05-29-2003, 02:29 PM
Hi,
In a nutshell, time-traveling requires existance of wormholes.
Not quite. Wormholes do provide some of the models which permit time travel. So does an infinitely long massive rod (and the "infinite" requirement is there because we can't handle the equations in three dimensions, thus can't handle end effects. A suitably long rod with correctly shaped end pieces would probably work.) So do two strings which are moving relative to each other. And the possibilities in M theory are pretty well wide open.
If time-traveling happens, you have a bunch of paradoxes in your hands, like for instance the `killing your grandpa before being born' thing. There are only two plausible ways out.
1. A wormhole is a gateway to another universe, so when you time-travel, you're also traveling between universes.
2. Wormholes simply don't exist and it is impossible to time-travel, period.
Nonsense. Not that these two aren't "plausible" but that they are not the only two ways out. There are closed loop theories of time travel (and the universe might have been in such a loop prior to the "big bang". That permits a universe with a past that is infinite and yet bounded.) Indeed, any attempt to apply our present "logic" in the question of time travel is as likely to prove wrong as Newton's application of his "logic" on the questions of space and time. It is intuitively clear that if two people have relative motion along the path of a photon, they will measure a different speed for that photon. Unfortunately, intuition is wrong. All the arguments for or against time travel are nothing but intuition.
Nowadays, it is common belief among scientists that wormhole formation should get some obstruction from Quantum Gravity effects.
As you pointed out, quantum gravity is not a field of study. It is a postulated field of study. Until either someone figures out a new way to re-normalize the fields (and that seems to be impossible since the infinities seem to be essential) or comes up with a totally different approach, all that can be said about quantum gravity is that people "believe" it will behave one way or another. Nature has had scant concern for the beliefs of physicists till now, I doubt that that will change in the future.
Sorry, I have as much respect for the prevalent opinion on time travel (which includes FTL travel) as I do for the Copenhagen Interpretation. Which is to say, nearly none.
--Pete
In a nutshell, time-traveling requires existance of wormholes.
Not quite. Wormholes do provide some of the models which permit time travel. So does an infinitely long massive rod (and the "infinite" requirement is there because we can't handle the equations in three dimensions, thus can't handle end effects. A suitably long rod with correctly shaped end pieces would probably work.) So do two strings which are moving relative to each other. And the possibilities in M theory are pretty well wide open.
If time-traveling happens, you have a bunch of paradoxes in your hands, like for instance the `killing your grandpa before being born' thing. There are only two plausible ways out.
1. A wormhole is a gateway to another universe, so when you time-travel, you're also traveling between universes.
2. Wormholes simply don't exist and it is impossible to time-travel, period.
Nonsense. Not that these two aren't "plausible" but that they are not the only two ways out. There are closed loop theories of time travel (and the universe might have been in such a loop prior to the "big bang". That permits a universe with a past that is infinite and yet bounded.) Indeed, any attempt to apply our present "logic" in the question of time travel is as likely to prove wrong as Newton's application of his "logic" on the questions of space and time. It is intuitively clear that if two people have relative motion along the path of a photon, they will measure a different speed for that photon. Unfortunately, intuition is wrong. All the arguments for or against time travel are nothing but intuition.
Nowadays, it is common belief among scientists that wormhole formation should get some obstruction from Quantum Gravity effects.
As you pointed out, quantum gravity is not a field of study. It is a postulated field of study. Until either someone figures out a new way to re-normalize the fields (and that seems to be impossible since the infinities seem to be essential) or comes up with a totally different approach, all that can be said about quantum gravity is that people "believe" it will behave one way or another. Nature has had scant concern for the beliefs of physicists till now, I doubt that that will change in the future.
Sorry, I have as much respect for the prevalent opinion on time travel (which includes FTL travel) as I do for the Copenhagen Interpretation. Which is to say, nearly none.
--Pete
How big was the aquarium in Noah's ark?