# Faster than the Speed of Light

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?

pervect
Staff Emeritus
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.

As far as your book goes, the author probably wrote it to make money :-).

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

Magueijo doesn't buy it. His VSL (Varying Speed of Light) presupposes a speed of light that can be energy or time-space dependent. Before you declare that he's out of his mind, understand that this man received his doctorate from Cambridge, has been a faculty member at Princeton and Cambridge, and is currently a professor at Imperial College, London.

Has anyone read this book at all??

Awner!

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.

:uhh:

"There are 3 types of knowledge in the world, knowledge, understanding, imagination."

pervect
Staff Emeritus
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" http://www.houstonbookclub.com/VSL.htm [Broken]
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".

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I believe that the author did this because of inflation