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No. 188 "Vital Articles on Science/Creation" February 1989
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The Mystery of the Earth's Magnetic Field
by Russell Humphreys, Ph.D.*
Copyright (c) 1989 by I.C.R.
All Rights Reserved
* Dr. Humphreys is an ICR Adjunct Professor of Physics and a physicist
at Sandia National Laboratories, Albuquerque, New Mexico. The
Laboratories have not supported this work, and they neither affirm nor
deny its scientific validity.
________________________________________________________________________
The earth's magnetic field has been a mystery to man ever since 13th-
century philosophers first noticed lodestones (magnetic rocks) turning
north.[1] In 1600 A.D., William Gilbert, Queen Elizabeth's physician,
shed light on the mystery by showing that "the terrestrial globe itself
is a great magnet."[2] Today, scientists think the earth is an
_electro_magnet; the source of the magnetic field is probably a large
electric current -- billions of amperes -- circulating in the earth's
fluid core. But there is still a mystery today: _How did the current
get started, and what keeps it going? Scientists, who assume that the
earth is old, conjecture that complicated flows of the fluid in the core
somehow started the current and have maintained it for billions of
years. However, such "dynamo" theories are complex, implausible, and
incomplete. In the last two decades, they have run into serious
problems from magnetic observations on earth[3] and in the solar
system.[4]
In 1971, Dr. Thomas Barnes, a creationist physicist, proposed that
_nothing_ keeps the current in the core going except its own inertia.[5]
His simple and rigorous "free-decay" theory would mean that the current
is running down slowly, like a flywheel without a motor; thus the
strength of the earth's magnetic field would be steadily decreasing over
the centuries.[6] Barnes cited some historical data[7] (not well known
at the time) showing that the overall strength of the earth's field has
indeed steadily declined by about 7% since 1835, when it was first
measured. The decay rate depends on the electrical resistance of the
earth's core, and the observed rate is consistent with the estimated
resistance of materials at core temperatures and pressures.[6,8] The
field strength should decrease by a constant percentage each year, and
the data are consistent with such a decrease, implying that the field
loses half its strength every 1400 years. Such a rapid decay could not
have continued for more than about 10,000 years; otherwise the initial
strength of the field would have been impossibly high. Since the field
probably started when the earth was formed, the present rapid decay of
the field is strong evidence for a young earth.
Old-earth proponents, however, correctly point out that the earth's
magnetic field has not always decayed smoothly.[9,10] Archaeomagnetic
(magnetism of pottery, bricks, etc.) data indicate that the present
steady decay started around 500 A.D. For several millennia before that,
the overall strength of the field had fluctuated up and down
significantly. Paleomagnetic (magnetism of geologic strata) data
provide persuasive evidence that the field reversed its direction scores
of times while the fossil layers were being laid down.[11] Since the
field has changed so violently in the past, old-earthers ask, how do we
know the present decrease in the field is a decay, not a fluctuation or
a reversal? Furthermore, if a "dynamo" process did not start up the
current in the core (as is becoming obvious by the problems with the
theory), then how did the current originate?
History of the Field
This article summarizes five technical papers I have published to
answer such questions. The discriminating reader will want to read them
to understand more fully the model which is only summarized below.
Figure 1 shows what I think is the history of the earth's magnetic
field. It can be divided into the following five episodes:
(1) Creation. In 1983, I pointed out that when God created the
earth's original atoms He could have easily created the earth's magnetic
field also, merely by bringing the atoms into existence with the spin
axes of their nuclei all pointing in the same direction.[12] Many
atomic nuclei spin, and thereby generate tiny magnetic fields. There
were so many spinning nuclei in the earth at creation that, if aligned,
their fields would have added up to a large field of sufficient
magnitude. As thermal collisions disoriented the nuclear spins, the
laws of electricity predict a startup of an electric current within the
core of the earth to sustain the field. The resulting initial field
strength is consistent with the present geomagnetic data and a
6,000-year age for the field. Thus we have a plausible explanation for
how the current in the core got started.
In 1984, I extended my theory to the sun, moon, and planets,[13]
explaining the magnetic fields measured by the space probes of the last
few decades, and predicting the approximate strength of the fields of
Uranus and Neptune. In 1986, Voyager 2 verified the Uranus
prediction,[14] and we should find out about Neptune in early 1990.
