A popular opinion would be that if we ever "invent"
time travel, than we should be seeing
time travelers now, coming from the future to help us with our problems, etc.
But if you consider the possibility
the beating of a butterfly's wings in China causes a hurricane in Florida, it may become clear to you messing with time would be a
very dangerous thing, and outlawed once time travel is possible.
Personally, though, I believe time travel as we know it from sci-fi movies and the like is impossible, simply for the fact that...
Now is only a memory. You cannot return to a point that has once been. The past can be remembered and documented, but never returned to. The future has not even happened yet, so it can not be traveled to either.
It is quasi-known that "time" can be warped, as in the cases of light speed and black holes. It can supposedly be "slowed down". But that is not time travel. And those are of course still theories until they can be backed up by solid evidence.
You may be able to construct a processor able to compute the future, and make it known, or calculate the past, but you can never, ever go forward or backward in what we call "time".