Question

what is at the bottom of black hole

Answer 1

At the bottom of black hole u can calculate a spot that is infinitely dense and infinitely small ; a hypothetical concept called singularity

Answer 2

Well there are two convincing

1) Einstein's theory of general relativity

2) Loop quantum gravity

While Einstein's theory says that the black hole ends in a mass of infinite density called "singularity"

But the Loop Quantum gravity called LQG doesn't support this singularity theory.I don't want to make the things complicated than they already are. LQG is based upon sudden opening of a door.

LQG tells us that black holes are the doors to other universe.

If we support the general relativity then, then when we fall into black hole we won't fall down but rather travel some distance then get stopped due to singularity.

If we support the LQG , then when you fall the gravity will suddenly increase and on reaching the end of black hole you will get vacuumed out into other side.

But what is at the other side we don't know.There may be another universe, or a road to other parts of the universe that we haven't explored yet or some kind of spacetime suspension.That thing nobody really knows

Hope This helps You!