Science Frontiers ONLINE No. 22: Jul-Aug 1982 Issue Contents

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Large changes of the earth's magnetic fields in historical times

By measuring the magnetic properties of bricks and other accurately dated human artifacts, geophysicists can reconstruct the history of the local magnetic field. Near Loyang, China, the field was as much as 54% higher in 300 A.D. than it is now. It was 15% higher in 1500 A.D. In 1000, it was less than today's value.

(Wei, Q.Y., et al; "Intensity of the Geomagnetic Field near Loyang, China, between 500 BC and AD 1900," Nature, 296:728, 1982.)

Comment. Direct measurements of the earth's field go back only a few hundred years, but they are consistent with the data reconstructed from artifacts, both showing a steady decrease since 1500. No one has estimated the effects of these substantial changes on radiocarbon dating and, perhaps, human biology.

From Science Frontiers #22, JUL-AUG 1982. © 1982-2000 William R. Corliss

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Science Frontiers Sourcebook Project Reviewed in: Icarus: Volume 41, Issue 3, p. 470-470 1984, Vol.56:3, P.615 1983, Vol.58:3 June 1984, Vol.60:3 Dec 1984, Vol.72:3 Dec 1987 Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 1987 American Journal of Physics, Volume 52, Issue 8, p. 764 August 1984 Quotes "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada>, Vol. 81, no. 1 (1987), p. 24., 02/1987