Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Faster than light?

  1. Oct 6, 2008 #1
    I know that with todays knowledge, nothing can travel faster than light and nothing with mass can travel at the speed of light.

    I say with todays knowledge because physics is a living science which changes as new discoveries are made. Some of Einsteins findings overturned Newtonian physics. Perhaps, some day, far in the future, someone elses theories will overturn Einstein.

    I want to hear if there is any logic to this idea.

    Imagine that you are in an infinitely large movie theater. When a certain frame occurs, you decide to stop time and move farther away from the movie screen and start time again. Because the light needs an infinitesimally small period of time to travel through the space, would it not appear that the same frame in the movie happened again to the observer?

    Now, i know im breaking boatloads of rules, like stopping time. But in a similar vein, what if the observer could travel faster than the light being projected from the movie screen?

    The frame in the movie would occur; the observer would travel faster than light to surpass the frame, then turn around and watch the frame pass him again.

    This is all just theoretical, seeing as how we are nowhere near traveling even close to the speed of light, let alone faster than it, if it is possible at all...

    In theory, does my idea make sense?
  2. jcsd
  3. Oct 6, 2008 #2
    I doubt very much that a person could ever move faster than the speed of light.

    I have however read past posts that say things along the lines of, this isnt quoted btw just roughly:

    A ship for instance could possibly travel faster than the speed of light or distort time to seem faster by compressing everything at the front and expanding at the back.

    I may just be talking nonsense here but that all i can remember lol.
  4. Oct 6, 2008 #3
    Well, in answer to your first idea, yes, I think that could happen. However, the idea that the speed of light is the greatest possible velocity is a corner stone of relativity and it is likely that this were proven to be incorrect certain aspects of relativity would have to be rectified. However, there are certain problems which GR cannot explain and therefore it is likely that there will be additions to the theory in the future.

    Your second idea would work in theory if you could stop time, which you cannot. You certainly cannot move through "stopped time." - therefore this would never happen.

    Your idea of moving "faster than light" would also, I think, not work (even if faster than light travel was possible) as special relativity states that the speed of light is constant to all frames of reference. Therefore the "frame" of the person moving "faster than light" would
    observe the light from the screen to still be at 300,000,000 m/s and the light would therefore still reach them just once.

    I'm not 100% sure about it, as it is all hypothetical, but that's the best answer I can give.

    Yes, this is called the Alcubierre drive and takes a similar concept to the "Warp Drive" in Star Trek. The idea is that "tropical matter" (whatever that is) would warp space time around an object in such a way (contract space-time in front, expand behind) that the object rides a sort of "bubble" of space time. This bubble would then be able to "move" faster than the speed of light since the ship itself is not moving faster than the speed of light, it is simply being "carried along for the ride," as it were.

    I think that's the general idea but reading the wikipedia page would probably give a better impression for you:
  5. Oct 6, 2008 #4
    Traveling faster than the speed of light constitutes some practical problems, besides having infinite mass. There are quite a few objects in space and all it takes is one asteroid, planet or sun to kill off your multi billion dollar "faster than speed of light" ship. Since you're traveling faster than the speed of light, you have no way to navigate (or no current known way of navigating).

    But there are a few ideas (theoretical) that currently exist to make deep space travel possible. The most prevalent in science fiction is worm hole technology. Basically the idea is that you bend space and time to go from point a to point b pretty much instantaneously. The best example of this is to take a sheet of paper and mark two different corners a and b. Now fold the sheet of paper so the points a and b touch. Worm hole theory comes from quantum and the idea of energy levels (IE an electron is never between energy levels, so current theory indicates that the electron some how "transports" from energy level to energy level in the atom).

    Relativity is also on our side in that as you approach the speed of light, the time with respect to the passengers on the ship decreases per gigameter traveled with respect to the time on earth. So, in other words lets say that it takes 10 years for a ship to travel from point a to point b. But the actual time experienced by the crew of the ship is only like one year (it varies with respect to your velocity).

    Long story short, there are theories that support deep space or intergalactic travel. But, there are quite a few problems that need to be solved first which, hopefully, LHC will shed some light on. Unless there is a major (and i mean MAJOR) advancement in the way we think about the universe and our "place" in the universe, I highly doubt we will see deep space exploration with manned spacecraft in our lifetime.
  6. Oct 6, 2008 #5

    George Jones

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    In this thread, people are talking about using warp drive to "travel faster than light." These are interesting, but very, very speculative concepts. For another thread on wormholes, see


    For a technical review of wormhole and warp drive spacetimes, see


    The speed of light is an absolute speed limit in the following two senses. Suppose that I travel to planet A using one of these speculative ideas. At some time during the trip, I can fire a laser in a direction such that the laser light reaches planet A before I do.

    Also, if, at any time during my trip, I measure the speed of any massive object near me, I will find this speed to be less than the speed of light.
  7. Oct 6, 2008 #6
    Perhaps, but not by "much." Just as Einstein did not overturn Newtonian physics in the regimes in which it was known to be valid, it seems vastly unlikely that Relativity will ever be overturned in the regimes in which it is known to be valid. Newton did not get cast into the dustbin when Einstein came along; the vast majority of physics is still Newtonian. Relativity will almost certainly not be entirely trashed either, because it is always so right when predicting outcomes of experiments now. Whatever theory supplants it must have Relativity as one of its limits, just as Newton's theory of motion is the low-energy limit of Einstein's. I say this because admitting that Relativity is probably wrong in certain regimes that we have been unable to test does not give carte blanche to think that anything goes.

    No, it's not theoretical. The Theory implies that your scenario is impossible.

    But I think that we can be confident that the light from the movie screen follows a certain trajectory through spacetime, and if you're there to receive it (however you get there), then there's nothing to stop you from doing so.
  8. Oct 6, 2008 #7
    Can you explain this in more detail, please?

    I am assuming that faster than light travel will be possible at some point in the future. I think that is my only assumption. Everything else to me seems logical.

    I should have been clearer on this earlier though. I was wondering whether traveling faster than light would also constitute traveling backwards in time. I know that there are various theories on faster than light travel, but im assuming that it is possible.
  9. Oct 6, 2008 #8
    I mean only that you are posing a scenario that current theory says is impossible, and since theoretical predictions are the way scientists answer questions, it is difficult to figure out how you want people to answer the question.

    In other words, your hypothetical theory in which it is possible to exceed c breaks the currently known rules. And if it breaks that rule, it can break any, and probably will. Thus it is impossible to answer the question scientifically. Any answer you get will be metaphysics.

    Now, Relativity does permit wormholes, and if you do this travel through wormholes, then sure, you can see the frame as many times as you care to by wormholing to more and more distant regions of the universe.
    Last edited: Oct 6, 2008
  10. Oct 6, 2008 #9
    oh! i used the word theory improperly.

    i meant to say hypothetical.

    my apologies.

    thanks for fixing that ZikZak.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook