Dynamic entities

Tor Nørretranders has a poetic description of dynamic entities in his answer to this year's Edge question.

My body is not like a typical material object, a stable thing. It is more like a flame, a river or an eddie. Matter is flowing through it all the time. The constituents are being replaced over and over again.

A chair or a table is stable because the atoms stay where they are. The stability of a river stems from the constant flow of water through it.

98 percent of the atoms in the body are replaced every year. 98 percent! Water molecules stays in your body for two weeks (and for an even shorter time in a hot climate), the atoms in your bones stays there for a few months. Some atoms stay for years. But almost not one single atom stay with you in your body from cradle to grave.

What is constant in you is not material. An average person takes in 1.5 ton of matter every year as food, drinks and oxygen. All this matter has to learn to be you. Every year. New atoms will have to learn to remember your childhood.

These numbers has been known for half a century or more, mostly from studies of radioactive isotopes. Physicist Richard Feynman said in 1955: "Last week's potatoes! They now can remember what was going on in your mind a year ago."

But why is this simple insight not on the all-time Top 10 list of important discoveries?

To see my discussion of static vs. dynamic entities see "Emergence Explained" and "If a tree casts a shadow is it telling the time?"