A question
Why do we need to sleep?
A calm, true answer. Then, if the wondering keeps going, the whole episode.
The short answer
Because a great deal of maintenance can only happen while you are offline. During deep sleep the brain rinses waste away and files what the day taught you into longer-term storage.
Sleep is not one flat state either. It moves in cycles of roughly ninety minutes, between light sleep, deep sleep and dreaming, several times a night. Everything that sleeps does its own version of this, from bees to whales.
Go deeper tonight
Sleep: The Nightly Tide
The full episode, in one calm voice, with nothing that startles.
0:00
13:23
Sleep timer
Read the guide for this one in the morning.
This connects to
One idea turns up in many different nights. Follow one and the library starts to join up.