Time travel is almost surely not possible
I’m practically certain that only the present moment exists and thus time travel would be impossible. If history and/or the future existed, it would take an incredible amount of copies of the universe to record all the needed data and to think that there would be 1 copy of the universe for each nanosecond or whatever is quite insane. Or even if the universe had an optimized way to record that data, like in a compressed movie format, it would still take a crap load of space to record it and the data would probably have to exist outside the universe. NASA etc. seem to have calculated that with 98% chance the universe is flat and not a sphere, so where would the data be and how very unlikely it would be for us to be able to access it?
Many people also argue that if time travel was possible, we would see time travelers every now and then but they fail to understand that it would probably have to be doable only through some physical device that has to have existed and be turned on for time travel to be possible to that time.