Gilbert, William (1544–1603)

GILBERT, WILLIAM (1544–1603)

GILBERT, WILLIAM (1544–1603), English scientist and physician. Gilbert is best known for his revolutionary theories on magnetism, published in his book De Magnete (or De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure ; On the loadstone and magnetic bodies, and on the great magnet the Earth) in 1600. Remarkably little is known of Gilbert's life. Born in Colchester to a prosperous magistrate, he received a B.A. from Cambridge University in 1561, an M.A. in 1564, and an M.D. in 1569. By the mid-1570s, he was practicing medicine in London, where he became a member of the Royal College of Physicians (and was elected president of the group in 1600). There, he also came into contact with navigators, compass makers, and practical mathematicians, and pursued his research on magnetism. In his successful medical practice, he was consulted by members of the aristocracy, was appointed as one of Elizabeth I's personal physicians (1600–1603), and, after her death in 1603, served as James I's physician until a plague epidemic that November took his own life.

Navigational accuracy assumed greater importance with the overseas explorations by the Spanish and Portuguese in the fifteenth century, and during the sixteenth century Dutch and English navigators compiled observations that were of significant use to Gilbert. It was not lost on Gilbert or his contemporaries that discoveries about magnetism would be politically and commercially useful. Despite the widespread use of nautical compasses on Spanish, English, Dutch, and French ships, none of his contemporaries understood why compass needles behaved as they did: attraction, repulsion, variation, dip, bipolarity, and the discovery of latitude were recognized empirically, but poorly understood. Through his experiments on magnets and magnetic bodies (especially the lodestone, that is, naturally magnetized iron ore), Gilbert methodically investigated a wide range of magnetic behaviors.

In fact, Gilbert's book went far beyond being a useful navigational treatise, and represented the first comprehensive analysis of magnetism, featuring a revolutionary new theory about the Earth's magnetic force. In formulating his views, Gilbert insisted on using his own empirical data rather than relying on past scientific authorities. His book is full of carefully contrived laboratory experiments that he urged his readers to replicate. He assailed credulous acceptance of myths (such as the power of a magnet to detect adultery), rejected Aristotelian explanations, and invented his own language to describe magnetic phenomena, including the terms electricity, electric force, electric attraction, and magnetic pole. To explain the phenomena he investigated, he concluded that the Earth was alive with magnetic potency or force, and he likened this to sexual attraction. Hence, for him, magnetism was an immaterial, innate force operating in the universe, with occult and vital properties.

The stunning claim of Gilbert's book was that the Earth behaves in the heavens as a spherical magnet does on earth. He based this assertion on his experiments with spherical magnets and on his deduction that the Earth itself was a giant spherical magnet. Reasoning by analogy, he stated boldly that the Earth rotated daily on its own axis by its magnetic power, just as a perfectly spherical lodestone aligned with the Earth's poles would spin on its axis. Declaring himself an adherent of astronomer Nicolaus Copernicus (1473–1543), whose theory about the Earth's rotation around the heavens had been published in 1543, Gilbert added new magnetic arguments to the arsenal of the Copernican polemic.

INFLUENCE ON LATER SCIENCE

Subsequent natural philosophers including Francis Bacon (1561–1626) and Galileo Galilei (1564–1642) hailed Gilbert's handling of empirical and experimental evidence, and others applauded his rejection of Aristotle's erroneous ideas about physics and astronomy. Johannes Kepler (1571–1630) and Sir Isaac Newton (1642–1727) pondered Gilbert's magnetic forces before devising their own physical explanations of astronomical motions. And, although many parts of Gilbert's new magnetic theories were soon rejected, including his analogy of the Earth and the spherical lodestone, he is still acknowledged for some of his discoveries about electricity and magnetism (such as the distinction between magnetic and static electricity), and for correctly recognizing that the fixed stars are not all the same distance from the earth.

See also Astronomy ; Bacon, Francis ; Copernicus, Nicolaus ; Exploration ; Galileo Galilei ; Kepler, Johannes ; Newton, Isaac ; Shipbuilding and Navigation.

BIBLIOGRAPHY

Gilbert, William. On the Loadstone and Magnetic Bodies, and on the Great Magnet the Earth. Translated by P. Fleury Mottelay. New York, 1958.

Pumfrey, Stephen. Latitude and the Magnetic Earth. Cambridge, U.K., 2002.

Roller, Duane H. D. The De Magnete of William Gilbert. Amsterdam, 1959.

Martha Baldwin