Today I Learned (TIL)

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TIL the Hairy Ball theorem (wikipedia.org)

submitted 1 week ago* (last edited 1 week ago) by vatlark@lemmy.world to c/til@lemmy.ca

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The theorem has been expressed colloquially as "you can't comb a hairy ball flat without creating a cowlick" or "you can't comb the hair on a coconut".

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[–] Maalus@lemmy.world 1 points 6 days ago

By moving the entire comb parallel, sure. But you can move one end slower than the other (i.e. as if you planted one end and pivoted it around, just with some speed, not stationary) and you can comb it without it.