25th October 2011, 01:24 PM
Yeah evidence of time travel............depends on the nature of time/reality.
Last I heard physicists currently claim that traveling into the future is possible, but not into the past.
But based on the fact that the basic laws of the universe are up for a major re-jig (speed of light, universal constant not being constant, quantum world vs string theory) I'd wait and see on that one.
The problem (obviously) stems from information sent into the past will alter the conditions that created the information, hence changing the information. Thus you get a spiraling feed-back system like noise feedback at a gig.
I suspect that sending information/energy into the past would also break the (current) law of conservation of energy.
However, as with the speed of light (many things do travel faster than it) many theoretical particles are thought to travel back in time. If information could be attached to these particles you've got a working telephone to the past or a device that destroys the universe.
But..........to understand the ins and outs of possible time travel you need to understand time.
Its fairly easy to slow down (your own) seconds, traveling into the future is actually (according to current theory) easy. All you need is a spaceship that can travel very fast (close to the speed of light). I think the maths works out that if you travel to Alpha centuri (I think its a light year away) at close to the speed of light, then come back, it takes you just over two years..........but when you get back 50 years have passed on earth. Hence you've traveled into your own future without causing any nasty paradox.
Butif you can move space time in one direction and travel close to the speed of light in the other, your relative speed can be faster than light. Can't remember why but some claim that this can be used to send information into the past. Problem is you need something like a spinning black hole to spin space-time.
The big interesting thing (to me) is that if time-travel into the past is possible sometime in the future, it is possible in all time - you just have to nick a device. But of course people claim that if this was so we'd be aware of these travelers.
Kevin is correct though (in one theory of time travel) that some (including Asimov and S hawking I think) claim that there wouldn't be any evidence as everyone (including the traveler) will only be aware of their current time (having no other frame of reference)............makes me think where did the previous information from the previous time-line go; physicists get upset if information is destroyed.
I like to think of time as an infinite number of tree-like webs of paths of possibles. A single person in time is only aware of one path which seems linear (birth to death). But an observer free of time would see the web of possibles and could travel to any point in any web. This would of course alter the paths of several (or hundreds) people plodding on their linear paths.........but as they are not aware of their own futures (the paths they went along in the travelers past) nothing will have changed for them and they will continue merrily along their own linear time-paths but into a completely different future.
So thats ok, no paradox's there.........and interestingly creates a universe (or multiverse) of parallel worlds - isn't this predicted in string theory?
Ah but.....you cry, what if the traveler goes back in time and kills their own ancestor or even them self? Surely thats a paradox? The travelers present is changed by what he doe sin the past.
No, its not. The traveler is free-of time (otherwise he/she couldn't travel back in it) and not plodding along their own linear time-path. All that does is send some (or hundreds) of people along a time-path where the traveler isn't born.
Ah but what if the traveler goes back in time and kills a rival from their own present, surely that would create a paradox. Simple answer is, they can't.
If the traveler tries all that will happen is he/she goes back into the past...kills the rival (sending people along a new time path). If the traveler then returns to his own 'present' (although the term doesn't really apply), nothing will have changed as he/she has returned to the time-path where the rival wasn't killed.
The traveler would be better off traveling to the parallel time-path where his rival wasn't born if he/she wanted to feel smug and satisfied.
Last I heard physicists currently claim that traveling into the future is possible, but not into the past.
But based on the fact that the basic laws of the universe are up for a major re-jig (speed of light, universal constant not being constant, quantum world vs string theory) I'd wait and see on that one.
The problem (obviously) stems from information sent into the past will alter the conditions that created the information, hence changing the information. Thus you get a spiraling feed-back system like noise feedback at a gig.
I suspect that sending information/energy into the past would also break the (current) law of conservation of energy.
However, as with the speed of light (many things do travel faster than it) many theoretical particles are thought to travel back in time. If information could be attached to these particles you've got a working telephone to the past or a device that destroys the universe.
But..........to understand the ins and outs of possible time travel you need to understand time.
Its fairly easy to slow down (your own) seconds, traveling into the future is actually (according to current theory) easy. All you need is a spaceship that can travel very fast (close to the speed of light). I think the maths works out that if you travel to Alpha centuri (I think its a light year away) at close to the speed of light, then come back, it takes you just over two years..........but when you get back 50 years have passed on earth. Hence you've traveled into your own future without causing any nasty paradox.
Butif you can move space time in one direction and travel close to the speed of light in the other, your relative speed can be faster than light. Can't remember why but some claim that this can be used to send information into the past. Problem is you need something like a spinning black hole to spin space-time.
The big interesting thing (to me) is that if time-travel into the past is possible sometime in the future, it is possible in all time - you just have to nick a device. But of course people claim that if this was so we'd be aware of these travelers.
Kevin is correct though (in one theory of time travel) that some (including Asimov and S hawking I think) claim that there wouldn't be any evidence as everyone (including the traveler) will only be aware of their current time (having no other frame of reference)............makes me think where did the previous information from the previous time-line go; physicists get upset if information is destroyed.
I like to think of time as an infinite number of tree-like webs of paths of possibles. A single person in time is only aware of one path which seems linear (birth to death). But an observer free of time would see the web of possibles and could travel to any point in any web. This would of course alter the paths of several (or hundreds) people plodding on their linear paths.........but as they are not aware of their own futures (the paths they went along in the travelers past) nothing will have changed for them and they will continue merrily along their own linear time-paths but into a completely different future.
So thats ok, no paradox's there.........and interestingly creates a universe (or multiverse) of parallel worlds - isn't this predicted in string theory?
Ah but.....you cry, what if the traveler goes back in time and kills their own ancestor or even them self? Surely thats a paradox? The travelers present is changed by what he doe sin the past.
No, its not. The traveler is free-of time (otherwise he/she couldn't travel back in it) and not plodding along their own linear time-path. All that does is send some (or hundreds) of people along a time-path where the traveler isn't born.
Ah but what if the traveler goes back in time and kills a rival from their own present, surely that would create a paradox. Simple answer is, they can't.
If the traveler tries all that will happen is he/she goes back into the past...kills the rival (sending people along a new time path). If the traveler then returns to his own 'present' (although the term doesn't really apply), nothing will have changed as he/she has returned to the time-path where the rival wasn't killed.
The traveler would be better off traveling to the parallel time-path where his rival wasn't born if he/she wanted to feel smug and satisfied.