By: David Rice
To: Mark Fox
Re: Magnetic Fields
cc: J.J. Hitt
DR> Mark claimed that the Earth's magnetic field is
DR> "decaying," when in fact it is not.
MF> 1835...8.558 x 102 amps per meter
MF> 1945...8.065 x 102 amps per meter
MF> 1965...8.017 x 102 amps per meter
MF> Measuring by a consistent rate, the magnetic rate it is
MF> declining at a half life rate of 830-1400 years (26 nanoteslars
MF> per year)-- half life every 830 (Magstat)-1400 years (Barnes).
That's from the Creationist Thomas Barnes in his "magnetic field
decay" idea, as published in the Institute for Creation Research
cult's Technical Monograph called _The Origin and Destiny of the
Earth's Magnetic Field_. Barnes's assumptions are rather. . . how
shall it be put. . . "unique." You present these numbers as if
they were factual, but that is not even close to the truth.
Barnes's data rests on the following falsified assumptions:
1) Exponential extrapolation is justified far beyond his data (x50)
2) A uniform decay of a process known to not change in a uniform manner
3) An out-of-favor model for the source of the earth's magnetic field
4) There is no force that "drives" the field (i.e., no energy input)
5) The non-dipole component of the field can be ignored
6) A better straight-line fit to the data can be ignored
You are encouraged to read (Dalrymple, 1983) or (Dalrymple,
1986, pp. 54-57). References:
Dalrymple, G. Brent, 1983, "Can the Earth be Dated from Decay
of Its Magnetic Field?", Journal of Geological Education, 1983,
Vol. 31, pp. 124-133.
Dalrymple, G. Brent, 1986, "USGS Open-File Report 86-110:
Radiometric Dating, Geologic Time, and the Age of the Earth: A
Reply to ``Scientific Creationism''", U.S. Geological Survey,
The latter paper (Dalrymple, 1986) is an excellent introduction
to radiometric dating and Creationist criticisms thereof. It
is available from the Government Printing Office for $14.
It's trivial to shoot Barnes's propositions full of holes, but
it is even better to try to test them by measuring the strength
of the Earth's magnetic field back beyond Barnes's limited
data. This can be done by measuring the remnant magnetism in
lava flows and archaeological objects (e.g., clay pots). If
Barnes were correct, then the data would confirm his
exponential extrapolation. However, THE DATA REFUTES BARNES.
The diagram I've seen appears originally in (Chapman, 1980) and
is reproduced in (Dalrymple, 1983) and (Dalrymple, 1986, Figure
15). It shows a decreasing trend over the last 2500 years (or
so), preceeded by an increasing (on average) trend that covers
The data indicates that the strength of the magnetic field from
about 8,000 years ago to about 4,000 years ago was slightly less
than its present strength. (Barnes's "model" predicts that the
strength of the field would have been approximately 20 TO 50
TIMES its present value, during that same interval.)
There is no support from the measurement of remnant magnetism
for a continuous field decay, linear or exponential. This is
not too surprising, as there is ample evidence that the entire
field has reversed itself several times through history --
meaning that any unidirectional extrapolation would be senseless.
Champion, D. E., "Holocene geomagnetic secular variation in the
earth's magnetic field in the western United States:
Implications for the global geomagnetic field", Ph.D. Thesis,
California Institute of Technology, 1980.
Dalrymple, G. Brent, 1983. See Section (I).
Dalrymple, G. Brent, 1986. See Section (I).
666 - number of the beast.
700 Club - church of the beast.