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Physicists Theorize New Method for FTL Travel

  1. Aug 23, 2008 #1
    New method would not break Einstein's Theory of Relativity

    -xCross
    Source: http://www.dailytech.com" [Broken]
     
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Aug 23, 2008 #2
    Interesting, but any form of FTL also allows for time travel, which suggests to me, anyway, that it is very unlikely.
     
  4. Aug 23, 2008 #3
    Why? I never understood that connection.
     
  5. Aug 23, 2008 #4
    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.
     
  6. Aug 23, 2008 #5
    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.
     
  7. Aug 24, 2008 #6
    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...)
     
  8. Aug 24, 2008 #7

    cristo

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    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.
     
  9. Aug 24, 2008 #8
    Thanks!
     
  10. Aug 24, 2008 #9
    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.
     
  11. Aug 25, 2008 #10
    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 :)
     
  12. Aug 29, 2008 #11
    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?
     
  13. Aug 29, 2008 #12
    non-zero imaginary-valued mass
     
  14. Aug 29, 2008 #13
    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?
     
  15. Feb 10, 2009 #14
    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...
     
    Last edited: Feb 10, 2009
  16. Feb 11, 2009 #15
    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)?
     
  17. Feb 14, 2009 #16
    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.
     
  18. Feb 14, 2009 #17
    Not that I am a fan of FTL travel but
    is it not exactly the best hope for FTL travel ?!
     
  19. Feb 15, 2009 #18
    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.
     
  20. Feb 18, 2009 #19
    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.

    Rich
     
    Last edited: Feb 18, 2009
  21. Feb 19, 2009 #20

    Demystifier

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    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:
    http://fqxi.org/community/forum/topic/259
    (see PDF)
     
    Last edited: Feb 19, 2009
  22. Feb 22, 2009 #21
    I distinguish between movement and connection over a static field. A static field connects, but doesn't move. Light passes through space and can't be faster than c in the frame of reference of the sender. In respect to itself it stands still. Now think, that the space we observe isn't 'reality', but spacetime itself. In that 'space' we have infinity as speed of a connection and c as speed of observed movement of light in the reference frame of the observer.
    So we can't move faster than c in the FoR of earth, but once in movement, we don't move at all (in respect to ourselfs), since than we would be the ones, that measure time.
    So in this spacetime view, we have a universal simultinaity with infinite speed over static fields and c is only a limit for light in vacuum in respect to any observer.
     
  23. Feb 22, 2009 #22
    This is correct, I've also recommend this: http://en.wikipedia.org/wiki/Novikov_self-consistency_principle

    However, Novikov speculates about billard balls, but what happens to entropy in the closed time-like loops?

    Also, it could be an interesting way to test different interpretations experimantally. For example, I suspect that transactional interpretation should give different results in such conditions. Also, as noted in the article, it is not known if Novikovs principle is consistent with MWI.
     
  24. Feb 22, 2009 #23

    George Jones

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    Careful, this, by itself, is not sufficient to prevent Closed Timelike Curves. In fact, the whole point behind CTCs is that it's possible for an observer to travel into the observer's past while staying within the observer's future light-cone. In other words, there is an event [itex]p[/itex] on the observer's worldline such that the intersection of the past and future light-cones at [itex]p[/itex] is non-empty.
     
  25. Feb 23, 2009 #24

    Demystifier

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    For an outside observer, at some point entropy reaches its maximum, after which it starts to decrease. But this is not how it will be perceived by an observer whose brain entropy also behaves in that way. Instead, it will be perceived as TWO observers that eventually meet and die at the point of maximum entropy.

    It is consistent with MWI. In this case, the Novikov principle is to be applied to the wave function.
     
  26. Feb 23, 2009 #25
    WOW, what I marked BOLD was unexpected to me - I did not think about it - but it must be true as our perception of time just point in the direction where entropy increases.

    So 1 of the split-observers is a unique conditions - his personal time is another direction as physical time. He would see the whole universe (outside the loop) rolling back in time...

    But it would be really interesting to trace light rays to understand, what would observers actually see. It is especially interesting how he would see his 'twin'.

    What can you say about the splitting event, when 1 observer is 'split' into 2? Did you think about drawing some diagrams to better understand it? What can you say about the memories of these observers?
     
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