is a rather large leap that is not supported in any of the science I have read. The only relationship I have seen is that negative energy is required for certain predicted phenomena; nowhere have I seen any claim that anything related to the Casismir effect is the actual source of that negative energy.

    108. Re:What did I tell you? by metacell · · Score: 1

      Oops, sorry. I meant that you could send a faster-than-light signal to an object which travels close to the speed of light, which then relays it back to you, and you get it before you sent it.

      This is possible because in the fast-moving object's reference frame, the events of sending and receiving the return message are simultaneous, but in your reference frame, the event of receiving it can take place years before the event where the fast-moving object sends it.

    109. Re:What did I tell you? by metacell · · Score: 1

      With respect to you (the original sender).

      But I phrased it wrong... I meant that you could send a faster-than-light message to a fast-moving object, who then relays it back to you, and it arrives before you sent it (in your frame of reference).

    110. Re:What did I tell you? by metacell · · Score: 1

      This is a common misunderstanding. We are able to see further than the hubble sphere because scale is changing in flight.

        If I remember correctly speeds of thousands of times the speed of light have been observed as measured by red shift.

      Hm... I think those're stars which were within the Hubble sphere when they emmited the light which now reaches us, and that light has been red-shifted by the expansion of space, not by the speed of the stars as such.

      Is that what you mean by scale changing in flight?

    111. Re:What did I tell you? by pmontra · · Score: 1

      I'm still not convinced. In my reference frame I write the message, put it into a warp drive bottle, send it to a starship moving at near light speed at 1 light year from me. That bottle is fast and it will take only one minute to catch the ship. The ship receives the bottle, istantaneusly sends it back to me and after another minute it's on my desk. That's two minutes in my future. How can I receive it in my past?
      Furthermore I don't see how the speed of the starship affects the experiment. If it travels at a speed close to c its passengers will look like moving very slowly to me (and I look speeded up to them) but that's all, or I'm missing something? It has been a long time since I studied relativity so I won't be surprised if I'm neglecting some important point.

    112. Re:What did I tell you? by metacell · · Score: 1

      There's no universal "now" in relativity theory. Which events are simultaneous, depends on the observer. Two events can be simultaneous for you, while being years apart for an observer moving close to the speed of light.

      So when someone sends a message which arrives instantly in their reference frame, it MUST appear before it was sent in some other reference frame (and after it was sent in yet other reference frames).

      The sense of "now" gets skewed at all speeds, but the lightspeed barrier is sufficient to slow down signals so they don't arrive before they were sent in any reference frame.

    113. Re:What did I tell you? by colinrichardday · · Score: 1

      Except that with respect to my reference frame, the fast-moving object received both messages from me.

    114. Re:What did I tell you? by Jane+Q.+Public · · Score: 1

      I will add a tidbit that I picked up last night shortly after I wrote the above.

      You mentioned that since the ground state (not your exact words) of the vacuum is "defined" to be 0, then the energy must be negative.

      I understand that logic. The problem is that the premise is incorrect.

      Planck's equations, as refined by Einstein et al. in 1913, show that in fact the vacuum energy of a quantum system must always be above its "potential well", or the theoretical zero state. Thus, "zero-point" energy is NOT "defined" to be zero, but in fact is always positive, and the Casimir effect then, even using your own framework, is not "negative energy".

    115. Re:What did I tell you? by Jane+Q.+Public · · Score: 1

      By the way:

      If you are going to refer to Maxwell's equations, you should use caution. Because often what are referred to as "Maxwell's Equations" are actually just Maxwell's simplifications of Heaviside's and Hamilton's quaternion equations, with introductions of arbitrary "constants" to cancel out inconveniences, much like Einstein's "cosmological constant".

      There is a good deal of modern evidence that Maxwell's attempt to simplify things may have been wishful thinking, and that Heaviside and Hamilton had it right all along. We rely much on Maxwell, but his conclusions are assumptions. Not only are they not proven, there is significant counter-evidence.

    116. Re:What did I tell you? by Jane+Q.+Public · · Score: 1

      In fact I thought it was pretty obvious to most people that the fact that "zero point" energy is NOT in fact zero (it is actually pretty huge), has been the motivation for finding ways to "Maxwell's Demon" the quantum vacuum fluctuations. There is nothing theoretically preventing it; one team this year found a possible means of exploiting it. We shall see.

    117. Re:What did I tell you? by khayman80 · · Score: 1

      Which team?

    118. Re:What did I tell you? by khayman80 · · Score: 1

      Continued here.

  3. I'll believe it when I see... by BitterOak · · Score: 4, Insightful

    I'll believe it when I see time travelers from the future who have used their warp drives and FTL travel to come backward in time to tell us about it. (According to special relativity, the ability to travel faster than light is equivalent to the ability to travel backwards in time.)

    --
    If I can be modded down for being a troll, can I be modded up for being an orc, or a balrog?
    1. Re:I'll believe it when I see... by CajunArson · · Score: 5, Insightful

      If this thing truly "warps" space (no idea if it does) you could travel at effectively faster than light speed through a vacuum while never actually accelerating past the speed of light doing it...

      --
      AntiFA: An abbreviation for Anti First Amendment.
    2. Re:I'll believe it when I see... by Idbar · · Score: 2

      You non-believer. Don't you see that now it's not impossible, but perhaps just 99% impossible? You'll see!

    3. Re:I'll believe it when I see... by roc97007 · · Score: 2

      Maybe they don't want to talk to us.

      --
      Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
    4. Re:I'll believe it when I see... by Tanuki64 · · Score: 1, Informative

      ...while never actually accelerating past the speed of light doing it...

      Does not matter. Special relativity does not make provisions how you travel. If you travel from point A in space to point B in space, be it by warp drive, be it by wormhole, be it by magic, faster than a beam of light could do it in vacuum, you travel ftl. And this means timetravel.

    5. Re:I'll believe it when I see... by kaws · · Score: 1

      But this isn't really talking about moving faster than the speed light. In fact, the actual space ship will be basically parked. It's the space around it that will be moving.

    6. Re:I'll believe it when I see... by Tanuki64 · · Score: 1

      For timetravel according to special relativity it does not matter. If you reach a point B from a point A faster than a beam of light could do it in vacuum, you travel ftl.

    7. Re:I'll believe it when I see... by aled · · Score: 2

      of couse not! that would create a paradox that can destroy your post!

      --

      "I think this line is mostly filler"
    8. Re:I'll believe it when I see... by Dyinobal · · Score: 1

      It's all relative.

    9. Re:I'll believe it when I see... by roc97007 · · Score: 1

      And my post must live!

      --
      Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
    10. Re:I'll believe it when I see... by wierd_w · · Score: 3, Funny

      (Gigglesnort)

      I am reminded of various tougne-in-cheek jests by physicists about the universe hating the LHC.

      Perhaps if you activated the alcubierre drive, you could only ever travel outside the vehicle's light cone, but never return back to It, because "mysterious, seemingly random events" will always, without fail, prevent you from pressing the button?

      Now there would be a funny thing to put in science fiction!

    11. Re:I'll believe it when I see... by Eponymous+Hero · · Score: 1

      i think they mean the space-time outside the craft's bubble. you could travel through space by pulling the fabric of time around you toward you -- but space is inseparable from time, so you could theoretically pull yourself toward the past or (relatively) distant future.

      --
      insensitive clod overlords obligatory xkcd car analogy russian reversals whoosh pedant fanbois ftfy in 3...2...1..PROFIT
    12. Re:I'll believe it when I see... by Anonymous Coward · · Score: 3, Insightful

      But that's the point of how warp drive works - you bend space so that you don't travel faster than light.

    13. Re:I'll believe it when I see... by aitikin · · Score: 1

      ****post destroyed by paradox****

      --
      "Don't meddle in the affairs of a patent dragon, for thou art tasty and good with ketchup." ~ohcrapitssteve
    14. Re:I'll believe it when I see... by Chris+Burke · · Score: 5, Interesting

      As far as I understand it warp drive doesnt break the speed of light locally, so I recon no weird time reversal stuff can happen.

      In Relativity, traveling faster than light relative to any reference frame, via any method, presents problems with causality. And the whole point of a Warp Drive is that someone will agree that you went faster than light, and thus went backward in time.

      When I last read about the Alcubierre drive, one relevant point that was mentioned was that the inside of the warp field is causally separated from the outside, which solves the problems of causality while in transit, but raises the question of how one starts or ends the journey.

      The ridiculous amount of energy required was another problem, more of a practical "how would you do that?" issue rather than a "how is it even possibly in theory?" question.

      But the thing is -- it may actually be possible to do this in our universe. And the assumptions of constant c and General Principle of Relativity may also be correct. Which may mean that the assumption of causality isn't. What a universe that would be.

      --

      The enemies of Democracy are
    15. Re:I'll believe it when I see... by sexconker · · Score: 1

      Wrong. If you're warping spacetime it's equivalent to moving the two points closer together. The problem with this is that there's stuff in that space, including the traveler. If you manage to do it, that wrinkle/pinch/wormhole/whatever you want to call it is going to have effects on everything around it. So either deal with travelers warping small chunks of spacetime as they travel (effectively capping them at near light speed since they'd have to spend time warping pace) or maintain wormholes by warping space between two gates, then moving one gate far away while maintaining the wormhole with insane amounts of energy.

      Basically it's laughable even in theory, and you never get FTL and you never get time travel due to compressed space.

    16. Re:I'll believe it when I see... by Samantha+Wright · · Score: 3, Informative

      I don't think you quite understood—the relative motion would be FTL, but so is the relative motion of two beams of light going in opposite directions when measured from an absolute frame of reference. That gets you up to 2c. No time travel. Hilarious amounts of dilation, sure, but nothing wibbly-wobbly.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    17. Re:I'll believe it when I see... by Space+cowboy · · Score: 4, Interesting

      No.

      In the real world, today, the phase velocity of light can easily exceed the speed of light in a vacuum. There is no time travel. There's no information transfer, either, due to the conditions of travel at that speed, but there's no time travel.

      From
      "On the other hand, what some physicists refer to as "apparent" or "effective" FTL[1][2][3][4] depends on the hypothesis that unusually distorted regions of spacetime might permit matter to reach distant locations in less time than light could in normal or undistorted spacetime. Although according to current theories matter is still required to travel subluminally with respect to the locally distorted spacetime region, *apparent* FTL is *not* excluded by general relativity."

      Also worth reading the 'difficulties' of the 'worm bubble' effect, and how those difficulties might be addressed by this new research.

      I'm not saying it's possible, but it's too soon to rule it out, either.

      [section: not entirely serious, but...]
      My personal take is that Gene Roddenberry was an alien whose goal was to nudge us in the generally correct direction without apparently doing so. To do this, he (it?) created a TV series called 'Star Trek' in which all advances we'd need were demonstrated to agile minds. Once it has been conceptualized, if it is possible, someone somewhere will eventually do it...
      [/section]

      --
      Physicists get Hadrons!
    18. Re:I'll believe it when I see... by snowraver1 · · Score: 1

      You seem to understand things better than I: I've always wondered what would happen if you were travelling 99.99999% of the speed of light and you shone a flashlight forward? Would the light trickle out (relative to you) or would it be normal. What is the speed of light relative to?

      --
      Copyright 2010. All rights reserved. This comment may not be copied in any way including, but not limited to caching.
    19. Re:I'll believe it when I see... by Tanuki64 · · Score: 1, Informative

      *sigh* I know, it is hard to understand. But even if you use the warp drive you travel faster than light. The problems with time travel and the resulting paradoxes are not triggered by any kind of movement. Being at point A and suddenly being at point B in shorter time than a beam of light could go from A to B in vacuum is all that is needed.

    20. Re:I'll believe it when I see... by Nethemas+the+Great · · Score: 1

      You have no idea what the hell a warp drive is do you? The ship in question actually isn't moving. There are no infractions of the universal speed limit and thus no time-travel.

      --
      Two of my imaginary friends reproduced once ... with negative results.
    21. Re:I'll believe it when I see... by Tanuki64 · · Score: 4, Insightful

      c is in vacuum always c. Regardless of your movement.

    22. Re:I'll believe it when I see... by TFAFalcon · · Score: 1

      Doesn't warp drive effectively change the distance between those two points? So point A and point B are closer together for a while, you move between them, then let them resume their original positions.

    23. Re:I'll believe it when I see... by Chris+Burke · · Score: 5, Interesting

      But that's the point of how warp drive works - you bend space so that you don't travel faster than light.

      You locally don't. The warp ship doesn't actually accelerate at all. This is how you get around the relativistic energy equation.

      However, someone will observe you traveling faster than light, going from point A to point B faster than light would travel the same distance. If nobody sees you traveling faster than light, then how can you say you did so at all?

      And the whole point of relativity is that the laws of physics have to hold everywhere. That observer, depending on their own velocity in space-time, potentially see you arrive at your destination before you left, violating causality according to them.

      Given a few such warp ships, you could even arrange it so that that person would receive a message they had written and sent with you before they had actually written it. And then causality is broken for everyone.

      But hey, maybe it's not a causal universe! I await their experiments.

      --

      The enemies of Democracy are
    24. Re:I'll believe it when I see... by blueg3 · · Score: 4, Informative

      This is actually one of the fundamental observations that led to relativity (and why the speed of light is the fastest information or energy can travel).

      Light moves away from you at exactly the speed of light, regardless of what your velocity is. If you're travelling at 0.99c (relative to a "stationary" observer) and you shine a light forward, it looks like it's moving at speed c away from you. Shine a light backwards, looks like it's moving speed c away from you. To the stationary observer, both beams of light *also* look like they're travelling at exactly speed c (and you look like you're travelling at 0.99c). So the stationary observer's perception of how you and the beams of light are moving relative to one another is different from your perception of the same thing. (However, both are equally valid.)

    25. Re:I'll believe it when I see... by Anonymous Coward · · Score: 1

      What is the speed of light relative to?

      The OBSERVER!

      To someone observing you travelling 99.999x, the light moves forward from you at c.
      You also see the light move forward at c.

      However, distances you measure are different from distances the other observer measures.

    26. Re:I'll believe it when I see... by SciBrad · · Score: 4, Insightful

      That's only true in special relativity. In general relativity where you are dealing with the expansion or warping of space this constraint is not there globally. For example, objects that recede past our cosmic event horizon are moving away from us faster than the speed of light, but only because the space between us is expanding such that it appears that way. Locally nobody is traveling faster than light, but on a global scale this is essentially what is happening. That is why we have a cosmic event horizon. However the necessity of exotic matter, as alluded to in a previous comment puts a dampener on the whole thing sadly.

    27. Re:I'll believe it when I see... by TFAFalcon · · Score: 1

      I think the beam of light would still travel away from you at the speed of light (by your perception), since the time dilation would slow down your personal time that much.

    28. Re:I'll believe it when I see... by Anonymous Coward · · Score: 1

      You seem to understand things better than I: I've always wondered what would happen if you were travelling 99.99999% of the speed of light and you shone a flashlight forward? Would the light trickle out (relative to you) or would it be normal. What is the speed of light relative to?

      The speed of light is exactly the same in any reference frame (this is a postulate of Special Relativity, but is well confirmed by experiment). In other words, if you are traveling at 99.99999% the speed of light and shine a flashlight forward, that ray of light travels away from you at the speed of light. It also travels away from an observer at rest at the speed of light.

      This is difficult for many people because they use Galilean transformations automatically to try and figure out relative velocities. However, Galilean transformations are only low energy approximations to the much more general Lorentz transformations, which properly described the above behavior. You should be able to find extensive discussions on Lorentz vs Galilean transforms with a google search.

    29. Re:I'll believe it when I see... by cbhacking · · Score: 1

      Although an outside observer would say that the light beam is travelling only very slightly faster than you, *you* would see the beam travel at exactly 1.0*c away from you. From your frame of reference, light in a vacuum *always* travels at this speed relative to its source.

      The apparent discrepency is resolved by noting that at that speed, the time dialation you'd be experiencing is so great that after one second (as you experience it), the wave front of the light is one light-second ahead of your curent position. To an outside observer, one second after you turn on the light the wave front has progressed by one light-second from its initial position and you're only about 30m behind it... but that's because, to you, only a tiny fraction of that second has occurred yet.

      --
      There's no place I could be, since I've found Serenity...
    30. Re:I'll believe it when I see... by NEDHead · · Score: 1

      "sigh" all you want, but you are incorrect, sir.

    31. Re:I'll believe it when I see... by Tanuki64 · · Score: 1

      *apparent* FTL is *not* excluded by general relativity.

      No kind of ftl is excluded by anything. Be it general or special relativity. You just have to explain how to handle or prevent the paradoxes if you travel ftl.

    32. Re:I'll believe it when I see... by wierd_w · · Score: 5, Interesting

      If going 99.9999% C, it would take you an outrageous amount of (outside) time to flick the switch. The universe could end before then!

      Still, assuming you did indeed flick the switch, it would be the same as with sound propogation. An ambulance travelling at 99% speed of sound with sirens blaring will emit a higher frequency sound, until after it passes, and then the tone will be dialated the other way.

      The light won't move faster. Instead, the frequency will be insanely high. Your infrared emitting tungsten filament bulb will be emitting gamma ray photons.

      If you are going 100% speed of light, you will *never* succeed in toggling the switch.

      Here is where the whole FTL thing becomes unnecessary:

      If you are taveling 50% of C, the degree of seperation between internal and external clocks will be sufficient that even though it takes you 400 years to reach that star 200 light years away, a considerably shorter time will be recorded by the ship's onboard clock.

      The closer to C you travel, the less "time" you experience. So, FTL is not necessary. The crew will be alive and well, and feel only a few months have passed on their 400 year journey. Everyone they left back home will be dead and buried, but for them, only a few months will have passed.

      If all you care about is *your* lifetime, FTL is not needed to explore the universe.

    33. Re:I'll believe it when I see... by SomeJoel · · Score: 2

      an absolute frame of reference.

      I'm pretty sure those don't exist. Which is why, from any relative frame of reference, the top speed really is c. You can't go c+1 mm/year in any frame of reference, let alone 2c.

      --
      <Complete your profile by adding a signature!>
    34. Re:I'll believe it when I see... by Your.Master · · Score: 5, Informative

      Here is a relatively understandable explanation of why beating a photon to its destination implies time travel, even if you don't locally travel faster than light: http://www.theculture.org/rich/sharpblue/archives/000089.html. Basically, if you can pass stuff along at FTL between people at sub-light speed, and those people are moving relative to one another, you can send stuff into the past.

      There *are* workarounds. A fairly comprehensive list is here:

      http://www.physicsguy.com/ftl/html/FTL_part4.html#subsec:specialframe

      They're all kind of about relativity being wrong, and there's no evidence any of these are true. Mostly wishful thinking on the part of people that want to believe we can have an interstellar civilization but can't quite let go of causality. Briefly:

      1. FTL takes you to a parallel universe. So if you try to kill your past self, there's no paradox and you keep living because it was actually your counterpart in a different universe.
      2. There's some unknown physics that would prevent using FTL to violate causality. So even though there's technically time travel in some sense, it has no practical use and therefore you could say it isn't "really" time travel.
      3. A specific case of the above: perhaps the act of travelling FTL prevents any other FTL travel within a certain spacetime "radius".
      4. Violate relativity by having a "true" frame of reference with a "true" sequence of events. All FTL takes place in that context and is theoretically unlimited in speed. Within any other frame of reference, it looks like a speed limit, but still possibly faster than light speed.

    35. Re:I'll believe it when I see... by shentino · · Score: 2

      Temporal prime directive.

    36. Re:I'll believe it when I see... by Tanuki64 · · Score: 1

      If you say so. Thanks for enlightening me, Mr. Einstein.

    37. Re:I'll believe it when I see... by shentino · · Score: 1

      I think GP meant two beams of light on a head to head collision course.

    38. Re:I'll believe it when I see... by Jessified · · Score: 1

      RTFA

      It's sort of like how waves can travel but the individual molecules of water aren't necessarily moving along with the wave.

    39. Re:I'll believe it when I see... by Tanuki64 · · Score: 1

      There *are* workarounds. A fairly comprehensive list is here:
      http://www.physicsguy.com/ftl/html/FTL_part4.html#subsec:specialframe

      Don't give people too much hope. Those are not really workarounds. A workaround is IMHO something you can do. But this is only a list how the universe had to be so that ftl travel is possible. If it is not... tough luck.

    40. Re:I'll believe it when I see... by grim4593 · · Score: 1

      With a cosmic event horizon limiting the edge of the visible universe would it be possible to warp space to a position that is causally disconnected from us due to the speed of light? I am not sure how practical that would be but it would prevent casualty violations.

    41. Re:I'll believe it when I see... by cyberjock1980 · · Score: 1

      My understanding is that if you are traveling at any velocity up to the speed of light and you measured the speed of light it would always be the same. However, I think weird things would happen if you were traveling at or greater than the speed of light and shone a flashlight in front of you.

    42. Re:I'll believe it when I see... by hexagonc · · Score: 1

      Not saying that I'm an expert but special relativity was subsumed by general relativity almost a hundred years ago. The whole point of this article is that you are not locally traveling faster than light. Light in your vicinity would get to the destination faster than you as expected. It has already been well established that space can expand between two objects faster than light (or any other information) can traverse the distance.

    43. Re:I'll believe it when I see... by myowntrueself · · Score: 4, Funny

      But that's the point of how warp drive works - you bend space so that you don't travel faster than light.

      You locally don't. The warp ship doesn't actually accelerate at all. This is how you get around the relativistic energy equation.

      However, someone will observe you traveling faster than light.

      So you use stealth technology. Duh.

      --
      In the free world the media isn't government run; the government is media run.
    44. Re:I'll believe it when I see... by epiphani · · Score: 1

      I've always grasped the limitations of special relativity - it's made this conversation especially interesting to read. That said, you just touched on one thing that has consistently been beyond me. Can you expand on this a bit? General relativity - and many of the corollaries in the early universe (specifically the inflationary period) have been things I've struggled with.

      How can you have two objects moving away from each other at greater than the speed of light, whilst maintaining special relativity? For inflation to work, that has to be the case, correct?

      --
      .
    45. Re:I'll believe it when I see... by inputdev · · Score: 1

      Given a few such warp ships, you could even arrange it so that that person would receive a message they had written and sent with you before they had actually written it. And then causality is broken for everyone.

      Not that I think this is a reasonable warp drive, but I don't think you are right about the arrangement leading to the message coming back before it left - there would be plenty of light cones being crossed, but the message would always come back after it was sent, I think.

    46. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      Er... no, away from each other. The net velocity is 2c.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    47. Re:I'll believe it when I see... by Anonymous Coward · · Score: 1

      A lot of these explanations of why you're wrong aren't correct either. The truth is that time travel is only "possible" with relative motion; the idea is, as you speed up, objects "behind" you are further back in time than their light-distance would imply, since the space is contracted, so if you were to able to travel instantly (from your perspective) you would arrive in the past for objects *behind you*. This doesn't work if you travel instantaneously in the direction of compression, which is actually what the warp drive relies on. You would time travel, but only into your own future, so there'd be no information-getting-into-the-past issues. The relativistic effects are limited to your delta-v with conventional locomotion like normal.

    48. Re:I'll believe it when I see... by monkeykoder · · Score: 1

      According to every physics class I've ever taken your statement is indeed false.

    49. Re:I'll believe it when I see... by joelsanda · · Score: 1

      I'll believe it when I see time travelers from the future who have used their warp drives and FTL travel to come backward in time to tell us about it. (According to special relativity, the ability to travel faster than light is equivalent to the ability to travel backwards in time.)

      Or a Delorean.

      --
      The Luddites were ahead of their time.
    50. Re:I'll believe it when I see... by frieko · · Score: 2

      Spacetime is by no means a flat plane with a fixed notion of distance. It doesn't matter how far apart points A and B were, warp drive simply makes the necessary corrections to the universe such that there is a shorter path to get there. For example, we can see galaxies which are 46 billion light years away. Those stars "warped" to their current locations in a mere 13 billion years. Nothing FTL about that. The question isn't whether spacetime is malleable, it's whether there is any practical way of doing it.

    51. Re:I'll believe it when I see... by Drishmung · · Score: 2
      At the quantum level, Feynman treated anti-particles as being particles traveling backwards in time. However, point 2 (or something like it) does in fact seem to hold sway, as set out by the Temporal Consistency Principle and formalized as the Novikov self-consistency principle.

