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Near Light Speed Travel Possible After All?
DrStrabismus writes "PhysOrg has a story about research that may indicate that close to light speed travel is possible. From the article: 'New antigravity solution will enable space travel near speed of light by the end of this century, he predicts. On Tuesday, Feb. 14, noted physicist Dr. Franklin Felber will present his new exact solution of Einstein's 90-year-old gravitational field equation to the Space Technology and Applications International Forum (STAIF) in Albuquerque. The solution is the first that accounts for masses moving near the speed of light.'"
Theres no point in travelling at close to light speed if your have no way of stopping.
Mind that planet!
What planet?
SPLAT
liqbase
Can't
Can
Can't
Can
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Wake me when someone actually accomplishes something. I'm sick and tired or the back and forth debate over ethereal concepts that can neither be proven or disproven in our lifetime.
What was making impossible near-lightspeed travel? Only FTL was prohibited. Problems like engines, fuel, shielding etc. are only technological problems.
For more information, see Dr. Felber's recent works on arXiv.org:
Weak 'Antigravity' Fields in General Relativity
Exact Relativistic 'Antigravity' Propulsion
Personally I'm a bit skeptical about his claims, however energy appears to be conserved. This method uses gravitationally-mediated kinetic energy exchange - this is the same principle that allows gravitational slingshot to work.
One thing I have often wondered is if an object moves fast enough, could its relativistic mass become so large that it would look like a black hole relative to a laboratory frame?
"The White House is not an intelligence-gathering agency," -- Scott McClellan, Whitehouse spokesman.
This guy seems to be saying that if you have an anti-gravity machine, you could counteract that.
.577c is another question.)
Nonono: he's saying that a mass travelling near the speed of light creates an "antigravity beam" in front of it. This sounds hokey, but it's not unprecedented - frame dragging is a similar situation where general relativity basically says that a moving body can "push" others nearby. So in this case the near-light-speed object is "dragging" its frame forward. Calling it an "antigravity beam" sounds wacko, but it's probably quite straightforward. It's almost like the objects would be riding the "wake" of the NLS object, caused by the fact that the object is moving faster than space can respond.
He's essentially saying that you can pretty much effortlessly accelerate something to really high velocities with little effort by hitching a ride on a bigger object.
(Where to find a star moving at greater than
Bussard ramjets are just cool and fine, and i liked the idea, too.
But the physics dont work out.
You get at most 2% or so of the mass converted into energy by the fusion process, even if you could fuse everything together perfectly efficient. But once your spaceship is moving quite fast (more than 10% or so of the speed of light), you will need to use more energy to move and collect the particles in your flightpath than you could possibly get by fusing them together.
It just doesnt work out if you look at the big picture.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
Buick? You mean the size of a dust mote. If a dust particle weighs 1/100 of a gram, and you are going roughly the speed of light, the kinetic energy of the dust particle relative to you (assuming that the dust particle is roughtly standing still) is
.00001kg x (2.998 x 10^8 m/s)^2
898800400000 Newtons
9806 or so Newtons Per Ton
1,000,000 tons per MegaTon
20 Megatons per Hydrogen bomb
Thats 4.6 Hydrogen Bombs of energy that the dust particle has relative to you. Do you want to collide with 4.6 Hydrogen Bombs? I don't think that NLST is practicle, even if it turns out to be possible. What we need is a way to simultaniously transport stuff.
No, we have reduced to the problem of how to accelerate only part of the ship, while the other parts can hitch a ride on the first. I suspect the sweet spot would be the first part at 2/3 of the total mass.
If you're correct, then we're done:
--MarkusQ
Oh wait, I almost forgot:
I'll believe it when I see it.
Er, or maybe when I don't see it.
-S
--- What parts of "shall make no law", "shall not be infringed", and "shall not be violated" don't you understand?
