his work is based on the book Origin and Destiny of the Earth's Magnetic Field by Thomas G. Barnes, I.C.R. Technical Monograph No. 4, copyright July, 1973, by the Institute for Creation Research. Barnes earned an A.B. degree in physics from Hardin-Simmons College, Abilene, Texas in 1933, and an M.S. degree from Brown University in 1936. In 1950, the re-named Hardin-Simmons University awarded Barnes the honorary degree, D.Sc. He is emeritus professor of physics, University of Texas at El Paso, where he joined the faculty in 1936.
In this book, Barnes advances the argument that the observed exponential decay of the Earth's magnetic field proves that the Earth cannot be more than about 10,000 years old. It is my intention to show that this argument is flawed in the extreme, and is therefore without any merit. At this time I have not seen the second edition of the book, though I know that one exists. All of my comments and arguments are therefore directed only towards the first edition, cited at the top of the page. So far as I know the second edition is out of print at this time.
I have inserted a few additional references that came to my attention only after this article was essentially finished. I just stuck them into the numbered sequence with little letters; it's a lot easier than going through and renumbering all those references each time I find something. I could refine and rewrite forever, but I have to stop and submit it someday. Nevertheless, I believe the reference list is quite complete, and should provide broad exposure to all sides of the argument.
The first thing I want to try to do is to introduce the reader to the basic concepts needed to, hopefully, make sense of the various arguments. However, of necessity I cannot embark on a detailed and technical explication of the physics involved. There are references that one can consult to learn more of those details, for those who wish to do so. The books by Merrill & McElhinney , and J.A. Jacobs , do treat the technical details, but also carry enough more general material that the less mathematically inclined readers should be able to get something out of them. The less timid, or more mathematically inclined, can go after the two books [3, 4] that comprise the proceedings of the 1992 NATO Advanced Study Institute on the theory of solar and planetary dynamos.
There are two primary methods by which one can generate a mathematical description of the Earth's magnetic field, or any other field for that matter. One way, which I will call the physical model, is to derive the form of the field directly from the equations that govern the physical processes by which the field is generated. The other, which I will call the empirical model, is to use the known value of the field at some set of points, as a basis for guessing what the value would be, at points where no measurements were made. By now, scientists have used both methods extensively, but historically the empirical model was developed first, since at the time the Earth's magnetism was first discovered and studied, the physics by which it could be generated was completely unknown.
The standard empirical method for modeling the values of any three dimensional field is called spherical harmonics. This mathematical tool was invented by the ubiquitous German mathematician, Carl Freidrich Gauss, circa 1835, for the purpose of evaluating the Earth's magnetic field. This ingenious method uses an infinite sum of trigonometric functions to evaluate a field, on the surface of a sphere embedded in the field. Since any surface can be evaluated, then the complete three dimensional shape of the field can be returned by extending the analysis to an integration over a family of nested, concentric spheres, which fills the space of interest.
Of course, in practice, real computers cannot carry out an infinite sum, and have to stop summing after a finite number of terms. But, as you might imagine, modern computers can add a lot of numbers together very fast, so while this may have been a fundamental problem for Gauss, it is no longer all that bothersome. One can approximate the true shape of the field by extending the sum to an arbitrarily large number of terms, the only limitation being the practicalities involved. In practice, the magnetic field is measured constantly at a number of official magnetic observatories all over the world, as well as at universities, or by other scientific teams and expeditions, and now several spacecraft measure the field well above the Earth, and out into deep space. These data are then fed into computer programs which use spherical harmonics to create a model for the field everywhere on the Earth. These models are actively tested and refined until they match the observed field to within the limits set by natural and unavoidable experimental uncertainties.
It is very important to keep in mind that the empirical model is built entirely from a statistical analysis of the data themselves. It is essentially independent from whatever physics might be involved in generating the field. One of Barnes' many mistakes is to insist that only the dipole component of the magnetic field is generated by currents within the Earth, and that all lesser components (called 'higher order components' in physics jargon) are generated by some other process, such as magnetic rocks or telluric currents (electric currents induced in the crust, for example, by lightning in thunderstorms, or induced as a reaction to currents in the ionosphere). This is a poor idea, as it is very hard to reconcile with the spatial extent of these higher order components, as illustrated by figure 2.5 in [1, page 25]. It is very hard to imagine a field of magnetic rocks, or a coherent telluric current, either of which is as large as one half or one quarter of the Earth. But Barnes is essentially forced to commit this error as a natural result of his rejection of dynamo theory, and his model of an exponentially decaying current in the Earth's core as the source of the Earth's magnetic field. I make note of this error in order to emphasize that Barnes' failure has a lot to do with very fundamental aspects of the problem, which he hides behind a smoke screen of superfluous detail, as we shall see.
The physical model for describing the Earth's magnetic field carries the impressive looking name magnetohydrodynamics (MHD), but is also commonly called dynamo theory. Simply stated, it has been shown that turbulent motions within an electrically conductive fluid will generate magnetic fields. However, the mathematical equations which govern the physics of the problem are frightfully complicated, and may well constitute the single most difficult mathematical problem in all of geophysics. MHD models require the simultaneous solution of a full set of coupled non-linear vector differential equations. This problem, so far as I know, still does not have a completely general analytical solution, though some special cases do. The complex cases are invariably modeled numerically with high speed computers. These methods are less well developed than the empirical models, but much progress has been made over the last few years. Their eventual solution promises to deliver results that empirical models cannot, namely an understanding of the complex physics involved. At this time computational MHD models act like real, observed magnetic fields, and there is little doubt but that MHD will eventually deliver a full description of the Earth's magnetic field.