      Now, bashing quantum theory and general relativity together into a consistent whole is something that we've not managed to do yet. Both seem to be true in their respective domains---(almost magisteria to listen to the debates) yet they stubbornly resist categorization into a One True Theory of Everything---so far.

      --
      Protoplasm. Quiet Protoplasm. I like quiet protoplasm.
    52. Re:I'll believe it when I see... by Tanuki64 · · Score: 3, Informative

      Here you find a better explanation in the links:

      http://science.slashdot.org/comments.pl?sid=3124243&cid=41369449

      http://science.slashdot.org/comments.pl?sid=3124243&cid=41369345

      I'd say you take a few more physics classes.

    53. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      You're picking at semantics and missing the point. If you're standing in a room and shining two beams of light away from each other, the photons appear to have a net velocity of 2c. Nobody's exceeding c. If you were inside of one of the beams, the other would look weird to you, sure, but that's due to time dilation. If we were to replace the beams of light with two ships, you'd still be able to cover twice the ground relative to one another. For practical purposes, and not the gratification of the people who feel an urge to measure how fast things are moving while in transit, the parent frame perceives you getting to your destination twice as quickly as you otherwise would. I think. (IANAP.)

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    54. Re:I'll believe it when I see... by BitterOak · · Score: 1

      Doesn't warp drive effectively change the distance between those two points? So point A and point B are closer together for a while, you move between them, then let them resume their original positions.

      Ah, but there's the problem: it's letting them return to their original positions. If a point returns to its original position faster than light, carrying you with it, then you're traveling faster than light. If it returns slower than the speed of light, then you aren't really accomplishing anything.

      --
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    55. Re:I'll believe it when I see... by Anonymous Coward · · Score: 1

      time only moves in one direction. however, time is a relative perception. while you might might travel 1000 light-years in one second, 1000 years would have passed in the world around. your 'FTL' is not really FTL. you have simply created a bubble of space-time where time passes more slowly or where the laws of physics react more slowly.

    56. Re:I'll believe it when I see... by Sez+Zero · · Score: 4, Funny

      But hey, maybe it's not a causal universe!

      Dang.

      I was really looking forward to Causal Friday.

    57. Re:I'll believe it when I see... by monkeykoder · · Score: 3, Insightful

      Again completely false they could not see you at your destination before you left because you would not be there yet. They would see you arrive at your destination faster than the speed of light but not before you left. At no point would you be violating causality unless you used the type of wormhole that links two different times which has yet to be conclusively proven impossible. As well there is no real reason to believe that my future self could not go back in time and have caused the universe to be in the state that it is currently in. Which makes the causality argument shaky at best. Also it looks like you don't have a firm understanding of special or general relativity.

    58. Re:I'll believe it when I see... by Tanuki64 · · Score: 1

      Three times 'I think'. Gutfeeling physics?

    59. Re:I'll believe it when I see... by nine-times · · Score: 4, Informative

      the relative motion would be FTL, but so is the relative motion of two beams of light going in opposite directions when measured from an absolute frame of reference.

      Nope. First, there's no such thing as an "absolute frame of reference". That's the really cool thing that Einstein proved, which gets referred to as "relativity". When two beams of light going in opposite directions are measured from any frame of reference, both are going c, neither are going 2c. Even if you were traveling along behind one of the beams of light going at 99% c, each would still only be going c.

    60. Re:I'll believe it when I see... by MMC+Monster · · Score: 2

      I know a bit about physics, and can understand part of the problem.

      However...

      Here's a thought exercise: You have a FTL ship that can reach Alpha Centuri in a second. You then make a U-turn and come back to Earth a second later. How much time has elapsed on Earth? How much time for the passenger of the ship?

      --
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    61. Re:I'll believe it when I see... by rollingcalf · · Score: 1

      The laws of physics allow for space-time itself to be warped or stretched faster than light. It's traveling through space which is limited by the speed of light.

      --
      ---------
      There is inferior bacteria on the interior of your posterior.
    62. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      In the real world, today, the phase velocity of light can easily exceed the speed of light in a vacuum.

      That's because phase velocity is not a "thing", it's a logical description of frequency distribution. Just like "the dot made by a laser" is just a logical description of where a laser beam is interacting with an object. Sweeping the laser across the moon would have the location of the spot moving FTL, but it's not a "thing". The actual things are the photons from the laser moving from the laser to the moon.

      There's no information transfer, either, due to the conditions of travel at that speed, but there's no time travel.

      There's no time travel because there's no information transfer because phase velocity is not a thing.

      A warp ship bringing people across the universe is a thing that conveys information, and so you have causality problems.

      --

      The enemies of Democracy are
    63. Re:I'll believe it when I see... by Nyrath+the+nearly+wi · · Score: 1

      Not to put too fine a point on it, but the whole point of Einstein's Relativity is that there are no absolute frames of reference.

    64. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      For example, objects that recede past our cosmic event horizon are moving away from us faster than the speed of light

      Well yeah, and by virtue of doing so there is no possible way that we can ever interact with them, ergo no possible causality conflict.

      The question is what would happen if they were coming at us. Oh sure maybe in their local space they aren't traveling faster than c, but if a ship leaves Vega and heads to earth at Warp 10, then I'll witness their arrival before I witness their departure.

      At this point it's no different than if they somehow traveled FTL through unwarped space, or simply *poofed* here by magic. From my reference frame, the two events have a space-like separation, and causality has been violated.

      Which is why the descriptions of Alcubierre drives I have read suggest that the ship itself would be separated causally from the rest of the universe, and that there's no known way to actually get the ship in or out of the bubble and that the bubble has to already exist.

      What I find very interesting is the possible implication that such "effective FTL" is okay as long as there can't be any causality violations as a result.

      --

      The enemies of Democracy are
    65. Re:I'll believe it when I see... by nedlohs · · Score: 1, Interesting

      Maybe you should try some different physics classes. It's just special relativity. If you have a faster than light travel/signalling then there will be an interial frame of referance in which that travel/signal went back in time. Since the first postulate or relativity says that the laws of physics are the same in all inertial reference frames that means backwards in time travel/signalling is possible in all inertial frames of reference and we have killed causality. Or alternatively the postulates of special relativity (and hence the theory) are wrong.

      http://www.theculture.org/rich/sharpblue/archives/000089.html has some reasonable spacetime diagrams for an example.

    66. Re:I'll believe it when I see... by Nyrath+the+nearly+wi · · Score: 1

      No, that is not how this "warp" drive works. The drive in the original article is a variation on the Alcubierre warp drive, which only warps a bubble around the ship. It does NOT effectively change the distance between the start and destination. You can read the original paper here:

      http://arxiv.org/abs/gr-qc/0009013

    67. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      They would see you arrive at your destination faster than the speed of light but not before you left.

      You're at Vega, 25 light years away. You send a radio message "I'm coming!" and hop in your warp drive and head to earth at 5x the speed of light. In 5 years I see you arrive at earth. 20 years later the message announcing your departure arrives.

      So yes, I saw you arrive before I saw you leave.

      As well there is no real reason to believe that my future self could not go back in time and have caused the universe to be in the state that it is currently in.

      Causality is just an assumption, sure.

      Also it looks like you don't have a firm understanding of special or general relativity.

      But an assumption fundamental to both theories (and all of physics).

      --

      The enemies of Democracy are
    68. Re:I'll believe it when I see... by HappyEngineer · · Score: 4, Insightful

      There are several issues here, but I'd like to comment on your linking of light and causality.

      First, objects traveling faster than sound do not violate causality for a bat. Just because the sound they receive is confusing does not mean that the universe broke or that anyone traveled through time. A supersonic object can make two sounds at two different times and a listener at a certain position would hear the sounds reversed. That's confusing, but it doesn't violate causality (except in the strict sense that a bat would sense that events occurred in the wrong order). Sound and light are not the same of course, but getting your data out of order just means that things are confusing for the viewer.

      The reason sound and light are not the same is because sound is not synced with time. Being supersonic does not affect time significantly whereas getting closer to the speed of light causes you to experience time differently than others traveling at different velocities relative to you. Furthermore, time dilation and your speed of travel are synced such that light travels away from you at the same speed no matter what speed you are traveling at (assuming you aren't magically warping space).

      I don't know enough to comment on how exactly warping space to travel ftl works with special/general relativity, but I've never seen it debunked. The real problem is that there is no known way to warp space to create this warp drive.

    69. Re:I'll believe it when I see... by Nyrath+the+nearly+wi · · Score: 1

      Moving a ship between point A and point B faster than light can do it is the same as time travel. That's all that is needed. And time travel destroys causality.

    70. Re:I'll believe it when I see... by Nyrath+the+nearly+wi · · Score: 1

      Heh. But didn't you hear? There ain't no stealth in space

      http://www.projectrho.com/public_html/rocket/spacewardetect.php#id--There_Ain%27t_No_Stealth_In_Space

    71. Re:I'll believe it when I see... by nine-times · · Score: 1

      Our current understanding (i.e. General Relativity) specifies that faster than light travel would permit time travel into the past. It's hard to explain, but it helps to look at a light cone. Anything that is in the top "future light cone" is definitely in the future. Anything in the "past light cone" at the bottom is definitely in the past. Anything outside the light cone could be happening at the same time. It's not necessarily happening at the same time, but it could be, depending on your frame of reference.

      Confused yet?

      So you see the plane called "hypersurface of the present"? Well every point along that plane is the present, but the slope of the line changes depending on your frame of reference. Is that clearer or less clear?

      Well anyway, if you can travel fast enough to get outside of the "future light cone" (i.e. faster than light), then you could pick some slope of the plane labelled "hyper surface of the present" where you would be below the plane. In other words, according to some frame of reference, you would arrive at your destination before you left. If you turn around and return to your original point in space, you can arrive in the "past light cone" and get there before you left.

    72. Re:I'll believe it when I see... by Hizonner · · Score: 1

      Right. "Apparent" FTL is not excluded by General Relativity. However, what General Relativity, and even Special Relativity, do say is that, if you have "apparent" FTL, you also have "apparent" time travel, and "apparent" violations of causality.

      Neither time travel nor violations of causality are the sorts of things you'd expect to miss on Earth, because you'd have people coming back in time to violate causality all over the place.

      So, where are the time travel and causality violations, then? Seems we have pretty strong evidence that FTL, "apparent" or otherwise, is not possible in the actual world.

    73. Re:I'll believe it when I see... by spike+hay · · Score: 3, Informative

      For chrissake:

      Here

      FTL implies at least backwards communication is possible under any method you can think of. If you get get to Alpha Centauri by stuffing yourself in your ass, it will still allow backwards time travel.

      --
      If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
    74. Re:I'll believe it when I see... by EdIII · · Score: 1

      Hilarious amounts of dilation, sure, but nothing wibbly-wobbly.

      Can you knock out a +5 informative on what wibbly-wobbly means?

    75. Re:I'll believe it when I see... by Bent+Mind · · Score: 1

      However, someone will observe you traveling faster than light, going from point A to point B faster than light would travel the same distance. If nobody sees you traveling faster than light, then how can you say you did so at all?

      I'm a little confused by this idea. At no point does the warp ship go from point A to point B faster than light would travel the same distance. The path that the ship takes is shorter than the path that the light takes. The distance is not equal.

      If an observer were near point B, I can see how it might appear that the ship arrived before it left. However, this would be an optical illusion based on the greater distance that the light traveled.

      --
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    76. Re:I'll believe it when I see... by Anonymous Coward · · Score: 4, Insightful

      You can't go backwards in time using FTL. You can violate Causality, but that's not the same thing and isn't actually a big deal.

      Picture it this way: You have a ship that can travel to Jupiter in 5 seconds. The method doesn't matter. You leave Earth, go to Jupiter, come back faster than light, and it's still 10 seconds into the Earth's future. You did not go so fast that you ended up in the Earth's past. You did not return while they were still counting down to your launch.

      But what DID happen is that you outpaced your own light cone.

      Since relativistic observers cannot exceed the speed of light themselves, and events can only propagate at the speed of light, then for all events, all relativistic observers will see the cause before the effect. That's Causality. But a lot of people get caught up on the whole "no absolute reference" thing and they take it a bit too far. Once something happens, it's done. You might not know about it yet, but it already happened and there's nothing you can do about it.

      So what would it mean if we could outpace our own light cone? Not much, actually.

      You could see the effect of some events before the cause, but you wouldn't be able to do anything about it. The cause already happened. The cause has its own light cone, but you're coming at it from a weird angle, so you haven't run into it yet. You might not even see the cause until you slow down and let it catch up to you "naturally".

      Similarly, some observers would see you as moving backwards, but that's just because you're moving faster than the photons you're emitting. Anyone who saw that wouldn't be able to do anything about it, though, even if they could travel instantaneously. You've already long since passed them. If they could travel faster than you, they might be able to intercept you in the future by plotting out your course from what they observered, but they wouldn't actually be able to use what they saw to affect the past. Like if I found a blog post from you that said you were hiking from DC to Hollywood starting a week ago, so I figure out how long that will take and board a plane to meet you there. The Universe wouldn't much care.

    77. Re:I'll believe it when I see... by wisnoskij · · Score: 1

      Well that is why the definition of a warp drive is that it warps space so that traveling a short distance actually brings you a far distance. You are traveling slower than light, but covering greater distances.

      The magic is that you are not traveling, it is more like instantaneous teleporting.

      --
      Troll is not a replacement for I disagree.
    78. Re:I'll believe it when I see... by Samantha+Wright · · Score: 4, Informative
      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    79. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      Here's a good description.

      Note that the method of FTL communication does not matter. The author uses an "ansible", what is essentially a magical instant communication device from Sci-fi. It can be assumed that the ansible itself violates no laws of physics.

      All that matters is how the various sub-luminal reference frames see the ordering of events as a result.

      I understand how this solution to GR allows one to avoid going FTL locally. I do not see how this gets around the larger perspective of how the sequence of events appears to other refererence frames. The whole point of Relativity is that the laws of physics must appear to hold according to everyone.

      --

      The enemies of Democracy are
    80. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      Not to put too fine a point upon it, but that doesn't affect my argument. If you have two ships going c in opposite directions for 1 hour, and then they stop moving, the distance between them will be twice that if only one was moving. You can replace 'absolute frame of reference' with 'starting frame' or 'parent frame' if you really need that itch scratched.

      --
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    81. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      I'm mystified as to how you can relate so much detail and yet miss what I was saying.

      Two ships travel at c in opposite directions for a period of time. When they decelerate and return to the same frame of reference that they started from, the distance between them will be equivalent to one ship having travelled at 2c for the same period. It doesn't matter what the people in each ship perceive from within their reference frames while they're moving.

      This same effect is why the sky will eventually go dark—the universe is expanding at such a rate that light from the furthest side will eventually never be able to catch up to us. I.e., the relative velocities are above c.

      --
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    82. Re:I'll believe it when I see... by shutdown+-p+now · · Score: 1

      If you're standing in a room and shining two beams of light away from each other, the photons appear to have a net velocity of 2c.

      That doesn't really make sense. From the perspective of a stationary observer, the photons in one beam would appear to have a velocity of c, and so would the photons in another beam. I have no idea what "net velocity" is supposed to look like, and how an observer would actually observe that.

      On the other hand, if you were "inside" one of the beams, the other beam would also have a velocity of c relative to you, not 2c.

    83. Re:I'll believe it when I see... by RabidReindeer · · Score: 1

      Not to put too fine a point upon it, but that doesn't affect my argument. If you have two ships going c in opposite directions for 1 hour, and then they stop moving, the distance between them will be twice that if only one was moving. You can replace 'absolute frame of reference' with 'starting frame' or 'parent frame' if you really need that itch scratched.

      That would be true in Newtonian physics. But the whole point here is that we're dealing with relativistic physics, where space and time are intimately intertwined and there is no such thing as an "absolute" frame of reference and the "starting frame" is not merely a locus defined in space, but in time as well.

      Ergo, not only wibbly-wobbly, but timey-wimey too.

      Or to quote Einstein himself: "There was a young lady named Bright..."

    84. Re:I'll believe it when I see... by shutdown+-p+now · · Score: 3, Informative

      The light won't move faster. Instead, the frequency will be insanely high. Your infrared emitting tungsten filament bulb will be emitting gamma ray photons.

      Not to you, it won't. Only to that observer, relative to which you were moving at 0.99...c in the first place.

      If you are going 100% speed of light, you will *never* succeed in toggling the switch.

      You can't reach c while having any mass, so if you're going at c, then there's no switch.

    85. Re:I'll believe it when I see... by shutdown+-p+now · · Score: 1

      I think weird things would happen if you were traveling at or greater than the speed of light

      Fixed that for you.

    86. Re:I'll believe it when I see... by NEDHead · · Score: 4, Insightful

      don't need a physics class, as I already have my degrees in the field. All that you reference is true in its own context (spec rel). Alcubierre warp drive is valid within Gen Rel, and does not lead to time travel. It has other issues, but not this particular one.

    87. Re:I'll believe it when I see... by immaterial · · Score: 2

      It is the periodic 5th-dimensional motion perpendicular to your current spacetime trajectory that is produced when things go timey-wimey.

    88. Re:I'll believe it when I see... by RabidReindeer · · Score: 1

      FTL is easy. It's ETL (equal to light) that's hard. That's because that's where the Lorentz-Fitzgerald equations end up doing a divide-by-zero.

      In fact, once you pass the speed of light, going even faster gets easier the faster you go (assuming the equations still hold). The difficult part is actually reaching c, since it would require infinite (contracted) time and infinite energy to accelerate the resulting infinite mass.

      On the other hand, if you could tunnel around the actual speed of light and go directly from 0.99c to 1.01c, it would be relatively easy. No pun intended.

    89. Re:I'll believe it when I see... by rubycodez · · Score: 1

      wrong. this is outside the realm of special relativity, it is NOT adding to relativistic mass of an object, your objections are moot

    90. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      The velocity of one minus the velocity of the other. If the vector describing the movement of one beam is [c, 0, 0] and the other is [-c, 0, 0], then the difference between them is [2c, 0, 0]. The distance between the photons (let's pretend they're particles to keep this simple—I really prefer using spaceships for this kind of thing) in each beam increases at a rate of 2c. They will reach targets placed x metres away from the starting position in half the time it would take a single beam of light to shine from one target to the other.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    91. Re:I'll believe it when I see... by RabidReindeer · · Score: 1

      If by weird you mean "red shift" and "blue shift", you're quite correct.

      However, once again, it's all relative. If the observer is also moving identically at the speed of light along the same vector, the relative velocities of light source and observer would be zero and the observer would see no net shift. A stationary observer (in terms of the oncoming light, however, would see a shift.

    92. Re:I'll believe it when I see... by rubycodez · · Score: 1

      special relativity covers one and only one situation, noninertial reference frames. it also only covers the case of changing velocity by adding or removing relativistic energy. this proposed drive is not in the realm of SR, just as an atomic clock following a trajectory around the earth is not covered.

    93. Re:I'll believe it when I see... by rubycodez · · Score: 1

      oops, meant to say SR is the realm of inertial reference frame, the GR covers noninertial. this drive is a GR situation, SR is irrelevant.

    94. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      Alright, I can accept that. So what would happen if you had a shuttlecraft moving at c in one direction, a space station moving at c in the opposite direction, and an independent observer witnessing both these events? Would the shuttlecraft appear to move past the surface of the station at 2c, or not? What would happen to time inside the station and the shuttle, and what would it matter?

      --
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    95. Re:I'll believe it when I see... by iggymanz · · Score: 4, Insightful

      you are the one in need of more physics classes, you are linking a SR page (inertial reference frames only, changing relativistic mass to change velocity only) and this drive is outside the realm of SR, it is a GR engine. your SR arguments are meaningless.

    96. Re:I'll believe it when I see... by Tanuki64 · · Score: 1

      That is only the energy aspect of the problem. I don't care much about that. Warp drives or wormholes might be a fine solution to that. If they exist. I think the causality problem is much worse, because it cannot be circumvented by any technical means.

    97. Re:I'll believe it when I see... by Grishnakh · · Score: 2

      A PhD physicist invented the Alcubierre Drive, and physicists at NASA are now working on this warp drive concept, but a couple of armchair physicists on Slashdot think they know physics better than the experts.

    98. Re:I'll believe it when I see... by mt1955 · · Score: 1

      My personal take is that Gene Roddenberry was an alien whose goal was to nudge us in the generally correct direction without apparently doing so. To do this, he (it?) created a TV series called 'Star Trek' in which all advances we'd need were demonstrated to agile minds. Once it has been conceptualized, if it is possible, someone somewhere will eventually do it...

      Best thinking I've seen on /. in ages -- had I mod points you'd be +5 right now

    99. Re:I'll believe it when I see... by nine-times · · Score: 4, Interesting

      Two ships travel at c in opposite directions for a period of time. When they decelerate and return to the same frame of reference that they started from, the distance between them will be equivalent to one ship having travelled at 2c for the same period. It doesn't matter what the people in each ship perceive from within their reference frames while they're moving.

      No, they won't.

      Let's say that three ships are stationary relative to each other, sitting right next to each other, and two of them accelerate very quickly to just under the speed of light in opposite directions. Each ship travels for what their clock says is one year, and the third stays where it is. After a year, they stop very quickly, and measure the distance that they are from each other. How far away from each other will they be?

      The correct answer is 1 light-year. Only 1, not 2.

      From each ship's point of view, when it took off going almost the speed of light, the other ship travelled very slowly in the opposite direction. The third ship that didn't move saw each ship travel away at almost the speed of light. However, from the third ship's point of view, only half a year passed, which explains why they're only 1 light-year apart. That's what we call "time dilation".

    100. Re:I'll believe it when I see... by Grishnakh · · Score: 2

      I'm sorry, I don't see the problem here. Back before radio was invented, messages had to travel by ship. If someone stuck a message in a bottle and threw it in the ocean before getting in their wooden sailing ship, you'd also see them long before you got the message. BFD.

      So what if a radio signal goes slower than a spaceship? That doesn't mean anything. It just means your means of communication is slower than your means of travel, and there's little point to bothering with it. This doesn't imply time travel at all.

      This is no different to how I can see things happen before I hear them happen. Everyone knows sound travels slower than light, but that doesn't have anything to do with time travel either.

      Strange how real physicists have no trouble with this stuff, and even invent things like "the Alcubierre drive" (named after the physicist who invented it), and are now proclaiming that it might be possible (with some advances we haven't figured out yet, namely how to warp the continuum, possibly using exotic matter), while some yahoos who took a physics class at some point think they're experts and are proclaiming how impossible it is.

    101. Re:I'll believe it when I see... by nine-times · · Score: 1

      Though, honestly I don't like this example, because the issue of acceleration screws it up and makes it too complicated, and so as a result what I said is not quite right. It'd be better to explain it with the ships already in motion, but when I started to write that example, it was going to be too complicated.

      So I gave you an explanation that simplifies things quite a bit, at the cost of some accuracy.

    102. Re:I'll believe it when I see... by wierd_w · · Score: 1

      Agreed, both counts. Massed particles would require infinite energy to attain C. Infinite energy does not exist in our universe in any useful form. It was a theoretical "If you COULD attain C", then you would never be able to flick the switch, because you would experience zero seconds of time internally, and infinite time externally.

      The lightbulb would appear to radiate normally to the onboard observer who flicks the switch. The person outside the accelleration frame caught in the headlights would be roasted. (Then destroyed in an unbelievable nuclear explosion when they hit the windshield a few nanoseconds later.)

    103. Re:I'll believe it when I see... by Grishnakh · · Score: 1

      Gene Roddenberry also showed us how women in the future should dress. Too bad they screwed it up in TNG and the later shows with women wearing pants. At least Troi had some nice outfits.

    104. Re:I'll believe it when I see... by MikeBabcock · · Score: 2

      No, you don't. The whole point of warping space-time is to arrive at another point by moving that point closer to you.

      The typical explanation is to take a large surface, fold it in half, and punch a hole through. Now push a marble through the hole and unfold it again. The marble didn't move very fast, and didn't travel far, but arrived somewhere previously very far away.

      Warping spacetime is all about making distant locations closer so that we don't have to violate ftl rules.

