The Earth’s Magnetic Field and the Age of the Earth

As early as 1971, creation scientist Dr. Thomas G. Barnes, then Professor of Physics at The University of Texas at El Paso, drew fresh attention to the fact that the strength of the earth’s magnetic field was decreasing.1 He noted that between 1835 and 1965 geophysicists had made some 26 measurements of the magnetic dipole moment of the earth’s magnetic field. When plotted against time (that is, the year of measurement) these data points fitted a decay curve which Barnes calculated had a ‘halflife’ (halving period) of only 1,400 years. On this basis he concluded that the earth’s magnetic field was less than 10,000 years old, and so the earth must likewise be that young (see Figure 1).

Which hypothesis? Evolved or created?

Needless to say, because of the powerful implications of this evidence Barnes received much opposition from the evolutionary community. Evolutionist geophysicists simply poured scorn on Barnes’ conclusions because they argued that any ‘decay’ of the earth’s magnetic field merely represented the latest phase in the ongoing history of waxing and waning field strengths as the field repeatedly reverses during multiplied millions of years.2 But Barnes stoutly repulsed this objection by denying the validity of the ‘fossil’ magnetism (palaeomagnetism) measurements of reversed magnetic polarity (direction) in rock strata.3

Evolutionary geophysicists were already ‘locked into’ their multi-million-year timescale not only because of the radioactive dating of the rocks in which the palaeomagnetic reversals were measured, but because of their presumed ‘dynamo’ mechanism for operation of the earth’s magnetic field. It is generally believed that the earth’s magnetic field is generated by electric currents in the earth's innermost region, the core, which is presumed to consist of a metallic iron-nickel mixture. However, according to the ‘dynamo’ hypothesis, these electric currents are believed to be produced by the slow circulation of molten material that carries unequal amounts of positive and negative electric charge. The energy for this is thought to come from the earth’s rotation and/or its internal heat.4^,5

Humphrey’s models for the history of the earth’s magnetic field (adapted from Humphreys—see reference 10). [Ed. note: Full-scale images available in Creation.]

So the generating mechanism is presumed to operate like a dynamo, (similar to an electricity generator) causing the field and maintaining it over large periods of time. Consequently, a reversal of the earth’s magnetic field (which is difficult for them to explain anyway) could be expected to be a slow process. Thus the evolutionary view has been that a transition from one magnetic polarity (direction) to the other generally took millions of years, or several thousand years at the very least.6 However, this so-called dynamo hypothesis, the operational mechanism preferred by most geophysicists, has many problems associated with it which have been well documented. 7^,8^,9^,10

Reversals have occurred

More recently, creation scientist Dr. D. Russell Humphreys (Physicist at the Sandia National Laboratories, Albuquerque, and Adjunct Professor of Physics at the Institute for Creation Research, San Diego) has reviewed the evidence for the validity of these ‘fossil’ magnetism11 studies and has found that fully half of all the 200,000 plus geological samples tested have a measurable magnetization whose direction (‘polarity’) is reversed with respect to the earth’s present magnetic field. He was forced to conclude that the variety, extent, continuity and consistency of the reversal data all strongly suggest that most of the data are valid, so that there is no option but to accept that reversals of the earth’s magnetic field must have occurred.

So how can these reversals of the earth’s magnetic field be reconciled with Barnes’ evidence that the earth and its magnetic field are less than 10,000 years old? Barnes and Humphreys have both argued convincingly for a viable alternative hypothesis to the evolutionists’ dynamo idea. They propose that the earth’s magnetic field comes from freely circulating electric currents created initially with a high built-in energy. As these currents subsequently lose their energy due to friction, the magnetic field will decay as the current strength decays.12^,13^,14^,15^,16

However, a collapsing magnetic field cutting across a conductor (the earth’s iron-nickel core) will generate more current, which helps to retard the rate of decay, otherwise the field would vanish more quickly. In fact, if we were to calculate how much current is being generated from the measured rate of collapse of today’s magnetic field, this current is sufficient to account for the actual known strength of the field as it is today! Besides being a good confirmation of the model, this means that the evolutionist’s ‘dynamo’, if it ever existed, must now be switched off.

