Two quick thoughts:
- Keeping in mind that time is a human construct that measures progression throughout the universe, ‘travelling back in time’ would literally be a regression of the universe, in reverse order, to a specified marker to a system which we made up.
- Travelling into the future seems much more realistic. If your goal was to travel 100 years in the future, it would simply be a matter of figuratively (maybe literally) freezing yourself for 100 years. If there was a way to keep your body and mind in a form of stasis which allowed you to remain healthy for an extended period of time, this would effectively be time travel. Assuming that you don’t have to endure what feels like 100 years of sleep and that the transition is more instantaneous (perhaps a bold assumption), this would effectively be like taking a nap and waking up 100 years in the future. Sounds a lot nicer than most modern forms of travel.
There is however another way of looking at this. Infinite universes, infinite timelines, infinite possibilities. At that point though, I think we’re talking about inter-dimensional travel and not time travel.