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TIL the Hairy Ball theorem (wikipedia.org)

submitted 1 month ago* (last edited 1 month ago) by [email protected] to c/[email protected]

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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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[-] [email protected] 5 points 1 month ago

For mathematicians in Germany, this is known as the "Hedgehog Theorem" ("Satz vom Igel", as in "you can't fully comb a hedgehog")

[-] [email protected] 3 points 1 month ago

I think it would be hard to find a hedgehog that would allow itself to be combed.

this post was submitted on 19 Apr 2025

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