Would faster than light travel imply time travel?

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Offline thedoc

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gorjenk1 asked the Naked Scientists:
   
Why is it said that to travel faster than light is to go back in time?

If I could travel from Earth in 2012 to the next nearest star, 4 light years away, at twice the speed of light, I would arrive at the star in 2014. On Earth the star would be seen as it was in 2010, but I would see it as it is in 2014, so as far as I can see I have not travelled back in time.

What do you think?
« Last Edit: 17/07/2012 08:30:01 by _system »

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Offline Soul Surfer

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Re: Would faster than light travel imply time travel?
« Reply #1 on: 17/07/2012 08:34:09 »
Yes and that is precisely why it never happens in our macroscopic world.
Learn, create, test and tell
evolution rules in all things
God says so!

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Offline imatfaal

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Re: Would faster than light travel imply time travel?
« Reply #2 on: 18/07/2012 17:59:01 »
If you agree Special Relativity - which is amazingly well tested, then if you have faster than light transmission  you cannot have causality as we presently understand it.  Effects would happen before causes.   Secondly, the equations show that macroscopic objects with mass cannot reach let alone surpass the speed of light.

So anything, information, radiation of some sort, massive or massless particles travelling at over the speed of light means that our laws of physics are almost irreconcilably wrong - that in turn means that you cannot use those same laws to predict what will happen in your impossible situation.

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