The important thing to remember here is that the problem is not solved. One should not conclude from this that scientists do not know anything at all. On the contrary, they know a great deal, as a perusal of the references I gave above will show. They just don't know everything, and cannot answer every question. Nobody knows, yet, by exactly what mechanism specific fluid motions generate the Earth's specific magnetic field, but the presence of turbulent motions in the Earth's fluid outer core can hardly be denied, and physical models do show that the expected velocities will, in general, generate magnetic fields. The short verdict is that there is no useful competing theory for the existence of the Earth's magnetic field.
I will start with a brief outline of the book itself, for which the table of contents, reproduced in table 1, will serve. The first section, Origin and Destiny of the Earth's Magnetic Field, is in the author's words, a "self contained treatment for the layman, teaching him the elementary physics involved and showing him how it applies to the source of the earth's magnetic field." The following three sections are reprints of Barnes' original technical papers, published earlier in the Creation Research Society Quarterly (the original publication dates and/or citations are not given in the book, but they can be found in other sources, and I have inserted them here in parentheses, where "CRSQ" is the Creation Research Society Quarterly). The technical development is therefore a bit confused, with some repetition. However, the table of contents is detailed and so provides a pretty good outline of the book's contents. The presentation is a bit unusual; there are only 64 numbered pages, but all of the pages are printed on only one side.
|I||Origin and Destiny of the Earth's Magnetic field|
|A||Natural and Artificial Magnets|
|B||Representation of the Magnetic Field by Lines of Force|
|C||Thermal Demagnetization of Materials|
|D||The Earth's magnet is an Electromagnet|
|E||The Magnetic Field Shields the Earth from Radiation|
|F||Source of the Current in the Electromagnet|
|G||Observed Decay in the Earth's Magnetic Field|
|H||Half-Life of the Earth's Magnet|
|I||The Earth's Magnetic Clock|
|J||Self-Induction Slows the Decay of the Magnetic Field|
|K||Clues to Properties of the Earth's Core|
|L||Present Value of Current in the Earth's Core|
|M||Electric Heating in the Earth's Core|
|N||Vanishing Date for the Earth's Magnetic Field|
|O||Consequences of the Decay of the Magnetic Field|
|P||Initial Value of the Earth's Magnetic Field|
|Q||Origin of the Earth's Magnetic Field|
|R||Weaknesses in the Traditional Reversal Hypothesis|
|S||Origin of the Earth|
|II||Decay of the Earth's Magnetic Moment and the Geochronological Implications (CRSQ 8: 24-29, 1971)|
|A||Magnetic Moment: Source of the Earth's Main Field|
|B||Historical values of the Earth's Magnetic Moment Indicate the Decay|
|C||Exponential Decay of the Earth's Magnetic Moment|
|D||1,400 Year Half-Life for the Earth's Magnetic Moment|
|E||Secondary Magnetic Fields|
|F||Effect of the Strong Magnetic Field in the Past on Radio Carbon Dating|
|III||Young Age vs. Geologic Age for the Earth's Magnetic Field (CRSQ 9:47-50, 1972)|
|A||Present Decay Rate of the Magnetic Field|
|B||Conflicting Views on the Source of the Magnetic Field|
|C||Lamb's Solution support's the Young Age Theory|
|D||Long Age Theory Requires a Dynamo|
|E||Association of Reversal Magnetization with the Age of the Rocks|
|F||Difficulties with the Reversal Hypothesis|
|G||Permanent Magnetization of Rocks is Found to be Ill-Defined|
|H||Stresses and Folding May Alter the Orientation of Rock Magnetization|
|IV||Electromagnetics of the Earth's Field and Evaluation of Electric Conductivity, Current, and Joule Heating in the Earth's Core (CRSQ 9: 222-230, 1973)|
|A||Derivation of Solutions in the Core|
|B||Matching of Field Solutions at the Boundary|
|C||Reduced Solutions for the Field Components and the Time Constant|
|D||Evaluation of Time Constant and Conductivity|
|E||Current in the Earth's Core|
|F||Joule Heating in the earth's Core|
The obvious place to start is with the fundamental assertion of the book, that the Earth's magnetic field is exponentially decaying. If this turns out to be untrue, or unsupportable, then Barnes' entire thesis is immediately nullified. So the next most obvious thing to do at this point is to present the reader with the data. These data, which follow in my table 2, are taken from Barnes (pages 33 & 61). Barnes in turn credits the ESSA report of McDonald & Gunst  as his source. I once saw a copy of that report, but am not able to find it now. I presume that Barnes can copy, and that the data are as given in . In any case, these are the data that Barnes presents in defence of his own thesis, so the enterprising reader can examine the data as they see fit, in order to gauge compliance with the exponential decay hypothesis. Multiple values for one year indicate separate determinations, reported in separate original references. Those references are given by Barnes, but I have omitted them here.
(× 1022 amp-meter2)
Before we go any farther, the attentive reader should have already spotted at least one problem. This table does not show any experimental uncertainties associated with any of the data points. This is the manner in which Barnes presents the data, and nowhere in his book is the subject of experimental uncertainty mentioned at all. I have not seen the McDonald & Gunst paper in preparing this article, so I cannot say whether or not they presented the data without uncertainties as well, but if they did, then their own argument suffers from the omission just as Barnes' argument does here.
From these data Barnes has determined that the Earth's magnetic field is decaying exponentially. Throughout his book, whenever he mentions this exponential decay, he points the reader to section II-D, page 36 to view the justification. On that page of his book, he justifies the exponential decay conclusion as follows, the emphasis is mine. B0, as referred to by Barnes, is the equatorial magnetic field strength, which is included in his tables, but omitted from mine.
