The history of geomagnetism began around the year 1000 with the discovery in China of the magnetic compass. Methodical studies of the Earth's field started in 1600 with William Gilbert's "De Magnete" and continued with the work of (among others) Halley, Coulomb, Gauss and Sabine. The discovery of electromagnetism by Oersted and Ampére led Faraday to the notion of fluid dynamos, and the observation of sunspot magnetism by Hale led Larmor in 1919 to the idea that such dynamos could sustain themselves naturally in convecting conducting fluids. From that came modern dynamo theory, of both the solar and terrestrial magnetic fields. Paleomagnetic studies revealed that the Earth's dipole had undergone reversals in the distant past, and these became the critical evidence in establishing plate tectonics. Finally, the recent availability of scientific spacecraft has demonstrated the intricacy of the Earth's distant magnetic field, as well as the existence of magnetic fields associated with other planets and with satellites in our solar system.
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Chronology of Geomagnetism
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History is an integral part of scientific knowledge. It not only provides the framework of its field, explaining how its concepts arose and developed, but it also provides an insight into the actual path of progress, something scientific articles and texts generally omit. Geomagnetism is of particular interest, because it may well claim to be the oldest discipline in geophysics. In its long history, several threads can be distinguished, now and then intersecting but largely independent. It is this pattern which the article is meant to highlight.
Next Section: Early Discoveries
Author and Curator: Dr. David P. Stern
Mail to Dr.Stern: earthmag("at" symbol)phy6.org .
Last updated 31 January 2003