The density of interstellar space is about one atom per cubic centimeter. If the spaceship were going near the speed of light (3 x 10^10 cm/sec), it would be hit by 3 x 10^10 relativistic particles per cm^2/sec. This is about the equivalent of one Curie per cm^2, which would kill a human and cripple any electronics on board
A very heavy magnet could deflect the protons, but the neutral atoms would be unaffected by the magnetic field.
Moving faster than 57.7% of c? Relative to what?
Right now, the earth is moving through space at a speed greater than 57.7% relative to something. No, I don't know what, or where, but rest assured there's some body out there somewhere in whose frame of reference the Earth is moving at greater than 57.7% of c. And there's some other body in whose frame of reference the Earth is moving at greater than 10% of c, and another body where Earth is moving at 95% of c, and another body where Earth isn't moving at all (Hey, like me!).
So why isn't the Earth emitting such an antigravity beam, repelling masses in its path? Rest assured that if it were, we'd be seeing its effect, like ferinstance as it played havoc with GPS satellites.
Or, heck, there are cosmic rays which occasionally smack into the Earth's atmosphere at a speed that's only infinitesimally smaller than c in Earth's FOR. They should *definitely* be emitting some sort of antigravity, if this guy's correct. Should be trivial to observe, but we haven't seen it.
This smells like bullshit.
Ok, I've worked in gravity for a while, but unfortunately I haven't time right now to go through this guy's paper. Several things are setting off my B.S. detector, though.
First, this guy is not a "noted" physicist, let alone a noted gravitational physicist, as far as I can tell. He published some papers in accelerator physics while affiliated with the Naval Research Lab. He has no publications, or as far as I can tell, training in general relativity. He's now affiliated with some company ("Starmark, Inc.") in San Diego. Furthermore, gravitational physicists generally give talks at gravity conferences (or at least physics conferences), not space engineering conferences (which have drastically lower standards when it comes to gravity, since the organizers of the conference typically have no GR background).
Second, I skimmed the preprint of his (unpublished) "antigravity" paper. He claims that a distant observer watching a particle fall into a black hole, in the (initial, local) rest frame of the particle, will see the black hole to approach the particle, and then cause the particle to accelerate away from the black hole. This is not in any weird "warp drive" spacetime, but in ordinary Schwarzschild spacetime — such as the spacetime outside of a star or a planet (!). Yes, you read that right, according to him, even planets create antigravity (if you're traveling fast enough). This bears no relation to anything I know about orbits of particles in Schwarzschild spacetime.
Then he mentions performing a Lorentz transformation of a particle trajectory into the frame of a distant observer. This is impossible. You can only apply a global Lorentz transformation to a flat (Minkowski) spacetime, not a curved spacetime (such as Schwarzschild). Well, you can apply a transformation to a flat tangent space at a point in a curved spacetime, but you can only transform a vector in the tangent space at that point, not an entire trajectory that spans a continuum of points. It is true that Schwarzschild geometry is asymptotically flat for "distant" observers, and he's speaking of transforming into the frame of a distant observer, but the fact remains that you cannot Lorentz transform a worldline that is not entirely within an approximately flat region of spacetime (and his trajectories definitely aren't always far from the gravitating body).
Now, you're free not to buy my suspicions, because as I said I haven't the time to go through all his calculations and see what's up (general relativity calculations are a pain in the ass). My bet, however, is that he's simply misinterpreting a coordinate quantity as having physical meaning. This is a common error for GR beginners (and you can see a prime example of it in the crackpot A. Mitra, who claims that black holes contradict the Einstein field equations based on his misinterpretation of coordinate derivatives in Schwarzschild spacetime). The thing about GR is that you can write solutions in any coordinate system you want, and you have to make sure that the quantities you're calculating are physically meaningful, and not just an artifact of whatever coordinates you happened to choose. Anyway, that's my guess based on what this guy has written so far and the kind of errors I see people make when making "wild" claims in GR. But it's also possible he simply made a math error. I am not betting, however, that he has suddenly discovered antigravity lurking within the ordinary Schwarzschild metric.