"When values of the magnetic moment, M, in table 1 are plotted against time, t, on semi-log coordinate paper, the points lie approximately on a straight line, as one would expect for an exponential decay of the Earth's magnetic moment. This is also true, of course, for a plot of B0 against t. We therefore assume that the decay is exponential and write ... "
This, of course, is no justification at all. Barnes simply assumed that the decay was exponential. However, later in the book, at the beginning of section IV, page 52, Barnes makes a slightly more heroic attempt to justify the exponential decay theory as follows:
"All data were processed on a CDC3100 electronic computer. A least square exponential fit was employed to evaluate the time constant. As a separate check it was noted that the variability was smaller for this exponential fit than for a straight line fit, as one would expect from the exponential solutions obtained from Maxwell's equations."
In these two passages we see the full and entire text of the justification for deriving an exponential decay from the tabulated data. Anyone reading this who has had experience with numerical approximations, data curve fitting, and etc. should be able to recognize at once that the argument is very poor. First, it should be obvious that one cannot perform an unweighted fit, completely ignoring any experimental uncertainties. The early data from the mid 1800's, which are derived from experimental methods that are far less accurate and precise than modern methods, necessarily have much larger uncertainties associated with them, and should be weighted accordingly in any attempt to fit the data to a curve. Second, Barnes' reference to the "variability" of the exponential versus straight line fit is highly ambiguous. Is "variability" supposed to mean "variance"? If the variance of the fit is greater than the experimental uncertainties, then the line and exponential cannot be distinguished, in fact, one from the other. And what does "smaller" mean? Was the difference in variance between the two fits (if that is what "variability" means) significant or not? These kinds of curve fitting exercises are fraught with peril, and relying on the difference in variance between fits, where it is obvious that in fact either an exponential or a straight line will produce a "good" fit, is an exceptionally unreliable procedure.
Even without a plot, just by looking at the data tabulated above, the reader should be able to see that the moment values since 1935 appear essentially flat around a value of about 8.047 +/- 0.029, while the data prior to 1935 show a clear downward trend. One could easily argue that two straight lines fit the data better than one, and even better than one exponential (this is an exercise that I have not undertaken, but the motivated reader is welcome to see if my intuition is trustworthy). That fact alone will easily explain why a single exponential will fit the data better than a single straight line, as the slight curve of the exponential can better approximate the kink in the data. These considerations make it extremely difficult to use the data alone as an a-priori justification for any particular curve fit over another. In fact, one could over interpret the data even to the extent of claiming that the field was in decay until about 1935, when it then stopped decaying.
At this point we can see that the claim of an exponential decay is quite without merit. Since this is the central edifice of Barnes' hypothesis, we could simply end our criticism right here. However, Barnes also argues strenuously against the standard theory of dynamo action generating the Earth's magnetic field. But in making such an argument Barnes is required to make a number of highly unreasonable assertions that I will outline here. As I already pointed out in the introduction, I will not go into the details of dynamo theory myself, but refer the reader to the sources indicated in my reference section.
Barnes gives two reasons for rejecting dynamo theory, both completely inadequate. His primary reason is a bold assertion that all dynamo models are ruled out by Cowling's theorem. This theorem was derived by T.G. Cowling [6a] while he was working under Oliver Lodge on the problem of sunspot magnetic fields. But, it is a general theorem, which proves that an axially symmetric field cannot be maintained through a self sustaining dynamo by an axially symmetric current. Barnes has a great deal of faith in the ability of Cowling's theorem to disable dynamo theory. In section I-F, on page 9, Barnes says (I have not included his references) ...
"In every case this dynamo theory has been shown to be inadequate and untenable. It is supposed to be related to hypothetical movements of fluid in the core of the earth. However, rigorous mathematical analyses, such as that by T.G. Cowling, prove that any plausible motion of fluids in the earth's core cannot produce the dynamo, even if the hypothesized motions did exist."
And again, in section III-D, pages 44-45, Barnes has this to say (I have once again not included his footnotes, the emphasis is from Barnes' original):
"To make matters worse for the dynamo concept, Cowling (1934) proved that is not possible for fluid motions to generate a magnetic field with axial symmetry (such as the dipole field of the earth). Cowling's theorem is indeed a blow to the evolutionary efforts to develop a dynamo theory. It eliminates the possibility of a straight forward theory for a self-exciting dynamo to sustain the earth's magnetic field. Nevertheless, futile efforts continue and one still finds claims, but no proof, of a dynamo in the core of the earth."
[ ... ]
"Note that the only possibility of having a dynamo in the earth's core requires motion of fluid in the core of the earth; that such motion cannot be a simple rotation, or any other symmetric motion; and that all proposed motions have been unreasonably complex motions. As of now there is no physical evidence, seismic or otherwise, that there is any motion within the core."
The second passage, from page 45, is certainly amazing. How could there not be convective, turbulent motion in a rotating fluid shell heated from below [6b]?
While Barnes was certainly satisfied with the power of Cowling's theorem, it is not evident that he had done his homework. Cowling himself did not see things this way, and in 1957 , 16 years before the publication date of Barnes' book, Cowling has this to say:
[The abstract reads ... ]
"A general type of mathematical argument is described, which applies to all the cases in which dynamo maintenance of a steady magnetic field by motion in a uniform mass is known to be impossible. The number of general classes of motion to which this type of argument applies is shown to be strictly limited. It is suggested that all proofs of the impossibility of dynamo maintenance for general classes of motion must be reducible to this type."
[The concluding sentences read ... ]
"The argument is certainly not complete, but it is plausible. If it is indeed sound, further search for a general theorem on the impossibility of dynamo maintenance would appear to be pointless."
