A 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.

Closed timelike curve is the jargon for time travel. It means you go out, come back and meet yourself in the past.

If you have a wormhole, then you can turn them into time machines for going backward in time.

Gravitational waves will bring us exquisitely accurate maps of black holes - maps of their space-time. Those maps will make it crystal clear whether or not what were dealing with are black holes as described by general relativity.

A 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.

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.

When gravitational waves reach the earth, the waves stretch and squeeze space. This is a tiny stretch and squeeze. Far too small to detect with ordinary human senses.