William Gilbert

1544-1603

English Geophysicist and Physician

William Gilbert earned his place in annals of science with the publication of De magnete. A landmark in the history of experimental science and widely influential, it records his pioneering researches on magnetism and electricity.

Nothing is known of Gilbert's early life other than that he was born on May 24, 1544, at Colchester in Essex, England. In 1558 he matriculated at St. John's College, Cambridge. After earning his A.B. in 1561, M.A. in 1564, and M.D. in 1569, he was elected a fellow of St. John's College. He established a successful medical practice in London in 1673 and became a Fellow of the Royal College of Physicians. He served as censor of that body (1582, 1584-87, 1589-99), treasurer (1587-94, 1597-99), consiliarium (1597-99), and elect (1596-97) before being elected president in 1600. That same year he was appointed physician to Queen Elizabeth I, serving in that same capacity for James I. He died in London on December 10, 1603.

Gilbert began studying magnetic phenomena sometime after leaving Cambridge. He published his findings in 1600 under the title De magnete, magneticisque Corporibus, et de magno magnete tellure (Concerning Magnetism, Magnetic Bodies, and the Great Magnet Earth). The work's emphasis on direct observation and rigorous experimentation earned Gilbert praise from Galileo (1564-1642), who considered him the founder of the experimental method.

De magnete begins by reviewing the history of magnetism and discussing the properties and behavior of lodestones. Gilbert experimentally refuted many superstitious beliefs concerning the nature and curative properties of magnets such as garlic's ability to nullify magnetism. He also demonstrated how the magnetic effects of lodestone could be increased by arming them with soft-iron pole-pieces and that steel rods could be magnetized by stroking them with lodestones. He further showed that iron magnets lose their magnetism when heated to red-hot and cannot be remagnetized while remaining so. Gilbert introduced the idea of Earth as a giant spherical lodestone with magnetic poles (a term he introduced), an equator, and the ability to attract objects to itself. He also noted that compass needles align themselves along a north-south axis and argued they point toward Earth's magnetic poles.

Gilbert established the discipline of electrostatics by carefully distinguishing the amber effect from effects due to magnetism. It had been known since antiquity that amber, when rubbed, acquired the ability to attract light objects. Gilbert extended knowledge in this area with experiments that revealed substances other than amber exhibiting this same attractive force when rubbed. He referred to all such substances as "electrics" (from the Greek elektron, meaning amber) and believed they attracted objects through the emission of an effluvium that seized and pulled inward the particles of other bodies. This eventually led to the idea of electric charge. Gilbert's versorium—a light metallic needle turning about a vertical axis—was specifically designed to test for such effects.

Gilbert extended his magnetic theories to the cosmos, though most of his conclusions were not well supported by experimental results. He believed the "fixed" stars were in the same category as the Sun and, following Nicholas of Cusa (1401-1464), believed they were not all equally distant from Earth. He accepted the diurnal rotation of Earth but incorrectly attributed this motion to magnetic effects. He rejected the reality of solid celestial spheres and speculated that magnetic attraction maintained the planets in their orbits. Johannes Kepler (1571-1630) sought to apply Gilbert's ideas in a similar fashion, but his use of magnetic attraction as the motive force of his astronomical theory failed. Though Gilbert never championed Nicolaus Copernicus's (1473-1543) system in writing, his ideas were effectively exploited by others in arguing for Copernican heliocentrism.

STEPHEN D. NORTON