What makes time travel possible?

Answer 1

It's not, exactly. Travel into the future is possible, at least theoretically, and in fact we're all doing it at one second per second. You could increase the rate by accelerating in space; according to the theory of relativity, this has the effect of making time pass more slowly for you, which is virtually the same thing as traveling into the future. At the speed of light, all times are the same time and all places are the same place.

As a practical matter, any speeds we can achieve have a negligible effect on time, but the theory is sound.

Traveling into the past is thought to be impossible because it would violate causality. As an illustration, consider the question "what if you went back in time and killed your grandfather before your father was conceived", also known as the Grandfather Paradox... you prevented your father from being born, so you can't have been born either, but if you weren't born you couldn't have killed your grandfather, so your father was born and thus so were you, except then you could go back and kill your grandfather...

The easiest solution to the problem is to assume that anything that violates causality is impossible.

Additional evidence that time travel into the past is impossible comes from, again, relativity. Traveling faster than light is effectively traveling into the past, and faster than light travel is impossible, so it makes sense that traveling into the past is also impossible.

Answer 2

Nothing we know of; time travel is currently impossible given what we've got but scientists believe they CAN make it possible if they find something faster than the speed of light.

Answer 3

I wish it was possible :( I don't think the scientist's have tried X(