The History of the Earth’s Magnetic Field

Dr. Matthew Pevarnik

The Earth’s Magnetic Field

The Earth’s Magnetic Field

• The magnetic field has been decaying by about 5% per century from at least 1840 when C.F. Gauss devised a method to measure it
• But what was it doing before that? We don’t have the actual measurements scientists hadn’t invented the method for measuring it yet!
• This is done in two main ways today—through archaeomagnetism (studying the magnetic moments of pottery and other archaeological findings) and paleomagnetism (measuring the magnetic moments of lava flows and other geological features)
• These methods can help yield more average numbers but it can be challenging to get specific timestamps as scientists are dependent on either ancient people groups actually making pottery that contains magnetic atoms (i.e. iron which is quite common) or on ancient lava flows that heated rocks above their curie temperature and froze information of the magnetic field as they cooled

The Past 180 years

• The data we have direct measurements of is in the red box
• That is the portion that YEC Thomas Barnes extrapolated backwards exponentially
• This graph shows a linear fit to the curve which matches quite well (as well) at least for the 180 year period
• But how do we get the magnetic field before that point?

Exponential Decay?

• Here is a study that measures the magnetic field strength in 315 rock samples from 1590 to 1840 finding that the strength was quite constant in that period: Fall in Earth's Magnetic Field Is Erratic in 2006

The Exponential Decay of YEC

• From the past 150 years, an exponential decay curve was assumed by Thomas Barnes in 1973
• "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 ... "

The YEC Community Today

• There are two components of the main YEC argument today
• The first is the exponential decay of the Earth’s magnetic field (now described in terms of its total energy which is proportional to the integral of the magnetic field squared)
• https://answersingenesis.org/evidence-for-creation/5-rapidly-decaying-magnetic-field/
• The second are the geomagnetic reversals of Russel Humphreys

Exponential Decay is Confirmed?

• Reading only the AiG article, one could get the impression the field has been decaying in its overall strength
• We’ve already seen recent geomagnetic rocks falsify this claim
• Judean pottery also helps falsify this claim where we see the magnetic field strength double in ~500 years and then decrease to the levels before the spike
• Six centuries of geomagnetic intensity variations recorded by royal Judean stamped jar handles
• Source of graph on right: Geomagnetic spikes on the core-mantle boundary

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Further Measurements of the Earth’s Magnetic Field in the Past

• Here is the strength of the dipole normalized to 1 (present day strength) over the past 10,000 years and the non-dipole power
• Top: Multi-centennial fluctuations of radionuclide production rates are modulated by the Earth’s magnetic field
• Bottom: Reconstructing Holocene geomagnetic field variation: new methods, models and implications

Since the Last Reversal

• It’s been about 800 kya since the last time the Earth’s magnetic field switched and it has not been decaying at all, let alone exponentially
• From: Magnetic Polarity Reversals in the Core

Remarkable Success for the YEC Model?

• The next several sources discuss the remarkable success of the YEC model in describing the Earth’s magnetic field
• Unfortunately none of these remarkable success were published in geophysics journals
• It says the dynamo contradicts some basic laws of physics but doesn’t say which ones (we will come back to this)
• “Reliable, accurate, published geological field data have emphatically confirmed the young-earth model: a freely-decaying electric current in the outer core is generating the magnetic field” will give us an opportunity to compare data with the YEC models

Reliable Accurate Data Validate Humphreys

• The paper referenced is Reversals of the Earth’s Magnetic Field During the Genesis Flood (we will come back to this)
• I don’t actually see anything in the paper that supports that the ‘freely-decaying’ model is accurate
• The only thing I can think of is figure 5 which is the only actual data of the Earth’s magnetic field which consists of data points + Humphreys best fit line

What Kind of Fit is That?

• “Reliable, accurate, published geological field data have emphatically confirmed the young-earth model”
• Why does Humphrey’s graph dip down below the actual data 3.7 kya and then dramatically shoot up far above the data? Is there any data to support the exponential decay that he presented?
• How does this data actually confirm the young-earth model? This paper is supposed to be about geomagnetic reversals but the actual archeomagnetic data has no reversals—where do Humphreys’ reversals come from in a later graph?

Dynamo Theory—Violating Physics?

• With some digging it became clear what basic law of physics AiG and the YEC community thought Dynamo Theory was violating
• I find it rather remarkable that geophysicists who devote their lives to building models and making measurements would be so incompetent that they would continue using dynamo theory when it was in contradiction to other simpler physical laws
• I also find it rather interesting that the article didn’t bother to state which basic law of physics the dynamo model was violating

Dynamo Theory—Violating Physics?

• It turns out that the basic law of physics is Cowling’s Theorem: http://farside.ph.utexas.edu/teaching/plasma/Plasmahtml/node73.html

Dynamo Theory—Violating Physics?