(2) Pre-flood decay. After creation (and the Fall), the electric
current in the earth's core would decay slowly, as would the field, for
1656 years, until the Genesis flood. During this period, the field
would have been more than ten times stronger than it is today, thus
shielding the earth from cosmic ray particles more effectively, reducing
the production of carbon 14 in the pre-flood atmosphere, and making the
earth a healthier place.[5]
(3) Rapid reversals during the flood. In 1986, I suggested that
there was a powerful release of energy in the earth's core at the
beginning of the Genesis flood, and that the resulting strong movements
in the core field produced rapid reversals of the earth's magnetic
field, about one per week, during the year that the flood was laying
down the fossil layers at the earth's surface. General physical laws
allow rapid reversals, a likely physical mechanism exists to cause the
reversals, and observations of the sun's magnetic field demonstrate
reversal cycles in nature today. This rapid-reversal model not only
explains the general features of the paleomagnetic data, but also some
specific features which have puzzled evolutionists.[15]
(4) Post-flood fluctuations. The disturbances in the core fluid
during the flood would disrupt the electric current, chopping much of it
up into small swirls oriented in different directions. Then the earth's
field during and after the flood would not have the simple "dipole" (two
poles, north and south) shape it has today. Instead, it would have a
more complex shape, with strong "higher-order" components: quadrupole
(four poles), octopole (eight poles), etc. Paleomagnetic data confirm
the existence of such components in the field in the past. Standard
electromagnetic theory predicts that, after the flood, the higher-order
components would die away faster than the dipole part. Because the
higher-order components can have either polarity, the strength of the
field would fluctuate up and down, as different components died away at
different rates.
Figure 2 shows world-averaged archaeomagnetic data.[16] Since the
dates conventionally assigned to the data points are based on
radiocarbon dating, I have plotted the data on a time scale crudely
corrected for changes in the percentage of carbon 14 in the atmosphere
since the flood. The curve shown is a statistical fit using just the
three simplest of dozens of possible components. The data need to be
re-analyzed, allowing for a more complex field shape, but the curve fits
the main features of the data, in particular, an initial rise and fall,
the broad maximum at about the time of Christ, and the subsequent,
steady decay.[15]
(5) Recent decay. Around 500 A.D., the last remaining higher-order
component became small compared to the main dipole component, and the
field decayed smoothly after that.
Conclusion
Though complex, this history of the earth's magnetic field agrees
with Barnes' basic hypothesis, that the field has always freely decayed.
I have merely made explicit two features which were always implicit in
the free-decay theory: (a) that motions in the core fluid can disturb
the field, and (b) higher-order modes of decay are possible. Both of
these features have a firm basis in theory, experiment, and natural
phenomena. In contrast to dynamo theories, the reversals and
fluctuations I picture _dissipated_ energy. The field has always been
losing energy despite its variations, so it cannot be more than 10,000
years old. We now have simple explanations for the field's origin,
history, and present state. In this light, the earth's magnetic field
is no longer a mystery; it is a testimony of God's handiwork.
References
1. Pregrinus, Petrus. _Epistole de Magnete_ (1279). Trans. by
Silvanus P. Thompson, _Epistle of Peter Periginus of Maricourt,
to Sygerus of Foucaucourt, Soldier, Concerning Magnets_. London:
1902.
2. Gilbert, William. _De Magnete_ (1600). Trans. by P. Fleury
Mottelay in _Great Books of the Western World_, Vol. 28, R.M.
Hutchins, ed. Chicago: Encyclopedia Britannica, 1952.
3. 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 1985), pp. 47-49.
4. Parker, E.N. "Magnetic fields in the cosmos," Scientific American
249 (Aug. 1983) pp. 44-54, see remarks on Mercury and Mars, p. 52.
Hood, L.L. "The enigma of lunar magnetism," EOS 62, (21 April
1981). pp. 161-163. Dirscoll, E. "That magnetic moon: How did it get
that way?" Science News 101, (27 May 1972), pp. 346-347. For
comments, see ref. 13.
5. Barnes, T.G. "Decay of the earth's magnetic moment and the
geochronological implications," CRSQ* 8 (June 1971), pp. 24-29.
6. ---- "Electromagnetics of the Earth's field and evaluation of
electric conductivity, current, and joule heating of the earth's
core," CRSQ 9 (Mar. 1973), pp. 222-230. Decay rate implies
conductivity of 40,000 mho/m.
7. 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. Govt. Printing Office, Washington, D.C.,
Table 3, p. 14.
8. Stacey, F.D. "Electrical resistivity of the earth's core," _Earth
and Planetary Science Letters_. 3 (1967), pp. 204-206. Likely
core materials imply conductivity of roughly 33,000 mho/m,
agreeing with ref. 6.
9. Young, D. A. _Christianity and the Age of the Earth_. Grand Rapids:
Zondervan, 1982. pp. 117-124.
10. Dalrymple, G.B. "Can the earth be dated from decay of its magnetic
field?" _Journal of Geological Education_ 31 (March 1983), pp.
124-132.
11. Humphreys, D.R. "Has the earth's magnetic field ever flipped?"
_CRSQ_ 25 (Dec. 1988), in press.
12. ---- "The creation of the earth's magnetic field," _CRSQ_ 20 (Sept.
1983), pp. 89-94.
13. ---- "The creation of planetary magnetic fields," _CRSQ_ 21 (Dec.
1984), pp. 140-149.
14. ---- "The magnetic field of Uranus," _CRSQ_ 23 (Dec. 1986), pp. 115.
15. ---- "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 Ave., 1986. pp. 113-126.
16. Merrill, R.T. and M.W. McElhinney. _The Earth's Magnetic Field_.
London: Academic Press, 1983. pp. 101-106.
* CRSQ: Creation Research Society Quarterly, P.O. Box 969, Ashland, OH
44805-0969
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and "Tenets of Biblical Creationism."
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