I'm not talking about the speed of the spaceship. If we can deform space-time we needn't any type of propulsion. And how can the travel affect to it's pilots? Can they survive?
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3$\begingroup$ Answers would necessarily be high speculative and this means of propulsion are completely theoretical at this time. $\endgroup$– dmckee --- ex-moderator kittenMar 16, 2012 at 0:55
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$\begingroup$ This is a difficult question to answer, though, because we don't know. $\endgroup$– mate64Mar 16, 2012 at 2:32
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3$\begingroup$ I'm not sure you realize what you're asking here. The question of physical possibility of such travel is already a difficult one, but you're asking something far harder: whether humans will be able to build something like this and whether pilots will survive. Predicting human capabilities with regard to progress of medicine and technology is tremendously difficult if not impossible and hence I think your question is basically unanswerable. I don't actually see how this is a question about astronomy at all. $\endgroup$– Adam ZalcmanMar 16, 2012 at 9:53
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2 Answers
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The Alcubierre Warp Drive hasn't been proved theoretically impossible; although requiring an amount of energy equivalent to several solar masses appears to be one of the less difficult engineering challenges that would confront anyone attempting to build one.
answered Mar 16, 2012 at 12:51
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$\begingroup$ This is the answer i'm searching for… yeah. $\endgroup$ Mar 16, 2012 at 20:12
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1$\begingroup$ To say it hasn't been proved theoretically impossible is a bit of a stretch. It violates energy conditions. In general, I can make up any metric I like, including one in a topology with a handle where my closet (and only my closet) opens up to the Andromeda galaxy. This type of thing is only forbidden by energy conditions. So the burden of proof is on Alcubierre to show the energy conditions can be violated to do this, otherwise GR has no content, every metric gives a stress tensor realizing it. $\endgroup$ Jul 17, 2012 at 3:52
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$\begingroup$ @RonMaimon: I agree that there is no reason to believe in the feasibility of building an Alcubierre drive, but Hawking radiation also violates energy conditions, so there is a thing that everyone believes in that does violate the classical energy conditions. $\endgroup$ Jul 17, 2012 at 4:42
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1$\begingroup$ @JerrySchirmer: It's misleading to say Hawking radiation violates an energy condition, although it is technically correct. It violates weak energy condition, just because it makes the black hole shrink. But the shrinking it produces is only allowed precisely because the actual entropy of a black hole isn't infinite, and the entropy of the outgoing light balances the entropy lost by shrinking the hole. The violation and the effect go away in the classical limit, where black hole entropy is infinite. A violation of energy conditions in the classical limit is a violation of thermodynamics. $\endgroup$ Jul 17, 2012 at 4:48
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1$\begingroup$ @diffeomorphism: It's ok only if there is corresponding emitted gross entropy equal to the lost entropy, but A's warp drive is imagined to be static machines with no heat sink, without huge entropy emissions. I see now you are right, that you have to make the argument carefully, for situations where the hypothetical FTL machine spews out enormous entropy (like constantly emitting huge amounts of thermal radiation) to compensate for the lost entropy of BH. I think this could violate Bekenstein bound but one has to think carefully, thanks for pointing it out. $\endgroup$ Jul 18, 2012 at 4:54
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the Alcubierre drive has problems far worse than the energy violations; you need to distribute the exotic matter in a space-like direction before you can ride over it.
Even if you could produce enough exotic matter, you will have to distribute it first by conventional travel. No amount of exotic matter will avoid this.
If you use exotic matter to stabilize some quantum foam wormhole to a macroscopic scale (and there is the big question of where the other end takes you, but lets assume for the sake of discussion that you always get the two ends nearby) you'll still have to move one of the ends by conventional travel to wherever you want to set up shop.
energy-condition-violating fields are allowed by thermodynamics law as long as creating them requires at least the same amount of entropy that they could take away from a black hole (just like Hawking radiation does).
We know this is also physically possible because squeezed vacuum has already been created experimentally for a single EM mode. You still would have to squeeze a gigantic range of the EM spectra (probably up to scales too small for normal materials to create) to localize enough dark energy to stabilize one of these 28th century toys
