Phibonacci

Phi, the Golden Ratio, the Golden Mean, continues to fascinate me. Here are three videos by Vi Hart on exactly what Phi is, and, if you make it all the way to the third video, even an explanation of why it turns up so often in nature.

Bonus suggestion: The first of Vi's videos that I saw and loved was How To Snakes (embedding disabled; sorry). snakesnakesnakesnakesnakesnakesnakesnakesnakesnakesnakesnakesnakesnakesnake
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