Time Travel

[kags]

I realise there have been questions about time travel before, but not for a few years, and this is something I can't get my head round. If time travel were possible, would it be possible to travel back in time and influence events? (a prize for guessing which film I watched yesterday - in it events in the present were being influenced by things from the future that had been shaped by those events)

[Moog]

If it was Donnie Darko then I highly recommend you visit the website www.donniedarko.com. What you're describing is the time travel paradox, if you could travel back in time and for example kill your Mum what would happen and has been used as a key arguement against the possibility of time travel [another being the apparent lack of visitors from a future time when time travel has been perfected]. There must be hundreds of websites out there about this, but I seem to remember that Einstein's theory of relativity proved that time travel is not possible in the sense of travelling back in time, however we are all travelling forwards through time if you think about it!

[Moog]

Have a look at this: http://www.rubak.com/article.cfm?ID=16

[Moog]

Was it Donnie Darko, because if it was then the film is not really about time

[Moog]

... travel

[kags]

actually it was Terminator 2 - haven't seen Donnie Darko but maybe I should

[LeMarchand]

You might find this article interesting (it's specific to the first 2 "Terminator" movies): http://www.mjyoung.net/time/terminat.html . There are articles about a lot of time travel movies elsewhere on the same site. Personally, I see a good deal of sense in the theory Moog mentioned: if time-travel is possible, where are the travellers? The other possibility (assuming time travel is possible) is that any changes simply create a new timeline: for example, if I found your question offensive and jumped back in time and killed you before you posted the question (not that I do or would!) then it would create a new timeline where no-one sees your question, but hasn't benefitted me as I return to my original timeline where your question was posted (hence no paradox). I suppose that if it were possible to "side-step", I could go to the question-free timeline, but then there would be two of me.

[anthomson]

Moog was correct about Einstein, to travel backward in time you would have to travel faster than the speed of light but this is not possible since you would have infinite mass ( and require infinite energy to move you at this speed ). Time is relative in that it moves forward at different rates. You can age quickly or age slowly or even stop ageing althogether (if you fall in to a black hole) - but you never age backwards.

[incitatus]

There is aan implicit possibility for time travel in using a massive spinning cylinder, apparently. Anyway, according to Stephen Hawking, Britains answer to Davros, time travel is technically possible, but paradox isnt. What he says is that paradox would represent a high energy state of possibility, and that phase space, like normal space, would not support the high energy state for long before relaxation took place. The upshot of which is you might be able to shoot your mother but she would unshoot herself within milliseconds because the universe takes a dim view of that sort of thing. As for the "where are the time travellers" argument, why should they reveal themselves? it would be an end o any normal existence...."what are the winning lottery numbers?" "Who do i marry" "who wins the election" Yould go daft.

[Moog]

Hawking isn't very relaible on time travel as he originally took the Einstein line saying it was not possible, then changed his mind saying it is theoretically possible, but a lot depends on your definitions.

[darth vader]

Einstein said time travel was theoretically possible but only in a relative sense :-) what he meant was that you could slow time down (to stop it would mean travelling at the speed of light which others have correctly said is 'currently' impossible), but only in an observatory fashion - you cannot affect what has already happened. I think this may explain why time travellers from the future may have travelled back to our times, but only in an observatory sense therefore we are unaware they travelled back here.

[darth vader]

please note that as all answers here suggest, the subject is very much still an unknown area and only answerable by hypothesis. Unless YOU are from the future in which case who wins the 3.30 at Kempton please?

[Hippy]

If it's Wednesday then it must be Magic.