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Faster than light travel!

  1. Sep 18, 2012 #1
  2. jcsd
  3. Sep 18, 2012 #2

    jedishrfu

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  4. Sep 18, 2012 #3

    Ryan_m_b

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    What jed said. There are a plethora of published papers on warp drives and wormholes but all rely on unobtanium that at best isn't impossible but there's no reason to think it exists and at worse violates an energy condition.
     
  5. Sep 18, 2012 #4
    What I've never gotten about these types of propulsion methods is that if they contract space in front of the ship and expand it behind the ship to make it move whilst staying still, doesn't that mean that when space returns to normal (space in front expands and space behind contracts) the ship will be in the exact same spot it was before.

    Like putting a dot on a half stretched rubber band, stretch it behind, and let it contract in front. Yes, it is closer to the destination, but once the band goes back to the way it was and the dot is in the exact same position.


    Or if the ship actually does move in a pocket of "normal" space, doesn't that mean that the contracted space in front has to normalize in that pocket that the ship is passing through making it so the ship has to travel the same distance anyways?

    Or if they ship passes through the contracted space, as the ship is still a part of the universe, would then contract itself, and thus, have to pass through the same distance again.

    Kinda makes this method of propulsion seem useless to me, unless I'm missing something.
     
  6. Sep 18, 2012 #5
    Just some questions here - firstly, how does "exotic" matter make this Alcubierre warp effect possible? Are we talking about dark matter here? I thought its existence hasn't even been definitively proven. And even then, what exactly does dark matter do that regular matter doesn't? I'm told that it would have "negative mass" - meaning it produces a gravitational field that repels matter instead of attracting it. How does this get you moving faster than light?

    From what I've read, this Alcubierre concept is to produce expanding space behind you and contracting space in front of you, while you are motionless inside the span of space between. So you are sitting motionless in this "patch" of space, while the "patch" slides along very quickly like a magic carpet. This is then supposed to circumvent any lightspeed limitations.

    The original concept apparently had prohibitively high mass-energy requirements, but now recently further calculations show that it could be achieved with a more practical amount of mass-energy.

    http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023492_2011024705.pdf

    So I was reading that thing, which doesn't seem like a real physics paper, and it talks about a "warp field interferometer" (ie. a laser interferometer attuned to detecting tiny perturbations in spacetime). So is a "warp" a transient perturbation in spacetime, or a lasting distortion? Is it again the natural gravitational field created by ordinary matter and alleged exotic dark matter? Can ordinary matter be said to generate a "warp field"? If a "warp" is a perturbation, then are we talking about gravity waves here?

    There are already large gravity wave detectors like LIGO. So how do these "warp" researchers intend to detect waves or perturbations any better than those setups? Can they somehow create a "warp" artificially, without the use of exotic matter?

    What really is a "warp field" and how is it created?
     
  7. Sep 19, 2012 #6
    The point of the matter is "feasibility".
    Is or will it be feasible given the required energy and technology to achieve spacetime warping for travel? If the numbers add up and such technology although unattainable at present should be available in the future then obviously it will be implemented. But, I am interested if it is even theoretically possible.
     
  8. Sep 19, 2012 #7

    Ryan_m_b

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    Short on time but quickly wanted to point out that this is fallacious. Not only because possible-in-theory is not a synonym of possible-in-practice but also necause possible-in-practice is not a synonym of will-be-practiced.
     
  9. Sep 19, 2012 #8
    Through further surfing, I see that White says they plan to use their laser interferometer to produce the warp effect as well as detect it. So I'm very curious on how they plan to do this.

    I've been reading lately about how "attosecond pulse" lasers are being used to push the bounds of physics, and study the nature of quantum phenomena in greater detail. I'm wondering if such lasers could be used to manipulate spacetime (or rather the virtual particle sea underpinning it)
     
  10. Sep 19, 2012 #9
    Well, Alcubierre's warp drive concept is based within the framework of known theoretical physics, and what he is saying is that while there is a speed limit on how fast matter can travel through space, there is no similar limit on how fast space can travel through space.

    But Alcubierre's idea depends on some kind of exotic matter with "negative mass", but White's current efforts are seeking to create some kind of tiny space warp in the lab, using lasers instead of the exotic matter.
     
