Ask A Scientist© Physics Archive

Question:  It would appear that the earth's magnetic poles have 'swapped' many
times, with N & S switching positions.  If this should happen in the current
era, what would be the effect? Obviously all navigational instrumentation would
be affected, but what about the effect of a reversal of the magnetic field
on electronic devices and electro-magnetic equipment? Would such a massive
change affect national power grids?
SBradley, School Dist.  Technology Director
steve
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Answer:  Excellent question! actually, most modern navigational equipment
does not use the Earth's magnetic field because there are many
"magnetic anomolies" that cause compasses not to point due north.
Geomagnetic reversals are common (on geological time-scales)
occurring on average once every 200,000 years.  From geological
evidence (magnetic fields "frozen" in old rocks) it appears that
the reversal process itself takes on order of 1000 years, so the
effects would not be noticeable in your lifetime.  The evidence
also suggests that during this period, the Earth's magnetic field
decreases in strength by a factor of 5 or so..
John Hawley
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