Everyone will tell you that radioactive decay rates are fixed. Everyone is wrong.
Radioactive decay rates are used by many scientists to calculate the ages of the earth, the moon, and the universe. Among the assumptions used in these calculations is the assumption that the radioactive decay rates are invariable and fixed.
The Institute for Creation Research has published an article that discusses recent research which indicates that radioactive decay rates are, in fact, variable. This situation seriously brings into question the age calculations of many scientists. Read the ICR's article here.