This shows that by 1957 it was already known that Cowling's theorem was not the all powerful anti-dynamo theorem that some, even Cowling, thought it was when the theorem was first presented. Barnes seems quite unaware of the research that had gone into Cowling's theorem in particular, in the years before his book was published. He also seems unaware of the 1970 review by E.N. Parker  into the origin of the solar magnetic field. This review, also published before Barnes' book, demonstrates the weakness of Barnes' claim that dynamo theory is shown to be inadequate. I shall present here a somewhat lengthy, but appropriate paragraph, from page 9 of Parker's paper (emphasis is from Parker's original) ...
"First of all, the original derivation of the dynamo equations (Parker 1955b, 1957), was heuristic, based on separate formal calculations of the separate aspects of the interaction of the cyclonic convective motions with the toroidal field. The whole picture, leading to equation 6, was then assembled through physical arguments, as presented above. Thus the theory did not represent a formal mathematical proof from the hydromagnetic equation 1 that fluid motions can regenerate a magnetic field. There was real concern at the time that some subtle aspect of the problem was overlooked in the construction of the dynamo equations, and that regenerative dynamos were not possible, i.e. there was concern that Cowling's theorem was but a special case of a general 'impossibility' theorem for homogenous dynamos. Cowling's theorem was not itself directly applicable, of course, because in view of the individual convective cells, the dynamo did not have axial symmetry nor was it stationary in time. But the dynamo did have axial symmetry and was stationary in time, if one averaged over the individual convective cells, as was done in constructing the right hand side of 6. There was no reason to assert that the dynamo equations were wrong, i.e. in violation of Cowling's theorem, but a rigorous proof of the existence of some sort of dynamo would be an important philosophical point. Consequently Backus (1958) constructed an idealized two-stage dynamo that could be handled rigorously. he avoided the poor convergence of the formal expansions of the stationary dynamo, used in earlier attempts at formal calculation, by turning on the two different fluid motions (corresponding to the nonuniform rotation and the cyclonic convective motions) alternately in short bursts, followed by extended periods of quiet. During the quiet periods the higher modes decay away, leaving only the lowest mode for the poloidal field and for the toroidal field. In this way he was able to show rigorously that there exist velocity fields in conducting fluids which regenerate magnetic fields."
My point has been to show that, well before the publication of Barnes' book, there was already a sufficient body of knowledge available in the open literature, to show that both of Barnes' main arguments thus far appear either weak, or simply false. But in reality, Barnes is simply playing a trick on us. He knows that Cowling's theorem is limited to special cases, and even says so himself in the passages I quoted above, from pages 44-45. By this time Barnes is already working on the assumption that the exponential decay of the magnetic moment is a proven fact, no longer open for discussion. He uses this fact to support an oblique assertion that the Earth's magnetic field is therefore necessarily generated by an exponentially decaying current, flowing in a circular path within the Earth's core. indeed, he goes to great length to draw on research done by Horace Lamb in the late 1800's, and even goes so far as to hint that the exponential decay theory is "Lamb's theory". If this exponentially decaying current model were valid, then Barnes could properly appeal to Cowling's theorem, since the axially symmetric current, and the pure dipole component, together fit the limited class of conditions in which Cowling's theorem prohibits dynamo maintenance.
Barnes spends very little time in the book actually justifying his claim that the field is seen to decay exponentially, or his surprising claim that appropriate fluid motions cannot occur in the regime of the Earth's core. Yet by now we can see that these claims are actually central to his entire thesis, and their failure brings his argument tumbling down in ruins. Good stage magicians will do their tricks very quickly, right in front of you, and you won't see it. The rest of the show is just that, show, with lots of colored lights, and dancing girls. Barnes does the same thing, pulling his real tricks very quickly, and distracting the reader with many pages of superfluous details, and pages of detailed mathematics that are all based on false premises anyway. But all the while, he has already played his trick.
The single most important point to take away from this article is that the alleged empirical demonstration that the Earth's magnetic field is decaying exponentially is false. As long as that is understood, all of the rest of Barnes' arguments are seen as resting on false premises.
Barnes also spends some effort to refute the notion that the Earth's magnetic field has ever reversed its polarity. Jacobs' book  gives a good review of the subject, so I won't go into extensive discussion. However, I will point out that here, too, Barnes has managed to construct a remarkably weak argument. Sections III-E through III-H, pages 46-49 are devoted to a one-sided discussion of the known phenomenon, that some rocks will self-reverse their own remnant magnetism. As far as Barnes is concerned, that is enough to label the field reversal "hypothesis' as false, or at least unsupportable. However, at no time does Barnes ever talk about what the real data are. He never mentions the extensive strips of oppositely polarized sea floor sediments in the Atlantic ocean, nor the extensive drill core data from the continents, nor that fact that all of these data sets, from continents and sea floors all over the world, are correlated. This clearly does not happen if all of these reversals are local in nature, as in rocks self reversing, as opposed to global in nature, as in the real field reversing. Barnes' ignoring of the global systematic nature of the data renders his limited objections quite weak. There is an excellent review article, written for the non-specialist, on the current status of the study of geomagnetic field reversals, in light of recent advances in dynamo theory, in the September-October, 1996 issue of American Scientist . Finally, I also note (as described later in this report) that creation scientist D. Russell Humphreys has accepted the reality of field reversals, though he thinks they happened on much shorter time scales than do main stream physicists.
Origin and Destiny was first published 23 years ago, at a time when some of Barnes' arguments might even have looked as if there were some merit attached to them. His arguments are repeated without modification today. However, the real state of dynamo theory has progressed somewhat in the intervening decades, and it is probably a good idea to take stock of that status at this point. Despite the abject failure of Barnes' arguments, it is still at least fair to ask the question, whether or not dynamo theory really is a reasonable idea to explain the existence and behavior of the Earth's magnetic field. As far as I am concerned, the answer is an unqualified yes.
