One of the earliest arguments against an older earth is the observed fact that the earth magnetic field is decaying. Unfortunately, such early models of the earth's planetary magnetic field did not supply any evidence for a specific age for the earth, only an upward limit. Such early models placed upper limits on the age of the earth at around 12,000 at which point the internal heat of the earth's core from the generating current would be so great that it would blow the earth apart, not to mention that the magnetic field would be stronger than that of a neutron star. That would also make the magnetic field strong enough to kill you by just pulling the iron out of your blood.
This prompted old earth proponents to develop what is known as the Dynamo Theory of Planetary Magnetic Fields. This model explains the measured decay in the earth magnetic dipole, by claiming that the field energy simply cycled to other aspects of what is a more complex field. The idea is that the Earth’s magnetic field is constantly flipped back and forth maintaining its energy over billions of years. The claim is that what is actually being measured was the field going through one of these flips. They point to evidence of magnetic reversals, on the ocean floor and other places, that this was the correct model.
However, the Dynamo Theory has its problems. The First and most obvious one is how to get the dynamo started in the first place. In order for this model to work there needs to be a complex churning of the fluid rock within the outer core, and there is no known way of getting it started. In fact, attempts to model this hypothetical internal structure requires paddles to generate the needed circulation, and even then, they cannot get a self-sustaining magnetic field. Another big problem is that further measurements of the decline of the earth's magnetic field show that its total energy is also decreasing. Now while this would extend the maximum age of the earth back further, it still does not come anywhere close to the 4.5 billion years claimed at the age of the earth.
The solution to this dilemma is Dynamic Decay Theory developed by Dr. Russell Humphreys. In this model how he started with the Biblical description of the Earth starting off as water. He describes the earth's magnetic field as starting off with God aligning the magnetic fields of the water molecules within that body of water. When God converted this water into the rock of the earth, the collapse of the magnetic field generated an electric current in the outer core to help to maintain it. He then assumed that there were fluctuations during the genesis flood the drought its current faster than normal. He was then able to produce not only the present-day magnetic field strength but the observed decay of both its dipole and its energy level. The result is that we now have a model of the earth's magnetic field that shows not only how it got started, the models fits perfectly and it also produces an age for the earth of only around 6000 years.
Naturally old Earth proponents have attacked this model and Humphries himself. Sadly, these attacks are often not honest criticism but just that, attacks. This gets even more interesting because Dr. Humphreys has not stopped with the Earth’s magnetic field. He immediately modeled the magnetic fields of the other planets, producing clear predictions about future observations. This is where dynamic decay theory shines, that is in its explanatory and predictive power.
This discussion will be continued in upcoming articles to prevent this one from getting too long. However, the story with this model only gets better. It goes on explaining and predicting observations while dynamo theory does neither very well.
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Earth's Mysterious Magnetism: and that of other celestial orbs
Starlight & Time by Dr. Russell Humphreys Ph.D.