In Finding Darwin’s God, Kenneth Miller addresses another argument used by some young earth creationists, and in particular, by the late Henry Morris. The earth’s magnetic field, as Morris points out, has been weakening for the past 150 years. Working backwards using its current rate of decay, the earth’s magnetic field would have been too strong for us to survive 10,000 years ago. Therefore, the earth must be less than 10,000 years old.

Miller writes that he spoke with a geologist named Peter Gromet, who explained that the earth’s magnetic field periodically reverses. “As Gromet patiently explained,” says Miller, “when rocks are formed, their magnetic minerals orient themselves in the earth’s magnetic field. This means that the rocks of the earth’s crust carry within them a record of that field at the time of their formation… From core samples of sedimentary rock an interesting fact has emerged:  The earth’s magnetic field has gone through innumerable reversals and fluctuations over time. In other words, the current weakening of the field that Morris referred to is nothing more than the latest ebb in a series of fluctuations that come and go with surprising regularity.”

The people at Answers In Genesis acknowledge that the magnetic field reverses periodically. They counter in this article, arguing that the reversals often happen rapidly and ultimately do not stop the magnetic field’s weakening. It seems that they have documented pretty well that the magnetic field has changed very rapidly in the past, but I do not know where they get that reversals do not stop the field’s weakening.

Does anyone know about this topic well enough to comment?

Growing up as a YEC, I often read arguments for a young earth, but now that I have been reading about these things from a different perspective, I see that there are good answers to their arguments. Why are YECers so often not told the scientific community’s reply?