Asked by Sebastian Paul
The simple answer is that we don’t know. A black hole is defined as a region of spacetime from which extremely strong gravity prevents anything, including light, from escaping.
We know that matter falling into black holes is no different from the matter which can be found lurking around the rest of the Universe. However, the closer we get to the centre of a black hole, the faster our understanding of physics breaks down. Thanks to General Relativity, we think we understand what happens in this extreme gravity and with the help of Quantum Mechanics, we can make an intelligent estimate as to what happens at smaller, microscopic scales. But if the two theories are combined – like they would be at the centre of a black hole – they break down, leaving us with no idea as to what’s going on!
To get around the problem, astrophysicists need a theory of gravity that is compatible with Quantum Mechanics that might just describe the physics inside a black hole. At the moment though, no such model exists but physicists are working on it.
Image credit: Alain r