http://www.nytimes.com/2004/07/13/science/13magn.html?pagewanted=allWill Compasses Point South?
July 13, 2004
Will Compasses Point South?
By WILLIAM J. BROAD
The collapse of the Earth's magnetic field, which both guards the planet and guides many of its creatures, appears to have started in earnest about 150 years ago. The field's strength has waned 10 to 15 percent, and the deterioration has accelerated of late, increasing debate over whether it portends a reversal of the lines of magnetic force that normally envelop the Earth.
During a reversal, the main field weakens, almost vanishes, then reappears with opposite polarity. Afterward, compass needles that normally point north would point south, and during the thousands of years of transition, much in the heavens and Earth would go askew.
A reversal could knock out power grids, hurt astronauts and satellites, widen atmospheric ozone holes, send polar auroras flashing to the equator and confuse birds, fish and migratory animals that rely on the steadiness of the magnetic field as a navigation aid. But experts said the repercussions would fall short of catastrophic, despite a few proclamations of doom and sketchy evidence of past links between field reversals and species extinctions.<snip>
Some experts suggest a reversal is overdue. "The fact that it's dropping so rapidly gives you pause," said Dr. John A. Tarduno, a professor of geophysics at the University of Rochester. "It looks like things we see in computer models of a reversal."<snip>
"It would be significant" in terms of planetary repercussions, he said in an interview, "but not catastrophic." High levels of ultraviolet radiation would spread down from polar regions as far south as Florida.<snip>
To better understand the current collapse, the European Space Agency plans to launch three satellites in 2009. The spacecraft, flying in polar orbits a few hundred miles up, are to map its intricacies until perhaps 2015.<snip>