The earth has a magnetic field pointing almost north-south—only 11.5° off. This is an excellent design feature of our planet: it enables navigation by compasses, and it also shields us from dangerous charged particles from the sun. It is also powerful evidence that the earth must be as young as the Bible teaches.
In the 1970s, the creationist physics professor Dr Thomas Barnes noted that measurements since 1835 have shown that the field is decaying at 5% per century1 (also, archaeological measurements show that the field was 40% stronger in AD 1000 than today2). Barnes, the author of a well-regarded electromagnetism textbook,3 proposed that the earth’s magnetic field was caused by a decaying electric current in the earth’s metallic core (see side note). Barnes calculated that the current could not have been decaying for more than 10,000 years, or else its original strength would have been large enough to melt the earth. So the earth must be younger than that.
The decaying current model is obviously incompatible with the billions of years needed by evolutionists. So their preferred model is a self-sustaining dynamo (electric generator). The earth’s rotation and convection is supposed to circulate the molten nickel/iron of the outer core. Positive and negative charges in this liquid metal are supposed to circulate unevenly, producing an electric current, thus generating the magnetic field. But scientists have not produced a workable model despite half a century of research, and there are many problems.4
But the major criticism of Barnes’ young-earth argument concerns evidence that the magnetic field has reversed many times—i.e. compasses would have pointed south instead of north. When grains of the common magnetic mineral magnetite in volcanic lava or ash flows cool below its Curie point (see side note) of 570°C (1060°F), the magnetic domains partly align themselves in the direction of the earth’s magnetic field at that time. Once the rock has fully cooled, the magnetite’s alignment is fixed. Thus we have a permanent record of the earth’s field through time.
Although evolutionists have no good explanations for the reversals, they maintain that, because of them, the straightforward decay assumed by Dr Barnes is invalid. Also, their model requires at least thousands of years for a reversal. And with their dating assumptions, they believe that the reversals occur at intervals of millions of years, and point to an old earth.
The physicist Dr Russell Humphreys believed that Dr Barnes had the right idea, and he also accepted that the reversals were real. He modified Barnes’ model to account for special effects of a liquid conductor, like the molten metal of the earth’s outer core. If the liquid flowed upwards (due to convection—hot fluids rise, cold fluids sink) this could sometimes make the field reverse quickly.5,6 Now, as discussed in Creation 19(3), 1997, Dr John Baumgardner proposes that the plunging of tectonic plates was a cause of the Genesis Flood (see online version). Dr Humphreys says these plates would have sharply cooled the outer parts of the core, driving the convection.7 This means that most of the reversals occurred in the Flood year, every week or two. And after the Flood, there would be large fluctuations due to residual motion. But the reversals and fluctuations could not halt the overall decay pattern—rather, the total field energy would decay even faster (see graph above).8
This model also explains why the sun reverses its magnetic field every 11 years. The sun is a gigantic ball of hot, energetically moving, electrically conducting gas. Contrary to the dynamo model, the overall field energy of the sun is decreasing.
Dr Humphreys also proposed a test for his model: magnetic reversals should be found in rocks known to have cooled in days or weeks. For example, in a thin lava flow, the outside would cool first, and record earth’s magnetic field in one direction; the inside would cool later, and record the field in another direction.
Three years after this prediction, leading researchers Robert Coe and Michel Prévot found a thin lava layer that must have cooled within 15 days, and had 90° of reversal recorded continuously in it.9 And it was no fluke—eight years later, they reported an even faster reversal.10 This was staggering news to them and the rest of the evolutionary community, but strong support for Humphreys’ model. (See also Dr Humphreys’ online article The Earth’s magnetic field is young.)
The earth’s magnetic field is not only a good navigational aid and a shield from space particles, it is powerful evidence against evolution and billions of years. The clear decay pattern shows the earth could not be older than about 10,000 years.