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Faster than the Speed of Light

  1. Dec 16, 2004 #1
    I've two questions:

    1.Why does travelling faster than the speed of light causes time - reversible?

    2.I saw the book "Faster than the Speed of Light"(can't remember the author) in a bookshop, the author has the theory that light travels at a faster speed at the early stage of the universe than now. Why is that?
  2. jcsd
  3. Dec 16, 2004 #2


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    Guessing that you mean "why does travelling faster than light reverse time", the answer is that it doesn't.

    You might look at this thread on the board where someone asked the exact same question.

    As far as your book goes, the author probably wrote it to make money :-). The notion of varying 'c' with time is about as useful as varying the number of cm in an inch as a function of time. 'c' is just a conversion constant, there isn't any utility to varying it.
  4. Dec 16, 2004 #3
    I did a google and found the author to be Joao Magueijo, some of you probably already know him.

    From his academic record, the idea of faster than the speed of light would only damage his reputation, that is if he doesn't have a sound theory to back it up. As this passage from

    http://frontwheeldrive.com/joao_magueijo.html says

    Has anyone read this book at all??
  5. Dec 16, 2004 #4

    well, according to SR, you can never reac c. And if you did, (in my opinion), the universe would calapse on itself or something (Such as black holes). But lets say that you did obtain an infinite amount of energy, and you traveled faster than c, according to the equasion t=Tsqr(1-v^2/c^2), if v is greater than c, the number is "undividble", or perhaps the number would be really negative. But does that mean that that is how the universe operates? No. Im my opinion, one should hyphotetcly reverse time if they exxeded c, but this is very sceptical.


    "There are 3 types of knowledge in the world, knowledge, understanding, imagination."
  6. Dec 16, 2004 #5


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    I never heard of this guy before - and I obviously haven't read his book.

    There's a review of "Faster than the speed of light" here
    which doesn't sound particularly interesting to me, as I don't really care about the details of the authors personal life, or care to look at pictures of his girlfriend.

    A little more interesting (and much cheaper) is the abstract on xxx.lanl.gov here

    Having apparently had very many reactions to proposals of "varying c" similar to my remarks (one objection was even phrased very similarly, "asking whether "c" has varied over cosmic history is like asking whether the number of liters per gallon has varried"), the author manages to come up with a reasonably coherent explanation of why and when it might make sense to think about varying 'c' - when the choice of units makes the equations and analysis simpler.

    Currently, though, there appears to be very little in the way of actual evidence to support his theories - the author, though apparently fond of talking about his personal life and otherwise seeking publicity, is still honest and analytical enough not to get caught up in his own "hype".
  7. Apr 26, 2011 #6
    I believe that the author did this because of inflation
    i had a question;
    most scientists say we are unable theoretically to reach the edge of the universe unless we travel faster than light. The universe has been expanding for 13 billion years, if you ignore inflation for a few seconds. The center of the universe to the edge is therefore 13 billion light years, if we assume it has a center. So, we should be within range of the edge. But most scientists say we aren't. When we add inflation in, we must conclude that inflation was faster than the speed of light if we are within reach of the edge. As this is probably highly improbable, as a time-traveling universe would make a mess, either we are within reach of the edge of the universe, or VSL is true, according to my thoughts
    can anyone confirm or refute this?
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