Joseph-Émile Barbier

Joseph-Émile Barbier was a French astronomer and mathematician, born on 18 March 1839 in Saint-Hilaire-Cottes, Pas-de-Calais, known for Barbier's theorem on the perimeter of curves of constant width. He studied at the College of Saint-Omer and then at the Lycée Henri-IV in Paris, entered the École Normale Supérieure in 1857, and in 1860 published the paper containing his theorem, which also presented a solution to Buffon's needle problem that avoided the use of integrals. He then worked as an assistant astronomer at the Paris Observatory, leaving in 1865, and in his later period published ten more papers and announced a generalization of Bertrand's ballot theorem. He was given the Francoeur Prize several times and died on 28 January 1889.