Scientists trying to explain the universe’s accelerating expansion usually point to dark energy, which seems to be pushing everything apart.

But an Indiana University professor has a new theory, reports New Scientist: We’re inside a black hole that exists in another universe. Specifically, a black hole that rebounded, somewhat like a spring.

Some fairly mind-blowing physics is involved here, but the gist is that Nikodem Poplawski of IU-Bloomington used a modified version of Einstein’s general relativity equation set that takes particle spin into account.

Including this variable makes it possible to calculate torsion, part of the geometry of space-time. It also gets rid of the black hole singularity, a phenomenon that general relativity cannot explain.

In a study published earlier this year, Poplawski said when the density of matter reaches epic proportions, torsion counters gravity. This prevents matter from compressing indefinitely to a singularity of infinite density. Instead, matter rebounds like a spring, and starts expanding again.