Now we have already seen that this decay is real, having been measured for over 160 years, as pointed out by Barnes and documented by McDonald and Gunst.17 So this Barnes-Humphreys mechanism can account for this realtime decay of the earth’s magnetic field over the past 160 years, the current generated from such field decay correlating well with calculations of the amount of current actually present within the core. Furthermore, Humphreys maintains that it can also account for the magnetic reversals recorded in the rocks having taken place in only days to weeks!18^,19

The flood and rapid reversals

Now measurements of this ‘fossil’ magnetism in rock strata (being the local field direction and strength) are different to the global measurements of the strength of the earth’s total magnetic field as reported by Barnes, yet the ‘fossil’ magnetism (palaeomagnetism) does record the behaviour of the field during the earth’s history. Geophysicists have now recognized a continuous sequence of roughly 50 magnetic polarity (field direction) reversals in the magnetism ‘fossilized’ in rock strata that span the last 600 million years of the evolutionists’ timescale, from the so-called Cambrian period when the first metazoan (multi-celled) fossils ‘appear’ in the rock record to the present. However, since some fossiliferous strata also have reversed polarities preserved in them, the magnetic field must have been reversely polarized when those sediments were being laid down.

Many creationists argue that Noah’s Flood produced most of these fossiliferous rock layers in a single year. Thus, these reversals of the earth’s magnetic field have to be envisaged as occurring on average every week or two during the Flood year. If this were the case, we should then be able to find field evidence of the reversal process having occurred this rapidly, otherwise the Barnes-Humphreys freely decaying electric currents mechanism for the generation of the earth’s magnetic field in less than 10,000 years is also in trouble.

But the field evidence has now been found. As already reported,20 palaeomagnetic measurements of a lava flow at Steens Mountain in Oregon have shown that one of these magnetic polarity transitions (part of a complete reversal) took place in about two weeks, the time period over which the lava would have cooled. As would be expected, the investigators, both evolutionists, were astonished by these results and had difficulty accepting them, but finally had to admit:

‘…even this conservative figure of 15 days corresponds to an astonishingly rapid rate of variation of the geomagnetic field direction of 3∞ per day. …The rapidity and large amplitude of geomagnetic variation that we infer from the remanence directions in flow B51, even when regarded as an impulse during a polarity transition, truly strains the imagination.…We think that the most probable explanation of the anomalous remanence directions of flow B51 is the occurrence of a large and extremely rapid change in the geomagnetic field during cooling of the flow, and that this change likely originated in the (earth’s) core.’21

The sun’s magnetic field

In order to further bolster his case for rapid magnetic polarity reversals, Humphreys22 has also pointed to a natural object, namely the sun, which demonstrates that a large body can rapidly reverse its magnetic field.23 Observations show that the sun reverses the polarity of its general magnetic field every 11 years, in synchronism with its sunspot cycle. When the number of sunspots is at a minimum, the observed field on a large scale has its lines of force going mainly north and south. As the number of sunspots begins to increase, the strength of the north-south part of the field diminishes. In about 5.5 years the north-south component has diminished to zero and the number of sunspots is at a maximum. Then things begin to happen in reverse. A south-north part of the field appears in the opposite direction from its predecessor and the number of sunspots starts to diminish. After another 5.5 years, the number of sunspots is at a minimum again, and the field is back to its original shape, but with the north and south poles of the field having switched places, that is, the sun’s magnetic field has reversed its polarity.

Physicists and astronomers do not yet have a theory that completely explains this complex reversal phenomenon. One probable reason why they have had difficulty explaining the sun’s reversals is that, because they believe the sun’s magnetic field is also generated by a dynamo, they have been looking for a mechanism which would not only reverse the sun’s field, but also regenerate and maintain it for billions of years. But if the sun is relatively young (only thousands of years), there is no need for the regeneration requirement. The sun would merely be winding up and unwinding whatever magnetic field it had at creation, losing magnetic energy each solar cycle. Its long-term behaviour would thus be a steady decay modulated by the solar cycle of reversals.

Earth’s physical mechanism

Dr. Humphreys has now proposed a physical mechanism for reversals of the earth’s magnetic field during the Flood.24 We have already seen there is agreement that the earth’s magnetic field is generated in the earth’s metallic iron-nickel core, most evolutionary scientists preferring a dynamo, as opposed to the free-decay model of Barnes and Humphreys. The latter involves an initial endowment of energy in the core at the time of creation and that energy has dissipated and decayed freely as electrical currents in the core since then, the currents generating a magnetic field at the earth’s surface and beyond, which has decayed in step with the decay of electrical currents.

