Whether you can go back in time is held in the grip of the law of quantum gravity. We are several decades away from a definitive understanding, 20 or 30 years, but it could be sooner than that.
Kip ThorneIf you have a wormhole, then you can turn them into time machines for going backward in time.
Kip ThorneA black hole really is an object with very rich structure, just like Earth has a rich structure of mountains, valleys, oceans, and so forth. Its warped space whirls around the central singularity like air in a tornado.
Kip ThorneClosed timelike curve is the jargon for time travel. It means you go out, come back and meet yourself in the past.
Kip Thorne