system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it that when people close their eyes, there are faint splotches of different abstract things visible?
gpt
They're called phosphenes. Apparently the retina produces them even when at rest and in the absence of light. It's sort of the same way that fireflies can glow; there are cells within our eyes that emit biophotons which are light particles that are produced by our eyes themselves.