An award-winning Canadian science journalist tells the story of the Earth’s magnetic field.
Deemed “a fleeting magic” by the ancients, our planet’s magnetic force—generated in the Earth’s core—holds matter together and makes a giant magnet of the Earth, with north and south poles. With the help of modern scientists, Mitchell (Malignant Metaphor: Confronting Cancer Myths, 2015, etc.) traces our growing understanding of the phenomenon through the “investigations of the Middle Ages, the electrical exploits of the Renaissance, and the compulsions of the Victorians.” Leading geophysicists and others walk the author through the lives and experiments of many pioneering scientists, beginning with the 13th-century French engineer Petrus Peregrinus, who first tested the properties of magnetism. Mitchell takes us to an unmarked corner of rural France, where physicist Bernard Brunhes (1867-1910) discovered evidence in a “fabled” piece of rock that Earth’s two magnetic poles have often switched places (most recently 780,000 years ago). By 1840, notes the author, 30 permanent observatories were studying magnetism. As she recounts the stories of scientists like Hans Christian Oersted, a Dane who studied the relationship between magnetism and electricity, the Italians Luigi Galvani and Alessandro Volta, Michael Faraday, inventor of the transformer, and seismologist Inge Lehmann, who discovered Earth’s inner core, she makes vivid the process of science and the culture of scientific meetings. For all that is known, scientists still do not fully understand “the mysterious goings-on” at the planet’s core. We cannot predict when the poles will next reverse, though such a reversal could have devastating impacts in our high-tech, networked world: the magnetic field protects against solar radiation. Mitchell’s text sometimes borders on the technical, but patient readers will be rewarded by her combination of thoughtful conversations with, say, the editor of Faraday’s papers and her encounters with geophysicist at various conferences.
A complex, well-told account of “this spinning magnet we live on.”