Francois Jean Dominique Arago (1786-1853), french physicist and astronomer. Arago was born near Perpignan in the Catalan south of France into the family of a government official. An early interest in the military led to his education in the mathematics required for service in the artillery. However, Arago found the science more compelling and joined Biot on a mission to complete the measurement of a meridian arc and establish the precise standard length of one metre. At the end of the expedition he was captured while at sea and held in north Africa for three months. Arago contributed much to the understanding of magnetism and to the wave theory of light, especially polarisation. In later life he was increasingly involved in politics, becoming president of the Executive Power Commission and de facto head of state until the coup d'etat of Napolen III.