A question
How do monarch butterflies know where to go?
A calm, true answer. Then, if the wondering keeps going, the whole episode.
The short answer
Nobody fully knows, which is the remarkable part. Monarchs use the sun as a compass, corrected for the time of day by an internal clock, and probably sense the Earth's magnetic field as well.
What makes it strange is that the butterflies flying south have never been there before. The ones that arrive back north are the great-grandchildren of the ones that set out. No single butterfly ever sees the whole journey, and none of them is following anyone who has.
Go deeper tonight
Monarch Butterfly Migration: The Living Relay
The full episode, in one calm voice, with nothing that startles.
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.