KnowraHairy ball theoremLinked fromLinked fromThe 3 pages that link to Hairy ball theorem, each with the reason it gives.All 3Broader topic 2Related 1Poincaré–Hopf theoremBroader topic: The sphere’s nonzero Euler characteristic forces a zero by Poincaré–Hopf.Characteristic classBroader topic: The Euler class explains the obstruction to a nowhere-vanishing tangent field.