According to William J. Broad in today's New York Times, the Earth's magnetic field has been collapsoing for 150 years. "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." The European Space Agency has approved the world's largest effort at tracking the shift, using three satellites collectively called Swarm. Swarm will conduct precise studies of the Earth's interior and climate, and make high-precision and high-resolution measurements of the magnetic field.

The reversal of the magnetic field, if it happens, will take as much as 2,000 years, scientists believe, and could cause significant disruptions.

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.

Even though a complete reversal may be hundreds or thousands of years away, the decline in the strength of the field is already damaging satellites. What other effects might we see in the short-term? That's not completely clear, though consensus seems to be that changes will be slow enough that we (and other beasts) will have time to adapt.

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