system
Given the following post, respond as if you're commenting on Reddit:
human
If helium keeps floating up and up, how do we still have helium left on Earth after more than a billion years? Also, helium is a gas. Where do you actually go to find helium on Earth?
gpt
Helium on Earth is typically produced by the radioactive decay of larger elements, which produces alpha particles, which are helium nuclei. A lot of it remained underground, and was extracted as a byproduct of hydrocarbon extraction.