New method would not break Einstein's Theory of Relativity
Interesting, but any form of FTL also allows for time travel, which suggests to me, anyway, that it is very unlikely.
Why? I never understood that connection.
As I understand it, if you can travel outside of your own future light cone, than from some reference frame you are traveling backward in time. And if you can travel backward in time in one reference frame, you can do it in all of them.
It's kind of obvious if you think about it properly. Imagine looking at a distant star. You see it as it was long ago in the past. Now imagine somebody would leave this star at a certain time in a frame where both you and the distant star are at rest, and travel faster than light towards your planet. He would reach you before the light carrying the image of him leaving even made it. When he would look back, he would see that distant star as it was before he even left ! Therefore, he could also come back to the distant star at another point in space on his planet at the moment he left. Faster than light travel would thus amount to both time travel and also to teleportation. All those are somehow equivalent.
Where is their paper? The only source I see is space.com and in a quick search I didn't have a lot of luck with finding any of their actual work. Whatever they're doing I doubt it is the way space.com depicts it, or if it is I doubt that they actually have proposed a mechanism for performing the act they want to perform (i.e. maybe this is just another case of "if you can do N impossible thing, you can travel faster than light". The revelation that if you can do one impossible thing you can do other impossible things also is not surprising...)
Here is a link to one of their papers: http://arxiv.org/abs/0712.1649. There is also a more popular one, posted to the popular science section of the arxiv.
Dead on arrival, I'm afraid. If it's faster than light it implies closed, or nearly closed, timelike curves in a spacetime. And global hyperbolicity doesn't jive with those curves.
Rich is floating around these fora, although I haven't seen him lately.
You might send a PM to robousy and see if he will join the discussion :)
What would happen if I threw in the hypothetical tachyon? any response/explanation from someone far more experienced than me? From what I have heard, it arrives at its destination before departure, but what property would allow it to do that that the massless photon has not? charge?
non-zero imaginary-valued mass
So the tachyon has imaginary mass, and the photon has no mass, ergo no volume. Why isn't it a point particle? and if I i am right (which I most likely am not) if it has no volume, how can it be real?
I've been thinking that dark energy was "the key" to FTL travel. It seems pretty obvious, since dark energy allows the Universe to expand faster than the speed of light...
I understand that in Special Relativity, moving faster than light (that is, travelling out of your light cone, which is tachyonic motion) implies time travel. However, how is this also the case with Warp Drives and Wormholes (which do not need tachyonic motion of the traveller)?
Isn't it actually space-time itself that's expanding? So things aren't actually moving away from eachother, but the space between them is getting bigger.
Not that I am a fan of FTL travel but
is it not exactly the best hope for FTL travel ?!
The electron has a non-zero mass, but it also has no volume in our current theories (it is described by a point-like particle). It turns out that there is no meaningful quantum analogue to volume.
The photon is a point particle. It has no volume and it is real, and as I have explained this is because quantum mechanics. Before going "beyond the standard model", I think you would enjoy learning about quantum mechanics.
Just noticed you guys talking about a paper we brought out in 07. Nice to see some interest.
I thought I'd jump in and address some issues that seem to be cropping up.
We avoid issues of CTC's and the grandfather paradox by placing the hypothetical spacecraft inside a bubble of asymmetric expanding and contracting spacetime analogous to the Alcubierre bubble. This link should help in visualizing the concept. A stationary spacecraft with the ability to create such a bubble would always move inside its own light-cone, thus avoiding said problems.
Our approach was similar in spirit to the Morris-Thorne-Yurtsever wormhole paper (Phys.Rev.Lett.61:1446-1449,1988) in the sense that our starting point was the question: "What limitations the laws of physics places an arbitrarily advanced civilization?" i.e imagine a technology that could achieve 'anything' as long as it did not defy the known laws of physics. What could it do?
What makes this work unique and original is the fact that we adopt an approach that is fundamentally quantum field theoretic in nature, which contrasts to the traditional GR approach taken by previous warp drives papers. Casimir energy, extra dimensions and dark energy play a critical role in our model, and the combination of ideas has never been explored in this context.
Another important aspect of this work was the fact that many young people feel that physics is 'boring', 'difficult' and 'irrelevant', and thus an unattractive career option. We believe that the exploration of novel ideas in interstellar propulsion, using advanced physics, encourages new minds to enter our subject. Indeed, this was our main reason for writing the 'laymans version you can find here.' The aim being to make these ideas accessible to a wider audience. We also felt that for those already studying physics, that this work would encourage them to tackle the subjects traditionally considered to be more challenging, i.e. GR, QFT and string theory.
Why do you think that time travel is unlikely? Because of the causal paradoxes? I don't think that time travel leads to any causal paradoxes:
http://xxx.lanl.gov/abs/gr-qc/0403121 [Found.Phys.Lett. 19 (2006) 259-267]
I fact, I think that "causal paradoxes" are an artefact of a failure to distinguish two very different notions of "time", where only one of them is really physical:
Separate names with a comma.