What we don’t know about black holes:
Of all the places in the entire universe, there is probably nowhere more mysterious than the inner workings of a black hole. This is because the two most accurate theories humans have ever created disagree about what happens in the center of one.
When a large star runs out of fuel, it no longer has the energy to resist its own gravity and starts pulling in on itself. If nothing stops the collapse before a certain point, the gravity will become so strong that not even light can escape. At this point, the star becomes a black hole; a massive celestial body that has the ability to tear apart stars.
For the most part, we have a good idea for what happens in the space around a black hole. Einstein’s theory of General Relativity tells us that black holes, as well as other massive objects, bend the fabric of space and time, leading to strange events such as time dilation. But the main point of controversy isn’t what happens around a black hole, but what happens in the very middle; the singularity.
General Relativity states that if a piece of matter falls into a black hole, it gets crushed into a single point in the center. Here, any information about what fell in is completely obliterated. However, quantum mechanics tells a different story. It is a well known rule in quantum physics that quantum information can’t be destroyed, and there must be some ambiguity to a particle’s position. Clearly, something is off here.
There are a lot of different theories that attempt to solve this riddle, often involving extra dimensions or new particles beyond the Standard Model, but none of them seem to be currently testable. But it’s possible that someday, someone will give us a new, testable theory, and it will give us insight into the inner working of black holes, and maybe even the first few moments of the Big Bang.