      --
      - Michael T. Babcock (Yes, I blog)
    105. Re:I'll believe it when I see... by MikeBabcock · · Score: 2

      If that's the reference you're using, I recommend a subscription to actual periodicals.

      --
      - Michael T. Babcock (Yes, I blog)
    106. Re:I'll believe it when I see... by MikeBabcock · · Score: 1

      Nobody would observe you moving faster than light at all. Technically from the right angle, they'd observe you moving instantaneously from what they perceive to be one point to what they perceive to be another.

      --
      - Michael T. Babcock (Yes, I blog)
    107. Re:I'll believe it when I see... by MikeBabcock · · Score: 1

      No, you saw me arrive before you received my message. I still arrived *after* leaving.

      --
      - Michael T. Babcock (Yes, I blog)
    108. Re:I'll believe it when I see... by Greyfox · · Score: 1

      Time travel would not only violate causality, but I think it would also violate thermodynamics. It would require putting shit back into the dog. So you're traveling backward in time using a drive that employs matter with a negative mass. That's a lot of laws of physics to be breaking, right there. It's going to be one hell of an interstellar traffic ticket!

      --

      I'm trying to teach myself to set people on fire with my mind... Is it hot in here?

    109. Re:I'll believe it when I see... by SoftwareArtist · · Score: 1

      It's more complicated than that. A warp drive implies something that many people view as the "moral equivalent" of time travel, but that doesn't mean you can actually build a practical time machine.

      Suppose you use a warp drive to travel faster than light. That means there exists a reference frame in which you appear to arrive before you left. More specifically, it's a reference frame that's moving very quickly relative to your starting point. That's very interesting. It implies some dramatic things about causality. But it's not what most people mean by "time travel". You really want to start at rest in some reference frame (say, the earth), and end at rest in that same reference frame, and have an observer in that reference frame see you arrive before you left. So far as I know, a warp drive does not allow you to do that.

      Instead, it means that someone zipping past in a spaceship at 99% of the speed of light will shout out, "Hey! He just arrived before he left!" But he won't be able to stick around to chat about it, because in the time it took him to say those words he's already moved on some millions of kilometers.

      --
      "I'm too busy to research this and form an educated opinion, but I do have time to tell everyone my uninformed opinion."
    110. Re:I'll believe it when I see... by Black+Parrot · · Score: 1

      If you get get to Alpha Centauri by stuffing yourself in your ass, it will still allow backwards time travel.

      Ah, but if you've stuffed yourself into your own ass, travelling backward will still be going forward.

      --
      Sheesh, evil *and* a jerk. -- Jade
    111. Re:I'll believe it when I see... by Black+Parrot · · Score: 5, Funny

      A PhD physicist invented the Alcubierre Drive, and physicists at NASA are now working on this warp drive concept, but a couple of armchair physicists on Slashdot think they know physics better than the experts.

      Why should physics be different than any other topic?

      --
      Sheesh, evil *and* a jerk. -- Jade
    112. Re:I'll believe it when I see... by disambiguated · · Score: 1

      Nothing is excluded by anything, if you can handle or prevent the paradoxes.

      What exactly does it mean for something to be excluded by theory, if it doesn't mean that it leads to a contradiction?

    113. Re:I'll believe it when I see... by bondsbw · · Score: 2

      Actually, that is not so much an observation as a thought experiment. The real observation came via the Michelson-Morley experiment.

      The Earth revolves around the Sun. Over the course of 180 days, its velocity relative to the sun (around 30 km/s) reverses direction. The difference is 60 km/s. Of course, the Sun revolves around the galaxy, which is itself moving.

      The Michelson-Morley experiment was created to measure the speed of light at one point in the year, and then measure it again a half year later when the earth is travelling the other direction. And because no artificial device in the late 1800s could travel 60 km/s, this allowed the best measurements relative to light-speed possible at the time.

      The expectation was that light travels at an absolute speed relative to some invisible space ether, and that we would be able to determine the nature of that ether by noting the differences in light speed throughout the year. But the difference was very small, within error of zero difference. This result (along with similar experiments) led to the theory of special relativity.

      --
      All my liberal friends think I'm a conservative, all my conservative friends think I'm a liberal.
    114. Re:I'll believe it when I see... by an+unsound+mind · · Score: 2

      You are using math valid only in a sub-FTL scenario to try to predict a super-FTL scenario.

      Let's assume all trees are green. This tree is red. Your argument is invalid.

    115. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      Okay. So simply have them stop when a year has passed from the non-moving ship's perspective instead. The passengers may not like having gone through two years of waiting for one light year of travel, but from the stationary ship's perspective, the other two ships have put two light years between them in the span of one. That still has its uses—especially if, say, there are no living passengers aboard either of the moving ships who would complain, and we're just delivering ore to an automated factory, or storing cargo in a designated bay.

      At any rate, TFA reveals that the warp engine design in question theoretically permits travel at up to 10c with no dilation at all.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    116. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      It's okay. We can just pretend there's instantaneous acceleration and deceleration. It's sufficient for the needs of the thought experiment.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    117. Re:I'll believe it when I see... by an+unsound+mind · · Score: 1

      It is a sad day when an AC calling people morons is the most insightful participant of a discussion.

    118. Re:I'll believe it when I see... by disambiguated · · Score: 1

      Toward each other or away from each other makes no difference.

      From your frame of reference, both light beams are moving 1c. From the frame of reference of either of the light beams, the other beam is moving at 1c.

      You are getting 2c because you are switching your frame of reference in the middle of your thought experiment. First you are using yourself as the frame of reference, and measuring 1c for each of the light beams (in opposite directions). Then you are switching your frame of reference to one of the light beams when you add 1c + 1c = 2c.

      You can't add velocities like that.

    119. Re:I'll believe it when I see... by disambiguated · · Score: 2
    120. Re:I'll believe it when I see... by viperidaenz · · Score: 1

      or towards each other, at -2c

    121. Re:I'll believe it when I see... by shutdown+-p+now · · Score: 1

      The velocity of one minus the velocity of the other.

      The result of that operation would not be a velocity of anything, however.

    122. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      That's the whole point -- they don't need to see you actually in transit. They only need to see two causally linked events -- you getting in your ship at point A, and getting out at point B -- with a space-like interval in between them from their reference frame.

      So whether it's a warp ship, or a wizard instantaneously teleporting, it still causes problems.

      --

      The enemies of Democracy are
    123. Re:I'll believe it when I see... by Requiem18th · · Score: 1

      They say so but I don't understand how FTL traveling is paradoxical and I don't understand how FTL traveling implicates time travel.

      "Apparent" time travel i understand. But don't really see how it affects causality.

      Let's say my sun explodes and I go to a nearby system 2 light years away at twice c. Once there I will warn everybody that the closest star is going nova in a year. Now let's say you want to prevent me from delivering these news. You look up to the sky and see my planet. Obviously it is still there isn't it? So you take my warp ship and try to go to my planet. By the time you get there you are only going to find a 2 years old cloud of hot gas.

      If you travel at 4 c you will find a 1.5 years old gas cloud. Travel at 8 c to find a 1.25 years old gas cloud. Travel there at 16 c to find a 1.175 years old cloud.

      Travel as fast as you want. You shouldn't ever get earlier than a year after my departure let alone prevent it. Now, it could be that someone find out about this and tries to intercept you by going there at twice your speed. They'll get there before you and it will surely take you by surprise but that's still not time travel from your point of view.

      --
      But... the future refused to change.
    124. Re:I'll believe it when I see... by viperidaenz · · Score: 1

      but there are four coordinates, not three. You forgot that time is one of them as well, and as you approach the speed of light relative to another frame of reference, time slows down when observed from that frame of reference. Velocity is distance/time. You may have observed twice the distance, but the observed time is twice as much also.

    125. Re:I'll believe it when I see... by Requiem18th · · Score: 5, Insightful

      Excuse me as I re-post what I already asked elsewhere in this article:

      I don't see how FTL traveling implicates time travel. "Apparent" time travel i understand. But don't really see how it affects causality.

      Let's say my sun explodes and I go to a nearby system 2 light years away at twice c. Once there I will warn everybody that the closest star is going nova in a year. Now let's say you want to prevent me from delivering these news. You look up to the sky and see my planet. Obviously it is still there isn't it? So you take my warp ship and try to go to my planet. By the time you get there you are only going to find a 2 years old cloud of hot gas.

      If you travel at 4 c you will find a 1.5 years old gas cloud. Travel at 8 c to find a 1.25 years old gas cloud. Travel there at 16 c to find a 1.175 years old cloud.

      Travel as fast as you want. You shouldn't ever get earlier than a year after my departure let alone prevent it. Now, it could be that someone find out about this and tries to intercept you by going there at twice your speed. They'll get there before you and it will surely take you by surprise but that's still not time travel from your point of view.

      --
      But... the future refused to change.
    126. Re:I'll believe it when I see... by mysidia · · Score: 1

      Special relativity does not make provisions how you travel. If you travel from point A in space to point B in space, be it by warp drive, be it by wormhole, be it by magic, faster than a beam of light could do it in vacuum, you travel ftl. And this means timetravel.

      If that were the case, it could very well indicate a problem with the theory of special relativity, requiring adjustment of the theory, to account for the additional geometry and other paths between point A and point B that do not require faster than light travel.

      By definition, if you bend space, there are now multiple paths from A to point B, and light can follow any of those paths

    127. Re:I'll believe it when I see... by viperidaenz · · Score: 1

      Or to quote Einstein himself: "There was a young lady named Bright..."

      Since when was Einstein a 78 year old woman named Geri Taran?

    128. Re:I'll believe it when I see... by DigiShaman · · Score: 1

      Please correct if this is wrong. Someone once explained the speed of light to me as the following...

      The speed of light is measured at 299,792,458 meters per second. But this is nothing more than an illusion because light is actually instantaneous in the universe. It just so happens everything else is moving *slower* which happens to give you the delta difference of...299,792,458 meters per second. Therefore, the perception of time is nothing but an illusion based on the delta difference between mass and light.

      If true, this makes a helluva lot more sense to me. Thus, nothing can move faster than light.

      --
      Life is not for the lazy.
    129. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      This is acceptable for (a) sufficiently short periods of time or (b) when no one's in either moving ship (or if they're in suspended animation) and hence there is no one around to care.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    130. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      What... is your point?

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    131. Re:I'll believe it when I see... by deimtee · · Score: 1

      It looks that way because time and space change as well. The guy travelling at .99C sees the light move away at C, but his time and dstance measurements are different to the outside observer.
      He measures the light travelling 1 light-second in one second, but the other observer sees the traveller's clock running at one second per 100 seconds.
      This is where it gets weird, because there isn't really a "stationary" observer. The traveller will think he's stationary, and see all the observations apply to the other guy. So they both see the other guy slowed down.

      --
      I'm guessing that wasn't on their radar screen...
    132. Re:I'll believe it when I see... by viperidaenz · · Score: 1

      If the universe crashes with an int 0h, I'm blaming you.

    133. Re:I'll believe it when I see... by Martin+Blank · · Score: 1

      The net separation speed from an outside reference is 2c. However, the relative separation speed from a photon in either beam is c because of time dilation. (I'm ignoring the stopping of time at c for demonstration purposes.)

      --
      You can never go home again... but I guess you can shop there.
    134. Re:I'll believe it when I see... by AshtangiMan · · Score: 1

      I looked it up in my gut ... and my gut says I'm right.

    135. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      Time dilation only affects the impatient. There are still numerous advantages to being able to make your relative velocity with another object appear to be 2c to an independent observer. You won't—for example—be any later for lunch.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    136. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      I'm glad we understand each other.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    137. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      No, I'm just measuring the rate at which the distance between them expands. I can do that from the first frame of reference.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    138. Re:I'll believe it when I see... by shutdown+-p+now · · Score: 1

      My point is that this concept of "net velocity" that you're trying to introduce as a subtraction of one velocity vector from another is a meaningless quantity. It's not a velocity itself; and it doesn't even describe anything directly observable. So the fact that it can be 2c is kinda ... duh. I can come up with other similar transforms that have even higher upper boundaries - for example, if you square the vectors before subtracting them, it's gonna be 2c^2. But what exactly does it prove?

    139. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      Little did I realise how much trouble saying 'velocity' instead of 'speed' would cause.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    140. Re:I'll believe it when I see... by EdIII · · Score: 1

      Thank you for a perfectly cromulent answer.

    141. Re:I'll believe it when I see... by Anonymous Coward · · Score: 1, Informative

      I can't believe this post was rated "+4, Interesting". Time dilation means that as you acquire more energy (i.e. the faster you go), time will pass slower and slower.

      So in effect you could in theory go through large distance (say, 1 light year) in what would subjectively (for the traveller) appear to be 1 second. If you take another second to come back, then the stationary element is now 2 years older : it saw the traveller spend one year to go one way and another year to come back.

      So in the case if your ships going opposite directions, if they go for a year (from the stationary point of view) in opposite directions at almost c, then they will be almost 2c apart. Except that from their perspective, they are only 2 light seconds apart now. And yes from each moving ships perspective, the other one would be looking like it's going faster than light, redshifting like crazy, etc.

      FTL "apparent" movement is not uncommon at all. For example, take alpha centauri. 1 light year away. Revolving around us in 24 hours. So doing a great 2 * pi * (1 light year) every 24 hours... apparently faster than light, except it's not.

    142. Re:I'll believe it when I see... by fikx · · Score: 1

      I've always (well, not always, took me a few tries to "get it") thought it made sense: c is not a speed in itself, it's the variable standing for the fastest something can go flat out...but light should be hitting that due to the no-mass thing (no mass, so it has nothing to slow it down), so c is light speed is c....
      anyway, for the universe to work, that is be consistent to all observers( be they people, flowers or just rocks that bump into each other), then the speed something can have traveled has to be limited to that same "flat out" speed....to "adjust" everything to work right, the time flow is what gets changed....hence the relative part. your time frame is "adjusted" to make it work since that's what keep things consistent. otherwise you get into some real trouble when two observers measure the same thing and get different answers...who's right? eliminate (thought experiments, we're allowed to do this in those) measurement error and such and two different measurements of the same object or sequence of events where both are accurate gives you a universe where there are multiple truths.....
      OK, no more caffeine for me late at night....time to start drinking something else...

      --
      AB HOC POSSUM VIDERE DOMUM TUUM
    143. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      So what if a radio signal goes slower than a spaceship? That doesn't mean anything.

      If the speed of light had no relationship to spacetime, if this was a Newtonian universe, then yeah, what would it matter? But this is not the case, and the speed of light is intimately related to the nature of space and time and as a consequence the ordering of events and causality.

      You can google "speed of light causality" to find that every source agrees. I like this page because it has graphs.

      Strange how real physicists have no trouble with this stuff

      Ha! And you think that's because they agree with you that there's no relationship between c and causality?

      No, physicists have "no trouble" with this because they know when they're looking at things outside the bounds of known physics. The Alcubierre drive is a valid solution for the equations of General Relativity, but that doesn't mean you can actually create one in this universe. In particular, the Alcubierre drive requires that the warp in space already exists, and there is no way to enter or exit it. Also, there are the implications with causality if you did exit it (if you didn't then you never interact with the rest of the universe so it's no problem). And that "exotic matter" you tossed out isn't just some engineering problem. Negative mass is also something not known in current physics.

      I'm not saying it's impossible. I'm saying it goes against the known laws of physics. Many people, especially physicists, hope that those laws are wrong and in such a way that FTL is possible.

      --

      The enemies of Democracy are
    144. Re:I'll believe it when I see... by Nyder · · Score: 1

      I'll believe it when I see time travelers from the future who have used their warp drives and FTL travel to come backward in time to tell us about it. (According to special relativity, the ability to travel faster than light is equivalent to the ability to travel backwards in time.)

      You know, if I was a timer traveler, I'd have better things to do then tell people what we have in the future. Chances are they wouldn't believe you, and if they did, they'd probably try to take it from you.

      --
      Be seeing you...
    145. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      You can still stand in a location and see the distance between two objects grow at 2c. That's got plenty of uses.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    146. Re:I'll believe it when I see... by mysidia · · Score: 1

      If you have a faster than light travel/signalling then there will be an interial frame of referance in which that travel/signal went back in time.

      If by "went back in time", you mean: observed the signal, earlier than the signal would have been observed, if the signal had travelled at the speed of light, then yes.

      If by "went back in time", you mean: observed the signal, before the signal would have been emitted, then no.

      Since the first postulate or relativity says that the laws of physics are the same in all inertial reference frames that means backwards in time travel/signalling is possible in all inertial frames of reference and we have killed causality.

      Laws of physics being the same in all reference frames, does not imply that the observation will be the same in all reference frames.

      There may be other occurences which are not considered by the theory.

      Also "physics being the same in all reference frames", is not required for special relativity to be valid. It is a premise. It is possible that a difference will occur in the laws of physics in some frames of reference, once "space has been bent"; in that case, there will be exceptional cases where special relativity does not apply, because one of the premises is not met in one case, even if the model is valid otherwise.

    147. Re:I'll believe it when I see... by mysidia · · Score: 1

      However, someone will observe you traveling faster than light, going from point A to point B faster than light would travel the same distance. If nobody sees you traveling faster than light, then how can you say you did so at all?

      What method could they possibly use to observe you travelling faster than light?

      If they watch for light emanating from you, it will only reach their eyes at the speed of light; the light emanating cannot move any faster.

      If they point a radar gun, and repeatedly shoot it at you.... the radar will actually never reach them and be reflected back, so you will never get a reading.

      How will they ever learned you travelled faster than light?

      Your movement could appear discontinuous, or you could disappear from sight entirely, but then, that could also be the result of any extreme change in speed, at a long distance, and in that case, the observer would never know you were there; it would be impossible to remotely distinguish that from the observed object not existing at all...

    148. Re:I'll believe it when I see... by mysidia · · Score: 1

      So yes, I saw you arrive before I saw you leave.

      The key word there is "before I saw you leave." , not "before you left."

      There are such things as optical illusions. Human vision and radio receivers are not the arbiters of time. If faster than light travel is possible; it is an inherent fact, that your arrival could overtake all currently known methods of observing you leave.

      But if you could send a faster than light signal announcing your departure, "I'm coming".... and then travel faster than the speed of light, then the message could still arrive ahead of you.

    149. Re:I'll believe it when I see... by bongey · · Score: 1

      The distance is correct, from the third ships point of view more than year would have passed.
      Time effectivity slows down in your reference frame such that you cannot go faster than the speed of light.
      Eistein even gave an example of this called the "Twin Paradox" which you have completely backwards, See more here http://www.pbs.org/wgbh/nova/einstein/hotsciencetwin/ .

    150. Re:I'll believe it when I see... by mysidia · · Score: 1

      c is in vacuum always c. Regardless of your movement.

      The physics is more a statement about your movement in a vacuum than light's. c is a fixed quantity, the rate of time light travels at, your experience of movement or magnitude of velocity and that of any observer is based on your position change per unit time, so if in a vacuum you have movement at a high rate, your experience of "time" slows, such that your change in position per unit time stays at or below c, and light always travels at c, regardless.

      You can continue to accelerate -- you will never observe yourself having a velocity exceeding c or be observed having a velocity exceeding c.

      You're also unlikely to reach near-light speed versus a planetary observer in the first place in your lifetime, regardless of how great your engine, the amount of energy required to accelerate any significant amount of mass near the speed of light is a large quantity, and at a rate of acceleration that humans could survive it would take hundreds of years to get anywhere near the speed of light, let alone "slow back down" after the experiment

    151. Re:I'll believe it when I see... by HJED · · Score: 1

      But your argument is a logical fallacy, if I sent a message by carrier pigeon saying "I'm coming" and then jumped in an F15 and got there first I would not have violated causality (such a situation has been proven possible) even though you will 'observe' me leaving after I arrived.
      Upon my arrival you could send out a hawk and intercept the carrier pigeon, but you could not stop the pigeon from leaving because it left before I arrived.
      If this is not the case, could someone please explain why?

      --
      null
    152. Re:I'll believe it when I see... by lister+king+of+smeg · · Score: 1

      not if you are still getting their after you left. then while you are merely their faster then if you traveled at light speed, but you will have experienced significantly less time than other non-space travelers, you will have only curved space time not looped it which will not destroy causality, just they same as walking throught a worm hole to the other end of the universe but at the same point in time would not destroy causality because you would not have gone backward in time mearly traveld faster then C.

      --
      ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
    153. Re:I'll believe it when I see... by lister+king+of+smeg · · Score: 1

      [section: not entirely serious, but...]
      My personal take is that Gene Roddenberry was an alien whose goal was to nudge us in the generally correct direction without apparently doing so. To do this, he (it?) created a TV series called 'Star Trek' in which all advances we'd need were demonstrated to agile minds. Once it has been conceptualized, if it is possible, someone somewhere will eventually do it...
      [/section]

      if he were an alien with the plans of seeding research into FTL travel then he must of laughed his ass of at the privet joke of his initials also being the abbreviation for general relativity

      Gene Roddenberry
      General Relativity

      --
      ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
    154. Re:I'll believe it when I see... by HJED · · Score: 1

      FYI your example doesn't violate causality, observing something before its effect is not the same as being able to interact with an event after it has occurred. ie. If I send you a message on ship saying that I'm leaving location X and then I travel to your location from location X on a supersonic jet I will arrive before you have observed me leaving, but that does not mean that you can stop my message or me from leaving.

      --
      null
    155. Re:I'll believe it when I see... by lister+king+of+smeg · · Score: 1

      I would be willing to wager that you might notice a red or blue shift in the light as it reflects back to you (the observer in the ship traveling at 0.99x*C do to the Doppler affect

      --
      ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
    156. Re:I'll believe it when I see... by lister+king+of+smeg · · Score: 1

      the time at which you witness it is immaterial what matters would be the traveler got there after he left not when the light catches up showing that he did.

      --
      ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
    157. Re:I'll believe it when I see... by complete+loony · · Score: 1

      an absolute frame of reference

      I know other people have picked on this statement already, here's another perspective.

      From your frame of reference you have a "light cone", eg light emitted from events inside that cone has already reached you. Events inside this cone can absolutely be said to have occurred in your past. Events inside this cone could have influenced you and caused you to do something. There is another light cone spreading out from you that includes events that you could influence.

      For an event that happens outside of these cones, there is no way for you to know if this event happens "before" or "after" your present time. In fact, there will be a frame of reference where an observer will measure the event as being before your present time, and another frame of reference that will measure this event as being after your present time. Attempting to establish the chronological ordering of events that occur outside of your light cone is meaningless.

      So if you could travel FTL, to a point corresponding to "now" outside your light cone. And another observer in a different reference frame does the same in the other direction. It is perfectly possible for both parties to arrive before the other one left, because both parties have a difference definition for "now" for events outside their light cone.

      --
      09F91102 no, 455FE104 nope, F190A1E8 uh-uh, 7A5F8A09 that's not it, C87294CE no. Ah! 452F6E403CDF10714E41DFAA257D313F.
    158. Re:I'll believe it when I see... by osu-neko · · Score: 1

      You're picking at semantics and missing the point. If you're standing in a room and shining two beams of light away from each other, the photons appear to have a net velocity of 2c. Nobody's exceeding c. If you were inside of one of the beams, the other would look weird to you...

      Actually, no, they don't, and from the perspective of either photon, the other appears to be moving at exactly 1c. That's how relativity works. You move off in one direction at 0.9c and I move off in the opposite direction at 0.9c, and I measure your velocity relative to mine, I get a result of less than 1.0c, not 1.8c as you might assume if you don't know/understand relativity.

      --
      "Convictions are more dangerous enemies of truth than lies."
    159. Re:I'll believe it when I see... by Tom · · Score: 1

      If nobody sees you traveling faster than light, then how can you say you did so at all?

      By evidence. If I go to some nearby earthlike planet, collect a few soil samples and come back, and it takes, say, a year then even though nobody watched, I can be fairly certain that it has actually happened.

      --
      Assorted stuff I do sometimes: Lemuria.org
    160. Re:I'll believe it when I see... by Grishnakh · · Score: 1

      Not as often as random people on Slashdot.

    161. Re:I'll believe it when I see... by Neil+Boekend · · Score: 1

      I find information on the intraweb of my company to be far more often true then information on the internet. However there isn't any information on warp drives there so your companies intraweb is probably different

      --
      Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
    162. Re:I'll believe it when I see... by ceoyoyo · · Score: 1

      That doesn't mean you can go back in time to to the SAME place in space.

