The sneaky answer is to say that since it is impossible for us to go faster than the speed of light, then the problem does not arise!
The speed of light appears to be a odd barrier – non of the particles we know of can go faster than light (photons travel at precisely that speed).
Then there are tachyons, theoretical particles that travel faster than light speed. I don’t know much about these apart from the fact that though they haven’t been detected yet and that they cannot travel slower that the speed of light.
So it seems to be a barrier that cannot be crossed. Weird!
If you were made of light, and you went on a trip around, say, the solar
system, then your watch would show that less time has passed since you left
earth, compared to one of your friends who stayed behind.
So it is your friend that looks like he travelled forwards in time from your
point of view.
Time is relative to any observer, so to get back to the present, you just
need to change the time on your watch!
I’m no expert, but I believe the current consensus is that i) you can’t go faster than light and ii) if you could you would go backward not forward in time.
I think getting back from the future is a problem, but I can’t quite remember if this is what I read in a Steven Hawking book, what I heard him say at a talk, or whether I just made it up myself. 🙂
I love the idea of time travel, and I think it would be great (not least for scientists interested in evolution) if we could go back in time and get more information about the past. At least fossils, rocks, writing and memories can go forward in time to bring us messages from the past.