• It turns out that the basic law of physics is Cowling’s Theorem: http://farside.ph.utexas.edu/teaching/plasma/Plasmahtml/node73.html
• This is not what an axially symmetric field looks like so we know for a fact that Cowling’s Theorem does not apply to the Earth!

The Physicists Aren’t Violating Physics

• What then should we say of the charge that physicists are building models that violate the basic laws of physics?
• Thomas Barnes, who originally began the magnetic field argument in the YEC community, appears to have misunderstood what Cowling’s Theorem prohibits to the point where AiG and others today just claim Dynamo Theory violates basic laws of Physics
• Interestingly enough, Mercury, Venus and Mars have had their magnetic fields dissipate to nearly zero thanks to their slow rotation periods and/or solid cores leaving them with axially symmetric dynamos which Cowling’s Theorem explains

Dynamo Theory and Electric Currents?

• The AiG article then reads: Furthermore, their model fails to explain the modern, measured electric current in the seafloor” which references an older paper from 1985 called Measurements of the Large-Scale Direct-Current Earth Potential and Possible Implications for the Geomagnetic Dynamo
• This one is rather confusing as this is a paper about a transatlantic wire and the abstract for the paper reads “such a small value of the mean potential implies that the toroidal and poloidal magnetic fields of the dynamo are approximately equal at the core-mantle boundary.”
• Interestingly, Humphreys cites this paper and adds: Science, 229, 47–49 reports measurements implying that the toroidal component of the earth’s magnetic field within the core is relatively weak. Most, and perhaps all, dynamo theories depend on the existence of a strong toroidal component. Hence these data imply that there is no such dynamo in the earth’s core today
• Is that what the paper says?

Dynamo Theory Can’t Explain The Reversals?

• None the less it goes on: “Nor can it explain the past field reversals, computer simulations notwithstanding”
• The AiG article references again Dr. Russ Humphreys who wrote “Can evolutionists now explain the Earth’s magnetic field” in the Creation Research Society journal in 1996 which is inaccessible
• I will note though that evolutionists do not study dynamo theory and magnetic fields, they study biology

Dynamo Theory Can’t Explain The Reversals?

• Now dynamo theory can explain reversals in the earth’s magnetic field
• It is really complicated to solve these equations!
• For example, this modeling in Magnetic reversals from planetary wave dynamos of the Earth’s dynamo switching back and then back again took the equivalent of 457 years worth of computing time!

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Salvaging Their Dynamo Theory?

• The article concludes: “To salvage their old earth and dynamo, some have suggested the magnetic field decay is linear rather than exponential, in spite of the historic measurements and decades of experiments confirming the exponential decay”
• I’m not sure who has said that it is a linear decay other than someone making a point that Thomas Barnes who originally assumed exponential decay could have just as easily been a linear fit—which highlights challenges to making best fit lines without a lot more data which we now have
• It is a lie to say that decades of experiment confirmed the exponential decay—they have done exactly the opposite and falsified the assumed best fit of exponential decay

What is Humphreys’ Model?

• Specifically I accused Humphreys of just making up this graph
• Is the paper on the right a promising way to go?

What is Humphreys’ Model?

• Before looking at the reversals, what was Humphrey’s original model that is part of the remarkably successful YEC literature for decades?
• The argument in 1983 begins with “the Bible implies that the earth just after its creation was one hundred percent water”
• And then God aligned 25% of the water dipoles in the same direction because “since we have no better information, let us assume that God did it with a minimum of deviation from what was to be the ordinary alignment, and a maximum of orderliness”

Humphreys’ Model

• After this supernatural aligning of 25% of the H2O molecule’s magnetic moments (the whole earth is made out of water) God let the dipoles go which quickly would remove the magnetic field of the earth
• To counteract this change in magnetic field, an electric current would be induced as per Lenz’ Law which would flow around the equator of the Earth
• At this time God would have transformed most of the water into other materials as it says in Genesis 1:9—but these materials would also start flowing current around again as per Lenz’ law
• Finally the field will decay exponentially—so let’s now go to the magnetic reversals

No, Not in This Paper

• In the actual paper Reversals of the Earth’s Magnetic Field during the Genesis flood there again is no data that actually shows any reversals (the closest being our figure 5 from before)
• Humphreys’ says in the conclusion (see red box) that Figure 6 summarizes the history of the earth’s magnetic field but there is no figure 6—did he mean figure 5? If so it definitely does not show what he’s claiming
• In numerous articles on YEC sites, this is the main paper they cite as evidence for his graph with the reversals during the flood but the figure is not in the paper—so where does the figure come from?

So Where Does the Graph Come From?

• I found this article by Humphreys in 1993: https://www.icr.org/article/earths-magnetic-field-young/ where he has his mysterious figure and writes:
• “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. Instead, the data show that the field intensity at the earth's surface fluctuated wildly up and down during the third millennium before Christ. [7] 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.”

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Reference [7]!