  11. Sep 19, 2012 #10
    Well, from what I interpret, this "warp" idea seems analogous to an "exciton" (electron-hole pair), in the sense that it's like a dip-and-peak in the spacetime fabric. So the idea is that you have the dip in front of you (contracting space) and the peak behind you (expanding space), with you in between the two. You are then traveling through space like a ripple (trough-and-peak). We already know that such dips and peaks exist in spacetime in the form of vacuum fluctuations, but this warp thing would be a macroscopic version perhaps. Or if you think of gravity, that is all dip, but the warp would be a dip-and-peak.
     
  12. Sep 20, 2012 #11
    How can a gravity wave be all dip with no peak? Don't you need both to propopage a wave?
     
  13. Sep 20, 2012 #12

    JesseM

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    Alcubierre’s original paper didn’t address the issue of how a warp bubble could be created, it just analyzed a spacetime where one already existed. I wonder, has White or anyone else actually found an exact solution to the equations of general relativity where a warp bubble is created in a previously bubble-free region of space, perhaps using a theoretical model of the "White-Juday Warp Field Interferometer" that Harold White & co. are using to try to create one? If there are no exact solutions, are there numerical simulations that show this happening? If neither, I’m skeptical that there’s much good basis for the claim that the White-Juday Warp Field Interferometer might plausibly be used to create one (I would imagine the argument would be fairly “handwavey” as physicists like to say).

    Also, this blog entry by a physicist gives another reason to be skeptical it would be possible even with the necessary exotic matter:
    And another physicist writes here:
     
  14. Sep 20, 2012 #13
    Ah, the Huffington post... a source of reliable, objective science information??
    Who knew??
     
  15. Sep 20, 2012 #14

    JesseM

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    Well, the story that NASA is funding this research is true. And the story has been reported a bunch of other places as well:

    http://www.usnews.com/news/articles/2012/09/18/nasa-head-bolden-warp-speed-ahead
    http://www.wired.com/wiredscience/2012/09/warp-drive-plausible/
    http://www.space.com/17628-warp-drive-possible-interstellar-spaceflight.html
    http://www.msnbc.msn.com/id/49064028/ns/technology_and_science-space/#.UFur_67x9H4
    http://techland.time.com/2012/09/19/nasa-actually-working-on-faster-than-light-warp-drive/

    ANd from NASA itself:

    www.jsc.nasa.gov/roundup/online/2012/0712.pdf

    Here's Harold White's paper on why he thinks it could be possible to produce warp bubbles (doesn't seem to have much detail on the question I asked above about the theoretical argument for thinking they could be produced in a region of space that didn't have them already):

    http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015936_2011016932.pdf
     
  16. Sep 22, 2012 #15
    So what I gather so far is that Harold White's lab apparatus will consist of a capacitor ring and laser interferometer. The capacitor ring is what will produce the "warp" and the laser interferometer will measure/detect it.

    So it sounds like what's being inferred here is that the potential gradient from an electric field will warp space - ie. it will cause a measurable difference in path length that can be detected with an interferometer.

    Is such a belief reasonable, and consistent with known physics?
     
  17. Sep 23, 2012 #16
    The trouble with only going ten times the speed of light it is still going to take a hell of a long time to get anywhere outside the solar system.
     
  18. Sep 23, 2012 #17
    It might take you a few years to get somewhere really interesting, but that's still better than centuries. Obviously, we are looking for travel on human timescales.

    Still, who believes that voltage can warp space? That means every time I use my camera flash bulb, I'm doing some "warp field engineering" :P

    Can electric capacitors really produce a measurable path length difference that can be detected by an interferometer?
     
  19. Sep 23, 2012 #18

    MTd2

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    Isn't the cosmological inflation, or even the concept of expansion of the universe, a kind of isotropic warp drive? As for the inflation, if there was a way to deflate space ahead and inflate behind, wouldn't that be a warp drive?
     
  20. Sep 23, 2012 #19
    Well, that's exactly what Alcubierre's Warp Drive concept proposes - a bubble with contracting space in front and expanding space behind, in order to achieve FTL.
     
  21. Sep 23, 2012 #20

    MTd2

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    Yes, I know. But I am actually thinking about a feasible mechanism. What was the energy density by the end of inflation? If we could compress matter at least that much, maybe we could do warp drive.
     
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