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Author Topic: Time travel impossible?  (Read 4425 times)

Offline Eric A. Taylor

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Time travel impossible?
« on: 03/06/2010 11:24:21 »
I think I see a problem with time travel into the past.

Energy cannot be created or destroyed. This means that every single bit of energy in the entire universe came into being at the moment of the big bang.

We know that, because of E=MC2 that matter and energy are really the same thing, so the matter/energy that makes up your body has existed from the moment of the big bang.

Think of a table covered in coins. Some coins are heads up, others are tails up. You can flip coins all you want (change matter to energy and energy to matter) but you can't add coins or take any away.

Were you to travel back in time you would essentially be creating energy in the past (something not possible) because the energy/matter that makes up your body is already there (in the past) before you travel there (even if it's not yet you). There would be some place where this energy is waiting to become you, and that energy would ALSO be you (the traveler).

Further you cannot even sent information back in time (getting next weeks lottery number would be good). To transmit data you need it carried by energy. You could send a radio transmission, but the energy making up the used in the transmission cannot be sent back any more than you could.

Am I off base here?


 

Offline graham.d

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Time travel impossible?
« Reply #1 on: 03/06/2010 12:29:55 »
I am not sure Eric. I think there are the problems of causality being breached - what if you shoot a parent before you were conceived etc. This is sometimes countered by ideas of a multiverse.

Energy conservation may not be right. As was pointed out to me in another thread, it is really energy-momentum that is conserved and it seems there are cosmological theories that do not conserve energy - I think the Dark Energy concept does not conserve energy. In any case, even without this idea, any energy conservation would be in space-time not just space. It is not clear that moving back in time would violate energy conservation. I think, though, this would have to be tied in with a multiverse idea, then there are some issues with energy (quite a lot for an infinite set of universes).
 

Offline Eric A. Taylor

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Time travel impossible?
« Reply #2 on: 04/06/2010 00:40:58 »
I am not sure Eric. I think there are the problems of causality being breached - what if you shoot a parent before you were conceived etc. This is sometimes countered by ideas of a multiverse.

Energy conservation may not be right. As was pointed out to me in another thread, it is really energy-momentum that is conserved and it seems there are cosmological theories that do not conserve energy - I think the Dark Energy concept does not conserve energy. In any case, even without this idea, any energy conservation would be in space-time not just space. It is not clear that moving back in time would violate energy conservation. I think, though, this would have to be tied in with a multiverse idea, then there are some issues with energy (quite a lot for an infinite set of universes).

Why does everybody want to kill their parents. All you need to do is prevent them having sex at the time you were conceived. If your mother misses becoming pregnant on the cycle that made you, the egg that became you will be flushed with her period and you will not be born.
 

Offline Geezer

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Time travel impossible?
« Reply #3 on: 04/06/2010 04:27:50 »
Time travel is not impossible. It depends on the extent. The greater the extent, the more difficult (i.e., requires a lot of energy) it becomes.

"All" you have to do is put the relevant "stuff" back where it was at a particular moment in time. Thereafter, who could possibly know the difference?

You might even get away with restoring a subset of the Universe to a former state. As long as that subset does not alter a future state external to the subset too dramatically, there may be no conflict.

If you think this is baloney, consider what happens when you replay any recorded event from the past.

 

Offline JP

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Time travel impossible?
« Reply #4 on: 04/06/2010 05:56:14 »
If we had enough energy, we could create a planet populated entirely by Geezers!  That is indeed a terrifying thought.
 

Offline Geezer

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Time travel impossible?
« Reply #5 on: 04/06/2010 06:14:27 »
If we had enough energy, we could create a planet populated entirely by Geezers!  That is indeed a terrifying thought.

Seems quite logical to me. Obviously, we would all agree with each other, thereby eliminating any unnecessary expenditure of energy.
« Last Edit: 04/06/2010 06:48:28 by Geezer »
 

Offline Eric A. Taylor

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Time travel impossible?
« Reply #6 on: 07/06/2010 12:22:42 »
If we had enough energy, we could create a planet populated entirely by Geezers!  That is indeed a terrifying thought.

Seems quite logical to me. Obviously, we would all agree with each other, thereby eliminating any unnecessary expenditure of energy.
But what if they're wrong? or they make a mistake?
 

Offline Geezer

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Time travel impossible?
« Reply #7 on: 08/06/2010 05:02:11 »
If we had enough energy, we could create a planet populated entirely by Geezers!  That is indeed a terrifying thought.

Seems quite logical to me. Obviously, we would all agree with each other, thereby eliminating any unnecessary expenditure of energy.
But what if they're wrong? or they make a mistake?

These scenarios are so obviously improbable that I think we can safely ignore them.
 

Offline JP

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Time travel impossible?
« Reply #8 on: 08/06/2010 05:22:11 »
If we had enough energy, we could create a planet populated entirely by Geezers!  That is indeed a terrifying thought.

Seems quite logical to me. Obviously, we would all agree with each other, thereby eliminating any unnecessary expenditure of energy.
But what if they're wrong? or they make a mistake?

These scenarios are so obviously improbable that I think we can safely ignore them.

Indeed--that would be a violation of the Geezertainty principle. 
 

Offline Geezer

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Time travel impossible?
« Reply #9 on: 08/06/2010 05:40:43 »

Indeed--that would be a violation of the Geezertainty principle.
 

Ah, good! I see you've read my paper then.
 

Offline pnorm

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Time travel impossible?
« Reply #10 on: 20/09/2010 21:30:31 »
Time Travel is definitely impossible. There's no way you'd ever manage to 'teleport' so exactly to the point in space and the time in space where you wanted to go. Also if you ever did manage to go back in time if you killed your parents there's no way that whole thread of your life could exist. Everyone who ever knew anything even a whisper of your name would need to be forgotten. So yes it could potentially happen, if you went back in time and killed your parents, everyone else except you would live. It'd probably be 'Inception'-esque where everywhere just starts blowing up around you. And then you'd wake up...

Personally, that's what I think this life is. I think this life is something tiny of something much bigger outside. A test or something. Like the Matrix. But not stupid. And outside there's something that we could never ever understand. It wouldn't be heaven it would be something better. Where anything is possible and there are no restraints so therefore my 'heaven' that I'm describing could just be you and your own memories, the ones you want and in them you can do whatever you like.
 

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Time travel impossible?
« Reply #10 on: 20/09/2010 21:30:31 »

 

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