Magnetism of earth materials and geomagnetism

Abstract

The discovery of the earth’s magnetic field belongs to the origins of physics. Although less well known than the beginnings of astronomy and celestial mechanics associated with Copernicus, Galileo and Newton, its history is nevertheless exemplary of the development of science. It was the existence of a real need by society (precise navigation using the magnetic compass), the experimental deduction by Gilbert, and the problem of the rationalization of action at a distance (the only scientific example for a long time being the force between magnets) that were responsible for this early progress. The demonstration by Gilbert in 1600 of the internal origin of the earth’s magnetic field based on the similarity of the lines of force around the earth and those around a naturally magnetic sphere of lodestone, is considered to be the first publication of modern physics, even before the solution by Galileo of a body falling under gravity. This internal origin along with the mystery of action at a distance probably contributed to the “diabolization ” of magnetism during the following centuries