    163. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      That's what I mean by "seeing" -- observing, according to some reference frame, FTL travel. The point of the warp drive is that within its own reference frame it is not traveling faster than light. But relative to some reference frame it must be (even if they aren't literally watching it with a telescope). And going FTL according to any reference frame violates relativity.

      --

      The enemies of Democracy are
    164. Re:I'll believe it when I see... by Intrepid+imaginaut · · Score: 1

      I'm fairly sure superluminal phenomena have been observed. They aren't going faster than light but they appear to be.

    165. Re:I'll believe it when I see... by ceoyoyo · · Score: 1

      From the third ship's perspective in your analogy, each ship travelled half a light year in half a year, in opposite directions. Those ships are one light year apart, therefore their relative speed was 2c, from the perspective of the third ship.

    166. Re:I'll believe it when I see... by metacell · · Score: 1

      If you have a faster than light travel/signalling then there will be an interial frame of referance in which that travel/signal went back in time.

      If by "went back in time", you mean: observed the signal, earlier than the signal would have been observed, if the signal had travelled at the speed of light, then yes.

      If by "went back in time", you mean: observed the signal, before the signal would have been emitted, then no.

      Not sure if you're just trolling, but: causality would be violated when you sent a signal back to the source of the first signal. If one of the objects were moving faster than light, it could be set up so the response signal arrives before the first signal is sent

      Since the first postulate or relativity says that the laws of physics are the same in all inertial reference frames that means backwards in time travel/signalling is possible in all inertial frames of reference and we have killed causality.

      Laws of physics being the same in all reference frames, does not imply that the observation will be the same in all reference frames.

      No, it just implies that causality can be broken in all other reference frames as well, as long as you can send signals to/from an object moving faster than light from the frame.

    167. Re:I'll believe it when I see... by ceoyoyo · · Score: 1

      Two seconds. For both. That's the point.

    168. Re:I'll believe it when I see... by metacell · · Score: 1

      It doesn't save causality, though. It doesn't matter if the signal travels from point A to point B faster than light, or just magically appears at point B without travelling the distance. In either case, you can set up a messaging system which sends a signal back to point A before the first signal is emitted.

    169. Re:I'll believe it when I see... by ceoyoyo · · Score: 1

      Special relativity limits only the speed through space. Actually, it only says that you need an infinite amount of energy to accelerate to c. In inflation, space is expanding. Nothing is moving through space at anything like c.

      Special relativity does NOT say that FTL travel is impossible, only accelerating to c in normal space.

    170. Re:I'll believe it when I see... by Max+Threshold · · Score: 1

      I'm sure you've heard of the analogy of the universe being a stretched and distorted rubber sheet, right? For a moment, just think in one dimension instead of two - a piece of elastic. Put two sets of marks on that piece of elastic, one set 5 cm apart and one set 10 cm apart. Now, over the course of one second, stretch the elastic to twice its original length. The marks that were 5 cm apart are now 10 cm apart, and so moved apart at 5 cm/s. The marks that started 10 cm apart moved apart at 10 cm/s. Put the marks far enough apart on a long enough piece of elastic, and they'll be moving apart faster than the speed of light. A photon from one will never reach the other.

    171. Re:I'll believe it when I see... by metacell · · Score: 1

      You're at Vega, 25 light years away. You send a radio message "I'm coming!" and hop in your warp drive and head to earth at 5x the speed of light. In 5 years I see you arrive at earth. 20 years later the message announcing your departure arrives.

      This doesn't violate causality... causality is violated when you (on Earth) send an FTL message to the moving spaceship, and the spaceship uses the same FTL technique to send a message back. In the space ship's frame of reference, the first message is received before it's sent out, so the space ship just needs to send an instant message back to Earth, to make it arrive before the first message was sent.

    172. Re:I'll believe it when I see... by Bert64 · · Score: 1

      I'm in a foreign country, i send a postcard home and then jump on a plane...
      Chances are the plane will arrive before the postcard.

      --
      http://spamdecoy.net - free throwaway anonymous email - avoid spam!
    173. Re:I'll believe it when I see... by metacell · · Score: 1

      If a spaceship moves at a high speed relative to Earth, events will occur in different orders in the space ship's frame of reference. Specifically, if an event on Earth and an event on the space ship are simultaneous in Earth's frame of reference, in the space ship's frame of reference, the Earth event will happen after the local event. This is after all optical effects are adjusted for.

      Now let's assume Earth sends an instant signal to the space ship. "Instant" means the signal is emitted on Earth and received by the spaceship simultaneously, where "simulteaneously" is defined by Earth's frame of reference.

      However, in the space ship's frame of reference, the emission of the signal from Earth occurs after it is received by the space ship. If the space ship sends an instant message back, it will be emitted from the space ship and arrive on Earth simultaneously. However, in the space ship's frame of reference, "simultaneously" means *before* the message was emitted from Earth.

    174. Re:I'll believe it when I see... by fahrbot-bot · · Score: 1

      You have a FTL ship that can reach Alpha Centuri in a second. You then make a U-turn and come back to Earth a second later. How much time has elapsed on Earth? How much time for the passenger of the ship?

      Make the trip in one second? According to whose clock - Ship or Earth?
      With relativity questions, you need to be more precise.

      --
      It must have been something you assimilated. . . .
    175. Re:I'll believe it when I see... by Tanuki64 · · Score: 1

      The physicist is just doing math. His equations are correct. They solve some problems of ftl travel. But this does not mean they solve every problem and it does not mean they are in any way applicable in this universe.

    176. Re:I'll believe it when I see... by Slutticus · · Score: 1

      Based on context, i'm going to assume this is a goatse link. It has to be....has to....

    177. Re:I'll believe it when I see... by darthdavid · · Score: 1

      My understanding of the problem is that, in our current models, causality only propagates at the speed of light...

    178. Re:I'll believe it when I see... by hweimer · · Score: 1

      Here is a relatively understandable explanation of why beating a photon to its destination implies time travel, even if you don't locally travel faster than light: http://www.theculture.org/rich/sharpblue/archives/000089.html [theculture.org].

      This reasoning is only valid for flat (Minkowski) space-time, and therefore does not apply to the warp drive proposals, which aim to create particular curved (i.e., non-Minkowski) spacetime configurations.

      A very intuitive counterexample: suppose you couple a photon into a very long fiber that is wound many times, with the end being at your neighbors desk. Clearly, you can walk over to him and have a chat with him about everything you like before the photon arrives. No laws of physics were harmed in the making of this experiment.

      --
      OS Reviews: Free and Open Source Software
    179. Re:I'll believe it when I see... by kaws · · Score: 1

      What I mean is you're not moving and when you aren't moving you won't be breaching the light speed barrier. Think of it like this, space expands ftl. If it were effected by time travel than I think that we'd see some stranger stuff than a more/less orderly expansion. This is an excerpt from the wikipedia page on "alcubierre drive". "If this is so, conventional relativistic effects such as time dilation would not apply in the way they would in the case of a ship moving at a very great velocity through flat spacetime, relative to other objects. This method of propulsion would not involve objects in motion at speeds faster than light with respect to the contents of the warp-bubble; that is, a light beam within the warp-bubble would still always move faster than the ship."

    180. Re:I'll believe it when I see... by pantaril · · Score: 1

      In Relativity, traveling faster than light relative to any reference frame, via any method, presents problems with causality. And the whole point of a Warp Drive is that someone will agree that you went faster than light, and thus went backward in time.

      How do you explain the current astrophysical consensus, that distant galaxies are traveling several times faster then light (and speeding up) from us due to our universe expanding exponentialy?

    181. Re:I'll believe it when I see... by svick · · Score: 1

      My personal take is that Gene Roddenberry was an alien whose goal was to nudge us in the generally correct direction without apparently doing so. To do this, he (it?) created a TV series called 'Star Trek' in which all advances we'd need were demonstrated to agile minds. Once it has been conceptualized, if it is possible, someone somewhere will eventually do it...

      Okay, then why did he also create Andromeda?

    182. Re:I'll believe it when I see... by arisvega · · Score: 1

      Given a few such warp ships, you could even arrange it so that that person would receive a message they had written and sent with you before they had actually written it.

      How so?

      --
      The three laws of thermodynamics:(1) You can't win. (2) You can't break even. (3) You can't even quit.
    183. Re:I'll believe it when I see... by Your.Master · · Score: 1

      1) Where relativity comes in is it implies some consequences of FTL travel -- time travel in particular. It doesn't outlaw either time travel or FTL though.
      2) If you're talking about index of refaction 0 http://oliphant.science.org.au/photonic2002/speakers/soukoulis/paper_soukoulis_4.pdf

    184. Re:I'll believe it when I see... by Your.Master · · Score: 1

      Your intuitive counterexample is just splitting hairs on how I phrased that. I was trying to use accessible terminology because most people here don't understand why anybody brings up time travel in the context of FTL in the first place (some of those people are getting downright abusive).

      Do you have a less-intuitive example of a non-Minkowski space-time that allows FTL but does not have causality issues, that does not fit into one of the counterfactual categories I listed?

    185. Re:I'll believe it when I see... by RabidReindeer · · Score: 1

      Alright, I can accept that. So what would happen if you had a shuttlecraft moving at c in one direction, a space station moving at c in the opposite direction, and an independent observer witnessing both these events? Would the shuttlecraft appear to move past the surface of the station at 2c, or not? What would happen to time inside the station and the shuttle, and what would it matter?

      You're trying to force the experiment into an absolute framework according to Newtonian rules. In Relativity, all 3 points are relativistic, not just the "moving" ones.

      Time proceeds normally at all 3 points. However time as seen from either of the 2 external observation points has slowed to a halt. That's as true for the shuttlecraft observing the observer as it is for the observer looking at the shuttlecraft.

      If your observer was in the middle of the line on which the shuttle approaches the space station, both shuttle and station would appear to be approaching the observer at the speed of light. However, from the shuttle's point of view, BOTH the observer AND the station would be approaching IT at the speed of light. Thanks to the relativistic compression of time and length.

      Presumably, however, you don't want to be at Ground Zero, you want to be off to the side somewhere. Makes little difference, since the trajectories are now vector equations and the only real difference is that the angles swept out as the respective objects zoom past are also affected by relativity. And on top of that, the light that shows you what's happening is also not merely relativistic, but (by definition) moving at the speed of light, and therefore the observation itself is relativistic.

      None of this is "playing dice with the Universe". Unlike quantum theory, everything is precisely mathematically predictable. It's just not immediately intuitive for people used looking at the Universe through a Newtonian lens. Then again, how intuitive is is that an apple falling from a tree should fall twice as fast at the end of 2 seconds as it does at the end of 1 second?

    186. Re:I'll believe it when I see... by Guignol · · Score: 1

      Since warp drives and biologists questioning relativity completely messed up causality

    187. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      Stand outside the beams. Witness that the distance between their leading edges grows at greater than c. Spend rest of day thinking about potential applications.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    188. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      If the vehicles accelerate and decelerate instantly, and stop moving after a fixed period of time t according to the observer's frame of reference, the distance between them will have changed by 2 * c * t, regardless of how long it takes for light to get anywhere or how they perceived movement. This is much more important than the time dilation and distorted observations witnessed by the pilots or other craft, and was my original point. (It even has applications.)

      --
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    189. Re:I'll believe it when I see... by hweimer · · Score: 1

      Do you have a less-intuitive example of a non-Minkowski space-time that allows FTL but does not have causality issues, that does not fit into one of the counterfactual categories I listed?

      Read the first link given in the summary.

      --
      OS Reviews: Free and Open Source Software
    190. Re:I'll believe it when I see... by Thugthrasher · · Score: 1

      That's what I mean by "seeing" -- observing, according to some reference frame, FTL travel. The point of the warp drive is that within its own reference frame it is not traveling faster than light. But relative to some reference frame it must be (even if they aren't literally watching it with a telescope). And going FTL according to any reference frame violates relativity.

      But what you're saying is that appearances are all that matters. Which is not the case. You're assuming, again, that the distance traveled is the same, when it's not.

      I can make it look like I break the laws of physics by "magic" using misdirection and tricks, but that doesn't mean that they are broken. And that's all this is, a misdirection. If I'm traveling using a warp drive and warping space, then you THINK I'm traveling from point A to point C using path A-B-C (which is X light years long) when in reality, I've warped space in such a manner that I'm traveling using path A-C or A-D-C or A-Q-C (which is Y light years long). It does not appear to ANYONE that I've traveled faster than light, as long as they understand what's going on. You're basically saying that by observing understanding technology that they don't understand, someone can break physics.

      If you are standing on one side of a wall that is 2 light-years long (1 light-year in either direction) and I am standing on the other, but there is a camera transmitting a view of me to you. You are sure that there are no doors in the wall (for whatever reason, you feel you know this is a fact). You then watch me walk beside the wall towards one end, leave the view of the camera, and then you see me walking towards you on your side of the wall, you've "observed" me going faster than light. In reality, I just used the door that you didn't know about, but you don't understand that that is possible. Did we just break physics? No. We just used technology you didn't understand to change the distance I had to travel to get from point A (my side of the wall) to point B (your side of the wall).

    191. Re:I'll believe it when I see... by Ogive17 · · Score: 1

      I'm fascinated with the topic but completely out of my element. Let me ask a basic question about FTL travel and time.

      If we make two identical time keeping devices that are exact and are completely impervious to outside influences, keep one on Earth and put the other on a space ship. If the space ship travels at FTL and ends up at Alpha Centari in 5 minutes, let's say, then turn around and travel back to Earth. Would both clocks still be the same?

      --
      "Action without philosophy is a lethal weapon; philosophy without action is worthless."
    192. Re:I'll believe it when I see... by hythlodayr · · Score: 1

      That only applies if when traveling faster than light within flat spacetime. A consequence of high speed travel is time dilation, where the elapsed time is noticeably different between, say, the earth and a traveler going at say 1/10th the speed of light.

      While the math is beyond me, the Alcubierre drive apparently works around this mess (while introducing others) by contracting spacetime itself. The most notable mess is the requirement of negative mass exotic matter, which we have no way of proving or disproving can even exist. This is the same type of exotic matter which can also be used to open worm-holes.

      That said, I would happily fund this sort of research out of my own pocket for the rest of my life. Maybe it's because I've watched/read too much sci-fi but I'd like to think humanity can accomplish far more than than the the Internet and combustion-based travel.

    193. Re:I'll believe it when I see... by spike+hay · · Score: 1

      Still irrelevant. These machines don't violate SR, instead use apparent loopholes on GR.
      Another explanation.
      More.

      Even in cases where SR doesn't apply, it still allows for causality violations (ie time travel) in GR. This is an absolute feature of any method of ftl. It does not matter whether it's a wormhole or a warpdrive or whatever. It sucks, but it's probably telling that every apparent superluminal phenomena (ie quantum tunnelling, entanglement) can't transfer informaton.

      --
      If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
    194. Re:I'll believe it when I see... by spike+hay · · Score: 1

      No one is saying Alcubierre is wrong, but his scheme would violate causality, like every other FTL method. If the universe is non-causal, this wouldn't be a problem. But it probably is.

      --
      If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
    195. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      How do you explain the current astrophysical consensus, that distant galaxies are traveling several times faster then light (and speeding up) from us due to our universe expanding exponentialy?

      It's actually expanding linearly, but over large distances this adds up.

      And the explanation is simple: Because these objects are moving away from us faster than light, we cannot ever see them or interact with them. No observation or experiment can ever be affected by them. They're out of the observable universe.

      So we can infer that they are travelling faster than light, but we can't ever observe this, and so there is no causality problem.

      --

      The enemies of Democracy are
    196. Re:I'll believe it when I see... by ArsenneLupin · · Score: 1
      The explanation on that page only works because it assumes that if you can send an FTL signal from A to B in A's frame of reference, then you can also send back a signal from B to A in B's frame of reference.

      ... which is not necessarily the case if you have some kind of hyperspatial tunnel, or other such construction. In that case, B might still be able to answer to A, but in A's frame of reference, and any time "gained" by sending the signal in one direction would again be "lost" sending the reply.

    197. Re:I'll believe it when I see... by Anonymous Coward · · Score: 1

      I can explain. If you go really fast it takes 1 second to get there. If you go the speed of light, it takes 0 seconds to get there. If you go faster than light, it takes -1 seconds to get there. This means you arrive at your destination before you actually departed. That is time travel.

    198. Re:I'll believe it when I see... by Ogi_UnixNut · · Score: 1

      AFAIK: Short answer. If using a warp drive, 2 seconds passed for the passenger of ship (minus overhead of turning ship around, prepping engines, etc...). Also, 2 seconds would have passed on earth.

      The nice thing about the warp drive is that you are shortening the distance between two points, you yourself never go at any fraction of C. As such there is no time dilation. You don't have to go on a long trip thinking about how everyone you know and love would be dead when you came back, even if the trip only took you a few seconds.

    199. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      The key word there is "before I saw you leave." , not "before you left." Human vision and radio receivers are not the arbiters of time.

      But the speed of light in a vacuum is. You're thinking of time as if there is a universal clock by which the timing and thus ordering of events can be measured irrespective of observation from . This is pre-Relativity thinking. In Relativity the passage of time is relative, all observer's clocks are valid, and the speed of light determines the earliest that an event is capable of affecting you (even if you don't actually "see" the event).

      Two observers in different reference frames will disagree on the relative timing of two events depending on their velocities with respect to the source of the event. However for all events with a "time-like" separation, meaning the time and distance is such that a signal traveling at the speed of light could go from one event to the other in that time, they will agree on the order. These are the events that can possibly have a causal relationship.

      For events that have a "space-like" interval (ones that do not obey d <= t*c), however, observers in different frames will disagree on the ordering of events. This is okay as long as there is no causal relationship, but if there is then it causes problems.

      While it may not be obvious how being able to observe someone arriving at their destination before they leave violates causality ("all you're doing is seeing it, that doesn't mean that's what happened"), the timing of events is defined in relativity by when you are capable of observing them. And this has real meaning because with the help of a couple Warp Drives, and a couple "regular" space ships traveling at high but sub-luminal velocity, you can take advantage of time dilation and create a closed causal loop -- sending yourself a message before you've written it. An obvious violation of causality.

      Here is an explanation for how you accomplish that. Or you can just google "speed of light causality" for many other explanations. Suffice to say the link between causality violation and FTL travel is well known.

      --

      The enemies of Democracy are
    200. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      Events happening out of causal order according to any observer is technically a violation of causality. What you've done is taken advantage of causality violation to create a paradox, which is a much more obvious problem.

      --

      The enemies of Democracy are
    201. Re:I'll believe it when I see... by Tom · · Score: 1

      That's what I mean by "seeing" -- observing, according to some reference frame, FTL travel.

      I don't think that evidence brought back from a trip necessarily counts as an observation in the relativistic sense. But I'd have to get out my copy of The Road to Reality or something to check.

      --
      Assorted stuff I do sometimes: Lemuria.org
    202. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      I'd love to see your explanation of how a ship jumping around the universe would arrive back before it left.

      Here's one with pretty graphs, but just googling it would show that this is correct.

      Time dilation and other such effects would not happen. Its why wormholes do NOT violate relativity.

      Ah, but given FTL travel/communication, and regular sub-luminal reference frames which do experience time dilation, you can use the FTL to send a message and a response that will be received before the original message was sent. Paradox.

      Note that in the explanation of how this occurs, it does not matter how the FTL is achieved. All that matters is that the sub-luminal observers see information pass from A to B faster than light.

      --

      The enemies of Democracy are
    203. Re:I'll believe it when I see... by nine-times · · Score: 1

      Yeah, as I said elsewhere, I kind of wish I'd modified the example not to use acceleration. Acceleration screws everything up a bit. The "twin paradox" requires the acceleration to work, but the time dilation happens even if everyone is at rest in their own frame of reference.

    204. Re:I'll believe it when I see... by nine-times · · Score: 1

      Thanks. I thought it was helpful for illustrative purposes, though it means that the math won't quite work right if you wanted to really talk about what would happen. Because of the acceleration, I believe what would happen from the point of view of one of the accelerating ships is that both of the ships it leaves behind would begin moving very slowly, which is why after a year, the other moving ship would appear not to have moved very far.

      However, once you showed your ship to return to rest, it would begin traveling away from you very very quickly. Still under the speed of light, but considerably faster than it would appear to be traveling relative to ship that is at rest.

      But I don't remember exactly how it all works out. It's been years since I had to actually do math related to general relativity.

    205. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      Here's one such explanation.

      Notice that in this example, the actual method of FTL travel/communication is irrelevant. They use the "ansible", an instantaneous communication device, but it could be warp ships or transporters or wizards for all it matters. The point is what the inertial observers in sub-luminal reference frames see -- and they'd see causality violated.

      --

      The enemies of Democracy are
    206. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      Fortunately the "speed of post" is not a physically significant value with no effect on the relative passage of time. The speed of light, however, is.

      --

      The enemies of Democracy are
    207. Re:I'll believe it when I see... by nine-times · · Score: 1

      But there is no frame of reference in which anyone is traveling 2c. The potential problem is your use of the word's "relative" and "perspective". If someone sitting in the stationary does the math according to Newtonian physics, he'll find that they are traveling 2c relative to one another.

      So when you say, "...their relative speed was 2c, from the perspective of the third ship," what you're saying is, "From one observer's frame of reference, trying to do calculations for another observer's frame of reference, using Newtonian physics, the speed will be 2c." The problem is the notion of "relative speed" becomes non-Newtonian at such high speeds, so that doesn't really work, strictly speaking.

    208. Re:I'll believe it when I see... by TheRaven64 · · Score: 1

      He didn't, his wife did after his death based on some very rough notes about a future series in the Star Trek universe.

      --
      I am TheRaven on Soylent News
    209. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      But what you're saying is that appearances are all that matters

      I'm not intending to do so in the trivial sense of "just appearances".

      But I am in the deeper, physical sense that different reference frames have different notions of space-time and thus the ordering of events. And all such reference frames views of event ordering are "correct" and must obey the laws of physics. This is the basis of Relativity -- it's literally the Relativity in the Theory of Relativity.

      It does not appear to ANYONE that I've traveled faster than light, as long as they understand what's going on.

      Yes it does. The shortening of the distance between A and C is a local effect only. Only you in your warp ship's reference frame is the distance shortened. Every other reference frame in the universe sees the distance from A to C as greater than what your travel time would allow at the speed of light. Not in a superficial "appears to be but really isn't", but in an actual, "that's how space-time actually is from their reference frame" sense.

      And given a couple such warp ships, and a couple sub-luminal rocket ships, you could send messages between them such that the first message sent receives a response before it is sent.

      What you're saying is that even though we've created a causal paradox according to multiple reference frames, because they "know" that according to your local reference frame you did not travel faster than light, the message that is in their hand doesn't exist and the paradox did not occur.

      This is untrue. All reference frames are valid. "Knowing" that the laws of physics were obeyed in yours does not matter. They do not care that you used a "trick", you violated causality according to their reference frames.

      --

      The enemies of Democracy are
    210. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      It surely does, but it would actually be after the true "capable of observing" sense determined by the speed of light in a vacuum. As in if the actual return of a sample occurs FTL then you're really screwed.

      The thing is, given a couple regular spaceships and a couple warp ships to act as relays between them, you could actually create a scenario where the sample is returned before the original warp ship left. As soon as you open up causally connected FTL travel you open the door to causal paradoxes.

      --

      The enemies of Democracy are
    211. Re:I'll believe it when I see... by LongearedBat · · Score: 1

      It was 20 years ago since I studied relativity, but if memory serves me right...

      However, someone will observe you traveling faster than light, going from point A to point B faster than light would travel the same distance.

      Isn't this the reason that the traveller would age differently from the observer?

      One observer stays on Earth while a traveller moves to Proxima Centauri. The traveller experiences the trip to Proxima Centauri as 1/2 year, but the observer doesn't see anything moving faster than light, thus experiencing the trip as 4 1/2 years. (Okay, so the observer will see the traveller being stretched out over space, but that stretching would not appear to occur faster than the speed of light.)
      So when the traveller returns to Earth, the observer has aged 8 years more than the traveller.

