The Great Gilbert

Worlds and Magnets

THE belief persisted until the 17th century that an adulteress could be identified by placing a magnet beneath her pillow as she slept. The magnetic force of it, so it was strangely believed, would literally hurl her out of bed. The first person to ridicule this idea, on the grounds that no one had done an experiment to prove it, was William Gilbert (1544- 1603), one of the great unsung heroes of physics, astronomy and cosmology. Anniversaries of the achievements of great scientists are often dull occasions because those who care about the scientist in question tend to know all about him or her, and don't want to hear any more. But Gilbert, for some curious reason, is more or less unknown. But it was he who first proposed, in his classic book of 1600 De Magnete (``About Magnetism'') that the planets circle the Sun because they are attracted to it by some invisible force, prompting Galileo (who suspected the existence of such a force but had no idea what it was) to call Gilbert ``great to a degree that is enviable.''

William Gilbert, English physician, late 16th century

Gilbert wrongly thought this force was magnetism, having observed that it was a vastly stronger force than gravity. (We know now that its strength exceeds gravity's by an astounding factor of 1 followed by 36 noughts!) He failed to realise that although much stronger in its force, a magnet only attracts at tiny distances, whereas gravity extends its grip across tens of millions of light- years. Yet a wrong belief can provoke the minds of others and help bring about a more successful investigation. In this case it caused Isaac Newton to discover the true role of gravity in holding planets in their orbits. Not that Newton gave Gilbert any credit - I don't know that he ever gave anyone any credit. Plenty of others, though, gave Gilbert credit at the time. The poet John Dryden declared: Gilbert shall live till lodestones cease to draw Or British fleets the boundless ocean awe. It chafed Gilbert that he could perform no experiment to test his idea about magnetism holding the planets. For he had nothing but contempt for people who theorised without experimental proof. ``May the gods damn all their sham, pilfered, distorted works, which do but muddle the minds of students!. . .Thus do pretenders to science vainly and preposterously seek for remedies, ignorant of the true causes of things.'' Even more than Francis Bacon, he was the father of experimental science. But for him, telescopes might never have come into use, since people might have believed they could learn everything about the universe just by thinking about it. He would not believe something was true just because he was told it was true, nor because reason and logic suggested it must be true, but only if he could see the truth of it for himself. He did not reveal whether he had ever lured a suspected adulteress to his bed and then surreptitiously placed a magnet beneath her pillow to see what would happen. But he did invent the word ``electric'' from his experiments with amber and electrostatic force, and today the strength of a magnetic field is measured in ``gilberts.