A question
How do fossils form?
A calm, true answer. Then, if the wondering keeps going, the whole episode.
The short answer
Slowly, and by replacement. When an animal is buried quickly, water seeps through the ground carrying minerals, and those minerals gradually take the place of the bone until what remains is stone in the exact shape of the bone.
It takes millions of years and it almost never happens. Nearly every creature that ever lived left nothing behind at all. Every fossil in a museum is a rare, lucky page from a book that mostly did not survive.
Go deeper tonight
Dinosaur Fossils: How Scientists Tell Time
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.
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