      Surely that would apply whether or not a warp drive was used?

    212. Re:I'll believe it when I see... by nine-times · · Score: 1

      Okay. So simply have them stop when a year has passed from the non-moving ship's perspective instead.

      Ok, that... gets pretty difficult to deal with. When you're dealing with these kinds of speeds and these distances, events don't happen in a specific order. You and I sitting next to each other can drop a penny "at the same time" and agree that it happens at the same time. If I'm traveling close to the speed of light though, I can drop a penny "at the same time" that you do, and you might totally disagree and believe that I dropped it much earlier or later.

      So the issue of stopping your ship when the "at rest" ship has experience 1 year becomes a bit complicated, because when "a year has passed from the non-moving ship's perspective" depends on your frame of reference, which changes as you accelerate and decelerate. I suppose you could work out a flight plan so that, when you come to rest relative to the stationary ship, a year has passed for that stationary ship. However, funny things would happen to the passage of time for both you and the other ship accelerating in the opposite direction, and you all wouldn't agree on what happened in what order, or how long it all took.

      That still has its uses—especially if, say, there are no living passengers aboard either of the moving ships who would complain, and we're just delivering ore to an automated factory, or storing cargo in a designated bay.

      I'm not saying that super-fast space travel wouldn't be useful, I'm saying that faster-than-light travel would enable time travel. And the issue isn't that anyone would necessarily need to "sit around waiting". The issue is that people simply wouldn't agree on what happened first, and what happened at the same time.

    213. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      How can you have two objects moving away from each other at greater than the speed of light, whilst maintaining special relativity?

      By having it be impossible for those two objects to interact. As SciBrad said, those objects are past an event horizon, and are as unreachable to us as the interior of a black hole.

      This is also the simplest explanation for the causality implications of an Alcubierre drive -- the interior of the warped space is causally separated from the rest of space-time, and there's no known way to enter or exit it. So you can travel "FTL" but you can't actually interact with anything.

      --

      The enemies of Democracy are
    214. Re:I'll believe it when I see... by nilbog · · Score: 1

      All you would need to do is drop some red matter into the exploding star. Just get there in time and you can save the day!

      --
      or else!
    215. Re:I'll believe it when I see... by RabidReindeer · · Score: 1

      If the vehicles accelerate and decelerate instantly, and stop moving after a fixed period of time t according to the observer's frame of reference, the distance between them will have changed by 2 * c * t, regardless of how long it takes for light to get anywhere or how they perceived movement. This is much more important than the time dilation and distorted observations witnessed by the pilots or other craft, and was my original point. (It even has applications.)

      I'm quite willing to admit I may just be full of it, but I'm fairly sure I'm not and that if I dug around in Einstein's works a bit, there's probably a treatment of exactly this question, and it should be something similar to this:

      1. Einstein space is not Newtonian space. In a relativistic cosmos, time and space are not separate and distinct, they are interrelated. In other words, a point exists not merely at x, y, and z, but also at t. Since instantaneous translation is ruled out (unless you have a warp drive!) that means that any point you observer is not merely "q" distance from you, it's "q" distance PLUS the RELATIVE difference in time between you and the point. You're not observing the point as it is "now", because "now" is a purely local phenomenon.

      2. The information that tells you that an object approaching you at a certain speed is travelling at the speed of light. As the rate of approach approaches c, the object being observed doesn't project the information ahead any faster, since c is as fast as it can get. Therefore instead, you get a frequency shift (the blue shift).

      3. If you are in the shuttle travelling at c, then, the space station approaching you is approaching at c, just as it would be if the shuttle was stationary. Time and distance appear normal to you, but if you could look in the window of the space station, (and things hadn't blue-shifted out of the visible spectrum) people within the station would appear immobile because their time frame relative to yours had stopped. They would say exactly the same thing about you.

      4. Now we get to the sticky point. From the third-party point of view, the inhabitants of BOTH moving objects are frozen in time, their motion dimensions have collapsed down to zero and their mass has increased to infinity, thereby warping space itself. Which is probably what ultimately keeps their relative motions limited to c even for third-party observers.

      That's about as close as I can get without RTFM'ing. Like I said, I might be seriously delusional here, but I don't think so. And the reason why is that the common-sense rules are based on an absolute conception of frames of reference, and relativity by its fundamental definition is not.

    216. Re:I'll believe it when I see... by Asmodae · · Score: 1

      Okay. So simply have them stop when a year has passed from the non-moving ship's perspective instead.

      Ok, that... gets pretty difficult to deal with.

      Not really. Time dilation is not that difficult to calculate, you would know a priori how much 'ship time' to run the engines to get the appearance of 1 stationary reference year of time traveled. Yes it's relative, but who cares? As long as everyone agrees on who's reference to use as a base, everyone can come to the same results, regardless of what the local clock says.

    217. Re:I'll believe it when I see... by putzin · · Score: 1

      But hey, maybe it's not a causal universe!

      Dang. I was really looking forward to Causal Friday.

      Nah, everyone gets casual everyday. I'm sitting here, at work, in jeans and a t-shirt. I'm the center of the universe, and master of all in it. Therefore, it is a casual universe. Feel free to use this excuse when you come to work on not so casual Monday in jeans and a t-shirt.

      --
      Bah
    218. Re:I'll believe it when I see... by dywolf · · Score: 1

      Imagine if you could get from A to B without going through the space in between. That does not mean time travel. you seriously misinterpret the rules. Going faster than light yes. But you never go faster than light. Theoretically the same artificial path you used light could also travel. So you never went faster than it.

      It's possible to create (or observe rather) and travel light paths in our own real world right now. And some of those paths, from the same source, to the same destination, are shorter than others. That doesn't mean that the shorter path involved time travel in any way, shape, or form.

      Only if you exceed the speed of light, if you actually have a actual velocity greater than light in the SAME REFERENCE FRAME AS YOURSELF are you correct.
      Just because you're comparing it to light that traveled a different path (different reference frame) doesn't mean it involves time travel.

      --
      The guy who said the election was rigged won the presidency with the second-most votes.
    219. Re:I'll believe it when I see... by nine-times · · Score: 1

      Ok, if it's not hard, give me the calculations. Remember to factor in acceleration. Tell me where each ship will be, in each frame, at various stages of the journey.

      I can't even remember where do begin on doing those calculations. Regardless, it's conceptually difficult. Here's part of the problem-- you go out on your trip, and when you start out, time is passing normally on the stationary ship. As you accelerate, time on the stationary ship slows to a crawl. You get near the end of your trip and it's time to decelerate, but the ship passing in the other direction has barely started its journey. So as you're slowing your ship down, the other ship has not yet started to slow down. In fact, it's going faster and faster.

    220. Re:I'll believe it when I see... by leonardluen · · Score: 1

      I agree that there is a problem with the link the GP posted.

      I do not see how this is violating any causality.

      lets see what happens from Victor's perspective...he is viewing form the side and is equidistant from Alice and Bob.
      say bob and alice are 1 light year apart. and their FTL signal is 2x the speed of light.

      timeline, According to victor:
      0 years : Alice Sends her message (Event A)
      0.5 years: Bob receive the FTL signal (Event B) and Bob Sends Reply to Alice
      1 years: The Light from Event A finally reaches Bob, he ignores it because he already replied. also Alice receives Bob's Reply, and then waves at him in thanks (Event C)
      1.5 years: the Light from Event B finally reaches Alice, but she doesn't care, she waved back half a year ago.
      2 years: the light from event C finally reaches Bob, and he fondly remembers how he was able help Alice a year ago...

    221. Re:I'll believe it when I see... by dywolf · · Score: 1

      It's not hard to understand. You are the one not understanding.
      They call it the warp drive, cause it actually warps space. It actually changes the distance between two objects. It actually warps reality. that is the whole point.
      Outside the field it may be 1 billion gazillion miles from A to B. But if inside the field it's now only 1 foot from A to B, and I make that step, and then let the field dissipate, I have changed reality for myself sufficient to travel a tremendous distance, withough violating the speed of light, and without time travel. The distance and speed and travel time of light OUTSIDE of the field is IRRELEVENT.

      It's two different paths: one is long, windy and through hill and dale, and the other direct as an arrow. Taking the shorter one does not in any way violate the other.

      --
      The guy who said the election was rigged won the presidency with the second-most votes.
    222. Re:I'll believe it when I see... by dywolf · · Score: 1

      Again, just because the radio wave took the long path doesnt mean a damn thing.
      You could just as easily send the radio wave via the warped "path", theoretically, and it would still arrive there ahead of you.
      there's nothing excluding the radio energy from traveling the warp field.

      --
      The guy who said the election was rigged won the presidency with the second-most votes.
    223. Re:I'll believe it when I see... by tibman · · Score: 1

      But isn't that about the same as mailing a letter to your neighbor that says you'll be headed over to their house. Then you walk over to their house. Three days later the letter arrives explaining that you are about to come over.

      --
      http://soylentnews.org/~tibman
    224. Re:I'll believe it when I see... by khayman80 · · Score: 1

      I've explained why FTL travel implies time travel.

    225. Re:I'll believe it when I see... by tibman · · Score: 1

      light-year is a distance. Just because a local year changes doesn't mean a light-year gets shorter.

      --
      http://soylentnews.org/~tibman
    226. Re:I'll believe it when I see... by nine-times · · Score: 1

      Well it depends on what you mean. In a sense, distances actually do become shorter when you travel faster. But I'm not sure exactly what part of my post you're responding to.

    227. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      What method could they possibly use to observe you travelling faster than light?

      Sorry, I don't mean literally observe you in transit breaking the universal speed limit.

      All that is required is that they see two causally linked events -- you getting into the spaceship at one place, and getting out at another -- which have a "space-like" separation according to their reference frame. Meaning according to their view of space-time, the two events were farther apart in distance and closer in time than would be allowed by the speed of light.

      This is why "cheating" by using a warp drive doesn't actually help you get around causality issues. The observer doesn't care how you got from A to B, they only care that the two events had a space-like interval from their reference frame.

      Of course if the warp ship never stops, and therefore is never visible or capable of interacting with anything in it's "past" ever again, then you never see this and there is no problem.

      --

      The enemies of Democracy are
    228. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      I'm a little confused by this idea. At no point does the warp ship go from point A to point B faster than light would travel the same distance. The path that the ship takes is shorter than the path that the light takes. The distance is not equal.

      Right, the ship in its own reference frame -- the warped space bubble -- would not be traveling faster than light.

      But in Relativity, all reference frames are equal. The laws of physics must appear to be obeyed according to all of them.

      And a reference frame that is somewhere else would observe the ship leave A and arrive at B faster than light, because from their reference frame A and B are separated by their "usual" distance. The warp bubble effect is a local effect, only experienced by the warp ship itself.

      If an observer were near point B, I can see how it might appear that the ship arrived before it left. However, this would be an optical illusion based on the greater distance that the light traveled.

      It's actually not an illusion, as the speed of light is intimately related to the notion of time in relativity. Things get even worse if the points A and B are not at rest relative to each other and instead are moving at relativistic (but sub-luminal) velocity. Then the difference between A and B's space-time axes would allow another FTL trip from B to A to actually arrive back at A before it left A in the first place.

      Causality was already broken, but now we've created a paradox.

      --

      The enemies of Democracy are
    229. Re:I'll believe it when I see... by mdmkolbe · · Score: 1

      It affects causality because in SR (special relativity) all velocity, both sub- and super-luminal(*), effect event ordering. Once you get to super-luminal speeds, event ordering is affected enough to break causality. This has nothing to do with "apparent" time travel. In fact, for the purposes of discussion, let's assume all observations have already had "apparent" time travel canceled out.

      To understand this, consider that in SR (as well as in Newtonian mechanics), non-accelerating movement is the same as being stationary. In your local reference frame, you are at the origin and the time axis lies along a line in space-time that you call "here". If you and I meet, but traveling at different velocities, then our here-lines will be skew relative to each other. At the current instant we might be at that same point in space, but in a moment we will be separated by some distance. We each follow our own here-line and each is equally valid as a non-accelerating reference frame.

      One of the results of SR is that not only can you have different "here" lines, but you can have different "now" lines(**). This is to say, that when you are traveling at velocity, the set of events that occur "now" is different than for someone traveling at a different velocity ... even when you cancel out the time it takes for the information to get to you. Velocity bends both the space and time axises of your local reference frame.

      Note that because you are always at the origin of your local reference frame, the effect of skewing the axises is quite small nearby but it grows larger for events further away. For example, the ordering of two events occurring several light-years away in opposite directions can be different by several hours for you and someone jogging quickly past you.

      Suppose an event is in the past for the jogger and in the future for you, and we have super-luminal communication. Then someone at that event could tell the jogger about what happened (because it is the in joggers past), the jogger could tell you (because you are right next to each other in the same present), and you could tell the original person about it before the event happened (because it is in your future). As long as nothing is faster than light, there is no problem as the amount that event orderings can get skewed is bounded by the speed of light, and information also can't travel faster than light in order to give you a causality cycle. However, once you get super-luminal travel, we can set up this cycle.

      Lookup "relativity of simultaneity" for more information.

      (*) Note that "speed of light" doesn't mean the "speed" of light. It really means the conversion constant between space and time units. Light happens to go at that speed, but if you figure out a way to make light go slower than you without you going faster than that conversion constant, then that doesn't count as super-luminal.

      (**) A now-line is really a 3-dimentional slice of 4-dimentional space-time, so it is not really a line, but I'm calling it that because it is easier to visualize as a 1D line in a 2D space-time.

    230. Re:I'll believe it when I see... by mdmkolbe · · Score: 1

      You can't go backwards in time using FTL.

      You are wrong and never should have been moded "Insightful".

      Similarly, some observers would see you as moving backwards, but that's just because you're moving faster than the photons you're emitting

      Even once you cancel out the effects of traveling faster than the photons you're emitting, you will still be seen to be traveling backwards in time by some observers.

      Lookup "relativity of simultaneity". Using that you can send a message back in time to back to the original person even before that person sent it. Or instead of a message, you could just send yourself and thus get "true" time travel.

    231. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      It would be the same if the "speed of mail" were a universal constant observed to be the same from all inertial reference frames, such that even if you traveled very rapidly, you would still see the mail traveling ahead of you by the same amount as you did when you were at rest with respect to the earth. Then one would be forced to conclude that space-time is not absolute and instead is relative to the proportion of your velocity to that of the mail, and that therefore if one could actually travel faster than mail, some observers would see this as traveling back in time and by using several such journeys you could actually create a causal paradox.

      Then they'd be the same, yes. ;)

      You can't use your Newtonian intuition to explain FTL travel, sorry.

      --

      The enemies of Democracy are
    232. Re:I'll believe it when I see... by RespekMyAthorati · · Score: 1

      You can't reach c while having any mass, so if you're going at c, then there's no spoon.

      FIFY.

    233. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      That's great, and all, but it doesn't really affect what I'm talking about. For some reason mentioning relativistic speeds at all makes everyone here foam at the mouth and worry about things like when we are able to perceive the motion has happened, or what the objects look like from the moving frame—none of that matters; the ships are still moving and we'll still be able to eventually verify that they moved as we said they did. And that fact has its uses: for example, you'll get superior broadcast times if you put a transmitter in the middle of the two ships rather than at one of them, and you can guide a ship to its docking bay on a giant space station twice as quickly if both are moving in opposite directions. What we perceive doesn't matter one bit—we can replace that with mathematical expectations, determined in advance.

      --
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    234. Re:I'll believe it when I see... by shutdown+-p+now · · Score: 1

      The spoon is the switch!

    235. Re:I'll believe it when I see... by david_thornley · · Score: 1

      Ah, another believer in some sort of absolute time, and hence somebody willing to discard Special Relativity.

      --
      "When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
    236. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      If I'm reading this all correctly the whole point of relativity is that there is no such thing as absolute time.

      Yes, but also that everyone's individual clocks are correct. Everyone must agree that cause happens before effect, but everyone having different notions of time is how FTL travel lets you break cause and effect.

      --

      The enemies of Democracy are
    237. Re:I'll believe it when I see... by ewibble · · Score: 1

      wouldn't that be the similar, just move move A1 closer A2 then A2 closer A3 ... until you get to B

    238. Re:I'll believe it when I see... by tibman · · Score: 1

      Thanks for that. I took from your explanation that you believe FTL can make you travel back in time. Or should i say the appearance of traveling back in time? Also, there's no reason to be a dick about my understanding of physics.

      --
      http://soylentnews.org/~tibman
    239. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      I took from your explanation that you believe FTL can make you travel back in time.

      You took correctly. Not arbitrary time travel -- it's limited by the speeds involved including the sub-luminal reference frames are traveling and for how long -- but more than enough to create causal paradoxes.

      And it's not just me who believes this. Einstein and everyone else agrees -- google "speed of light causality" or "FTL time travel" to find ample sources.

      Also, there's no reason to be a dick about my understanding of physics.

      Sorry. That was meant to be more of a humorous reminder that the speed of light is not like the speed of anything in daily life, but it did come off as rather dickish.

      --

      The enemies of Democracy are
    240. Re:I'll believe it when I see... by Pfhorrest · · Score: 1

      Here's a thought exercise: You have a FTL ship that can reach Alpha Centuri in a second. You then make a U-turn and come back to Earth a second later. How much time has elapsed on Earth? How much time for the passenger of the ship?

      Whose second did the trip take? An Earth second? A ship second?

      When speaking of sublight but still relativistic speeds (e.g. 0.999c), one second of travel for the ship could be aeons on Earth. One second of Earth time would be an imperceptible instant of ship time.

      Since you're using Alpha Centauri for an example, which is 4ly away, if we just say the ship travels at whatever speed necessary to get there in 1 second of ship time, and then comes back at the same speed (which could be less than light speed), you're looking at over 8 years of Earth time. If the ship travels for one second of Earth time... now you're in FTL territory and what the ship perceives depends on your method of supposedly being able to do that, but either way two seconds of Earth time have elapsed by the time it gets back.

      --
      -Forrest Cameranesi, Geek of all Trades
      "I am Sam. Sam I am. I do not like trolls, flames, or spam."
    241. Re:I'll believe it when I see... by Holladon · · Score: 1

      Sure, just jump into a black hole and you're good to go. Goodbye, known universe!

    242. Re:I'll believe it when I see... by Samantha+Wright · · Score: 1

      What the... No, I'm not saying that at all. I'm saying that there's a distance that grows at a rate of 2c according to a specific given reference frame, and that it's useful. This growth occurs in both Newtonian physics and GR, despite the differences between the two, and you're barking up the wrong tree.

      --
      Bio questions? Ask me to start a Q&A journal. Computer analogies available for most topics!
    243. Re:I'll believe it when I see... by metacell · · Score: 1

      Good point. But each observer has to deduct the time it took for light to reach them, when they observe events. According to an observer on Earth or Vega, the space ship left Vega at T=0, and arrived on Earth at T=5 years, so events happened in the right order for them. To see that events happen out of order, we at least need to consider an observer who is moving fast relative to Earth/Vega.

    244. Re:I'll believe it when I see... by metacell · · Score: 1

      Let's say my sun explodes and I go to a nearby system 2 light years away at twice c. Once there I will warn everybody that the closest star is going nova in a year. Now let's say you want to prevent me from delivering these news. You look up to the sky and see my planet. Obviously it is still there isn't it? So you take my warp ship and try to go to my planet. By the time you get there you are only going to find a 2 years old cloud of hot gas.

      If you travel at 4 c you will find a 1.5 years old gas cloud. Travel at 8 c to find a 1.25 years old gas cloud. Travel there at 16 c to find a 1.175 years old cloud.

      Travel as fast as you want. You shouldn't ever get earlier than a year after my departure let alone prevent it. Now, it could be that someone find out about this and tries to intercept you by going there at twice your speed. They'll get there before you and it will surely take you by surprise but that's still not time travel from your point of view.

      Let's say my sun explodes and I go to a nearby system 2 light years away at twice c. Once there I will warn everybody that the closest star is going nova in a year. Now let's say you want to prevent me from delivering these news. You look up to the sky and see my planet. Obviously it is still there isn't it? So you take my warp ship and try to go to my planet. By the time you get there you are only going to find a 2 years old cloud of hot gas.

      You need a relay station to make the warning message arrive before it was sent. Ideally, the relay station should move close to the speed of light, in a direction parallell to a line between star system A and star system B.

      When the explosion occurs at star system A, you send an FTL message to the relay station R. In A's frame of reference, the message travels faster than light, but still arrives after it was sent. However, if R moves sufficiently close to the speed of light, the message will arrive before it was sent in R's frame of reference.

      R then sends out a message to star system B. In R's frame of reference, it sends out a signal that merely travels faster than light, but in A's and B's reference frames, it will arrive before it was sent.

      So whether we look at it from R's, or from A's and B's, reference frame, one of the signals will be able to arrive before it is emitted. The closer to the speed of light we let R move, the more skewed its frame of reference will be compared to A's and B's, and the earlier its signal will arrive at B. We can also make the time-consuming portion of the trip arbitrarily short, by letting R pass close to one of the star systems when the message is relayed.

      In total, the message will be able to arrive at B before it was sent from A, given sufficiently high speeds of R. And if we can do that, it's trivial to use a second relay station R' to send a message back to A and warn them before the star explodes.

    245. Re:I'll believe it when I see... by ByteSlicer · · Score: 1

      Well, one is a compound containing an oxygen atom bonded to two hydrocarbon groups, and the other is a field that permeates all of space-time.
      But you probably meant aether ;-) .

      Aether was conceived as a substance that permeated 3-space. Light would travel through it, like a wave through water. It would cause the speed of light in vacuum to be variable, depending on one's velocity, which is not what was observed.

      The Higgs field seems to be a property of 4-space (space-time), or a field that permeates it (we're not sure at this point what it is exactly). Everything (including light) travels through 4-space, and the speed of light in vacuum measures the same in all reference frames.

      Personally, I think space-time is a 4-dimensional fluid, which we perceive as continuous, but which at the smallest scale consists of units that shift arrangements and interconnections (like molecules in water, but in 4D). Particles would be just waves in this fluid (like for example a vortex ring in 3D fluid). One such wave could even be observed as different particles (a bit like seeing a cloud and either recognizing a dog or a bunny). The Higgs field could then be a fundamental property of this fluid (something like viscosity of a 3D fluid), so it would affect both the waves/particles that move through it, and the fluid itself.

    246. Re:I'll believe it when I see... by metacell · · Score: 1

      If I wrote a message at 8pm, Jan 1, 2012 and sent it by warp to a destination 10 light years away and it arrived 1 second later, it would be received at 8:00:01pm, Jan 1, 2012.

      Now, if I sent that message at the speed of light, via the electromagnetic spectrum, to a destination 10 light years away then traveled by warp to the destination to arrive 1 second later. I would receive the message from myself 10 years later. I still sent the message before I received it.

      Ah, but what if the recipient of the message was moving close to the speed of light? In their reference frame, the event where you leave Earth could be years *after* the event where you arrive at the destination.

      Furthermore, if the recipient sent another warp ship back to Earth the moment they saw you arrive, it would take one second to get back to Earth in their reference frame, but in Earth's reference frame, it would arrive years before before you left the planet.

    247. Re:I'll believe it when I see... by TeknoHog · · Score: 1

      FTL implies at least backwards communication is possible under any method you can think of. If you get get to Alpha Centauri by stuffing yourself in your ass, it will still allow backwards time travel.

      In other words, going ass-backwards in time?

      --
      Escher was the first MC and Giger invented the HR department.
    248. Re:I'll believe it when I see... by ceoyoyo · · Score: 1

      "But there is no frame of reference in which anyone is traveling 2c."

      I didn't say there was.

      So when you say, "...their relative speed was 2c, from the perspective of the third ship," what you're saying is, "From one observer's frame of reference, trying to do calculations for another observer's frame of reference, using Newtonian physics, the speed will be 2c."

      No, I'm not. The third ship measures distance and time entirely in it's own frame, with no regard for any other frames and finds that the two ships have travelled one light year apart in half a year.

      Anyway, the entire analogy is unneeded. We see the evidence of warp movement all around us in the cosmic microwave background, and the universe hasn't ended in a puff of smoke because of causality violations.

    249. Re:I'll believe it when I see... by Tom · · Score: 1

      Which is why one of the hypothesis on this whole thing is that not relativity is wrong, but our understanding of causality.

