Fou ‧ cault, Jean Ber ‧ nard Lé ‧ on /ˈfuːkəʊ $ fuːˈkəʊ, ʒɒn ˈbeənɑː ˈleɪɒnǁʒɑːn berˈnɑːr leɪˈɑːn/ BrE AmE
(1819–68) a French scientist who studied the speed of light. He is known for inventing Foucault’s Pendulum, an object that swings on a wire and shows how the Earth spins around. He also invented the ↑ gyroscope .