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    Re: Annual Increase of Variation
    From: Brian Whatcott
    Date: 2002 Feb 13, 17:42 -0600

    At 01:36 PM 2/13/02, you wrote:
    >  gone to zero (if everything proceeds according to its current decay rate -
    >but it won't!)>
    >  Unless geology has changed theories again...I was taught that the
    > magnetic field HAS and will in fact go to zero and reverse, that there is
    > physical evidence in the rocks all over the planet that this is in fact
    > the normal cycle for our dear planet. I don't know about the dates and
    > timeline, just that over the ages the field does weaken and reverse on a
    > regular basis.
    There are scientists who have made a handsome living by writing books and
    articles concerning "saltatory evolution" and such like still, it is
    usually wise to suppose that things will carry on in much the same way that
    they have been carrying on. We have a name for  people who run around
    crying, "The sky is falling..."
    The other, more conservative approach is called gradualism.
    In the matter of the plate theory of continental drift, it was a powerful
    piece of evidence that a record of geomagnetic field reversals was found
    on  drillings sailed perpendicular to submarine sites marking plate edges.
    Some materials I have been looking at, suggest a variable magnetic reversal
    cycle varying between 4 megayears and 1.2 megayears depending on the
    geological epoch.
    On the face of it - suggesting that a reversal will happen in the next
    thousand years is a bet that's about 1000: 2,000,000 against or 1:2000 so
    the odds are not a betting man's delight.
    Still, the evidence such as it is, does not deny the possibility.
      I hear that the loss of a magnetic field, even temporarily would not be a
    very healthy environment.   It's not one of those dinosaur wasting impact
    events - but still there are things that a magnetosphere nicely deflects.
    On balance though, I guess we are more likely to get a new glaciation
    before a field reversal - and that could spoil your whole day. The cycle is
    only in the thousands of years, apparently.
    Brian Whatcott
       Altus OK                      Eureka!

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