      That is one of the most fascinating points of physics in a long time.

      --
      Assorted stuff I do sometimes: Lemuria.org
    250. Re:I'll believe it when I see... by Tanuki64 · · Score: 1

      It's not hard to understand. You are the one not understanding.

      I really should not answer. It is useless anyways. Let's suppose I don't do it for you, I do it for me.

      Do you believe that for two observers in two different inertial frames time moves with different speed? Yes? You believe that distances between to points could be different between two people in two different inertial frames? Yes?

      Do you believe, that simultaneity might also be dependent on the inertial frame a person lives in? That for two people in two different inertial frames an event might not happen at the same time? No? Sorry, is also a result of special relativity.

      So if for two people one an the same event does not happen at the same time, the event, which is in one persons past, is in the others persons future. This is usually no problem, both persons can never communicate with each other. Those inertial frames are causally decoupled.

      Causally decoupled unless the communication happens faster than light. With a faster than light signal both people can communicate an the one person can tell the other person what will happen in his future. This causes paradoxes.

      And no, it does not matter at all how the signal is sent. All that matters is the time when the information arrives. If it is earlier than it possibly could have arrived by normal means, e.g. with a laser, the information could have come from an inertial frame where a certain event, which is already in the past for the sender, is still in the future in the receiver's inertial frame.

      But of course, I will again get the answer, that there is not ftl communication because the A-ship never moves at all, and space is warped and warp bubble, and blah. No problem. If you like, tell me the earth is flat and the sun revolves around it.
       

    251. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      Indeed. The other possibility -- that the universe is causal (as we understand it, as in 'cause A must precede effect B in time', and that FTL is okay as long as it doesn't allow causality violations (quantum entanglement, universal expansion) also has fascinating implications imo.

      --

      The enemies of Democracy are
    252. Re:I'll believe it when I see... by Requiem18th · · Score: 2

      No, I have heard mdmkolbe's explanation before. His explanation allegedly works regardless of what method you use to travel or communicate FTL because his explanation is concerned about where-when are spacetime now-here and now-there at the moment of communication. Under S. Relativity.

      So much I understand. I just can't believe it is not an artifact of perception. Relativity of simultaneity doesn't actually change the order of events, only their simultaneity. Two events that are simultaneous for an observer might not be simultaneous for another one and such.

      Firstly however, I don't totally trust S.Relativity. I know it's well tested but wasn't it already superseded by General Relativity?

      All the explanations I've heard about FTL==Time-travel involve transference of information between objects in different inertial frames, either directly or indirectly. I can't quite shake the feeling there's something we are doing wrong.

      --
      But... the future refused to change.
    253. Re:I'll believe it when I see... by Requiem18th · · Score: 1

      I understand that "elsewhere, at the same time" is double plus ungood in S. Relativity. And I understand that there is no absolute time frame. But there are inertial frames that matter more than others.

      If I synchronize two clocks and launch one away at 0.5c the clock will slow down. My clock will also slow down too from the point of view of the other clock and this coincides with the delay it takes for light from that clock to reach me. I am simply not convinced that this is a coincidence. That the light-delay and reality-delay are the same or, in other words, that I'm supposed to accept that things happen exactly when I think they happen from my point of view.

      --
      But... the future refused to change.
    254. Re:I'll believe it when I see... by Requiem18th · · Score: 1

      And like I said earlier, every argument of this time I've heard involves instantaneous communication between objects in different inertial frames, meaning FTL works fine as long as as everybody is the same inertial frame. I believe it's possible to build a model for Causal FTL as long as one fiddles enough with the rules for communication between objects in different inertial frames.

      Not saying that's how FTL would work. I don't know if it can be done and understand that's likely to be impossible. I'm just not sure S. Relativity is as perfect as it could be.

      --
      But... the future refused to change.
    255. Re:I'll believe it when I see... by metacell · · Score: 1

      And like I said earlier, every argument of this time I've heard involves instantaneous communication between objects in different inertial frames, meaning FTL works fine as long as as everybody is the same inertial frame.

      Ah, but what prevents observers in different frames from relaying the message using ordinary, sub-light-speed transmissions?

      Say you send an FTL signal from point A to point B, which are in the same reference frame.

      At that moment, a fast-moving space ship (B') passes by B, and B relays the signal to B' using an ordinary, sub-light-speed transmission.

      At the same time, another space ship, A', passes by A. A' moves with the same velocity as B', and is in the same reference frame, so it should be possible for B' to send an FTL signal back to A'. Moreover, depending on the velocity of A' and B', the signal can arrive back at A' before A sends it.

      A' then relays the signal back to A using an ordinary, sub-light-speed transmission, and it arrives before A sent it.

    256. Re:I'll believe it when I see... by Chris+Burke · · Score: 1

      But but but... how can you communicate with the guy who SAW YOU?!

      You don't have to. The mere fact that they witness (or rather 'are hypothetically capable of witnessing') that you arrived someplace before you left according to their reference frame violates causality, and with a couple such instances allows for causal paradoxes. They don't have to be able to tell you that you violated causality for it to happen.

      And the information of your departure and arrival can propagate to them at the speed of light That's no problem either.

      --

      The enemies of Democracy are
    257. Re:I'll believe it when I see... by climb_no_fear · · Score: 1

      So, after reading the article and some of the explanations here, I really think I grasp what they're getting at. However, I think the the whole "ansible", wizard or whatever FTL communication is confusing some people, including myself. Can the paradox still be explained without comunication during the FTL travel? Because the way the FTL concept is explained (a "bubble of spacetime") it doesn't sound like this lends itself to communication between bubbles. Even they cannot communicate at all during FTL, are they paradoxes still present? If they stop for a second to communicate by old fashioned light beams, does this "fix" the problem by putting them (however briefly) in the same inertial frame of reference?

  4. still a lot of energy by AvitarX · · Score: 1

    So this is about 100 times human energy consumption.

    Still that's a shocking reduction from the mass of Jupiter.

    --
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    1. Re:still a lot of energy by wierd_w · · Score: 5, Interesting

      Agreed.

      Other important caveats not listed are things like, duration of field perturbation, and effective field size.

      If it takes 500kg of raw mass energy equiv, to send something the size of a football on an ftl hop for 1 sec, it is still very very impractical.

      If we are talking something the size of manhattan island being shot at FTL for over a year for 500kg mass energy, things are difficult, but interesting.

      This still doesn't sole several other noteworthy problems with the alcubiere metric though. Things like hawking radiation snowplowing on the event shock of the warp field, nuking the ship and everything around it when the field drops as the ship leaves FTL.

      (Basically, the spacetime bubble the ship occupies behaves the same as the event horizon of a black hole, as far as virtual particle interactions are concerned. The pocket tearing past at ftl speed forces the particle pairs to become real, robbing energy from the warp field, and plastering radioative exotics all over the shock front. When the bubble collapses, that radiation gets released.)

      If they can pull it off, alcubierre's metric would only be useful for short jumps, not continual cruising, making it impractical for visiting very distant objects. It would also be an energy hungy monster.

    2. Re:still a lot of energy by flappinbooger · · Score: 1

      So this is about 100 times human energy consumption.

      Still that's a shocking reduction from the mass of Jupiter.

      It's already been done. FTL.

      No I don't have proof, just the non-stop claims everywhere of how far ahead the black projects are.

      --
      Flappinbooger isn't my real name
    3. Re:still a lot of energy by Charliemopps · · Score: 1

      It's rather irrelevant how long the effect would last since time would become a joke as soon as a massive object was FTL. Which is the primary reason this entire exercise is nonsense.

    4. Re:still a lot of energy by Eponymous+Hero · · Score: 1

      it never said football-sized. it said football-shaped. like stewie or hey arnold. there's not enough information in the article to make any useful assumptions about how much energy it would take.

      --
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    5. Re:still a lot of energy by Anonymous Coward · · Score: 1

      So this is about 100 times human energy consumption.

      Where are you getting that? It says the energy contained in a mass "as small as 500 kg". TFA says roughly the mass of the Voyager 1 probe (773-ish kg). Assuming the latter -- since it's the larger of the two -- and recalling the famed relationship between mass and energy (E=mc^2), we get:

      E=(773kg)*(299,792,758 m/s)^2 ~= 6.9x10^19 J

      According to Wolfram Alpha, that's less than 70% of the energy consumed annually in the United States. In 2001. Not an insignificant value to be sure, but not "100 times human energy consumption" by a long shot.

    6. Re:still a lot of energy by wierd_w · · Score: 4, Interesting

      I believe that is exactly what I said, when I mentioned that it was a caveat not addressed by the article. "Football sized" had no bearing on the verbiage of the article, and was instead meant to be taken as-is. Eg, an effective warp bubble big enough to barely hold a football is not practical in any sense at the energy cost listed.

      In order to determine how far the ship could travel at 10xC with 500kg raw mass energy, we need to know how long (dialated ship time) that energy takes to be released, and how long (external observer time) the bubble will remain stable.

      That information was not provided.

    7. Re:still a lot of energy by Jarik+C-Bol · · Score: 2

      Things like hawking radiation snowplowing on the event shock of the warp field, nuking the ship and everything around it when the field drops as the ship leaves FTL.

      You know, I've now decided upon my personal theory of FTL, and you inspired it. acceleration of an object to FTL *may* be possible, through as of yet unknown means, however, the way the universe deals with the causality issues created by doing so is by using the built up ram pressure to reduce said object to loose electrons neutrons and protons when it drops out of FTL, and there is no way around that. So your options become 'never go FTL, or never stop once you go FTL'

      --
      I've decided to Diversify my Holdings. I've divided my cash between my left and right pockets, instead of all in one.
    8. Re:still a lot of energy by wierd_w · · Score: 4, Interesting

      That's what a tachyon is! (Well.. more or less...)

      A tachyon is a "particle", forced to always travel at FTL velocity, because it has "imaginary" mass.

      The alcubierre metric makes use of "negative mass energy" to negate 100% of the vehicle's effective mass, and a little more, causing the "vehicle + engine" composite to become essentially an enormous tachyon. (More or less...)

      This poses the problem of how to escape the bubble once created; theoretically speaking, doing so would not be possible! However, interaction with the hawking radiation might provide the solution. As the particles intersect the field, they steal energy from the field, by making the pair real. (One of the particles gets glued to the front, the other gets lost to space.) This loss of energy depletes the field, forcing its collapse. When that happens, the ship returns to being causally connected.

      (This however, makes the effect useless for anything but *really* distant objects, or with very very powerful fields.)

    9. Re:still a lot of energy by AvitarX · · Score: 1

      Hmm, I swear I dud the math the other way once and came up with 5kg, year, but clearly I fucked up, or remembered wrong.

      --
      Wow, sent an e-mail as suggested when clicking on "use classic" banner, and got a fast response that addressed my msg
    10. Re:still a lot of energy by lister+king+of+smeg · · Score: 1

      energy hog? not when compared to eating a Jupiter with every hop

      --
      ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
    11. Re:still a lot of energy by skelly33 · · Score: 1

      It didn't say it was the size of a football, it said it was the shape of one. Wouldn't be much of a "ship" if all it could carry was an ant colony.

    12. Re:still a lot of energy by Robert+Zenz · · Score: 1

      Jokes on you, Warp is not about getting an object to move faster then light, but to bend the space around it so that it does not have to move at all.

    13. Re:still a lot of energy by __aaltlg1547 · · Score: 1

      IR never said size at all. That's the trouble. Anything smaller than the hypothetical machine that could generate and contain the exotic matter ain't going to be a starship.

    14. Re:still a lot of energy by Eponymous+Hero · · Score: 1

      right, i misread your post as an implication that the football reference was to its size. i understand your example though.

      --
      insensitive clod overlords obligatory xkcd car analogy russian reversals whoosh pedant fanbois ftfy in 3...2...1..PROFIT
    15. Re:still a lot of energy by Prune · · Score: 1

      And what happens when the particles that get "glued to the front" are released upon return to sub-light speed? There won't be any ship left, that's for sure, or anything in the vicinity either.

      --
      "Politicians and diapers must be changed often, and for the same reason."
    16. Re:still a lot of energy by Deliveranc3 · · Score: 1

      Are you kidding? Load that sucker up with some Blue/Green Algae and a 5 Million year release cycle for a land plant and an amoeba and teraform a world.

      Hell a needle head would be enough to oxygenize a world in under 2000 years. Very practical.

    17. Re:still a lot of energy by wolverine2k · · Score: 1

      Go patent it quickly.... :)

  5. Can I have one? by angel'o'sphere · · Score: 4, Funny

    BTW: what is exactly ment with: warp drive could be powered by the energy of a mass as small as 500 kg In what time frame? I guess if you "annihilate" so much mass instantly ... you get indeed warped pretty hefty.

    --
    Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
    1. Re:Can I have one? by Nethemas+the+Great · · Score: 2
      It's the whole E=MC^2 Mass-energy equivalence bit. For comparison:

      E / m = c2 = (299,792,458 m/s)2 = 89,875,517,873,681,764 J/kg (9.0 × 1016 joules per kilogram).
      So the energy equivalent of one gram (1/1000 of a kilogram) of mass is equivalent to:
      89.9 terajoules
      25.0 million kilowatt-hours (25 GWh)
      21.5 billion kilocalories (21 Tcal)
      85.2 billion BTUs
      or to the energy released by combustion of the following:
      21.5 kilotons of TNT-equivalent energy (21 kt)
      568,000 US gallons of automotive gasoline

      --
      Two of my imaginary friends reproduced once ... with negative results.
    2. Re:Can I have one? by Nethemas+the+Great · · Score: 1

      Sorry, wiki link ref.

      --
      Two of my imaginary friends reproduced once ... with negative results.
    3. Re:Can I have one? by angel'o'sphere · · Score: 1

      That is what I asume,d but the question is: do you need so much energy to ignite it or during the travel :D over time?

      --
      Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
    4. Re:Can I have one? by El+Puerco+Loco · · Score: 1

      yeah, the mass equivalent of the energy released by the largest atomic bomb ever exploded (50MT) was around 2.3kg. Even that tiny amount of energy proves difficult to contain for practical purposes.

    5. Re:Can I have one? by lister+king+of+smeg · · Score: 1

      so that would be 3.05397727*10^9 bigmacs according to wolfram so a couple days worth of food produced by McDonalds daily around the wold.

      --
      ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
    6. Re:Can I have one? by Nostromo21 · · Score: 1

      Or you get fubared pretty hefty!!! ;) Converting 500Kgs of matter to energy would be like putting around half the annual energy consumption of all of the US in 2009 under your seat...instantly! :) For ref, the sun produces about 10 more zeroes of energy every second: http://answers.yahoo.com/question/index?qid=20070219102943AA0moQu -- No

    7. Re:Can I have one? by Neil+Boekend · · Score: 1

      Yes, but will you have to absorb that energy once you stop? You'd have to bring a planet as heat sink...
      Energy can not be destroyed, only converted and that usually goes to heat.

      It would be awesome if you could store it as potential energy available for your next warp jump, but there are some entropy issues there.

      --
      Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
    8. Re:Can I have one? by scsirob · · Score: 1

      Agree, 500kg of mass converted to energy in one go is pretty hefty..
      But nevertheless, can I donate my mother in law for a first try?

      --
      To Terminate, or not to Terminate, that's the question - SCSIROB
    9. Re:Can I have one? by RespekMyAthorati · · Score: 1

      If you burned down the Library of Congress, would that be enough?

  6. 500 kg mass-energy by Anonymous Coward · · Score: 1

    Yes, that's only the entire world's yearly electrical production in energy required. Much more possible. 10^19J.

  7. What about the radiation burst? by hawguy · · Score: 5, Interesting

    Does this theory at all reduce the chance that when the Warp Drive ship arrives at its destination that it will emit a huge gamma ray burst? This planet destroying side effect would sure put a damper on any kind of arrival party for the warp drive ship.

    1. Re:What about the radiation burst? by dtjohnson · · Score: 2

      No, while the early ships might be prone to the gamma ray bursts, the newer ships will have emission controls that will eliminate 99.99 percent of the gamma radiation.

    2. Re:What about the radiation burst? by roc97007 · · Score: 5, Funny

      "Hey look. An earthlike planet, with nobody living on it. What a coincidence."

      "Signal the colony ship."

      --
      Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
    3. Re:What about the radiation burst? by The+Grim+Reefer · · Score: 1

      This could probably be channelled in to the bubble through some fancy rotating warp bubble mechanism.

      Then this could be converted to energy and mass storage for use in some possible future matter collider + replicator-like device. With a small powerful matter smasher and fusor we could create any matter we needed as long as we have enough base materials. This could create a ship that is almost entirely self-sufficient.

      Of course, this is given that such a thing could be done, this is still all early work.

      Certainly not. Everyone knows you just need to reverse the polarity and channel it through the deflector dish.

      Come to think about it, screw warp drive. All it does is move you around and on the odd occasion get ejected to close space time disturbances. We must put all of our science behind inventing deflector dish technology. We can use it to protect the planet, channel excess heat from AGW, and solve global hunger and crime. And if we operate it in reverse I'm pretty confident it can even take us to warp. Now if we can just stop those bastards at CERN from tearing apart the space/time continuum we won't need a warp core to eject.

    4. Re:What about the radiation burst? by Anonymous Coward · · Score: 1

      Perhaps this technology is indeed in widespread use, just not by us:

      http://en.wikipedia.org/wiki/Gama_ray_burst

    5. Re:What about the radiation burst? by Howitzer86 · · Score: 1

      It's powered by Bad News, the fastest method of travel known to man!

    6. Re:What about the radiation burst? by Nostromo21 · · Score: 1

      But can it zoom in from orbit to get a clear shot of some royal titties...?

    7. Re:What about the radiation burst? by Tim12s · · Score: 1

      Great stuff... a military application.... NOW we are talking progress!

    8. Re:What about the radiation burst? by lorinc · · Score: 1

      Does this theory at all reduce the chance that when the Warp Drive ship arrives at its destination that it will emit a huge gamma ray burst? This planet destroying side effect would sure put a damper on any kind of arrival party for the warp drive ship.

      Hoho! It's going to get money from the DoD then...

  8. use the Naquadria drive by Joe_Dragon · · Score: 4, Funny

    use the Naquadria drive

    1. Re:use the Naquadria drive by Anonymous Coward · · Score: 1

      use the Naquadria drive

      No, Naquadria is the unstable one, Naquadah is the one to use.
      If it's good enough to power the stargate, it's good enough for us.

    2. Re:use the Naquadria drive by Anonymous Coward · · Score: 1

      If [Naquadah] is good enough to power the stargate, it's good enough for us.

      It doesn't. You need either fancy crystals, a few jiggawatts of electricity or some kind of cold fusion plant*.

      *See what I did there?

    3. Re:use the Naquadria drive by pwizard2 · · Score: 2

      The FTL drive from Destiny may be a better option. (way better than a dodgy Goa'uld hyperdrive powered by Naquadria) Getting a ship several billion light years to the other side of the universe in several hundred thousand years or so is really impressive.

      --
      "It is a denial of justice not to stretch out a helping hand to the fallen; that is the common right of humanity."
    4. Re:use the Naquadria drive by viperidaenz · · Score: 2

      You just need a bunch of ZPM's to power it

    5. Re:use the Naquadria drive by Joe_Dragon · · Score: 1

      Naquadria and Naquadah are easier to find then ZPM's.

    6. Re:use the Naquadria drive by Zibodiz · · Score: 1

      ...several hundred thousand years or so...

      It was actually a million years. But who's counting.

    7. Re:use the Naquadria drive by lister+king+of+smeg · · Score: 1

      nope it had solar scops that funneled in plasma from the surface of the nearest star for power. And if i remember my stargate lore well enough the destiny was built before the ancients discovered how to build a zpm. that is why the gate is built out of quarts and Naquadah. but as i recall we eventually just got the Asgard to give us their engines.

      --
      ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
    8. Re:use the Naquadria drive by Noughmad · · Score: 1

      Just make sure to call them ZedPMs,

      --
      PlusFive Slashdot reader for Android. Can post comments.
    9. Re:use the Naquadria drive by hairyfeet · · Score: 1

      Bah! Too unstable, you use Dilithium and then if there are any problems we can always recrystallize with any of the nuclear wessels we have handy.

      --
      ACs don't waste your time replying, your posts are never seen by me.
    10. Re:use the Naquadria drive by JMJimmy · · Score: 1

      *Zed-PMs ;)

    11. Re:use the Naquadria drive by FilmedInNoir · · Score: 2, Funny

      With Spice I can go all over the universe every weekend. All I need is a paper tube and a razor blade.

      --
      Sig. Sig. Sputnik
    12. Re:use the Naquadria drive by ryanmc1 · · Score: 2

      "Given the choice between a life of work here on Earth or a life wandering among the stars and exploring other worlds, I'd choose space" Of course you wouldn't have to work to pay for repairs your ship, or for fuel, or even food and clothes for your family. It would be a dream come true, you would meet friendly races along the way that would just give you everything you wanted for free.

    13. Re:use the Naquadria drive by TheLink · · Score: 1

      What would you consider a reasonable time frame for travel, and how many hours or days do you plan to spend looking at each planet?

      There are very many planets out there...

      If possible I'd have robotic ships do the exploring and then providing a shortlist of interesting ones.

      --
    14. Re:use the Naquadria drive by omnichad · · Score: 1

      It's got rechargeable batteries.

    15. Re:use the Naquadria drive by TemporalBeing · · Score: 1

      More than their engines. If you remember the Final Episode ("Unending") the Asgard in the Milky Way committed suicide to prevent their technology from falling into the hands of the Priors of the Ori.

      Except they did it not do due to the Priors, but b/c their race was dying on its own.

      --
      Truth is like the sun. You can shut it out for a time, but it ain't goin' away. - Elvis Presley (source: imdb.com)
    16. Re:use the Naquadria drive by viperidaenz · · Score: 1

      Providing you have the ability to sit inside a star to recharge them...

  9. Ring/toroid shape? by TWX · · Score: 5, Funny

    I thought that it was a cup of tea, not a donut, that led to FTL travel...

    --
    Do not look into laser with remaining eye.
    1. Re:Ring/toroid shape? by socceroos · · Score: 1

      Off to button moon, eh?

    2. Re:Ring/toroid shape? by girlintraining · · Score: 1

      I thought that it was a cup of tea, not a donut, that led to FTL travel...

      It wasn't tea. It was rather something sortof but not entirely unlike, tea.

      --
      #fuckbeta #iamslashdot #dicemustdie
    3. Re:Ring/toroid shape? by ekgringo · · Score: 1

      I believe FTL is made possible by the use of any source of Brownian motion, such as an advanced tea substitute.

    4. Re:Ring/toroid shape? by dbc · · Score: 1

      Any topologist can tell you that a cup and a donut are equivalent.

    5. Re:Ring/toroid shape? by circletimessquare · · Score: 1

      Yes

      "Tea, Earl Grey, Hot"

      usually precedes

      "Warp factor 9, engage"

      or

      "Make it so"

      --
      intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
    6. Re:Ring/toroid shape? by treeves · · Score: 1

      Only if it has a handle. Those little Chinese tea cups aren't topologically equivalent to a donut. They are equivalent to a fortune cookie though, so there is some sense to it.

      --
      ...the future crusty old bastards are already drinking the Kool-Aid.
    7. Re:Ring/toroid shape? by WoodburyMan · · Score: 1

      Silly. Everyone knows its Steppenwold that makes FTL possible.

    8. Re:Ring/toroid shape? by Sarten-X · · Score: 1

      It must be a very hot cup of tea. The problem with that is, of course, that a very hot cup of tea will evaporate too quickly to perform the necessary calculations. A donut, on the other hand, can be dipped in the hot tea, and the tea trapped in the donut will not evaporate nearly as fast.

      --
      You do not have a moral or legal right to do absolutely anything you want.
  10. My space-time travel... by TWX · · Score: 1

    ...only takes 1.21 gigawatts...

    --
    Do not look into laser with remaining eye.
  11. When they develop it I'll use it by future+assassin · · Score: 1

    to travel back using the gravitational pull of Earth's sun to perform the slingshot in time to this post and make a "First Post".

    --
    by TheSpoom (715771) Uncaring Linux user here. I have nothing to add to this but please continue. *munches popcorn*
  12. Re:No doubt by hawguy · · Score: 2

    I'm simply convinced that there is no way this massive universe is here without there being a practical way to travel it. There absolutely has to be a way.

