Slashdot Mirror
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."
Eject the core!
To all those anti-warp drive downers.. HAHAHAHA!!!!
by Cyphase ( 907627 )
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.
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.
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.
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.
guess you were travelling at impulse
I'm god, but it's a bit of a drag really...
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
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
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.
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.
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
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
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.