The marvels of human mathematics:

Could our universe be located within the interior of a wormhole which itself is part of a black hole that lies within a much larger universe?

The mathematical human (Nikodem Poplawski) explains:
Because Einstein's general theory of relativity does not choose a time orientation, if a black hole can form from the gravitational collapse of matter through an event horizon in the future then the reverse process is also possible. Such a process would describe an exploding white hole: matter emerging from an event horizon in the past, like the expanding universe.
I love this so much: "...matter emerging from an event horizon in the past." If I am reading this correctly, and there is a good chance that I am not, it means the stuff we are made of is much older than we can even imagine. The current and accepted theory has us at about 13 billion years. This new and spectacular theory makes matter much, much older than that.