You make the assumption that the dust mote would actually stop, only then would the bulk of the KE go into the target space ship. More likely is that since the KE of each atom in the dust mote is so much larger than the atomic bond energy holding the grain together, the dust mote to the spacecraft really behaves like a very densely packed bundle of cosmic rays. If the spacecraft walls don't stop individual particles of that energy (ie like cosmic ray protons) then it won't stop the dust particle. The atoms would go in one side, out the other radiating a small fraction of their relative energy as gamma rays as cherenkov radiation and compton radiation. The dust would go out the other side as a diverging cone shaped spray of plasma.
Time Dilation doesn't actually help much here. You have to accelerate to high speed and deccelerate at the end of the journey. Human beans can handle high accelerations for brief times with few ill affects, but we're talking months here. I suppose if you remain strapped into a squishy chair without having to move around too much then two or three g's might be more reasonable, but I'm pretty sure noone's done the studies.
Anyhoo, I typed "relativistic acceleration" into google, and two clicks later I was here.
It's a little disappointing. A traveller would only get up to 95% of the speed of light before it was time to start deccelerating. For longer trips, however, the effect would be greater.
Those people who think they know everything are a great annoyance to those of us who do. (Isaac Asimov)
Are you comfotable with the notion of time travel?
"The White House is not an intelligence-gathering agency," -- Scott McClellan, Whitehouse spokesman.
I've often felt the same way about 2+2 never getting up to 5. Come on science, you can put a man on the moon but you can't get 2+2 even a decimal place past goddamn 4?
"Everthing else [in science] is simply theory. Which is based on some authority and never allowed to be questioned."
Wrong, wrong, wrong, and a thousand times wrong!
The whole basis of science is that everything is open to question. There are few things more prestigious in science than to refute a previously accepted theory. Ever heard of a guy named Albert Einstein? Yeah, thought you might have. Used to be that Newton's theories were the accepted way in which the universe worked, but Einstein showed differently.
The main reason it seems like some theories are "unquestionable" is simply because most of the ways in which people choose to challenge them have been shown time and time and time again to be false.
If you get 100 people a day proposing a design for a perpetual motion machine using a series of cogs, wheels, and magnets, you're not going to take the time to explain to each and every one why their design won't work, instead, you're just going to tell them to bugger off and leave you alone.
Of course, scientists are human, and at times they will reject things inadvertently which they shouldn't. However, if you think you have a good explanation as to how/why we can, in fact, travel faster than the speed of light, instead of whining to Slashdot about how stuck in the mud scientists are, why not publish it? You'd be the next Einstein!
Curiosity was framed. Ignorance killed the cat.
Replying to my own post, as I forgot to mention something else, and Slashdot's "edit post" button has undergone a total existence failure...
The parent also mentioned that scientific theory is based on authority. This is utter nonsense. Authority counts for nothing in science.
We accept Einstein's theories as being correct. Why? Because he was a really smart guy, and therefore must have been right? No. Because he showed exactly how and why his theories were correct.
If I tell you that water turns to ice or steam sometimes, and that's the way it is, because I say so, and because I'm smarter than you, then you'd probably tell me to get stuffed (and rightly so)
On the other hand, if I tell you that cooling water to 0C causes it to freeze into ice, and heating it to 100C causes it to boil, giving off steam, then you can try for yourself in your own kitchen. It doesn't matter if you think I'm a genius or a raving lunatic - it doesn't even matter if I actually AM a raving lunatic. The only thing that counts is whether it works or not. And the things we accept in science are those that work - and if we don't know, we run with our best current explanation based on the avaliable data until a better one comes along.
That's the wonderful thing about science. It's perfectly possible for some unknown, uneducated nobody with a bright idea to overturn hundreds of years of accepted science.
(of course, it's also rather unlikely, as the simple fact is the vast amount of unknown, uneducated nobodies who try to do that are completely off the mark, and don't have the first clue what they're talking about... doesn't mean it can't happen though.)
Curiosity was framed. Ignorance killed the cat.