system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the atmosphere not stratify itself by the molecular mass of its components, with the heaviest gasses at the bottom?
gpt
It does! Gravity just isn't strong enough to make this effect noticeable down at the surface. But at the edge of space, light gases are more concentrated than down here - that is how helium can move up, all the way into space, where it's blown away by solar winds.