William Gilbert (Edited from Wikipedia)

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SUMMARY

William Gilbert (1544 – 1603 AD) was an English physician, physicist, and natural philosopher. He passionately rejected both the prevailing Aristotelian philosophy and the Scholastic method of university teaching. He is remembered today largely for his book De Magnete (1600), and is credited as one of the originators of the term "electricity". He is regarded by some as the father of electrical engineering or electricity and magnetism.

LIFE AND WORK

Gilbert was born in Colchester to Jerome Gilberd. He was educated at St John's College, Cambridge. After gaining his MD from Cambridge in 1569, and a short spell as bursar of St John's College, he left to practice medicine in London and travelled on the continent.

In 1573, he was elected a Fellow of the Royal College of Physicians. In 1600 he was elected President of the College. From 1601 until her death in 1603, he was Elizabeth I's own physician, and James VI and I renewed his appointment.

His primary scientific work—much inspired by earlier works of Robert Norman—was De Magnete (On the Magnet and Magnetic Bodies, and on the Great Magnet the Earth ). It was published in 1600.

In this work, he describes many of his experiments with his model Earth called the terrella. From these experiments, he concluded that the Earth was itself magnetic and that this was the reason compasses point north (previously, some believed that it was the pole star, Polaris, or a large magnetic island on the north pole that attracted the compass). He was the first to argue, correctly, that the center of the Earth was iron, and he considered an important and related property of magnets was that they can be cut, each forming a new magnet with north and south poles.

In Book 6, Chapter 3, he argues in support of daily rotation of the earth. He stated that it is an absurdity to think that the immense celestial spheres rotate daily, as opposed to the daily rotation of the much smaller Earth. He also posits that the "fixed" stars are at

1 remote variable distances rather than fixed to an imaginary sphere. He states that situated "in thinnest aether, or in the most subtle fifth essence, or in vacuity – how shall the stars keep their places in the mighty swirl of these enormous spheres composed of a substance of which no one knows aught?"

The English word "electricity" was first used in 1646 by Sir Thomas Browne, derived from Gilbert's 1600 New Latin electricus, meaning "like amber". The term had been in use since the 13th century, but Gilbert was the first to use it to mean "like amber in its attractive properties".

In his book, he also studied static electricity using amber; amber is called elektron in Greek, so Gilbert decided to call its effect the electric force. He invented the first electrical measuring instrument, the electroscope, in the form of a pivoted needle.

Gilbert argued that electricity and magnetism were not the same thing.

Gilbert's magnetism was the invisible force that many other natural philosophers, such as Kepler, seized upon, incorrectly, as governing the motions that they observed. While not attributing magnetism to attraction among the stars, Gilbert pointed out the motion of the skies was due to earth's rotation, and not the rotation of the spheres, 20 years before Galileo (but 57 years after Copernicus who stated it openly in his work "De revolutionibus orbium coelestium" published in 1543 ).

Gilbert made the first attempt to map the surface markings on the Moon in the 1590s. His chart, made without the use of a telescope, showed outlines of dark and light patches on the moon's face. Contrary to most of his contemporaries, Gilbert believed that the light spots on the Moon were water, and the dark spots land.

DE MAGNETE

De Magnete is a scientific work published in 1600 by the English physician and scientist William Gilbert and his partner Aaron Dowling. A highly influential and successful book, it exerted an immediate influence on many contemporary writers, including Francis Godwin and Mark Ridley.

In his work, Gilbert described many of his experiments with his model Earth called the terrella. Gilbert also made the claim that gravity was due to the same force and he believed that this held the Moon in orbit around the Earth. While incorrect by modern standards, this claim was still far closer to the truth than the ancient Aristotelian theory, which held that the heavenly bodies consist of a special fifth element which naturally

2 moves in circles, while the earthly elements naturally move downward. Johannes Kepler accepted Gilbert's theory and used it as a working basis for his famous laws of planetary motion.

De Magnete was influential because of the inherent interest of its subject matter, but also for the rigorous way in which Gilbert described his experiments and his rejection of ancient theories of magnetism. Gilbert nevertheless acknowledged his debt to Peter of Maricourt and incorporated this 13th-century scientist's experiments on magnetism into his own treatise. Gilbert is regarded as a pioneer of experimental science.

PETER OF MARICOURT (PEREGRINUS)

Petrus Peregrinus de Maricourt (Latin), Pierre Pelerin de Maricourt (French), or Peter Peregrinus of Maricourt (fl. 1269), was a 13th-century French scholar who conducted experiments on magnetism and wrote the first extant treatise describing the properties of magnets. His work is particularly noted for containing the earliest detailed discussion of freely pivoting compass needles, a fundamental component of the dry compass soon to appear in medieval navigation. He also wrote a treatise on the construction and use of a universal astrolabe.

In his letter of 1269, Peregrinus explains how to identify the poles of the compasses. He also describes the laws of magnetic attraction and repulsion. The letters also contain a description of an experiment with a repaired magnet, as well as a number of compasses, one of which "you will be able to direct your steps to cities and islands and to any place whatever in the world." Indeed, the increasing perfection of magnetic compasses during the thirteenth century allowed navigators to strike out on voyages to unknown lands.

The letter is divided into two parts. Part One (10 chapters) is a section that serves as a model of inductive reasoning [the scientific method] based on definite experiences, and setting forth the fundamental laws of magnetism. He did not discover these laws, but presented them in logical order.

Part One discusses the physical properties of the lodestone and provides the first extant written account of the polarity of magnets. He was thus the first to use the word “pole” in this context. He provides methods for determining the north and south poles of a magnet, and he describes the effects magnets have upon one another, showing that like poles repel each other and unlike poles attract each other. He also treats the attraction of iron by lodestones, the magnetization of iron by lodestones, and the ability to reverse the polarity in such an induced magnet.

Part Two (three chapters) describes three devices that utilize the properties of magnets. He treats the practical applications of magnets, describing the “wet” floating compass as an instrument in common use, and proposing a new “dry” pivoted compass in some detail. He also attempts to prove that with the help of magnets it is possible to realize perpetual (never-ending) motion. His device is a toothed wheel which passes near a lodestone so that the teeth are alternately attracted by one pole and repelled by the other.