André-Marie Ampère (1775-1836) was a child prodigy whose early life was marred by tragedy: Ampère's father was beheaded in his presence during the Revolution and, later, his wife died four years after their marriage. As a scientist, Ampère had flashes of inspiration which he would pursue to their conclusion. When he learned of Ørsted's discovery in 1820 that a magnetic needle is deflected by a varying nearby current, he prepared within a week the first of several papers on the theory of this phenomenon, formulating the law of electromagnetism (Ampère's law) that describes mathematically the magnetic force between two circuits.