The Hairy Ball Theorem revisited – a newer, shorter, proof

Once proved, mathematical theorems* tend to stay proved. Nevertheless, they can sometimes still be improved – say, by making them shorter. Take, for example proofs for The Hairy Ball Theorem. Mathematician Henri Poincaré first drew attention to the Hairy Ball Theorem in 1885 with his treatise ‘Sur les courbes définies par les équations différentielles (III)’ Journal de […]