What Happens Inside a Black Hole

The second step is called spaghettification. Gravity is stronger at your feet than at your head, and the difference grows as you get closer. Your body is stretched out, and for a small black hole this happens long before the horizon.

Interestingly, things are different for enormous black holes. There, the difference in gravity across the length of a human body is small, so you can cross the horizon without feeling anything unusual. There is no wall or flash at that point.

The third step is irreversible not because you lack speed. Beyond the horizon, every possible path leads inward: moving toward the center becomes as unavoidable as tomorrow.

At the center, the equations produce a point of infinite density. In physics, infinity almost always means not a property of the world, but that the theory has been pushed beyond its range of applicability.

The problem is that both gravity and quantum effects matter there, and we still don't have a theory that combines them. Existing descriptions make predictions that cannot be tested.

A separate line of reasoning concerns the fate of information. If everything that falls in disappears without a trace, one of the basic principles of physics is violated. The debate has lasted for decades and is considered one of the major unsolved problems.

There is also an observation about time. For the person falling in, everything happens quickly, but to an outside observer, the person will appear to approach the horizon forever, slowing down and becoming redder, and will never cross it.

Both descriptions are true at the same time. This is not a paradox or an error, but a consequence of the fact that the concept of simultaneity in such conditions stops being shared by different observers.

It is also worth clarifying that a black hole does not suck things in. If you replaced the Sun with a black hole of the same mass, the planets' orbits would not change at all - it would simply become dark. Gravity depends on mass, not density.