Zeitreisen und schwarze Löcher…

You’d have to travel around one or in a gravitational field so strong that time dilates, you don’t technically have to go into one. Although, it would most certainly be a one way trip, however you look at it.

While some theoretical models suggest rotating black holes aka Kerr holes could contain closed time like curves that theoretically allow for traveling to the past, these places are believed to be unstable and physically inaccessible and even if you could somehow access it, the universe has a way of stopping any information from going to the past and breaking causality, there is always something, physicists have tried (with equations), trust me.

Every event has a cause, and effects cannot precede their causes. The universe ensures this order through physical constraints most notably the speed of light, which prevents information from traveling faster than light and breaking the temporal order of events. 

While some interpretations of quantum mechanics or like wormholes suggest ways to circumvent this, wormholes are very unstable and collapse immediately when something enters.

You could travel to the future, in fact, if you fell into a black hole, you would see the entire future of the universe happen and when you reached the singularity, you would reach, from your perspective, the end of time itself. That’s at least what Einstein’s general theory of relativity states.

However, black holes are increasingly considered quantum, or „macroscopic quantum,“ objects and we all know what happens to Einstein’s theory on that scale.

So yes, you could travel to the future, however, it would most definitely be a one way trip and you couldn’t relay any information because it would break the law of causality.

In other words, you are allowed to go to the future, but sharing what you saw and know is forbidden.

Quite poetic, if you ask me.