Physics
Understanding Black Holes
Quick fact
A black hole's event horizon is not a physical surface; it is a point of no return. If you crossed it, you could still see the outside universe, but the universe would never see you again.
Why this is interesting
Imagine an object so dense that if you pointed a flashlight away from it, the light itself would fall back down. That object is a black hole — a place where the rules of ordinary reality seem to break down.