system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: if outerspace is a vacuum what stops it from sucking up our atmosphere?
gpt
The gravity of earth is stronger than the vacuum of space. One example of an element that is not, is helium. Its too light and after it has been released into the air, it rises and exits out atmosspere (which is why weather balloons use helium). The rest of the elements are too heavy ro escape without propulsion.