system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 how it is that a human can jump from 20-some-odd miles up in what essentially seems to me to be space and live while ships need a heat shield?
gpt
It's about orbital speed. Ships go into orbit, which means they need to be whizzing around the Earth *extremely* fast, like 17 thousand miles per hour. When things burn up on re-entry, it's not the speed of them falling, it's the speed of them orbiting. A balloon goes straight up, so there's no need to have the extreme speed that makes things burn up on re-entry.