    So you are an Intelligent Design believer?

  13. This is exciting by kiriath · · Score: 1

    Now if they can just nail transporter / replicator technology we'll be set!

    I call first member of Starfleet!

    1. Re:This is exciting by PPH · · Score: 1

      Fit that man for his red shirt!

      --
      Have gnu, will travel.
    2. Re:This is exciting by kiriath · · Score: 1

      I'll wear a red shirt. Picard wore a red shirt. Picard is a badass, and that cannot be denied.

    3. Re:This is exciting by kiriath · · Score: 1

      Hmm, I'll have to be more specific regarding my franchisical references... =D

    4. Re:This is exciting by lister+king+of+smeg · · Score: 1

      i think captain archer will look at him kinda funny if h's wearing a red shirt.

      --
      ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
  14. Volunteer by casca69 · · Score: 1

    Look, I'm no scientist, but I am a top technician/engineer. I would be happy to be the test monkey and keep GOOD notes!

    1. Re:Volunteer by Trilkin · · Score: 1

      He'll have SWORN he met an alien that took the shape of his dead dad, though. And there will be very strange periods of silence and static on the tape that don't fully chronologically match what 'actually' happened.

      Then he'll run off with Hannibal Lector. ...wait, no that isn't how it ends...

      --
      Nobody cares what the CAPTCHA for your post was.
  15. Says the man trying to sell warp drives by Scareduck · · Score: 2

    Please.

    --

    Dog is my co-pilot.

  16. how did Zefron Cochran do it? by Adult+film+producer · · Score: 1

    did the star trek ever explore the mechanics of his first warp flight? I remember one really bad movie where the crew of TNG met him but it was entirely superficial in regards to the technology.

    1. Re:how did Zefron Cochran do it? by cbhacking · · Score: 2

      Trek really wasn't "hard" sci-fi... it was harder than some (Star Wars, for example, though I like SW too) but it was both too futuristic and too mass-market targeted to go much into really hard sciency explanations.

      I believe if you read the various "supporting materials" (Star Trek encyclopedias and such) you'll find information on how warp is supposed to work canonically, but the details are obviously a bit fuzzy. We know it involves the generation of a "warp field" of normal space that surrounds the ship, and in a handful of episodes the drive was referred to using terms like "space-time warp" which would potentially be consistent with the Alcubierre drive. Additionally, the starship drives of the main shows and movies are anti-matter powered, which is in line with the energy requrements suggested here (smash 250 kilos each of matter and antimatter together, get 500kg-equivalent of energy).

      I forget any technical details I ever may have known of Cochrane's ship's warp drive beyond the general details of it having a warp field and such. I'm not even sure if it was AM powered - but then, it flew only a very short distance at a "slow" (for ST warp drive) speed.

      Also, you are of course welcome to hold your own opinions, but I personally think that First Contact wasn't bad at all. Not the best of Trek as an entire series (IMO), but generally considered one of the best movies by fans.

      --
      There's no place I could be, since I've found Serenity...
    2. Re:how did Zefron Cochran do it? by Wonko+the+Sane · · Score: 1

      Star Trek is more accurately classified as fantasy than sci-fi.

    3. Re:how did Zefron Cochran do it? by cbhacking · · Score: 1

      I'd agree for Star Wars (the Force in particular pushes it over that line) but I disagree for Star Trek. Some of the tech was actually explained in moderate detail - the weapons and tractor beams, for example, and certain elements of the sensors, shields, impulse drive, warp drive, combadges, transporters, replicators, etc. We may not know how to do any of it right now, and some of the details are certainly wrong, but that's normal even for moderately hard sci-fi when viewed decades after it was written (not that I'm claiming Trek is particularly hard... but it's not "futuristic fiction" either). For example, we currently can't even manufacture enough antimatter for a photon topedo, much less keep it around long enough to store in an armory and then launch as a self-guided projectile against an enemy ship, but the basic scientific concept of an anti-matter weapon is reasonably sound. Aside from a bad case of SciFi Writers Have No Sense Of Scale (the range at which ships battle, the time it would take to get anywhere at impulse, the sheer size of a planet, etc.), there aren't many consistent and obvious scientific mistakes that occur throughout the series. The telepath/empath stuff is probably the hardest to buy, aside from entities like Q.

      A few of the things in Trek are actually pretty realistic. Hyposprays, for example, are a real thing, if not currently quite as advanced as what we saw on the screen. Some of the astronomical phenomena they explored were also well done. Aside from their range and lack of anything we'd recognize as a power source today, combadges are possible Right Now (as in, there exist wifi-based versions for use in hospitals, complete with the ability to identify people by voice and locate the nearest apropriate recipient). Touchscreens and voice-driven and/or handheld computers (if not "true AI") are already in use. Considering when Star Trek was written, a lot of that stuff was pretty forward-looking, even if off by couple centuries

      Besides, sci-fi isn't really about the tech itself, a lot of it is about "if we have this tech, what can we do with it?". Some places this wasn't very well applied - the transporter has a lot of potential purposes that it's rarely if ever used for, for example - but there were some surprisingly clever things too. If we assume the presence of a transporter that can identify a life-form, and pick it out of its surroundings without either destroying those surroundings or bringing them along, then having filters on it that can detect known harmful life forms and remove them makes sense. If you've got a universal translator that can quickly learn the syntax and vocabulary of any new language (admittedly, the way this happens seems pretty magical, but hey, sufficiently advanced tech...), it makes sense that it would be confounded if it encountered a being that spoke entirely in metaphor rather than literal meaning (or rather, it would translate the metaphors, but not the background that makes them meaningful). There are tons of examples like that, ranging from well-played-out ones (aggressive AIs, strange diseases, hive minds, time travel, "the [THING] stopped working!", genetic engineering for supersoldiers, etc.) to very novel (preserving memory of your dying civilization in a system that lets other being re-live the lives of your people, the Greek gods as highly advanced aliens, diplomacy with alien races [at the time, aliens were almost always either implacable enemies and/or utterly incomprehensible], and so on).

      Ok, getting off the nerd box now.

      --
      There's no place I could be, since I've found Serenity...
    4. Re:how did Zefron Cochran do it? by Wonko+the+Sane · · Score: 1

      Star Trek is fantasy because in that universe technology is another form of magic. There was no consistent set of rules that applied to the story - new technobabble was invented as needed to serve the needs of the plot.

  17. Show me the calculations by Flipstylee · · Score: 1
    No, the Real ones, not TFA.

    "Harold 'Sonny' White of NASA's Johnson Space Center said Friday (Sept. 14) at the 100 Year Starship Symposium"

    After a line like this there needs to be math, lots of math, it's the whole "extraordinary claims require..." bit.

    I'm probably the layman here (i still have some faith in /. apparently), but i thought this was about testing our ability to confirm relativity (warp up space-time), rather than breaking it (FTLT, that would be excellent if we had infinite energy, if so we would have infinite time so the energy would be negligible?)

    1. Re:Show me the calculations by Punto · · Score: 1

      Look it's really complicated but apparently the requirement is now about 500 libraries of congress worth of energy to travel faster than light.

      --

      --
      Stay tuned for some shock and awe coming right up after this messages!

    2. Re:Show me the calculations by Nethemas+the+Great · · Score: 1

      Well, not sure about the wall sized white-board with hieroglyphics on it but they are supposedly going to go play with lasers to create some micro-warps so they may well be able to tease out some reality...

      --
      Two of my imaginary friends reproduced once ... with negative results.
    3. Re:Show me the calculations by PyroMosh · · Score: 2

      You can't really expect the math to be on Discovery.com. It's a general interest site for the public. It needs to be accessible (though perhaps it wouldn't hurt them to link to it...).

      Someone else posted the original paper, which can be found here.

    4. Re:Show me the calculations by lister+king+of+smeg · · Score: 2

      but a crazy archaeologist will realize that it isn't hieroglyphics at all its constellations and that is you dial six of them and use a seventh symbol as the point of origin, you will create a wormhole to another world

      --
      ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
    5. Re:Show me the calculations by lister+king+of+smeg · · Score: 1

      i thought that discovery was aimed at motorcycle gear-heads and grease-monkeys at least that is what i gathered last time i turn on their tv channel

      --
      ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
  18. Re:But is it impossible for me to get first post? by i_ate_god · · Score: 5, Funny

    guess you were travelling at impulse

    --
    I'm god, but it's a bit of a drag really...
  19. Less impossible? by twotacocombo · · Score: 3, Informative

    Even a little bit impossible is still entirely impossible in my book.

  20. Re:No doubt by AdamWill · · Score: 1

    sure there is. cryogenic freezing. hell of a lot more likely to be plausible than warp drives. you can get anywhere at walking speed if you or the universe doesn't die in the mean time...

  21. Solves energy problem, causality problems remain by Anonymous Coward · · Score: 1

    While this formulation puts energy requirements within practical reach, actual use for FTL travel still runs into the problem of effectively censoring the ship out of existence on account of an inability to pop the bubble once formed, never mind the Hawking Radiation.

  22. [Yawn] by PPH · · Score: 1

    Call me when they get the demand down to the output rating of my Mr Fusion.

    --
    Have gnu, will travel.
  23. Re:No doubt by aled · · Score: 2

    I'm simply convinced that there is no way this massive universe is here without there being a practical way to travel it. There absolutely has to be a way.

    So you are an Intelligent Design believer?

    That would be Intelligent Traveling believer.

    --

    "I think this line is mostly filler"
  24. What about the other problems? by Confusedent · · Score: 2

    That's great news, but there were a number of other difficulties with the Alcubierre drive, iirc. I don't see how this gets around any of those, like the spacetime "bubble" becoming filled with lethal radiation or the inability to create a bubble with a pre-existing non-superluminal mass inside it.

    1. Re:What about the other problems? by Nethemas+the+Great · · Score: 1

      Does everything have to be a polished final product before the scientists and engineers get some credit? Just because the final destination is still out of reach doesn't mean there aren't and won't be any interesting stops along the way of pursuing unlikely if not impossible dreams.

      --
      Two of my imaginary friends reproduced once ... with negative results.
  25. Less impossible? by Type44Q · · Score: 2

    So, more possible... but still impossible. Alrighty, then. :)

  26. Re:Make it so. by homey+of+my+owney · · Score: 1

    Yeah! Count me in!

  27. Impossibility Drive by pubwvj · · Score: 3, Insightful

    I love it when people say things are impossible. Then they go whizzing backwards into forgotten history as the impossible becomes the norm. Tomorrow will be like today. The future will be surprising.

    1. Re:Impossibility Drive by pubwvj · · Score: 1

      You've got verbal diarhea. My statement has nothing to do with selective memory. I did not say "all" or anything of the sort. I said I love it when people (a set of some existing people) say things are impossible. Your own statement proceeded to back me up. Thank you.

      You're also a coward. Too bad you don't feel confident enough about what you have to say to actually give your name and stand behind what you say. That right their drops the value of your statement into the negatives.

  28. Interesting potential by Immerman · · Score: 1

    I remember reading a somewhat later paper on an analysis of the Alcubierre warp drive that pointed out that a side effect of the space-bending was that there was no reason that the inside of the "warp bubble" had to be smaller than the outside, reminiscent of a certain blue box, so that you could conceivably fit a starliner (or a star for that matter) within an atomic-scale warp field, radically reducing its cross-sectional area and the hard radiation resulting from the annihilation of matter that enters the warped space. They don't mention anything about the size of the theoretical ship in the article, which makes me wonder if the energy requirements scale with warp bubble size, and if so if they factored in asymmetric dimensions. If not, well then I could see a future for planet-movers...

    Regardless though 500kg of mass-energy is *nothing* for something like this, only 4.5e19 J, or about 10% of annual global energy consumption. Though one problem I remember was that it's impossible to stop the "warp drive" from within the bubble, requiring instead some outside mechanism to return the contents to normal space, which could be a challenge considering that you won't be able to see a FTL vehicle coming to catch it. And heaven help you if you miss, though they didn't mention anything about steering so perhaps it would be possible to loop around for another attempt.

    --
    --- Most topics have many sides worth arguing, allow me to take one opposite you.
    1. Re:Interesting potential by Jarik+C-Bol · · Score: 1

      ... I am absolutely dumbfounded. Someone actually found an answer to the radiation question. There goes my special modified theory of FTL. (which was that the universe will allow you to accelerate to FTL, but the universe balanced the equation of you violating causality, by obliterating you when you decelerated)

      --
      I've decided to Diversify my Holdings. I've divided my cash between my left and right pockets, instead of all in one.
  29. Nedhead's Law by NEDHead · · Score: 2

    The power requirements for warp drive will diminish by a factor of 23 every year.

  30. Re:No doubt by WillDraven · · Score: 1

    My bet is on something similar, but instead of freezing our bodies, we just upload our minds into the ship and modify our perception of time in software.

    --
    This is my sig. There are many like it but this one is mine.
  31. possible without violating causality by doug141 · · Score: 1

    if compressing the space in front of you ALSO compresses the time dimension of spacetime, causing you to travel faster through time as well, keeping you in your light cone. Travelling this way would not be any different from the conventional way (and enjoying lorentz time contraction while you do so), except instead of rocket propulsion you have wave propulsion.

    1. Re:possible without violating causality by Your.Master · · Score: 1

      Right, that wouldn't violate causality because it wouldn't be FTL. But in principle the warp drive could let you travel at sublight velocity.

  32. I hope they try to transmit data with it by Punto · · Score: 1

    I know that a warp drive is exciting and all, but after they figure how to move an entire spaceship faster than the speed of light, they'll have 500 more problems before they can get anywhere near interesting with it. Transmitting data, on the other hand, is probably a lot easier, and there's a lot of cool real world uses for it. For example sending back images of astronauts hanging out at that Earth-like planet that is 20 light years away.

    --

    --
    Stay tuned for some shock and awe coming right up after this messages!

  33. Re:No doubt by jamstar7 · · Score: 1

    you can get anywhere at walking speed if you or the universe doesn't die in the mean time...

    The JOEs ('Just One Earth'ers) claim that since nobody's invented and developed a car, all we'll ever have is walking, and their feet hurt, so we're not going 2 kilometers away, so give up already and finance our $PET_PROJECT_OF_THE_MINUTE. The 'Warpers' say 'Why walk when we're in the process of developing a HumVee?'

    --
    Understanding the scope of the problem is the first step on the path to true panic.
  34. only hitch: space is not a vacuum by Ralph+Spoilsport · · Score: 3, Interesting

    There's about 1 hydrogen atom / proton per cubic meter. Even at sub-c speeds, they create seriously radioactive friction. And running into a grain of sand at some % of c would have the effect of a large bomb. So, you not only have to warp space, you have to move the matter IN the space, and do it at >c velocity. Since matter can't move >c, you can't get the protons and occasional neutrons and sand grains and other interstellar detritus out of the way. A grain of sand hitting anything at 10c would be catastrophic, and within a few hours of colliding with the interplanetary and interstellar medium would turn the ship into a glowing radioactive dead thing.

    --
    Shoes for Industry. Shoes for the Dead.
    1. Re:only hitch: space is not a vacuum by Tom · · Score: 2

      It's another problem that needs solving. People once thought you would suffocate if the train goes too fast.

      --
      Assorted stuff I do sometimes: Lemuria.org
    2. Re:only hitch: space is not a vacuum by argStyopa · · Score: 1

      Of course, you're assuming that whatever is traveling at >c is moving through our tangible universe. For example, the game Traveller2300 posited a "stutterwarp" drive that flicked the ship forward through an alternate dimension only about 100m. By cycling this drive say, 10 million times/second, you'd be traveling through our space at what, about 3.3c? yet not actually ever moving, building momentum, or (critically) having the problems you describe.

      I'm not saying such is even possible, but I guess if we're fantasizing about a warp drive, it's not too much less conceivable that it would somehow bend the laws of physics that little bit more.

      --
      -Styopa
    3. Re:only hitch: space is not a vacuum by Bill+Currie · · Score: 1

      Interesting that you bring up stutterwarp: it too had the radiation problem. After about 7.7ly (iirc, may have be pc), the charge built up on the components would collapse producing unshieldable hard-radiation (with what I'Ve since learned, probably just gamma rays at an intensity where sufficient shielding would make for an unmovable lump instead of a ship).

      --

      Bill - aka taniwha
      --
      Leave others their otherness. -- Aratak

    4. Re:only hitch: space is not a vacuum by Your.Master · · Score: 1

      I think this warp drive doesn't go through the space that's occupied by that matter at all. My understanding is that it's moving in a bubble of finite dimensions with finite mass inside.

      Imagining for a moment a different sort of warp drive where you were still in real space, I'm not sure that the grain of sand wouldn't just pass through you without you or the spaceship even noticing (not even leaving a hole) simply because it didn't have time to interact significantly.

    5. Re:only hitch: space is not a vacuum by martas · · Score: 1

      From what I understand, if you were using a warp drive in interstellar space to go at an "effective " 10c, you wouldn't collide with any atoms in that space at 10c (that is impossible, since it would mean two objects traveling at 10c relative to each other in a "traditional" way). I have no idea what would actually happen, though. Perhaps it would increase the density of the matter you're travelling through. Or perhaps that matter would first experience an immense contraction (passing through the front of the bubble), then return to normal density by the time it reaches the ship, then experience dilation upon exiting the bubble... But I'm not a physicist, so dunno.

    6. Re:only hitch: space is not a vacuum by Ralph+Spoilsport · · Score: 1
      No. Let's say this thing's warp field is roughly spherical (for sake of discussion and simplicity). It is at point A and occupies X volume of space. IT has to get to point B. Between point A and B is 1 light year. That's 9.4605284 × 10^15 meters. Let's say the frontal area in the direction the bubble is headed is 100 sq m. So, that mean if there is 1 H atom per cubic meter, then between A and B there is 9.4605284 × 10^17 atoms of H. Now, that's less than a litre of water's worth of H, but that's not the point.

      The problem is, each atom has to be MOVED through space as it is warped by the warp drive. The atom isn't going to disappear. It is not nothing. Space has no mass, so it can be warped at will (and is, usually by gravitation). So, if you warp the space so as to displace it and its contents to move this vehicle, and you do it at >c velocity, then you have to move that atom of H out of the way at >c velocity, which cannot be done. They've tried. A lot. As the velocity increases, the mass of the atom increases and the energy required to move it increases. To move the space the atom is in, is (comparatively) trivial. To move the H atom? Not so much.

      Therefore, warp drive is impossible - not because it won't warp space or move super fast through it - it's the fact that space isn't empty - that's the problem. And what space is full of doesn't like to move.

      --
      Shoes for Industry. Shoes for the Dead.
  35. It may be the science of a thousand years from now by Grayhand · · Score: 1

    Ultimately it may require making custom atoms to do specific tasks and possibly have very unusual configurations of subatomic particle. Just look at how different nano particles react compared to natural forms of the same elements. It may mean building atoms with opposite spins of particles or configurations of quantum particles that don't occur in nature. They've managed to build atom by atom but this would be orders of magnitude more difficult. We don't even have a science for affecting quantum particles let alone building them like tinker toys. It's a little like building a gravity drive that doesn't require mass. With current science it's impossible but when you start hand fabricating sub atomic particles all bets are off.

  36. Re:Make it so. by Anonymous Coward · · Score: 1

    A brief history of the future with warp drives:

    Cult/terrorist leader: We are now on a holy mission to destroy the infidels. Aim the ship at the planet earth.

    Engage!

    The planet Earth goes boom and intelligent life evolves somewhere else in the galaxy to repeat this cycle.

  37. Physics explanation by Issildur03 · · Score: 2

    The article doesn't explain what the warp drive actually does. As far as I can tell the idea can be roughly phrased as "rather than making a long journey, cause the road in front of you to become short, then make a short journey". The drive would contract spacetime between the object and its destination to make it really small. Apparently to do this, one has to also affect spacetime behind the object, expanding a region of it. Once spacetime is distorted appropriately, the long journey becomes short. Seems vaguely plausible - as much as physics ever does.

    On the other hand, the process of distorting space time should propagate at the speed of light at best. So the ship would spend a standard amount of time bending space-time and not moving, then move a short distance and arrive at the destination. And then after the trip, we'd still have all this distorted space-time to either fix or leave stretched.

    1. Re:Physics explanation by Jarik+C-Bol · · Score: 1

      i guess you could describe warp drive like surfing. you cause a wave in the surface of space, and ride it forward, (part of the theory states that even though you may be moving at some significant fraction of C, you would remain weightless, as you are effectively falling from somewhere behind you to somewhere in front of you.)

      --
      I've decided to Diversify my Holdings. I've divided my cash between my left and right pockets, instead of all in one.
  38. "Less Impossible"? by puppetman · · Score: 1

    I think something is either impossible, or possible. It's binary, and like a binary system, you can't have something between 0 and 1.

    You could argue that maybe the possibility is unknown (tri-state logic), but then the value is null, to indicate unknown.

    1. Re:"Less Impossible"? by PJ6 · · Score: 1

      Or you could just remove the law of excluded middle without having to introduce a third / null value.

      This also has some interesting uses in quantum mechanics.

    2. Re:"Less Impossible"? by Artifakt · · Score: 1

      What if you define 'impossible' as any event that has a probabilty of less than unity in the entire lifetime of the universe? Or to bring a little more precision into it, for many unlikely events we couid instead say "during the portion of the universe's lifetime that enthropy is low enough there is enough energy differential for that event to happen at all." Any event that doesn't happen at least once in the whole of space and during all the time that the energy differential available is great enough to power such an event is thus an impossible event. That's pretty much a binary definition, based around the concept of unity, and while it's complex, it fits one of our 'common sense' intuitions - that something either happens at least once, or not at all.
              As a variation though, we could include a fudge factor, some number between unity and zero, and say below that chance in the whole lifetime of the universe and all the space therein, we're confident it's utterly impossible. That fudge factor would address not knowing everything about quantum fluctuations and other such things that might occasionally produce very unlikely events in ways we don't entriely understand. Of course, such a fudge factor would be non-binary - we'd be saying the point where something becomes impossible IS somewhere between 1 and 0. But we'd be doing it somewhat like the five sigma rule in scientific discovery, saying that we've calcuated the chance to a level where we might as well believe it's simply flat out true, just as we calculate the chances for more probable events such as particle emissions and transformations.

      --
      Who is John Cabal?
  39. Less Unpossible by Jeremiah+Cornelius · · Score: 4, Funny

    Nearly not untrue!

    Give me a little more non-fake false hope, and I'll use the slingshot effect to go back in time and uncancel the original series!

    --
    "Flyin' in just a sweet place,
    Never been known to fail..."
    1. Re:Less Unpossible by tqk · · Score: 2

      You need either fancy crystals, a few jiggawatts of electricity or some kind of cold fusion plant*.

      Nearly not untrue!

      What does that even mean? True? Almost true? Nearly definitely true? Are you channeling Orwell?

      Give me a little more non-fake false hope, and I'll use the slingshot effect to go back in time and uncancel the original series!

      Sigh. Ibid.

      Fine, you win. Just take me with you. I want to talk to the Tok'Ra, Sam, Jack, Daniel and Teal'c. And Sheppard and Rodney. And Ronin and Tayla.

      --
      "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
    2. Re:Less Unpossible by Marxist+Hacker+42 · · Score: 1

      But isn't Slingshot Star Trek, rather than Stargate?

      --
      SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
    3. Re:Less Unpossible by tqk · · Score: 1

      But isn't Slingshot Star Trek, rather than Stargate?

      I'm pretty sure every SF medium that deals at all with space travel will do something sometime with the Slingshot Effect. I vaguely remember a SG:SG1 episode where Sam (Carter) utilized it, but I could be mistaken.

      --
      "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
  40. Re:Make it so. by mosb1000 · · Score: 1

    Since the actual kinetic energy of a ship traveling this way would not be proportional to the square of it's velocity, it's hard to say what would happen if were to collide with another body.

  41. Vulcan by leromarinvit · · Score: 1

    The picture in TFA looks like it could be the prototype of a vulcan ship!

    --
    Proud member of the Ferengi Socialist Party.
    1. Re:Vulcan by PJ6 · · Score: 1

      The picture in TFA looks like it could be the prototype of a vulcan ship!