Eight years after the first edition of Barnes' book was published, in 1981, Cowling followed up Parker's earlier review with another, for the Annual Review of Astronomy and Astrophysics . By then he was already able to say this (only slightly different in appearance, since my ASCII text will not reproduce mathematical symbols) ...
" Dynamo maintenance has been established for a wide range of steady motions. Childress (1967, 1970) and G.O. Roberts (1970, 1972) found that a spatially periodic motion could almost always provide maintenance. A number of investigations have considered dynamo maintenance in a liquid sphere, using numerical methods similar to those employed by Bullard & Gellman (1954) in their pioneering work on dynamos. Several authors (e.g. Gubbins 1973, Pekeris et al. 1973) found that the original Bullard-Gellman dynamo does not work, as shown by a breakdown of convergence and of maintenance. Gubbins (1973) found that, whereas antidynamo theorems prove that motions symmetric about an axis cannot maintain magnetic fields with similar symmetry, they can maintain fields with polar components proportional to cos(mphi) or sin(mphi), where phi is the polar angle. The multiplicity of successful solutions has led some authors to suggest that all patterns of steady motion are capable of maintaining dynamos if some antidynamo theorem does not explicitly forbid it.
Note that Cowling refers to work on antidynamo theorems by Gubbins (1973), which is contemporary with the publishing of Barnes' first edition, and that the work of Childress and G.O. Roberts predates Barnes' first edition as well. This, along with my earlier observations only reinforces the conclusion that research sufficient to disprove Barnes' hypothesis existed well before the book was even published. Also, Cowling's comment that almost any steady motion will generate a dynamo, expands on Parker's 1970 observation that velocity fields that were appropriate had already been proven to exist by Backus as early as 1958. Cowling goes on to discuss the pros and cons of dynamo theory in considerable detail; his viewpoint, like Parker's in 1970, was towards the solar magnetic field. Cowling's "Objections to Dynamo Theory" section begins ...
"So far, dynamo theory has been presented from the standpoint of a believer. Few doubts exist as to the applicability of dynamo theory in some form to the Earth's field, provided only that an adequate mechanism can be found to generate the necessary fluid motions. A solar dynamo is less certain, because of the high electrical conductivity of solar material."
Cowling then went on to discuss alternatives, in the case of the sun, mostly theories put forth by Piddington, which include turbulent fields or frozen in fields. But as Cowling says, dynamo maintenance for the Earth's field was already an essentially foregone conclusion.
The current status is extended essentially to the current time by the proceedings of the NATO Advanced Study Institute that I mentioned in the introduction [3, 4]. Published in 1993 & 1994, this is the most recent, or most current general review in book form that I can find (I am writing this in the fall of 1996). Although this study concentrates on dynamo theory in general, especially as applied to the sun, there are some papers of interest with regards the Earth, such as "Energy Sources for Planetary Dynamos" by W.V.R. Malkus, chapter 5 in , and in  we find "Turbulent Dynamo and the Geomagnetic Secular Variation" (pages 229-231) by Pilipenko et al., and "On the Role of Rotation of the Internal Core Relative to the Mantle" (pages 265-270) by Ruzmaikin. Since then it has been shown by some very nice seismological work that the solid inner core of the Earth actually does not rotate with the same axis, or at the same rate, as the Earth outside the fluid core [11a]. This gives some sudden importance to Ruzmaikin's "what if" scenario.
Beyond that, one must consult the technical journals for the very latest news on the details of dynamo theory. The days of its youth are long gone, that a dynamo of some kind is responsible for the Earth's magnetic field is no more in doubt now than it was when Cowling said as much in 1981. The most recent noteworthy results were accomplished by Gary Glatzmaier of Los Alamos National Laboratories and Paul H. Roberts from UCLA. They made use of the (now known) fact that the Earth's inner core rotates out of sync with the rest of the planet [11a], and included this effect in their detailed model of the geodynamo. The result was a long period of stasis followed by a rapid reversal in polarity, during which the field behaved generally as the Earth's field does during real field reversals; the energy migrates from the dipole component into the higher order components, and then reforms a main dipole, with polarity reversed. This very recent result is a major milestone in the history of dynamo theory, and is described in a trio of recent journal papers [11b, 12, 13a]. In particular, this result puts to rest once and for all, the notion advanced by Barnes, that "No acceptable dynamo theory to sustain or oscillate the earth's magnetic field has ever been conceived nor is one very likely." [III-I, page 49]. So much for Barnes' bold prediction.
Contrary to some opinions, the work of Glatzmaier & Roberts does not represent the first time that geophysicists have ever been able to make a computer model dynamo reverse polarity. Crossley, Jensen & Jacobs anticipated these results with realistic reversals in their models, published in 1986 [13b]. But they were unable to replicate physically realistic long-term field behavior. The work by Glatzmaier & Roberts was able to reproduce viable long-term behavior around the reversal, and that is the real value of their work. They also produced a much spiffier detailed analysis of the reversal event itself.
The McDonald and Gunst study  brings up the question of the short term variability of the Earth's magnetic field, which I did not spend much time on while preparing this article. Their approach, which was to consider only the dipole moment, is most appropriate to the study of historical data, where that is really the only reliable measure available. However, modern studies of field variability do not approach the problem in such a simple manner. Rather, the time variability of all of the field components are considered, and characteristic time scales derived for each. The Earth's magnetic field is quite variable over short time periods, and some of that variation is internal in origin. Both of the basic books I have recommended [1, 2] cover this topic in some detail. For a current look at how the short term variations are considered, there is a recent paper out of the U.S. Naval Research Laboratory  that addresses this issue.
