Any such change would affect different forms of decay differently, yet this has not been observed.
Falicies of radioactive dating
A very common claim of young earth creationists in trying to reject the evidence for an old earth is to loudly proclaim that radiometric dating methods “makes assumptions” and that these “assumptions” are somehow fatally flawed or not supported by evidence.
These claims generally land in three different categories: (1) radiometric dating assumes that initial conditions (concentrations of mother and daughter nuclei) are known, (2) radiometric dating assumes that rocks are closed systems and (3) radiometric dating assumes that decay rates are constant.
An isochron diagram is obtained by looking at many minerals from the same rock or from rocks forming from the same parent mineral.
Data is plotted on a simple two dimensional graph; the parent isotope on the x-axis and the daughter isotope on the y-axis.
This means that the while different rocks contain different absolute amounts of the two isotopes, the is same.
At the time of formation for a rock, the isotopes for an element are homogenized and so the composition of a certain isotope is the same in all the minerals in the rock.
As time goes on, the ratio of the parent to daughter nuclei will change and decrease (as more parent nuclei decay into daughter nuclei, the former decreases and the latter increases).
Measuring this ratio gives us an idea of how long ago the rock formed. Doesn’t this assume that the rocks are closed systems? Radiometric dating and testing for contamination and disturbances On of the great things about many forms of radiometric dating is that they are self-checking.
Both of these are divided or normalized by a stable isotope of the same elements as the daughter element.