CREATIONISTS AND "MAGNETIC FIELD DECAY"

 

by Lenny Flank

 

(c) 1995

 

One common creationist argument centers around the earth's magnetic field. This argument leans heavily on the theories first proposed by "Dr" Thomas Barnes (the doctorate is an honorary one), a creationist physicist who served as head of the ICR's "graduate school". Since Barnes' death, the magnetic field theory has been championed by Russell Humphreys.

Some of the Barnes/Humphreys arguments are highly technical (as are the counter-arguments made by geologists), and we will not delve into them here. (Among the scientific writers who have pointed out the technical flaws in the magnetic-field decay theory are Dalrymple, Strahler, Godfrey, and Montagu.) Briefly, the earth acts in many ways like a giant magnet, and produces a magnetic field which extends out into space and, among other things, is responsible for maintaining the Van Allen radiation belts and for making compass needles point north (compass needles actually point to the magnetic north pole, not the geographic north pole). In a bar magnet, there is a north pole and a south pole, and this field is said to be "dipole". The earth's magnetic field is much more complex, but can be treated mathematically as a dipole field with a number of non-dipole elements.

In 1971, Barnes pointed out that, according to the data he had, the strength of the dipole component of the earth's magnetic field (measured in a unit known as a "gauss") has decreased between six and seven percent since it was first measured in 1835. Barnes then made the assumption that ALL of the non-dipole measurements constituted meaningless "noise", and asserted that only the dipole elements of the magnetic field are generated by the core. He further concluded that, because of the measured decrease in field strength, this dipole field must be decaying exponentially, with a half-life of approximately 1,400 years. Thus, Barnes calculated, by about 10,000 years ago, the earth's magnetic field would have so strong that life would have been impossible. Therefore, he concluded, the earth cannot be more than 10,000 years old. As Morris puts it, "Thus, 10,000 years seems to be an outside limit for the age of the earth, based on the present decay of its magnetic field." (Morris, Scientific Creationism, 1974, p. 158)

Humphreys adds a few details to the basic picture outlined by Barnes, including an explanation of how the original magnetic field was formed and when and how it started to decay. Here are Humphreys' "scientific" explanations for the history of the earth's magnetic field:

 

"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." (Humphreys, ICR Impact, "The Mystery of the Earth's Magnetic Field", February 1989)

 

"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." (Humphreys, ICR Impact, "The Mystery of the Earth's Magnetic Field", February 1989)

 

And how does Humphreys "know" that the magnetic field of the earth decayed slowly for exactly 1656 years, or that the earth's magnetic field was produced by atoms with their spin axes aligned at the time of creation? Not through any scientific data.

The Barnes/Humphreys hypothesis does not stand up to analysis. Barnes is correct that the dipole element of the magnetic field has indeed decreased in strength since the 19th century. However, as geologist Brent Dalrymple points out, "Barnes completely neglects the nondipole field. The same observatory measurements that show that the dipole moment has decreased since the early 1800's also show that this decrease has almost been completely balanced by an increase in the strength of the total observed field which has remained almost constant." (Dalrymple, "Can Earth Be Dated from its Magnetic Field?", Menlo Park, CA, 1992)

Barnes also presents no evidence whatever to support his assertion that the magnetic field has been decaying exponentially, or that it becomes progressively stronger in the past. And, in fact, there is no need to speculate on what the strength of the earth's magnetic field was in the past, since we have a way to directly measure it. Metallic particles such as iron are partially magnetized by the earth's magnetic field and will line themselves up with the magnetic poles. By examining these particles, we can determine the strength of the magnetic field. And such examination shows that the earth's magnetic field has not been decaying steadily. Clay pottery and other archeological finds which date to about 6,500 years ago indicate a magnetic field that was about 20% weaker than today, while artifacts from just 3,000 years ago show magnetic fields that are 45% higher than today. Thus, rather than decreasing steadily since the time of creation, the earth's magnetic field has fluctuated, weaker at some times and stronger at others.

Humphreys, on the other hand, acknowledges that changes in the intensity and polarity of the earth's magnetic field have indeed occurred, but he compresses them all into the space of a single year, and attributes them to the Divine forces that God used to produce the Genesis 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." (Humphreys, ICR Impact, "The Mystery of the Earth's Magnetic Field", February 1989).

 

"Strong flows of the fluid in the earth's core could produce rapid reversals of the field during and after the Genesis Flood. The resulting disturbances would cause the field intensity at the earth's surface to fluctuate up and down for thousands of years afterwards." (Humphreys, ICR Impact, "The Earth's Magnetic Field is Young", August 1993)

 

Humphreys is, of course, unable to produce any scientific data whatsoever to substantiate any of his assumptions.

In fact, when rocks on the sea floor are scientifically examined, they demonstrate a striking magnetic pattern: on each side of the mid-Atlantic rift where the earth's plates emerge from the mantle, differing "stripes" of varying magnetic intensity can be found, each the mirror image of the stripes on the other side. As each area of crust emerges and solidifies, the metallic particles within it are magnetized, and take on the strength and polarity of the magnetic field within which they emerged. As the sea floor spreads apart through plate tectonics, new areas of rock emerge and are similarly magnetized. This produces a pattern of different magnetic strengths. (Some creationists have attempted to discredit these observations by arguing that the local rocks have undergone a process of magnetic reversal, but if this were true it would produce a patchwork pattern of random reversals, not the mirror-image pattern that is actually found.)

More surprisingly, such measurements show occasions when the earth's magnetic field has dropped to virtually nothing, and re-emerges with the magnetic poles reversed--the magnetic north pole is now the south pole and vice versa. Some 171 such magnetic reversals have been found, extending back over 76 million years. (By determining the strength and polarity of the magnetic signature of particular rocks, and by comparing the resulting patterns to sea-floor patterns, the rock can be roughly dated, a method known as "paleomagnetism"). Between 1953 and 1958, such a magnetic polarity reversal was also observed directly, in the sun. During this time, the sun's magnetic dipole field decreased in strength, dropped to almost nothing for a period of several years, and re-emerged with reversed polarity.

There is thus no justification whatever for Barnes and Humphreys to attempt to extrapolate their magnetic measurements for the last 150 years or so back to the moment of creation. It is apparent that the earth's magnetic field is not "decaying", and that it routinely fluctuates and even occasionally reverses itself completely. The only explanation that the creationists can invoke to deal with these fluctuations and reversals is to turn to their religious sources, and opine that these reversals were a result of the actions of God in bringing about Noah's Flood. The creationist "magnetic field decay" hypothesis is simply not capable of giving us any scientific estimate of the earth's age.

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