A second edition of Barnes' book was published in 1983 , and he wrote a response  to G. Brent Dalrymple [16, 17] in 1984, but I have found nothing from Barnes on the matter since then. However, the now well known and influential creation scientist D. Russell Humphreys has taken up the mantle of the Earth's magnetic field.
Inspired by Barnes, Humphreys devised a creation science theory for the origin of the Earth's magnetic field [18, 19], and then extended that theory to the planets in general . He then followed the journey of the Voyager spacecraft as it explored the outer planets, and hailed the Voyager measurements of the outer planet magnetic fields as a confirmation of his theory [21, 22].
Humphreys' theory  is typical of a style that he has held to ever since, a mixture of physics and divine intervention. In this case, he postulates that God created everything initially out of water, which is a strongly polar molecule. If the Sun and planets are created entirely out of water, and created with some substantial fraction of those water molecules sharing a parallel alignment of their magnetic moments, then the resultant magnetic field of the parent body will also be substantial. But those alignments will collapse rapidly after creation, and the collapsing magnetic field will induce an electric current such as to resist the field collapse (in physics this is called Lenz's law). That establishes the field and the exponentially decaying current. God then intervenes directly and transforms everything into its present constituents, leaving the fields and currents intact. The result is an exponentially decaying field and current system similar to that described by Barnes. As Humphreys put it [20, page 141] ...
"I know of no explicit Scripture which says that God created the heavenly bodies in the same way He did the Earth. But there is a hint, perhaps. The Hebrew word translated 'heavens' in Genesis 1 consists of two other Hebrew words that mean 'there, waters'. Let us assume that God created the Sun, Moon and planets as water, which He then transformed."
[The word for 'heaven' to which Humphreys refers is 'shamayim', wherein 'sham' means 'there' and 'mayim' means 'waters', according to Humphreys, with reference to 'A Concise Hebrew and Aramaic Lexicon of the Old Testament, by W.L. Holladay, 1971 - TJT]
The physics of Humphreys' theory, such as it is, can be represented by a single equation [20, page 142, equation 1]:
where Mc is the magnetic dipole strength at creation, m is the mass of the planet, mw is the mass of a water molecule, w is the magnetic moment of a water molecule, and k is the fraction (0 to 1) of the molecules which have their dipoles aligned at creation. Plug in the MKS units, and numerically we get [20, page 142, equation 2] (MKS units work out to Joules/Tesla or J/T):
Assume that the dipole today (M) is the result of an exponential decay since creation [20, page 143, equation 3]:
where t is the time since creation, and T is a characteristic decay time that depends on the core of the planet as in [20, page 143, equation 4]:
where 0 is the magnetic permeability constant (4 × 107 in MKS units of Henry per meter), is the core conductivity, R is the core radius, and is the usual 3.14159... Finally, if you know the time since creation, you can compute an expected characteristic decay time as in [20, page 143, equation 5]:
I have presented these equations, because this last one is actually quite important, in light of Humphreys' chosen method for testing his theory on the magnetic field of the earth. Humphreys uses a Barnes-type exponential fit to the dipole data for the earth, and derives a characteristic decay time (T) of 2049 +/- 79 years. Setting k = 0.25 he derives an Mc for the earth of 1.41 × 1024 J/T. He then plugs this value of Mc, the Biblical value of t and the current value of M into the equation above, and computes a value of T = 2075 years, concluding "This value agrees with the measured value in (7) to better than two percent, well within the experimental error" [20, page 143]. However, because k is a free parameter in the equation for Mc, so is Mc a free parameter in the equation above for T. This means that Humphreys could not compute a value of T from his theory that was not very close to his 'measured' value, since he can always find a suitable arbitrary value for Mc.
It is for this reason that I am not impressed by Humphreys' confidence in his theory's ability to predict the magnetic dipole moments for Uranus and Neptune, before the Voyager spacecraft observed them. Humphreys' predictions for Uranus [20, page 146] and Neptune [20, page 147] both state that the dipole strength should be "on the order of 1024 J/T". He connects these predictions to his theory by selecting a value for k = 0.25 in both cases, computing a dipole strength at creation, and then estimating a characteristic decay time assuming a core conductivity similar to the terrestrial planets. This brings on the estimate of 1024 J/T, but remember that the dipole at creation is an entirely free parameter. A peek at Humphreys' table II [20, page 147] shows that the dipole for Jupiter is 1.6 × 1027, for Saturn 4.3 × 1025, and for Earth 7.9 × 1022. From these values alone, with reference to no theory at all, one can immediately see that the dipole values for Uranus and Neptune must be larger that Earth's 1022 and smaller than Saturn's 1025, so that anything in the 1023 to 1024 range is an obvious guess anyway. All Humphreys has to do is come up with a dipole at creation that is about the same as Saturn's is now, and the result is going to be very nearly right. We now know the dipole values for Uranus [3.7 × 1024 J/T] and Neptune [2.1 × 1024 J/T], which do indeed agree with Humphreys' order of magnitude predictions. But to hail this as a confirmation of his theory is not very rewarding. Indeed, it is my position that Humphreys' theory cannot be confirmed, since it predicts at once every possible observed field, and is therefore useless for predicting anything.
