What happens in a black hole?

Answer

Actually, we don’t know.

The simplest thing we can say is that in a black hole everything falls down, because nothing can stop its own attraction. To an observer very far away, all matter is compressed into a point; but that observer is outside the black hole, and can’t see the point. For an ‘observer’ inside the black hole, time is stretched by the great gravitational force, and in his sense of time it takes an infinitely long time before everything is in a point.

In this picture it is therefore important that for gravitational forces as high as a black hole, we know of no physical mechanism that can counteract that attraction. Perhaps such a mechanism does exist, and we don’t know it, precisely because we have never been able to imitate such situations. That is partly what makes black holes so mysterious, and also popular: it is exotic, far from our experience, but that is precisely why we may never fully know.

If we don’t know something, we often dream about it. It is believed that the mathematics of black holes can be very complicated, and have many curious solutions; such as ‘wormholes’ that allow you to travel through space-time via a black hole. Whether this actually occurs in nature that we can observe remains to be seen. It’s all very unlikely if you ask me.