what is a black hole?

Question

askNib · Accepted Answer

Imagine a star far bigger than our sun, burning fuel for millions of years, until one day it runs out. When the fuel dies, gravity wins. Nothing pushes back anymore, so the whole star collapses inward on itself. It crushes down to a single point, packed so dense that its gravity becomes almost infinitely strong — a black hole is born. That circle is the event horizon — the point of no return. Cross it, and not even light moves fast enough to escape. Nearby gas and dust swirl in, heating up into a glowing disk before they vanish forever past the horizon. We can't see a black hole directly, but we see its pull bending starlight and its disk glowing — that's how we found them. A black hole isn't a hole at all — it's a star's leftover gravity, so strong that even light can't climb out.