Radioactive decay and absolute dating
With time, radiometric dating became more sophisticated and accurate, by 1931 radiometric dating had proven to be the credible method for determining the age of igneous rocks. For a good discussion on modern radiometric methods see 1. They were done without knowledge of isotopes or the decay rates and intermediate products of Uranium.
This indicated that radioactivity was a property of atoms, not molecules.Second, Pb/U ratios are a function of geologic age. Finally, as Arthur Holmes (1890-1965), a British geologist pointed out, ages obtained using these new methods were often in agreement with what many geologists had speculated (Dalrymple, 1991, pp. The fact that this new method of dating utilized empirical evidence gathered in the field and analyzed in the lab with methods based upon experimentally determined physical principles made it promising and powerful.It soon became clear that the Earth was much older than many of the earlier methods indicated. Even so, early work done by Bertram Borden Boltwood (1870-1927), an American chemist and physicist demonstrated several important consistencies.
First, the same Pb/U ratios are obtained in samples from the same geologic age.
Furthermore, this energy could penetrate cardboard and even walls to fluoresce barium platinocyanide.