Something that bugs me about time travel.

[pearcinator]

LOL THAT'S your problem with Time travel??!?

How about the fact that (multi-dimensional and other paradox-solving theories aside) even if you could travel through time you would not be able to change a single thing. Because doing so would eliminate the reason you went back in time in the first place; thus you wouldn't go back in time, thus nothing changes.

Let's say for example, you went back in time and killed Hitler when he was just a bub. Going back to the present, Hitler never existed to start WW2, therefore you wouldn't of had a reason to go back in time to kill Hitler, which results in Hitler still being alive and WW2 happening after all.

Same probably goes for travelling forward in time but I can't really get my head wrapped around it...

 

[Zack Alklazaris]

LOL THAT'S your problem with Time travel??!?

How about the fact that (multi-dimensional and other paradox-solving theories aside) even if you could travel through time you would not be able to change a single thing. Because doing so would eliminate the reason you went back in time in the first place; thus you wouldn't go back in time, thus nothing changes.

Let's say for example, you went back in time and killed Hitler when he was just a bub. Going back to the present, Hitler never existed to start WW2, therefore you wouldn't of had a reason to go back in time to kill Hitler, which results in Hitler still being alive and WW2 happening after all.

Same probably goes for travelling forward in time but I can't really get my head wrapped around it...

Earth moves its entire size in 7 minutes. 50 years would be insane... not to mention the solar systems moving, the galaxy is moving. You'd need a damn space ship just to pull it off. Then of course, you are still only one person. Our technology hasn't advanced so significantly than one man from our time can go off and kill Hitler. Not without help at the very least.

 

[McKitten]

Again, there is no absolute coordinate system. There is no good reason why a time machine would keep stationary relative to the sun, or the milky way, or the local supercluster rather than keeping stationary relative to earth.

 

[T.D.]

If we are talking fiction, then it's whatever timey-wimey nonsense you want i.e. Looper. Although I like Douglas Adams' explanation of time travel.

If however we are talking about non-fiction there are two main thoughts.

1: Parallel Universe

This one is badly explained ALL THE TIME. A parallel universe is created when either action is possible. THIS DOES NOT DIRECTLY APPLY TO HUMAN "CHOICE". Schrodinger's Cat is a good example. You place a cat in a box that you cannot perceive through, with a vial of poison that will break open at a RANDOM time. You close the box. Now there are 2 options inside the box. One where the cat is alive, and when it isn't. THIS would create a parallel universe, where one the cat is dead and the other not. The reason why THIS causes a parallel universe is because the vial will break open at a random point. I don't mean random like flipping a coin (which can be determined with enough info), but truly random means no matter how much info you have you can't predict the outcome with certainty, even if you had the Theory of Everything. Human choice i.e. giving a sandwich, going back in time, in comparison isn't random, if it was we wouldn't have psyhcologists. Obviously you could rig it so you made your choice based upon a random event.

2: Determinism

This is based on the idea of Laplace's Demon, where a creature with infinite computing power, the Theory of Everything, and knowledge about everything at one point in time, can determine the future and the past with 100% accuracy. See also Fate (although generally Fate is created by higher being in fiction). Simply, just as the past is unchanging so is the future.

Of course both of them can exist together where you have a multiverse of deterministic universes.

Personally I prefer 2, because the others imply creating energy, which is a big no-no in scientific thought right now.

Obviously this is all speculation as we don't currently have time travel (as far as I know).

EDIT: in response to recent posts about things moving in space. If we consider a bubble, inside the bubble time doesn't change, while outside including the bubble itself it does change (either forwards or backwards). This means that whatever direction Earth is moving, the bubble moves with it (as it is still affected by the laws of the Universe), and therefore the inside is too. So while yes the Earth isn't where it was 7 minutes ago, that doesn't necessarily stop the time machine moving with it.