Eventually the Humphreys theory has become distinct from the Barnes theory. Humphreys decided that the evidence in support of the hypothesis that the Earth's magnetic field has reversed its polarity a number of times is too convincing, and that such reversals must have occurred. In doing so, Humphreys also rejects Barnes' idea that the Earth's field has been decaying exponentially ever since creation, and has instead postulated a more complex history for the magnetic field, built around the presumption that the field reversals happened very rapidly, taking perhaps no more than a few days to a few weeks [23, 24]. Humphreys had already postulated this idea, when he found support from a paper by Coe & Prevot in 1989 , which showed evidence of a rapid change in the angle of the dipole moment of the Earth's magnetic field during the cooling time of a lava flow. Coe & Prevot have expanded on the observations and theory since then [26, 27a] (and so has Humphreys ), and the effect certainly appears to be real, or at least credible. Humphreys has interpreted these results as an implication that all field reversals are very rapid, and this allows him to concentrate all of them into the single year of the Genesis Flood. However, one must remember that the results reported by Coe & Prevot include only a few out of hundreds or thousands of examples of field reversal measurements. The vast majority of the known examples would have required the entire reversal to take place while the lava flows were still hotter than the Curie temperature, or worse yet, argue against rapid reversal by recording what appear to be the intermediate stages of a single reversal event. Finally, others have shown that the evident rapid reversals described by Coe & Prevot may be explained by processes not related directly to those in the Earth's core [27b], but rather by magnetic storm effects that may become significant at the surface of the Earth during a reversal, when the dipole field is relatively weak.
Humphreys outlined his postulated history for the Earth's magnetic field in [23, 24, 29a]. He has a created magnetic dipole decaying exponentially until the time of the flood. Atthe onset of the flood, the dipole moment plummets rapidly, and thenoscillates very rapidly (the rapid reversals) during the year of the flood. He the shows a series of fluctuations from about 4000 to 1500 years before the present, after which the field has been steadilydecaying. This invented scenario depends heavily on the idea that all of the field reversals happened very rapidly, and all during the year of the flood. This can be seen in the online version of Impact #242 [29a], an ICR publication.
There can be little doubt that Humphreys still holds to this idea quite firmly. He was asked about this by Carl Wieland, in an interview published by Creation Magazine in 1993 . Humphreys reiterated his confidence in what he called his successful prediction of magnetic field strengths from the Voyager observations, and spoke as if his notion that all field reversals happened within a few days was essentially a proven fact. This interview is available online via the creation magazine website. I have not seen any creation science writings on the Earth's magnetic field since then, and I presume that the theory of Humphreys is the one that is now ascending in the creation science community.
I certainly do not accept the ideas put forth by Barnes and Humphreys, concerning the physics and history of the Earth's magnetic field. However I do not believe that I have treated either with any undue harshness. Barnes, despite his considerable background in physics, did a horrible job, committing numerous blatant and trivial errors along the way. Humphreys never takes Barnes to task, and goes out of his way to avoid criticizing him at all. While Humphreys does a much better job with his physics than did Barnes, Humphreys is not out of the intellectual woods either. He has a strong tendency to over-interpret results, and to over-emphasize the degree to which his theories are predictive in nature, or to which they are congruent with reality. His mix of divine intervention and physics is quite natural for a creationist, but not at all acceptable to the non-creationist. Moreover, it is not consistent with an unbiased scientific investigation, in that it presumes what the result will be before the experiment is done. As is my custom, civilized critiques, comments and inquiries are always welcome, and I will do my best to respond. For those of you impressed by credentials, or who wonder if I am "qualified" to write such an article, I will point out that I have B.S. (1978) and M.S. (1985) degrees in physics, from California State university at Los Angeles, as well as a decade's worth of experience as a radio astronomer studying the magnetospheric environment of theouter planets.
Finally, allow me to acknowledge the outstanding efforts of Brett Vickers in maintaining the bottomless pit of the talk.origins archive, especially as this is all done on a volunteer basis. The research for this article was done at the library of California State University at Los Angeles, my alma mater, and the libraries at Caltech and JPL. However, concerned taxpayers may note that I did all of the work on my own time.
A note on the references: the Creation Research Society Quarterly is online through the CRS web page, but the papers cited here are too old to be on their website at this time.
 "The Earth's Magnetic Field" , by Ronald T. Merrill and Michael W. McElhinney; Academic Press, 1983. ISBN 0-12-491240-0 (hardback). ISBN 0-12-491242-7 (paperback). [Probably out of print as of this writing. I don't know if there is an updated edition. Nevertheless, a good basic book.]
 "Reversals of the Earth's Magnetic Field" by J.A. Jacobs; Cambridge University Press, 1994 (2nd edition). ISBN 0-521-45072-1 (hardback). [Extensive revision of the 1984 first edition. The only text that deals exclusively with this special area.]
 "Solar and Planetary Dynamos", edited by M.R.E. Proctor, P.C. Matthews, and A.M. Rucklidge; Cambridge University Press, 1993. ISBN 0-521-45470-0 (paperback). Proceedings of the NATO Advanced Study Institute "Theory of Solar and Planetary Dynamos", September 20 - October 2, 1992. Isaac Newton Institute, Cambridge University. (Contributed papers)
 "Lectures on Solar and Planetary Dynamos", edited by M.R.E. Proctor and A.D. Gilbert; Cambridge University Press, 1994. ISBN 0-521-46704-7 (paperback). ISBN 0-521-46142-1 (hardback). Proceedings of the NATO Advanced Study Institute "Theory of Solar and Planetary Dynamos", September 20 - October 2, 1992. Isaac Newton Institute, Cambridge University. (Invited lectures)
 "An analysis of the Earth's magnetic field from 1835 to 1965", by Keith L. McDonald & Robert H. Gunst; ESSA Technical Report IER 46-IES1. U.S. Government Printing Office, July 1967.
[6a] "The Magnetic Field of Sunspots" by T.G. Cowling. Monthly Notices of the Royal Astronomical Society, 94: 39-48 (1934).
[6b] "A Thermodynamic Formulation of the Equations of Motion and Buoyancy Frequency for Earth's Fluid Outer Core" by K. Johnk and B. Svendsen. Continuum Mechanics and Thermodynamics 8(2): 75-101 (1996 Apr).
