[MikeS (OP)]

Is the Universe a giant black hole? How can we tell? Recall John Wheeler's one-sentence summary of general relativity: "Spacetime tells mass how to move; mass tells spacetime how to curve."

Maybe our universe is a black hole in a larger universe.  If we assume that mass continues to accelerate toward the singularity after crossing the event horizon then it is traveling backward in time.  From our perspective inside the event horizon it is travelling forward in time and everything outside the event horizon is traveling backward in time.  What looks like expansion to us (if we live in a small enough patch) would look like contraction toward a singularity from outside the event horizon.

[loose_nukes]

Is the Universe a giant black hole?

I doubt it my friend.................For one thing, our universe is expanding with an ever increasing  rate. If we were inside a black hole, one would think it would be contracting. And also, while a black hole the size of our universe would make it possible for us to survive within the Scwartzchild radius for quite some time, eventually we would have to contend with the singularity. And that being the case, where would you surmise that this singularity might be? No, I don't think we are living within a universal black hole...................

[Emc2]

no one at all, knows exactly what happens to matter after it passes the event horizon.

 Math and Physics do not and can not say the results...
all that is available is best guesses, until we get better math and or physics, ot understanding some other avenue.

 So you may be right, it is possible, but do not know the "probability" of it.

  Black Holes may one day become familiar to us, and on that day, many doors may also be opened.,  and in other areas also.