system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do we sleep 8hrs on/16hrs off instead of, say, 24hrs on/48hrs off?
gpt
Daylight. Our bodies release different chemicals when the sun goes down to encourage sleep.

Interesting to the second part of the question, a famous experiment was done where a scientist remained underground cut off from time and day/night. It found that her body became confused and eventually she remained awake for about 24 hours and slept up to 12 hours, creating a 36 hour day for her.