I should warn you that we are entering uncharted scientific territory. For all we know, there may be undiscovered laws of physics that govern events at the center of the black hole. But until the next Einstein comes along, let’s perform a thought experiment.
If you could survive the trip into a black hole, you might emerge in another place and time in our own universe, circumventing the first commandment of relativity: Thou shall not travel faster than light.
Nothing can move through space faster than light, but space is not near emptiness. It has properties. It can stretch and shrink. It can be deformed. And when that happens, time is deformed, too.
Einstein discovered that space and time are just two aspects of the same thing - space-time. Space-time itself can deform enough to carry you anywhere at any speed. Black holes may very well be tunnels through the universe.
On this intergalactic subway system, you can travel through the farthest reaches of space-time. Or you might arrive in some place even more amazing.
We might find ourselves in an all together different universe. But how can a whole universe fit inside of a black hole, which is only a small part of our universe? It’s another magic trick of space-time. The phenomenal gravity of a black hole can warp the space of an entire universe inside it. Our local gravity may be a drag to us, but it’s really feeble compared with what goes inside of a collapsed star.
As far as we know, when a giant star collapses to make a black hole, the extreme density and pressure at the center mimic the Big Bang, which gave rise to our universe. And a universe inside a black hole might give rise to its own black holes, and those could lead to other universes.
Maybe that’s how our own cosmos came to be.