However, because the metallic iron-nickel in the earth’s outer core is in a fluid state, internal motions occur in this region due to convection flow, for which there is evidence even at present. Humphreys suggests that a powerful event in the earth’s core at the beginning of the Flood produced this convection, perhaps by the heating of the core due to a sudden increase of radioactive decay or cooling of the mantle above the core, but these are as yet tentative suggestions that need further analysis. However, once convection flows were initiated in the earth’s core, such flows moving upwards in the core towards the mantle would produce a magnetic flux up into the mantle, which would then be conducted to the earth's surface as a magnetic excursion.

These convective ‘updraughts’ in the earth’s core would have carried more magnetic flux to the surface than ‘downdraughts’ would have carried away from the surface, so the convective updraughts would have rapidly cancelled out any previous flux above it. The work done by these convection flows in pushing a magnetic flux upward would generate new electric currents, which in turn would generate new flux in the opposite direction. Thus a cycle of magnetic reversals are set up due to these recurring convection currents, which are maintained as long as there is a strong heat source within the core. In support of his model, Humphreys draws comparisons with convection currents within the sun, which we have already seen are responsible for a rapid magnetic reversal cycle there.

Earth’s magnetic field history

Humphreys’ model for the history of the earth’s magnetic field is more complex than Barnes’ original picture of a steady state decay from creation to now, but it does not differ on the essential hypothesis that the earth’s magnetic field has freely decayed since creation. Figure 2 shows Humphreys’ model for the history of the earth’s magnetic field, which he divides into five episodes:

1. Creation of the magnetic field along with the earth.
2. Steady decay for nearly 2,000 years until the Flood.
3. Rapid reversals during the year of the Flood.
4. Large fluctuations continuing for up to two thousand years after the Flood.
5. Resumption of steady decay from about the time of Christ until now.

The last period includes the historical measurements which show decay, as reported originally by Barnes.25

The model for the reversal process as proposed by Humphreys is simple compared to the evolutionary ‘dynamo’ theories. It differs fundamentally from the dynamo theories in that it is not intended to maintain the earth’s magnetic field for billions of years. Rather, it inverts a previously existing field over and over again. Far from maintaining a field indefinitely, this process accelerates the decay of a planetary magnetic field. The field strength at the peak of each cycle is less than the peak of the previous cycle, because the inverting process does not completely reproduce the flux. This means that the energy contained in the post-Flood magnetic field would be considerably less than that of the pre- Flood field.

According to Humphreys, even though creationist explanations of planetary magnetic fields are still in their infancy, they appear to be more complete and successful than the 40-year-old dynamo theories. Indeed, recent magnetic measurements by the Voyager spacecraft as it flew past Uranus and Neptune have confirmed Humphreys’ predictions on the origin of the planetary magnetic fields.26^,27 Furthermore, recent measurements have cast doubt on whether a dynamo really does operate in the earth’s core at present. 28 In addition, there is no dynamo theory which accounts for the extremely rapid variations reported at Steens Mountain by Coe and Prevot,29 but Humphreys’ model accounts for this data particularly well. Dynamo theorists even acknowledge that their theories are incomplete, very complex, and not very successful at making predictions. 30 As one such theorist has said:

‘…you would have thought we would have given up guessing about planetary magnetic fields after being wrong at nearly every planet in the solar system…’31

Age of the earth

If the creation scientist Humphreys is correct, and seeing that his predictions about planetary magnetic fields in the solar system have been verified, and his model for magnetic reversals here on earth does fit well to the geophysical and rock palaeomagnetic data compared to the woeful state of the dynamo model, then such a decrease in the energy of the earth’s magnetic field implies that it is not eternal but relatively recent. Consequently, Humphreys has extrapolated today’s energy decay rate back to a theoretical maximum energy,32 and so has derived an upper limit for the age of the earth’s magnetic field at 8,700 years.

However, he concludes that the rate of energy loss would have been greater during and just after the Flood, due to the postulated powerful heating event in the core at the time of the Flood which set in motion the convection flow, that in turn produced the magnetic reversals and rapid dissipation of the field energy. Figure 3 shows one scenario suggested by Humphreys in which about 90% of the earth’s magnetic field energy was lost during the Flood or shortly thereafter. He suggests, thereby, that this would make the age of the field about 6,000 years, thus again providing powerful evidence that the earth is as young as the text of Scripture clearly implies.