Video narration
Black holes are invisible. Even light can't escape them. So here's the big question: if we can't see a black hole, how do we know they actually exist? The answer is simple: we see what they do. Imagine a massive star orbiting an invisible object. Astronomers can track its motion and calculate the mass of the object pulling on it. If something incredibly massive is there, but we can't see it, a black hole can explain what we observe. We can also see superheated gas and dust spiraling around some black holes. This material can glow incredibly brightly, even though the black hole itself remains dark. And there's more. A black hole's extreme gravity can bend light passing near it, creating a phenomenon called gravitational lensing. So, we don't actually see the black hole itself. We see its effects on stars, matter, and light. Sometimes, the best evidence for something invisible is what it does to everything around it.