I don't think it is possible to travel backwards in time, and if we could do it, we likely wouldn't be able to change anything. Like going back in time to stop our grand parents from ever getting married would make us stop existing, but since we going back into the past is our present, it shouldn't change anything. The only thing we can do right now is travel into space and make the time run slower for us than for the people on earth - like in the movie Interstellar.