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Time travel when velocity> light speed

  1. Aug 25, 2009 #1
    Not sure if this will have anything to do with quantum mechanics.. but...
    Ok so if you're travelling faster than light speed, then what do you see?

    I'm not talking about the whole doctor who scenario, its like travelling faster than sound, if the jet pilot is traveling faster than the sound it makes, then he/she wouldn't hear that sound. Would this be of a similar case with your eyes?
  2. jcsd
  3. Aug 25, 2009 #2

    Doc Al

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    Staff: Mentor

    No massive body can travel faster than light, so the question isn't meaningful in light of current physics.
  4. Aug 25, 2009 #3


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    There are hypothetical subatomic particles which travel faster than c. As a group they are called tachyons. Just like our sublight particles cannot ever reach or exceed c, tachyons can never slow down to or slower than c. This means they are forever cut off from our universe.

    That being said, a tachyon is equivalent to a regular subatomic particle travelling backward through time.

    It won't do you much good though, since they still do not violate causality. Wiki has a note on http://en.wikipedia.org/wiki/Tachyon#Causality".
    Last edited by a moderator: Apr 24, 2017
  5. Aug 25, 2009 #4
    Remember also that at speed .99999999999999999999999999999999999C an observer STILL measures light at speed c, and color from a light source in his reference frame is normal (ok for reading a book).

    But at such incredibly high speed, light coming toward you from opposite the direction of your velocity appears shorter in wavelength and light coming from the rear direction is looooooooooooonger in wavelength.....relative to a "stationary" source...both out of the range of visible light. You can check out such effects by looking at references for red shift and blue shift....
    Last edited: Aug 26, 2009
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