Question: What is on the other side of a black hole?

Answer: There is no other side.

Science fiction has populated the idea that a black hole serves a portal to another world. If you could pass through, where does a black hole go? Perhaps you'll come to some other dimension, or re-emerge from some other part of the Universe?

No, a black hole only leads to death, for you, your spaceship, and another else that's unlucky enough to fall in.

Imagine you fell into a star like our Sun, there would be no question what would happen to you. The intense heat, gravity and pressure would kill you. If you compress more than 5x the mass of the Sun into a tight little area, you get a black hole. But the gravity, heat and pressure are all still there, just much more intense.

If you actually fell into a black hole, the tidal forces pulling at you are so extreme that the force on your feet is dramatically stronger than the force at your head. You would be stretched out and torn into pieces, and then those pieces would be torn into pieces. You would eventually be pulled into a stream of atoms, winding their way down to the surface of the black hole. For this process, scientists have a technical term: spaghettification.

Let's say you could survive this journey. Where does the black hole lead? No where. All of the mass of the star that came before the black hole is still there, pulling at you with all its gravity. This intense gravity would tear every molecule apart, and all the atoms. Protons and electrons would be crushed together to create neutrons, and then these would be crushed together even further into some kind of exotic form of superdense matter.

It's even possible that the heart of a black hole is single point of infinitely small size, containing the mass of many stars. This black hole is not a portal to anywhere, it's just a final destination.

Here's an article I did about how to maximize your time while falling into a black hole.