Time travel

One of the most controversial subjects in science is the one of time travel. If time is the 4th dimension, ¿can we go back or forth in time?

There are many points of view about this that is hard where to start. Einstein states in his theory of relativity that travelling at the speed of light one perceives time different, slower. while for the rest of the people it is at the same rate.

However, other scientists have stated that, if time travel is possible, why isnt there any proof of any time-traveller? why hasnt anyone from the future come to us to tell us anything? this argument is similar to the paradox of "If im going to travel back in time tomorrow to say hi to myself today, why isnt there another me waving at me?".

I think that time travel is possible, however only to the future and in very tiny amounts of time. and if it is in very tiny amounts of time it seems useless to try. i think it is impossible to go back in time because if you alter the past then the conditions for us to travel back in time would make us not to exist (and on a side note, theres the theory that states that in this situation, we would be travelling to another past parallel universe, not our past universe, but thats another subject that goes into the realm of quantum physics and not philosophy)