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No. 242 "Vital Articles on Science/Creation" August 1993
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THE EARTH'S MAGNETIC FIELD IS YOUNG
by Russell Humphreys, Ph.D.*
Copyright (c) 1993 by I.C.R.
All Rights Reserved
* Dr. Humphreys is an ICR Adjunt Professor of Physics and a physicist
at Sandis National Laboratories, Albuquergue, New Mexico. The Labori-
tories have not supported this work.
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The earth's magnetic field is a powerful witness for a world much
younger than the billions of years required by evolutionary theories.
Let's start the story with the most prominent feature of the field
today--its very rapid decay.
The Field Is Decaying Rapidly
The average "intensity" of the earth's magnetic field has decreased
exponentially by about 7% since its first careful measurement in
1829.[1] The field's intensity includes components of strength and
direction and tells us the amount of force turning a compass needle
northward. By estimating the field intensity everywhere (in, on, and
above the earth), we can calculate the total electrical "energy" stored
in the field. Such calculations show that the total energy in the field
has decreased by about 14% since 1829.
This rapid decay of both energy and intensity was not widely known, even
among scientists, until Dr. Thomas Barnes, a creationist physicist,
began publicizing it in 1971.[2] He pointed out that such a decay would
occur very naturally if the electrical current producing the field were
slowly losing energy because of the electrical resistance of the
core.[3] This theory is called "free decay." The observed decay rate is
exactly what one would expect from the electrical properties of the
materials most likely to be in the core.[4]
Evolutionary Theories Haven't Worked
The free-decay theory contradicts the evolutionary "dynamo" theories,
which claim that complex processes in the earth's core have converted
heat energy into electrical energy, much like an electric generator,
maintaining the field for billions of years.[5] Many intelligent
scientists have been working on dynamo theories for over four decades
without great success. Furthermore, recent measurements of electric
currents in the sea floor weigh heavily against the most popular class
of dynamo theories.[6]
Thus evolutionary dynamo theories do not have a good explanation for the
rapid decay of the field, whereas the free-decay theory does. However,
our historical data on the intensity of the field only goes back to
1829. Was the field decaying before that? Fortunately, there is a
scientific way to answer that question.
"Archaeomagnetism" is the study of the magnetization of bricks, pottery,
campfire stones, and other man-related objects studied by
archaeologists. Iron oxides in those objects retain a record of the
strength and direction of the earth's magnetic field at the time they
last cooled to normal temperatures. Archaeomagnetic data taken worldwide
show that the intensity of the earth's magnetic field was about 40%
greater in 1000 A.D. than it is today, and that it has declined steadily
since then.[7]
Such a rapid decay could not have been going on continuously for
millions of years, because the field would have to have been impossibly
strong in the past in order for it to still exist today. Creationists of
the 1970s extrapolated today's decay back into the past, showing that
the field could not be more than about 10,000 years old, assuming a
constant decay of intensity.
Unfortunately, the archaeomagnetic data do not support that
assumption.[7] Instead, the data show that the field intensity at the
earth's surface fluctuated wildly up and down during the third
millennium before Christ (see figure 1). A final fluctuation slowly
increased the intensity until it reached a peak (50% higher than today)
at about the time of Christ. Then it began a slowly accelerating
decrease. By about 1000 A.D., the decrease was nearly as fast as it is
today.
The Field Has Reversed Direction Many Times
"Paleomagnetism" is the study of magnetization locked into rocks at the
time of their formation. Paleomagnetic data show that while the geologic
strata were being laid down, the earth's magnetic field reversed its
direction hundreds of times. Reversals are a very severe departure from
steady decay of intensity.
Both archaeomagnetic and paleomagnetic data contradict the early
creationist assumption of constant decay of intensity. In 1988 I
published a review paper documenting the great diversity and reliability
of the data.[8]
A Creationist Theory for Reversals and Fluctuations
The validity of the data required a new theory to explain them. In 1986
I suggested that strong flows of the fluid in the earth's core could
produce rapid reversals of the field during and after the Genesis
flood.[9] The resulting disturbances in the core would cause the field
intensity at the earth's surface to fluctuate up and down for thousands
of years afterwards.
This "dynamic-decay" theory is a more general version of the free-decay
theory, since it takes account of motions in the core fluid. Dynamic
decay explains the main features of the data, especially several
features evolutionists find puzzling. In 1988, startling new evidence
was found for the most essential prediction of my theory--very rapid
reversals;[10] and in 1990, I showed a specific physical mechanism for
such reversals.[11]
The Field's "Energy" Has Always Decreased
According to the dynamic-decay theory, the "energy" in the field has
always decreased rapidly. In fact, the energy loss during reversals and
fluctuations would have been even faster than today's rate. This
information allows us to estimate the age of the field.
