Dr. Brandon van der Ventel, a Nuclear Physicist from South Africa, gave the following information to Creation Magazine on the subject of Radiometric dating:
"Radiometric dating does not measure the age directly, but rather the ratio of the radioactive (unstable) parent nucleus to the stable daughter nucleus, as well as the present decay rate. However, several assumptions need to be made to proceed with the calculation:
"First, one needs to assume that there were no daughter nuclei present at the start; that is, the presence of the daughter nucleus is entirely due to the decay.
"Second, there had to be no leakage of either parent or daughter nuclei into or out of the sample. But how can we be sure of any of these assumptions if no-one was present when the rocks were formed or if the change in the elements were not monitored over the entire geological history?
"Third, the equation is valid only if the decay rate (λ) is a constant, and there is much evidence against this."