      That is exactly the first thing I thought when I saw that (and the second thought was, wait... is that a football?).

  42. It's not hand-waving. by mosb1000 · · Score: 4, Insightful

    People have used metamaterials to achieve results that seem to violate the laws of physics (such as materials having a negative refractive index). Speculating that such an exotic material could be produced is not hand waving. Just because we don't know how to do something today doesn't mean we'll never figure it out.

    And no, the energy argument was not secondary. Before you could argue that even if we could make the materials necessary it would require a prohibitive amount of energy to work. Now the argument is only about the materials needed.

    1. Re:It's not hand-waving. by lessthan · · Score: 5, Funny

      That explains why I rode her all night long. (I kid, I kid. Your grandmother is a very nice lady, who says you should call more often.)

      --
      Space Shuttle was a program that strapped humans to an explosion and tried to stab through the sky with fire and math
    2. Re:It's not hand-waving. by mark_elf · · Score: 1

      Cremated, ocean, etc.

    3. Re:It's not hand-waving. by Genda · · Score: 1

      Friend you want to be real careful throwing straight lines like that out into a lion's den like this... I mean the "Grampa on the Wagon" jokes just write themselves.

    4. Re:It's not hand-waving. by hweimer · · Score: 2

      People have used metamaterials to achieve results that seem to violate the laws of physics (such as materials having a negative refractive index [wikipedia.org]). Speculating that such an exotic material could be produced is not hand waving. Just because we don't know how to do something today doesn't mean we'll never figure it out.

      Your comparison to metamaterials is interesting. These things work by structuring the medium on scales smaller than the wavelength of the light. On these scales, the laws of geometrical optics break down and one has to use a theory that does not rely on the approximation that all features are larger than the wavelength (e.g., solve Maxwell's equations). If your analogy is valid, this means to find negative masses, we would need to go to a scale where the current laws for the description of matter (i.e., the Standard Model of particle physics) break down. This is generally expected to occur at the Planck scale, which is about 10^16 times larger than what the LHC can probe. So yes, this is pretty much as impossible as things can get.

      --
      OS Reviews: Free and Open Source Software
  43. Re:No doubt by shentino · · Score: 1

    Depends on metric expansion of space. If you want to get somewhere receding from you faster than the speed of light you'll never get there as spacetime expansion is supposedly exponential.

  44. Re:Just kill NASA already... by shentino · · Score: 1

    A unicorn shitting cheeseburgers would be more economical.

  45. Re:Make it so. by Anonymous Coward · · Score: 2, Interesting

    I would think that the warping of space would be the big issue, not the kinetic energy. How much warping would it take to throw off the atmosphere or a chunk of the crust? What would happen if a chunk of the planet was temporarily missing and gravity forced the planet to round out--and then the piece comes back? No extra energy would be needed, just the gravitational potential energy stored in the planet.

  46. Re:No doubt by Artifakt · · Score: 2

    Ssshhh... You're supposed to forget about all that and enjoy the virtual simulation of ancient times you're currently emeshed in until the proximity alarm wakes us.

    --
    Who is John Cabal?
  47. Real world experiment by Anonymous Coward · · Score: 3, Funny

    White and his colleagues have begun experimenting with a mini version of the warp drive in their laboratory. ...
    "We're trying to see if we can generate a very tiny instance of this in a tabletop experiment, to try to perturb space-time by one part in 10 million," White said.

    I can imagine how it might go:

    White: "More ... power! We ... have ... got ... to get that ... table up ... to ... warp factor ... 0.00000001!"

    Technician: "Aye, professor, but I'm already given 'er all the power we've got. She can' take no more"

    Grad student: "My calculations indicate a slim chance of success if we reverse the polarity."

    Technician: "I canno' do it. You'll blow the whole rig fo' sure!"

    White: "We ... have ... no other ... choice. Reverse ... polarity!"

    (All occupants of lab now alternately grab railings to the left then to the right.)

    1. Re:Real world experiment by cowboy76Spain · · Score: 1

      Don't forget the ceiling falling on the head of that guy that was dumb enough to go to work wearing a red sweater.

      --
      Why can't /. have a rich-text editor? Editing your own HTML is so XXth century.
  48. If my calculations are correct... by skelly33 · · Score: 3, Funny

    The final shape should actually end up looking not like a toroid, but a disc, or... "flying saucer" if you will. The absolute first thing we should do with them though is send them back in time and play mind tricks on generations past, otherwise we'll miss many decades of inspiration on Hollywood films which ultimately serve to desensitize the populace towards first contact.

  49. Re:Just kill NASA already... by Jarik+C-Bol · · Score: 1

    however, once I learned that the American public collectively spends more on new cell phones each year than they do on NASA's budget, NASA spending money on silly things like this bothers me a lot less.

    --
    I've decided to Diversify my Holdings. I've divided my cash between my left and right pockets, instead of all in one.
  50. exotic matter may be discovered already by rubycodez · · Score: 2

    dark matter is a form of exotic matter. maybe there are other forms already available in nature that we can capture and put to use

  51. Re:Make it so. by Skarecrow77 · · Score: 1

    So, what you're saying is, the answer to the Fermi Paradox is "Religion"...

  52. 500kg mass-energy by cibyr · · Score: 1

    500kg mass-energy sounds like an awful lot.

    That's about 4.5e19 J, or about 0.5% of the world's oil reserves. Might be actually doable.

    --
    It's not exactly rocket surgery.
    1. Re:500kg mass-energy by slashmydots · · Score: 1

      Not if antimatter is introduced to that 500kg mass. That's actually what they mean by mass-energy, right? I have no idea myself, lol.

  53. everyone here already knew this! by slashmydots · · Score: 1

    Okay, raise your hand if you didn't know already that the shape of your warp field has to be precisely perfect for it to work efficiently? That was on 3 if not 4 star trek series multiple times :-P

  54. Tabletop version by __aaltlg1547 · · Score: 1

    TFA said they're going to try to construct a tabletop version. Only thing is, the whole concept rests on constructing (and containing) a ring of exotic matter. They don't have any of that, do they?

  55. Re:Make it so. by Anonymous Coward · · Score: 2, Funny

    Religion had to have the right answer to something.

  56. Re:Negative Mass by EGSonikku · · Score: 1

    So we just need anti-gravitons? I'm on it.

    --
    - "Scientia non habet inimicum nisp ignorantem"
  57. Re:Negative Mass by Jane+Q.+Public · · Score: 3, Informative

    "In fact, I propose that anti-matter has negative mass, not opposite charge as generally accepted."

    That might have been a viable theory half a century ago or more. But antimatter has been observed to have positive mass.

  58. So after reading the article, it seems... by EGSonikku · · Score: 1

    Step 1: Maths says maybe, if one ignores lack of negative mass
    Step 2: ???
    Step 3: Engage at Warp 2

    --
    - "Scientia non habet inimicum nisp ignorantem"
  59. Fermi's Paradox by FoolishOwl · · Score: 1

    As evidence that less impossible is still truly impossible, there is Fermi's Paradox. If it's possible for living things with minds like ours to have evolved elsewhere, and if practical interstellar travel is just out of our reach, we have to wonder why they aren't visiting us.

    1. Re:Fermi's Paradox by Bill+Currie · · Score: 1

      The answer is simple: why bother?

      Resources? Anything down here, there's more of out there, without pesky gravity wells.

      Bio-mass? If 500kg of energy isn't a problem, then converting the above resources will be more efficient.

      Contact? With friends like us, who needs enemies?

      Slaves? What, you think we got to (near) the top of the dung-heap without a fight?

      Extermination? Well, ok, but be glad space is big, very big. Obviously nobody capable within a 60ly radius.

      --

      Bill - aka taniwha
      --
      Leave others their otherness. -- Aratak

  60. Re:Negative Mass by Rei · · Score: 1

    You can do all sorts of crazy things if you start allowing random theoretically-possible particles to exist in your systems. For example, tether a charged ball of negative inertial mass to a same-charged one of positive inertial mass, and they both take off accelerating indefinitely toward c with no energy input ;) The negative inertial mass ball experiences an attraction toward the positive ball, while the positive one experiences a repulsion.

    The sort of craziness that comes out of most imaginary particles is, to me, highly suggestive of their nonexistence. Most seem like the sort of thing that could end up destroying the universe or at least leaving some pretty darned big signs of their existence. And given that the universe has built some pretty massive particle colliders on its own...

    --
    No, she's fine. My associate is vomiting for a totally unrelated reason.
  61. I have seen this episode. by warp_kez · · Score: 2

    Season 1 of Star Trek: The Next Generation. The episode was call "Where no one has been before" and it required the presence of a Traveller to make it work.

    But incidentally, Wesley reconfigures the wave to a donut shape.

  62. impossible vs unrealistic vs hope by swell · · Score: 1

    "less impossible" ? Does that sound a bit like 'slightly pregnant'? Possibility is a binary state- on, or off; no shades of grey allowed.

    As often happens, the /. blurb is a poor reflection of TFA, which says that warp speed "may not be as unrealistic as once thought".

    TFA seems a bit optimistic in posing a possible method for faster than light speed. The slashdot response tends to be antagonistic. The heartwarming thing is that all are excited about the idea. Deep inside we want to defy the rules, like Capt. James T. Kirk, and find a way. Who knows- that silly inner child in us may find a solution some day. Then what?

    --
    ...omphaloskepsis often...
  63. Re:Make it so. by tqk · · Score: 1

    A brief history of the future with warp drives:

    Cult/terrorist leader: "We are now on a holy mission to destroy the infidels. Aim the ship at the planet earth. Engage!"

    The planet Earth goes boom and intelligent life evolves somewhere else in the galaxy to repeat this cycle.

    At the last nanosecond, the deep space defense network trips the home defence network to rotate the dimensional phase of the Earth slightly, allowing the terrorists to shoot on by never to know whether they're still on the way to the target or just missed. "Ha haaa! Doofuses."

    Geez, I can't believe you missed that. "Good guys always win. Bad guys always lose." It's fundamental.

    --
    "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
  64. Re:Make it so. by Genda · · Score: 1

    So are you suggesting that an ancient inorganic intelligence build a warp drive billions of years ago on earth and that is how we ended up with the moon? Interesting? Too bad we don't have a tricorder to see if the moon has residual warp trace???

  65. Re:Negative Mass by Genda · · Score: 1

    Actually from what I've read antimatter has negative time. I'm going to guess the gravity is positive. There is a well known Physicist who just recently published a very interesting book. One of the things he proposes is that there is no dark matter or energy. He proposes that at the instant of the big bang, the polarity of the birth caused matter to go in one direction and antimatter to go in the other. That we are on a toroidal arc and at just past 7 billion years we hit the apex of our trajectory and that we are now accelerating towards the antimatter universe and its accelerating towards us. That in a couple billion years it will hit us and there will be a massive explosion as all matter is annihilated. And this will be the start of the next big bang. Cool idea, eh?

    For more information you can look up the "Big Bagle" theory

  66. Re:Negative Mass by Genda · · Score: 1

    While you're at it sparky, how about a little ice from the replicators, eh? Priorities puhleez!!!

  67. Re:Just kill NASA already... by 93+Escort+Wagon · · Score: 1

    Sounds like someone has peered into the storage room of his local McDonalds...

    --
    #DeleteChrome
  68. Re:Make it so. by lister+king+of+smeg · · Score: 1

    they would probably veiw stellar travel as a affront to their divinity of choice sort of neo-amish life style and before it is wide spread enough to be hijacked like an airliner we would already have multiple off earth settlements/colonies. more likely is religious groups going hiring a starship and go off creating a new earth away from the unrighteous infidels and heathens who commit the great sin of looking sounding acting or thinking differently. maybe he can do what happened in the hitchhikers guide and trick all of them into going on ship A while the rest of us go on ship B after.

    --
    ---Saying gnome 3 is better than windows 8 not so much a compliment as it is damning with light praise.
  69. Re:Negative Mass by tqk · · Score: 1

    I think it can have negative mass, but to make the observations work it would also have to have negative time.

    And you have a problem with that? Honest question. :-)

    Have you noticed all those guys over there fiddling around with Planck size Superstring stuff, and you're hesitant to consider negative time?

    It's all just a bunch of big, complicated equations that we plug values into hoping the Universe doesn't blow up when we do it, or $DEITY doesn't smack us down for testing it, yeah? I say we try it. Whatta we got to lose?

    --
    "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
  70. Won't happen by gmuslera · · Score: 4, Funny

    Will be cheaper to use Jupiter than paying the Apple lawsuit for using a Star Trek based device with rounded corners

  71. Re:Make it so. by RsG · · Score: 4, Interesting

    I'll assume, for the sake of argument, that conservation of energy still applies to the discussion. That is, you can't move a chunk of the crust into orbit without expending more energy than the gravitation potential energy thusly imparted into said chunk.

    Let's assume the energy to make the handwavium drive go is equal to the potential energy of a 500 kg mass, as it says in TFS. Presumably we've got matter-energy conversion or antimatter fuel to make this work, that's no more implausible than the handwavium required to make the FTL drive work in the first place.

    How much energy is liberated by converting 500 kg into energy, say in the form of 250 kg antimatter to 250 kg matter? About two hundred and fifteen times as much as was released by the largest nuclear weapon ever detonated. Make no mistake - that's a huge amount of energy, but nowhere near planet cracking levels. For another point of comparison, the impact that (probably) killed the non-avian dinosaurs was a couple million times as powerful.

    Further, if we've got some way of supplying that kind of power, in a package small enough to fit on a spacecraft, wouldn't the power plant itself be a more dangerous weapon than a handwavium suicide run? Dangerous in the sense of city busting, not planet cracking.

    --
    Erotic is when you use a feather. Exotic is when you use the whole chicken.
  72. Very well then... by metacell · · Score: 1

    ... what are you waiting for? Build one already!

  73. Re:Make it so. by metacell · · Score: 1

    What would happen if a chunk of the planet was temporarily missing and gravity forced the planet to round out--and then the piece comes back? No extra energy would be needed, just the gravitational potential energy stored in the planet.

    The chunk would need to be relocated to somewhere where it had the same potential energy (e.g, slightly closer to the sun), or the difference in potential energy would need to be taken from somewhere.

    Of course, the same problem would prevent ships from warping out of a solar system without expending huge amounts of energy in a very short time to increase the ship's potential energy. Circumventing this problem without expending the energy, would violate the conservation of energy, and provide a way to produce unlimited energy. Just warp water to the top of a mountain, and let it run down again, driving a turbine, over and over again.

  74. Solve every problem just by remodulating something by D4C5CE · · Score: 1

    if the intensity of the space warps can be oscillated over time, the energy required is reduced even more

    Knew it, Star Trek was real ;-) and Geordi did visit the 21st century to leave that piece of advice for cases when inverting the polarity of shield emitters wasn't enough.

  75. Re:Make it so. by Plekto · · Score: 1

    Of course, even if it only worked 1/10th as well as it could, consider what that would do to conventional drives. Getting rid of the effect of mass even to a very reasonable amount would allow us to either make much larger ships to, say, get to Mars, or it would allow us to get there in weeks or days. The original design says that it would allow for speeds up to 10x, but it also would allow a ship to go the speed of light (or close enough so that it doesn't matter) with a small fraction of the energy. That's impressive any way you slice it.

  76. Re:Negative Mass by ldobehardcore · · Score: 1

    Actually, It's not inverse mass. There are several pieces of strong evidence for inverse charge. The amount of energy it takes to push around a positron using magnetic fields is the same amount it would take to push around regular electrons. The fact that anti-matter can be trapped using fields of opposite polarity used to trap regular matter proves that antimatter has inverse charge to matter.

    Also, there are some interesting (calculated theoretical) behaviors to inverse mass objects. An inverse mass object will fall towards a massive object of equal absolute mass, but the regular mass object will fall away from the inverse mass object. There are also weird things that happen with infinite gravitational potential energy, and none of the effects have been observed as yet.

    Just remember that mass and charge are not interchangeable, and they have distinct effects when inverted. Electromagnetism is roughly 10^36 times stronger than gravitation, so a single particle with inverted mass but normal charge is unlikely to interact any differently at currently achievable energy scales than a particle of normal mass and normal charge. Especially when most of the experiments today use electromagnetism as the only input force to manipulate where particles go, and what they do.

    --
    Hectice, baby, Mercator says hello to you
  77. Where can we buy shares? by docilespelunker · · Score: 1

    Where can we buy shares? This opens the universe for trading. The return in investment could be one over a small infinity. Much better than one over a large infinity!

  78. Re:Just kill NASA already... by docilespelunker · · Score: 1

    Oh I say - unicorn burgers - now that's a good idea!

  79. Re:Negative Mass by Noughmad · · Score: 1

    Not really. Electromagnetic charge can be positive or negative, but (except of course on Voyager) there are no anti-photons. Or better, photons are their own anti-particles.

    --
    PlusFive Slashdot reader for Android. Can post comments.
  80. Re:We can have an interstellar civilization... by Your.Master · · Score: 1

    I think you and I have different definitions of civilization. I'm not saying humans can't get there, but I wouldn't call that an interstellar civilization. I would call that multiple stellar civilizations. When you separate people by a wall of time that is a significant portion of a human lifespan, you've effectively separated out civilization. Round trip communications from one end of your 16 light year radius is 64 years (diameter 32 light years, there and back). Feel free to insert your own terminology.

    I have to wonder what else you're assuming in your rejection of FTL

    I didn't reject FTL. I said FTL implies time travel. It sounds like YOU are assuming time travel is impossible. Which would be fine except for the hypocrisy.

    I also provided possible internally-consistent universes that could have FTL without causality violations. I honestly don't know how I could have given you more.

  81. Universal peace sign? by dimeglio · · Score: 1

    Coincidence? I think not.

    --
    Views expressed do not necessarily reflect those of the author.
  82. Re:Solves energy problem, causality problems remai by Magada · · Score: 1

    Presumably the Hawking radiation would bleed energy out of the warp, shrinking it. Cosmic friction, what?

    --
    Something bad is coming when people are suddenly anxious to tell the truth.
  83. Kids in the Hall by ThatsNotPudding · · Score: 1

    'I'm sorry I broke your hip, Mrs. Henderson.'

  84. Re:Negative Mass by gr8_phk · · Score: 1

    You can do all sorts of crazy things if you start allowing random theoretically-possible particles to exist in your systems.

    Yep, and if anti-matter gravitationally repels itself AND regular matter, then it would form an intergalactic gas pushing the universe apart like "dark energy" and also producing a bunch of gamma radiation emanating from the edge of the galaxy. But again, we need to know how it actually interacts gravitationally rather than make stuff up.

  85. Re:Make it so. by Asklepius+M.D. · · Score: 1

    "Good guys always win. Bad guys always lose." It's fundamental.

    Unfortunately, you don't find out which side you were on until after it's all over.

    --
    He who would be a man, must be a nonconformist. -- Emerson
  86. You forgot by Chas · · Score: 2

    "Thanks Wesley! We couldn't have done it without you!"

    --


    Chas - The one, the only.
    THANK GOD!!!
  87. 90% of humanity for a warp drive? by PeterM+from+Berkeley · · Score: 1

    I think you miscalculated the worth of a warp drive. Sure, it'd be cool. But think of this:
    1) Where would you go with it? You don't know, do you?
    2) If you knew 1), what would you do when you got there? How would you breathe? Eat? Set up a new civilization? We can't even set up self-sustaining habitats on *earth*.
    3) How would you support your life while you're traveling, assuming it's not so fast as to be trivial?
    4) If you got a "working warp drive", d'you think you could figure out how it worked without 90% of humanity? Or is "warp drive technology, and all required technologies to reproduce warp drive" what you really meant?

    Personally, I wouldn't trade 90% of humanity for a warp drive unless it came with solutions to all the above and more. And I'd think of it like this, is it worth a 90% chance of me personally dying immediately to assure that no single planetary disaster can ever cause humanity's extinction? Would my wife and other dependents go for that deal?

    --PM

    1. Re:90% of humanity for a warp drive? by cdrudge · · Score: 1

      1. Any place but here. Unless perhaps the spaceship's steering wheel was turned in which case it might actually be able to be here.
      2. What did the first astronauts do when they got to where they were going? They came back.
      3. The same way we support life with non-warp travel. With supplies we bring.
      4. Yes, I think warp drive (or any other similar gigantic leaps in science/technology can be made without 90% or even 99% of humanity. Ultimately if you want to go back far enough in the supply chain then everyone is involved, but I don't think a Chinese farmer who picked the grain of rice that ultimately ended up in the daily cafeteria meal for the person who ultimately has the eureka! moment really gets credit for supporting the endeavor.

  88. Re:Make it so. by potpie · · Score: 1

    Handwavium? I like it. I like it more than "unobtanium."

    --
    Esoteric reference.
  89. That's about right... by srussia · · Score: 1

    I would happily throw 90% of the human race under a bus for a working warp drive.

    Discard the rest of the male population and keep just the top quintile of the women.

    Hmm, on second thought you can keep your warp drive, I'm staying here!

    --
    Set your phasers on "funky"!
  90. OS/2 is so last millenium by jpvlsmv · · Score: 1

    Too bad IBM isn't sponsoring this research.

    I think I still have an IDE drive with Warp on it somewhere around here.

  91. Re:Negative Mass by mattr · · Score: 1

    Not happy now!

  92. Interstellar travel by T.E.D. · · Score: 1
    From TFA:

    With this concept, the spacecraft would be able to achieve an effective speed of about 10 times the speed of light, all without breaking the cosmic speed limit.

    For reference, the nearest star system, Alpha Centari, is 4.2LY away. With a ship or probe equipped with one of these drives, in theory it could go there and back in less than a year. The next closest system would take a year to get to.

  93. Re:Make it so. by onyxruby · · Score: 1

    Point well made.

  94. Wow by VirtualJWN · · Score: 1

    You mean that the "science consultants" from DARPA, JPL, CALTECH, MIT, and even NASA, and various other places that advised the Creator of Star Trek (Gene Roddenberrry) as well as the writers were RIGHT???? Wow, that is truly an AMAZING COINCIDENCE!!!! Next thing you know we will have communicators, Mr. Spocks data tablets, and selective lethality weapons!

    --
    "Any sufficiently advanced technology is indistinguishable from magic." - Arthur C. Clarke
  95. Mmmmmmm..... by bornagainpenguin · · Score: 1

    recent calculations showed that if the shape of the ring encircling the spacecraft was adjusted into more of a rounded donut

    Donuts....Is there anything they can't do?

    --
    Have a Virgin Mobile USA smartphone? Give VMRoms.com a try!
  96. Captn' Janeway is a beaut by Syirrus · · Score: 1

    If you set the subspace carrier wave to 7.1 terahertz and realign the di-lithium matrix with the deflector dish we could in theory achieve warp 9.5.

  97. Re:mass can be tricked can it not by wierd_w · · Score: 1

    This is more like what happens when you take a small paper boat, and rub one end of it liberally with bar soap.

    when you float it on the meniscus of the water, the soap (negative mass energy) alters the surface tension (spacial curvature) which propels the ship forward.

    In this case, we also place a heavy normal gravitational wake in front of the ship, (something that would contract the surface of the water, rather than spread it), causing the ship to be also "falling" forward at the same time.

    The net result is that a whole "chunk" of spacetime gets "loosened", and glides along without friction. the entire reference frame of the vehicle gets moved around.

    Understanding the higgs field will simply allow us to better understand how we could create effective anti-mass to push the ship with. (instead of a gravity "well", it creates a gravity "bump")

  98. Re:No doubt by RespekMyAthorati · · Score: 1

    We already have cryogenic freezing. It's just that it only works for embryos.

    A 1 liter bottle of frozen embryos could store millions of people, and they could travel for thousands of years with no food, water or oxygen.
    You would still need an artificial womb to birth them, and a teaching robot to raise them. We should be able to do that in a few centuries.

  99. Handwavium by ace37 · · Score: 1

    I have a new favorite material - it used to be unobtanium, but for discussions like this, handwavium is much more accurate!

  100. "less impossible" does not make sense by DekuDekuplex · · Score: 1

    Something is either possible, or impossible; hence, it does not make sense for something to be "less impossible." That's like saying that something "exists less" than another thing; things either exist, or they don't. For example, my barber exists, whereas barbers who shave all and only those barbers who don't shave themselves don't exist.