Re: Barne's Magnetic Data

From: George Murphy (
Date: Tue Mar 18 2003 - 15:01:12 EST

  • Next message: Michael Roberts: "Re: Barne's Magnetic Data"

    gordon brown wrote:
    > Many years ago I heard a talk by Jack Eddy in which he gave results on the
    > strength of the earth's magnetic field based on measurements made in tree
    > rings. I don't know the science behind it. It may be based on quantities
    > of certain isotopes. The conclusion was that the earth's magnetic field
    > had a relative maximum at a certain date in the past. (I believe it was
    > either 500 or 1500 A.D.) You ought to be able to find Eddy's paper in the
    > literature somewhere.

            If one assumes that the earth's field is simply frozen into a core with finite
    conductivity then it's easy to do a back of the envelope calculation & get exponential
    decay with a characteristic time of a few thousand years, & it's simple enough to fit a
    semi-log plot to a few data points. But this makes sense only if one has reason to
    believe that such a model is adequate to explain geomagnetic data & it isn't.
            But in a more fundamental way the whole enterprise is just silly because
    paleomagnetic data extends back millions of years. Beyond that, we're now getting
    detailed information - e.g., from the current Wilkinson Microwave Anisotropy Probe
    (WMAP) - about the condition of the universe ~13 _billion_ years ago. The whole YEC
    enterprise is just sad. It's not just that a lot of ignorant people buy into it, but
    that there are some who have real ability for science who have been misled into wasting
    their talents on a completely futile enterprise.
            BTW, is Jack Eddy the discoverer of Eddy currents? (:))


    George L. Murphy

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