The Brownian Movement: Feynman's Physics Explained
Watch a tiny smoke particle under a microscope and you see it jiggle in a jerky, random dance — Brownian motion. It is direct, visible proof that atoms are real: the particle is bombarded on every side by invisible air molecules, and now and then gets hit harder on one side and jumps. Einstein's analysis of this random walk gave one of the first accurate ways to measure the size of atoms.
The big idea
The random dance of dust is visible proof that atoms exist.
Think about it
If the air were perfectly still and smooth, would a smoke particle still jiggle? Why does it move at all?
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