What happens to matter and light that falls into a black hole, and what are some of the theories about the interior of a black hole?

When matter and light fall into a black hole, they are drawn towards its center due to the immense gravitational pull. This process is known as accretion. As they get closer to the black hole, they speed up and heat up, eventually forming an "accretion disk" around the black hole.

The fate of matter and light once they cross the event horizon (the boundary of the black hole from which nothing can escape) is a subject of ongoing research. According to general relativity, both should be crushed to a point of infinite density, a singularity, at the center of the black hole. However, this theory is thought to be incomplete because it doesn't take into account quantum mechanics.

There are several theories about the interior of a black hole. One is the aforementioned singularity. Another is the idea of a "quantum bounce", where quantum effects cause the matter to bounce back out before it can be crushed to a singularity. Yet another theory suggests that black holes could be wormholes to other parts of the universe.

However, these are all theories and the true nature of black holes remains one of the biggest mysteries in physics.