December 15, 2003 | David F. Coppedge

The Magnetic Sky Is Falling

Space.Com reports that the strength of Earth’s magnetic field has dropped 10% over the last 150 years.  At that rate of decline, it could vanish in 1500 to 2000 years.  Scientists gathered recently at a meeting of the American Geophysical Union pondered whether a reversal is occurring, but a Harvard scientist claimed that would be a rare event. 
    If the magnetic field continues to decline, life on Earth is in grave danger in the far future.  Atmospheric ozone would diminish, exposing life to deadly ultraviolet radiation, and high-energy cosmic rays and solar storms would put life at risk of ionizing radiation, leading to cancer, blindness and neurological diseases.

The strength of the earth’s magnetic field is one of the longest-measured physical properties of our planet.  It shows a steady decline over the past 150 years.  There is much we still do not understand about planetary magnetic fields.  What causes it?  (The leading dynamo theories are beset with complexities that perplex the experts.)  How big did it get in the past?  (Earth still has the strongest field of any rocky planet, by a large factor.)  Will it reverse and go back up to its former strength?  If it did so in the past, how did life survive the periods when it was weakest?  How long does a reversal take?  There is much we do not know, but one thing is clear from the empirical data: in the present epoch, it is dropping at “an alarming rate” (see Nov 6, March 4, and 11/25/2002 headlines).  Those who believe such a dynamic property can be sustained for 4.6 billion years must add secondary assumptions and subplots to their stories.

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Categories: Physics

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