A question
Why does an octopus have three hearts?
A calm, true answer. Then, if the wondering keeps going, the whole episode.
The short answer
Because its blood needs more pushing than ours does. Two of the hearts serve the gills, sending blood to collect oxygen, and the third pumps it onward to the rest of the body.
Octopus blood carries oxygen using copper rather than iron, which is what makes it blue, and copper-based blood is less efficient at it. Three hearts is the arrangement that keeps everything supplied. The body heart stops beating while an octopus swims, which is part of why it would usually rather walk.
Go deeper tonight
Octopus: Three Hearts and No Bones
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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