 "The Dynamo Maintenance of Steady Magnetic Fields", by T.G. Cowling; Quarterly Journal of Mechanics and Applied Mathematics, 10: 129-136 (1957). [received July 1956].
 "The Origin of Solar Magnetic Fields", by E.N. Parker. Annual Review of Astronomy and Astrophysics, 8: 1-30 (1970).
 "The Reversal of the Earth's Magnetic Field" by Mike Fuller, Carlo J. Laj & Emilio Herrera-Bervera. American Scientist, 84(6): 552-561 (November-December 1996).
 "The Present Status of Dynamo Theory", by T.G. Cowling. Annual Review of Astronomy and Astrophysics, 19: 115-135 (1981).
[11a] "Seismological Evidence for Differential Rotation of the Earth's Inner Core" by X.D. Song and P.G. Richards. Nature 382(6588): 221-224 (1996 Jul 18).
[11b] "A 3-Dimensional Self-Consistent Computer Simulation of a Geomagnetic Field Reversal" by G.A. Glatzmaier & P.H. Roberts. Nature, 377(6546): 203-209 (21 September 1995).
" A 3-Dimensional Convective Dynamo Solution with Rotating and Finitely Conducting Inner-Core and Mantle" by G.A. Glatzmaier & P.H. Roberts. Physics of the Earth and Planetary Interiors 91(1-3): 63-75 (September 1995).
[13a] "An Anelastic Evolutionary Geodynamo Simulation Driven by Compositional and Thermal Convection" by G.A. Glatzmaier & P.H. Roberts. Physica D 97(1-3): 81-94 (October 1, 1996).
[13b] "The Stochastic excitation of reversals in simple dynamos" by D. Crossley, O. Jensen & J. Jacobs. Physics of the Earth and Planetary Interiors, 42: 143-153 (1986).
 "Origin and Destiny of the Earth's Magnetic Field" by Thomas G. Barnes 2nd edition, institute for Creation Research, San Diego, 1983. [Currently out of print, from publisher Master Books].
 "Earth's Young Magnetic Age: An Answer to Dalrymple" by Thomas G. Barnes. Creation Research Society Quarterly 21: 109-113 (Dec 1984).
 "Radiometric dating and the age of the earth: a reply to scientific creationism" by G. Brent Dalrymple. Proceedings: Federation of American Societies for Experimental Biology, 42: 3033-3035 (1983).
 "Can the earth be dated from decay of its magnetic field?" by G. Brent Dalrymple. Journal of Geological Education, 31(2): 124-132 (1983).
 "Is the Earth's Core Water?" by D. Russell Humphreys. Creation Research Society Quarterly, 15: 141-147 (1978).
 "The Creation of the Earth's Magnetic Field" by D. Russell Humphreys. Creation Research Society Quarterly, 20: 89-94 (1983).
 "The Creation of Planetary Magnetic Fields" by D. Russell Humphreys. Creation Research Society Quarterly, 21: 140-149 (1984). http://www.creationresearch.org/crsq/articles/21/21_3/21_3.html
 "The Magnetic Field of Uranus" by D. Russell Humphreys. Creation Research Society Quarterly, 23: 115 (1986).
 "Good News from Neptune: the Voyager 2 Magnetic Measurements" by D. Russell Humphreys. Creation Research Society Quarterly, 27: 15-17 (1990).
 "Reversals of the Earth's Magnetic Field During the Genesis Flood" by D. Russell Humphreys. Proceedings of the 1st International Conference on Creationism, Creation Science Fellowship, 2: 113-126, 1986.
 "Has the Earth's Magnetic Field Ever Flipped?" by D. Russell Humphreys. Creation Research Society Quarterly, 25: 130-137 (1988).
 "Evidence Suggesting Extremely Rapid Field Variation During a Geomagnetic Field Reversal" by R.S. Coe & M. Prevot. Earth and Planetary Science Letters, 92(3-4): 292-298 (1989).
 "New Evidence for Extraordinarily Rapid Change of the Geomagnetic Field During a Reversal" by R.S. Coe, M. Prevot & P. Camps. Nature, 374(6524): 687-692 (April 20, 1995).
[27a] "The Hypothesis of Transitional Geomagnetic Impulses - Combining Paleomagnetic Data with a Cooling Model of Lava Flows" by P. Camps, M. Prevot, & S.C. Robert. Comptes Rendus de l'Academie des Sciences, Serie II, 320(9): 801-807 (May 4, 1995).
[27b] "Core Flow Instabilities and Geomagnetic Storms During Reversals - The Steens Mountain Impulse Field Variations Revisited" by P. Ultreguerard and J. Achache. Earth and Planetary Science Letters v135(1-4): pp91-99 (1995 Oct).
 "New Evidence for Rapid Reversals of the Earth's Magnetic Field" by D. Russell Humphreys. Creation Research Society Quarterly, 26(4): 132-133 (March 1990). [Humphrey's had already postulated the rapid reversals, and reports here to the creation science community on the 1989 paper by Coe & Prevot. -  TJT]
 "Creation in the Physics Lab - An Interview with D. Russell Humphreys" by Carl Wieland. Creation Magazine, 15(3): 20-23 (June-August 1993). http://www.answersingenesis.org/docs/1120.asp
[29a] "The Earth's Magnetic Field is Young" by Russell Humphreys, Impact #242, ICR, August 1993 http://www.icr.org/index.php?module=articles&action=view&ID=371
 "Spatial and Temporal
Power Spectra of the Geomagnetic Field" by M.G. McLeod.
Journal of Geophysical Research - Solid Earth v101(B2):
2745-2763 (1996 Feb 10).
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