It’s hard to argue with someone who says that the whole universe was created last Thursday. Everything in its place, a stage built and actors entering. Is this the way you picture reality? I hope not – you would be deemed troubled and therapy would be offered. Your friends would hope for a speedy recovery. And yet, if you believed nearly the same thing – a fully intact universe aged 6,000 years – well, you just might get elected to the school board.
I thought about this when I read an awkward piece by a “young-Earth geophysicist” who clearly has a lot of explaining to do. To make all of the Earth’s physics fit into a half dozen millennia takes some clever scientific juggling. As a geophysicist, he was undoubtedly trained in geology and physics, especially things like radioactive decay, heat flow, and magnetism as they relate to the planet. A cornerstone of geophysics is continental mobility – formerly continental drift, now refined as plate tectonics. Few young-Earth geophysicists reject crustal movement because it has been measured with stakes in the ground. It is as hard to deny as a photograph of a hand in a cookie jar.
When we measure the age of rocks by calculating the amount of radioactive decay that has taken place, we prove that we live upon a very old planet. I will not review the definition of half-life nor describe how the various elements and isotopes transform. I discuss this elsewhere on these blog pages. You probably already know a good deal about it, but the key is that about ten different isotopes differently disintegrate into about ten other isotopes over periods varying from millions to billions of years. Because a variety of unrelated decaying materials transform at different paces, we have multiple, corroborating evidence that the world is over four billion years old. It is like having several photographers capturing the cookie jar hand from several angles.
To claim that the corroborating radioactive evidence pretends the Earth is 6,000 years old rather than several billion requires a complete suspension of physical laws. Some young-Earth geophysicists are quite happy to contort the data and tell us that in the recent past, radioactive decay happened very rapidly but it has slowed down in the past few hundred years. Others don’t mess with varying the decay rates, they simply claim that the universe was assembled with partially decayed assemblages of isotopes. In that case, the Earth could have been put together very recently. Last Thursday, in fact.
Another issue that makes the young-Earth geophysicist’s life difficult is the zebra-striped magnetic pattern on the ocean floor. As crust is created at spreading rifts, it cools and retains the orientation of the Earth’s ever-oscillating magnetic field. Because the embedded magnetism is either positive or negative, the variations are often depicted as black and white zebra stripes.
Correlating such things as radioactive decay, heat dissipation, and the age of fossils atop the blocks of parting oceanic crust (fossils near an oceanic rift are young; those farther away are increasingly older), geophysicists have calibrated the age of the magnetic pole reversals. Magnetic orientation switches every million years or so, meaning that the planet’s magnetic field also reverses direction at roughly million year intervals. But for the young-Earth model to work, the zebra-striping has to switch every few decades. Otherwise you can’t squeeze so many reversals into just 6,000 years. If you could, this would mean that many senior geophysicists have first-hand experience with global magnetic reversals. We don’t – trust me, we’d remember.
Consternating even more ruminations among the young-Earth geophysicists is the issue of moving continents. The average rate of crustal motion is about 2 or 3 centimetres (an inch) each year. We know this because we’ve measured it. Even young-Earth geophysicists agree with the evidence of split supercontinents and the Wilson Cycle of ocean basins. To claim that the Atlantic Ocean was built in fewer than 6,000 years, such miscreant geophysicists require Europe and America to pull apart at a rate of about a kilometre a year, requiring phenomenally energetic mantle circulation. The amount of energy required to shift so much lithic material would generate enough heat to boil the oceans and melt the entire surface of the planet. After that, the crustal plates have to suddenly slow to 1/50,000 the speed to match what we observe today. And they would have to cool enough to support life. No wonder they call their idea Catastrophic Plate Tectonics. It is hard to explain how 40-kilometre-thick slabs of continent could zip along, melting the Earth’s surface, then suddenly slow to a near standstill. Actually, it is impossible to explain. However, there is an easy solution – the universe was created last Thursday. It just looks much older.