RADIOMETRIC FALLACIES

Now that we have carefully considered assumption number one, we move on to assumption number two. Assumption number two is that the sample (rock, mummy, etc.) has been completely undisturbed since it was new. If this assumption were true, then the amount of radioactivity remaining in the sample would tell us something about its age -- older samples would have less radioactivity, and younger samples would have more. But if the sample has been disturbed and this assumption is false, the remaining radioactivity tells us nothing about its age.

Let's consider the second assumption more closely. By saying that the sample has never been disturbed, the second assumption is really claiming the sample has been sealed off from the rest of the universe -- that no geological process, no weather phenomenon, nor anything else could possibly remove radioactive atoms from the sample. As we will see below, this assumption may be true for some carefully preserved once-living remains. But for rocks this assumption does not stand even a little examination.

In industry a technique called "zone refining" is used to purify molten materials such as silicon crystals used to make computer chips. In this process a rod of silicon or other material to be purified is passed over a heating coil which melts a segment of it. It is heated up to white heat. As the rod moves, impurities stay in the molten zone and are thereby carried to the end of the rod. This very process also happens geologically as molten magmas cool to form igneous rock. Natural "zone refining" can move compounds containing radioactive elements out of the rock. This can decrease the amount of radioactive elements in a way having nothing to do with radioactive decay. On the other hand, radioactive elements may be moved into the rock. Either way, the radioactive content of the rock changes in a way having nothing to do with radioactive decay.

An even more common way of removing radioactive material from rock is the exposure of rocks to rain water and ground water. Such exposure dissolves out of the rock compounds containing radioactive elements. The sample appears old as if the elements had been lost by radioactive decay. In fact, the very elements -- uranium, potassium and strontium -- most often monitored in radiometric rock dating all form compounds that dissolve in water (see Note 8). Furthermore, nowhere on earth do rocks seem to have been perfectly free of contact with water. The Soviets found water permeating even rocks at the bottom of extremely deep test wells (see Note 9). Assumption number two is clearly false for rocks.