Inside the Event Horizon
▶ DRILLThe closer you get to a black hole, the faster you'd have to go to escape. Right at the edge — the event horizon — that escape speed reaches light-speed, so only light can just barely crawl out, stretched infinitely red. Inside, escaping would need to be faster than light — impossible — so nothing gets out, not even light. That's why it's black, and why “out” stops being a direction you can travel: every path leads deeper in. Use the Explain it for a kid / a grown-up switch to set the depth.
The big idea — the closer you get to a black hole, the faster you'd have to go to escape. Right at the event horizon that speed hits light-speed; inside, it would need to be more than light-speed — impossible — so nothing escapes, not even light. That's why it's black. And "out" simply stops being a direction you can go: inside the horizon, every road leads deeper in. (A black hole isn't a hole you fall down — it's a region where the future itself points inward.)