## A Little of Gilbert
William Gilbert was born into a middle class family during a period of relative calm following the turbulence of Henry VIII’s reign and the future civil war in the early 17th century. During that century, Britain reorganized its entire society with the confiscation of Church properties, secularization of public education, and subsequent increase in general wealth and a middle class. London quadrupled in size and became an international center of trade and hub for British exploration of the Americas and East India. Gilbert’s father was a benefactor, serving as a prominent lawyer and benefited from these changes. Gilbert’s life was spent in civil service as both physician and private scientist, outside of a university. His was an illustrious career, subsequently serving as President of the Royal College of Physicians and the personal physician to Queen Elizabeth I and subsequently James VI as well.
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William Gilbert, 1544-1603
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Gilbert was born a year after Copernicus died (coinciding with the publication of *De Revolutionibus*) and a year before the Catholic Church’s Council of Trent was seated to try to recover after the simultaneous loss of influence in England (with Henry VIII) and Northern Europe (with Luther). Little is known of Gilbert’s early years, but for his education in his family’s home town of Colchester and subsequent study at St John’s College, Cambridge. There he took his medical training and absorbed, like everyone, the Aristotelianism that passed for advanced learning...and like his famous contemporaries, he rejected it in order to make intellectual room for a more reliable understanding of nature. Like Galileo, he taught Aristotle for a while as a “Master” at Cambridge, but like Galileo after him, he became convinced that the only route to understanding nature was through observation and experiment—not through appeal to authority and ancient writings. Unlike in Galileo's Italy, Britain was now free of the Church and its authority over what could and could not be written about.
Gilbert died in 1603 of bubonic plague and many of his personal effects were burned so we lack a detailed understanding of his life and research. We know that he never married and of course know of his professional success. His definitive book, *De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure* (On the Magnet, Magnetic Bodies, and the Great Magnet of the Earth, 1600, aka *De Magnete*) is enlightening and shows perhaps the first true experimental scientist at work. A relative (his brother?) later collected unpublished notes into a posthumous book, *De Mundo*, which shows a thinker, like Copernicus, with one foot in Medieval traditions and the other in modern times. Ironically, fire during the London “Great” plague of 1665 destroyed Gilbert’s London home as well as the library of the Royal College of Physicians where Gilbert had bequeathed many of his papers, so the second recurrence of that terrible disease in London spawned Newton’s imaginative scientific genius, but destroyed the last bits of Gilbert’s history.
At some point Gilbert became interested in both magnetism and electricity. Both were similarly magical and both magnetic and electrical effects seem to create forces without any intervening medium—without contact. Little was known, but much mysticism was invested in magnetism, especially. Rather than relying on hocus-pocus descriptions or ancient Greek authority, Gilbert set about to systematically study what materials were specifically influenced by magnets and what by static electricity. The Greeks and Chinese had discovered “Lodestones” which we know today to be a naturally magnetized minerals and both cultures had found that small iron magnets, when floated on water, would align themselves in a particular direction: North.
Gilbert’s book is a remarkable document for its orderly discussion of heretofore unstudied phenomena. He described past views on the phenomena and criticized them, often on the basis of his own experiments. He concluded that magnetism and electricity were different phenomena and categorized materials by their magnetic and electrical properties. How did he do that? He found that heat would dissipate electrical attraction but not magnetic. This is a conclusion, then, based on controlled experimentation.
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What he’s most famous for having figured out was that the Earth is a magnet, suggesting that its core was made of iron. He came up with this idea and then tested it in a variety of ways. He actually constructed spheres of lodestone and then did experiments on them with tiny magnets, determining how the angle of dip of a compass needle would vary with longitude on his test spheres, comparing that with actual compasses on the Earth at various locations. He even carved indentations into his test spheres to simulate valleys and mountains on Earth and subsequent changes to the compass needles.
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Gilbert made a model to demonstrate a magnet's behavior in the earth's magnetic field. From De Magnete.
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Having in hand an invisible force associated with the Earth, he then anticipated Kepler and proposed that it was magnetism that was responsible for the attraction of the Earth to the Sun—he was a Copernican and because he was in England, he felt little antagonism for these beliefs. Galileo was criticized by the Inquisition for having praised the “perverse and quibbling heretic” and he himself did experiments on lodestones, with Gilbert’s work as a guide.
While Gilbert taught mathematics, he held an entirely different view of mathematics and natural philosophy. Copernicus’ book was too complicated for him and he maintained that mathematicians’ jobs were to describe the phenomena of the heavens and not to reach conclusions about physical cause. He explicitly excluded magnetism as a topic worthy of mathematical explanation and was largely silent on the subjects of motion, let alone a mathematical description of the sort that Galileo championed.
And Gilbert also worked in electricity, especially on the “amber” effect—static electricity…he knew that if one rubbed an amber rod, that it would then acquire the ability to attract paper. He invented the electroscope, which had useful scientific applications into the 20th century. Finally, it is to Gilbert that we owe the word “electricity.” A very modern physicist for his time.
>As for the causes of magnetic movements, referred to in the schools of philosophers to the four elements and to prime qualities, these we leave for roaches and moths to prey upon. Gilbert, *De Magnete*, Book II, Chapter 3.