The data and the dynamic-decay theory imply that, ever since creation,
the field has always lost at least half its energy every 700 years.
Figure 2 illustrates the factors involved. The maximum energy in the
figure comes from another theory I proposed about the nature of the
field when God created the earth, a theory which successfully predicted
spaceprobe measurements of planetary magnetic fields.[12] Extrapolating
today's energy decay rate back (along the dotted straight line labeled
"free decay") to that limit yields a maximum age of 8700 years.
According to the dynamic-decay theory, the true age would be less than
that because of extra losses during the reversals and fluctuations. The
solid line (labeled "dynamic decay") shows that with a significant loss
of energy during the Genesis flood, the age of the field would be about
6000 years.
Are There Any Loopholes in the Logic?
The precise age limits above depend not only on the dynamic decay
theory, but also on the theory of planetary magnetic-field origins.
However, we can still set a rough maximum to the initial energy from
basic physical considerations, as Dr. Barnes has done.[2] Such a maximum
would limit the age to roughly 10,000 years.
It is also possible that a small percentage of today's energy decay is
not free decay, due to the core's electrical resistance; but rather is
dynamic decay, due to residual motions in the core fluid. In that case,
the resistance of the core would be less, and the maximum age of the
field would be greater. But even in this extreme case, the maximum age
would still be only about 100,000 years, far short of the billions of
years evolution needs.
Conclusion
At present, the only working theory for the origin, fluctuations, rapid
reversals, and decay of the field is a creationist theory_a theory that
fits all the data. Thus, according to the best theory and data we have,
the earth's magnetic field certainly is less than 100,000 years old;
very likely less than 10,000 years old, and fits in well with the
face-value Biblical age of 6,000 years.
References
1. McDonald, K. L. and R. H. Gunst. "An analysis of the earth's
magnetic field from 1835 to 1965," ESSA Technical Report IER
46-IES 1 (July 1967) U.S. Government Printing Office, Washington,
D.C., Table 3, p. 14.
2. Barnes, T. G. "Decay of the earth's magnetic moment and the
geochronological implications," _Creation_Research_Society_
_Quarterly 8_ (June 1971) 24-29.
3. Barnes, T. G. "Electromagnetics of the earth's field and evaluation
of electric conductivity, current, and Joule heating of the earth's
core," _Creation_Research_Society_Quarterly_9_ (March 1973) 222-230.
Decay rate implies conductivity of 40,000 mho/m.
4. Stacey, F. D. "Electrical resistivity of the earth's core,
_Earth_and_ Planetary_Science_Letters_3_ (1967) 204-206. Likely core
materials imply conductivity of roughly 33,000 mho/m, agreeing with
Ref. 3.
5. Inglis, D. R. "Dynamo theory of the earth's varying magnetic field,"
_Reviews_of_Modern_Physics_53_ (July 1981) 481-496.
6. Lanzerotti, L. J., et al. "Measurements of the large-scale
direct-current earth potential and possible implications for the
geomagnetic dynamo,"_Science_229_ (5 July 1986) 47-49.
7. Merrill, R. T. and M. W. McElhinney. The Earth's Magnetic Field
(London: Academic Press, 1983) 101-106.
8. Humphreys, D. R. "Has the earth's magnetic field ever flipped?"
_Creation _Research_Society_Quarterly_25_ (December 1988) 89-94.
9. Humphreys, D. R. "Reversals of the earth's magnetic field during the
Genesis flood," _Proceedings_of_the_First_International_Conference_
_on_Creationism_, Vol. II (Pittsburgh: Creation Science Fellowship,
362 Ashland Avenue, 1986) 113-126.
10. Coe, R. S. and M. Prevot. "Evidence suggesting extremely rapid field
variation during a geomagnetic reversal," _Earth_and_Planetary_
_Science_Letters _93_ (April 1989) 292-298.
11. Humphreys, D. R. "Physical mechanism for reversals of the earth's
magnetic field during the flood,"_Proceedings_of_the_Second_
_International_Conference_ on_Creationism, Vol. II (Pittsburgh:
Creation Science Fellowship, 362 Ashland Avenue, 1990) 129-142.
12. Humphreys, D. R. "The creation of planetary magnetic fields,"
_Creation_ _Research_Society_Quarterly_21_ (December 1984) 140-149,
records the predictions. Humphreys, D.R. "Good news from Neptune:
The Voyager II magnetic measurements,"
_Creation_Research_Society_Quarterly_27_ (June 1990) 15-17, reports
the confirmation of the predictions. See also Humphreys, D. R.
"Beyond Neptune: Voyager II supports creation," _ICR_Impact_ No. 203
(May 1990).
________________________________________________________________________
This "Impact" was converted to ASCII, for BBS use,
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