The new model isn't the first to propose that other universes exist inside black holes. Damien Easson, a theoretical physicist at Arizona State University, has made the speculation in previous studies.

"What is new here is an actual wormhole solution in general relativity that acts as the passage from the exterior black hole to the new interior universe," said Easson, who was not involved in the new study.

"In our paper, we just speculated that such a solution could exist, but Poplawski has found an actual solution," said Easson, referring to Poplawski's equations.

First off, this solution is stable, which means -- in principle -- that it can exist. Second off, it is possible that this can be generalized to make the space inside of it do other things besides remain completely static (like expand or contract). And third off, it brings up this amazingly interesting possibility that not only might our Universe be the inside of a black hole, but that each black hole that's come to exist in our Universe may house its own miniature Universe inside of it!