Why do black holes appear black?

Answer 1

Because the black hole sucks up light, it appears black and no light escapes.

EDIT: It's true that light can't escape black holes, but that's not why they are so "black". The reason why BH are black is because the event horizon of a BH is basically the outer rim of spacetime, so events that take place inside a BH are not concurrent with events that take place in spacetime. So, say two observers witness you falling into a BH. They can see you approaching the BH, but they never see you enter it (even though you, yourself, know that you did) because, within spacetime, you were APPROACHING the BH and since you leave spacetime the moment you crossed the event horizon, to the observers, you never crossed it. No one can see what happens in a black hole because nothing is happening, relative to them. The blackness of a black hole is what "nothing" would essentially look like.

Answer 2

Black holes are the end result of compressing an object smaller and smaller (beyond the Schwarzschild radius). Black holes form usually from stars (They can also form from gas clouds). Stars have to burn so hot in order to exist because of their immense mass, hence gravity is strong enough to collapse the star. To counter this, stars are constantly fusing hydrogen into helium in order to release constant energy to keep gravity at bay (Outward pressure against gravity's inward pressure). When a star reaches the end of its main sequence and runs out of hydrogen fusion stops, causing partial gravitational collapse which heats the core up even more allowing to to fuse helium via the triple-alpha process into carbon. Eventually it runs out, collapses more, heats up more and begins fusing the carbon into neon, so on and so forth up the atomic chain until it reaches nickel which decays into iron. Iron requires a lot of energy to fuse, more than is released by its fusion. Massive stars do fuse iron but only momentarily. Since the star can no longer keep gravity at bay, it instantly collapses within a supernova or hypernova. If it is massive enough, quantum degeneracy pressure will not stop it (No two of the same fundemental particles can occupy the same energy state) and therefore will not turn it into a neutron star which is formed via neutron degeneracy pressure. Instead it will fully collapse into a singularity, which is what is inside a black hole. However, it can form a quark star (Theoretical) if its mass is slightly heavier than neutron degeneracy pressure but not exceeding quark degeneracy pressuer.

Answer 3

A black hole is black becasue everything falls into it and nothing, not even light, comes out. So it looks like a hole in space that does not emit or reflect light.