system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can your body have a "sleep debt" but not a "sleep surplus"?

Why does my 15 hours of sleep on the weekend not counteract the 4 hours I get on a weeknight?
gpt
Your brain is like a trash can. Throughout the day it fills up with garbage, and at night that garbage is slowly removed. If you don't get enough sleep, only some of the garbage gets taken out. Over time, it builds up until your can is almost always full. A full can is bad and makes you fall asleep or hallucinate.


However if you sleep lots and lots, your trash-can can't get under 0% full. It will always only hold a certain amount of garbage.