system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what happens as a banana ages? The more brown the banana, the thinner the peel. Does the peel become the banana?
gpt
If you're only interested in the peel, it's pretty simple. The peel loses moisture through evaporation. It dries out. Since a large part of it is water, if it loses most of the water, it loses most of its mass (and volume), so it becomes thinner.