Time travel works like this:

You can't go forward, only back.

The future is at best unknowable, at worst, non-existent. The best temporal mechanics minds in the world cannot figure out why we move forward from moment to moment on our own, but can't jump ahead in the sequence a bit. The future remains unknowable and unvisitable.

The past, however, is fair game. Thing is, no one ever returns from a jaunt to the past. Old journals have turned up, detailing trips of hundreds of years, but never an exp