William Gilbert (physicist)

William Gilbert (about 1544 to 1603), also called Gilberd, was an English physician, physicist and natural philosopher, remembered largely for De Magnete (1600), the first sustained experimental study of magnetism. Born in Colchester and educated at St John's College, Cambridge, he took his MD there in 1569, practised medicine in London, became a Fellow of the Royal College of Physicians in 1573 and its President in 1600, and served as physician to Elizabeth I from 1601 and then to James VI and I. In De Magnete he described experiments with a model Earth, the terrella, and concluded that the Earth is itself a magnet, which is why compasses point north; he was also the first to argue that the centre of the Earth is iron. He rejected Aristotelian philosophy and scholastic university teaching. The unit of magnetomotive force, the gilbert, was named in his honour and has since been replaced by the ampere-turn.