• Thanks to the Regent Library we can access the graphs from this section:

Neither of these have any evidence of rapid reversals beginning in the 3^rd millennium before Christ

The Made Up Graph

• This one is based on a misrepresentation of archeomagnetic data he proposed in one of the ICR impact series. Humphreys completely fabricated the notion of rapid reversals of the field (Since archeomagnetic data show no reversals)! Furthermore, the strength of the dipole field does fluctuate and change through time. Currently, it is decreasing, but the field is still much higher than it has been in the past… Humphreys ‘theory’ is based on a misrepresentation of archeomagnetic data (e.g. drawing reversals and zero lines on a curve that shows neither)…--Christian geologist Joe Meert

But The Field Can Switch Quickly?

Do Rapid Reversals Matter?

• Does it matter if the Earth’s magnetic field can switch polarity relatively quickly?
• Not really because it’s the time in between reversals that is the real matter here regarding the ages of things and the 184 geomagnetic reversals that match seafloor spreading rates, radiometric dating of rocks on land and in the ocean, and even modern day GPS measurements

The Conclusion of that Article

• For many years studies of the paleomagnetism recorded in basalt lava flows on Steens Mountain in southern Oregon had provided impeccable evidence that reversals of the geomagnetic field polarity had in the past occurred extraordinarily rapidly, in a matter of only days to weeks. This has been a severe embarrassment to the conventional geoscience community because such a rapid rate for geomagnetic field polarity reversals is totally inconsistent with their preferred millions-of-years geodynamo model for the generation of the earth’s magnetic field. Their embarrassment was intensely heightened by young-earth creation scientists being able to use this evidence at Steens Mountain to support their young-earth freely-decaying electric currents model for the generation of the earth’s magnetic field and rapid polarity reversals during the Flood and its aftermath. This explains Coe’s recent efforts to use the results of a new untried rapid-heating technique to re-measure the paleomagnetism stored in those Steens Mountain basalt lava flows in order to “reinterpret” and overturn his earlier evidence of the extraordinarily rapid geomagnetic field polarity reversals. However, the original results using the long-established step-heating measurement technique are not so easily overturned and disregarded.

The Conclusion of that Article

• For many years studies of the paleomagnetism recorded in basalt lava flows on Steens Mountain in southern Oregon had provided impeccable evidence that reversals of the geomagnetic field polarity had in the past occurred extraordinarily rapidly, in a matter of only days to weeks
• This particular geomagnetic reversal could have been fast switch in polarity, but the time between reversals is more important as its been 800,000 years since the last full reversal plus the 180+ others before that

The Conclusion of that Article

• This has been a severe embarrassment to the conventional geoscience community because such a rapid rate for geomagnetic field polarity reversals is totally inconsistent with their preferred millions-of-years geodynamo model for the generation of the earth’s magnetic field. Their embarrassment was intensely heightened by young-earth creation scientists being able to use this evidence at Steens Mountain to support their young-earth freely-decaying electric currents model for the generation of the earth’s magnetic field and rapid polarity reversals during the Flood and its aftermath
• Note: The Steens Mountain reversals do not support a young earth freely decaying electric currents model
• All that they ever did was demonstrate the magnetic field could change relatively rapidly, but it turns out that the original conclusion was mistaken
• The actual fastest change in recorded history was 100 years which Snelling seems to have no problem to just conclude was really just much shorter anyways
• Again, Snelling misunderstands why this argument has nothing to do with an old or young earth. Which is why the authors write:
• This conclusion, though perhaps mundane, is important to set the record straight. Besides its influence in the professional and lay scientific literature, the Steens rapid-field-hypothesis was included in a widely-aired TV documentary (Copp, 2003a, 2003b), was applied to the Laschamp event in a science fiction novel (Sawyer, 2003), and was misinterpreted by creationists in their attempts to reconcile the geological and biblical timescales (e.g., Humphreys, 1990).

One Final Comment on Humphreys’ Mechanism

• Humphreys aimed to explain the mechanism for the magnetic field changing while ignoring the equations of fluid flow and electrodynamics
• “This section describes an effect which is crucial to the theory I am developing: Magnetic flux being moved rapidly generates new magnetic flux of the opposite polarity. I have not been able to find this effect described anywhere in the literature, but it follows straightforwardly from basic electromagnetic phenomena and the reasoning described below.”
• Is there is a reason such an effect is not described in the literature?

The Effect Nobody Has Ever Noticed?

• Is there is a reason such an effect is not described in the literature?
• The first part is straightforward enough—there are moving charges in the Earth’s core that generate a magnetic field (note: they do not generate a magnetic ‘flux’ that makes no sense and appears to misunderstand what magnetic flux actually means)
• It is entirely possible if this current started up suddenly it could generate a current in the opposite direction in other regions of the Earth’s interior—i.e. similar to Faraday’s law of induction
• These loops appears to be arbitrarily drawn and are nonsensical from a 2^nd semester freshman physics class