# Relative dating of fossil

Most radiometric dating techniques must make three assumptions: The major problem with the first assumption is that there is no way to prove that the decay rate was not different at some point in the past.It is possible to measure the ratio of the different radioactive parent isotopes and their daughter isotopes in a rock, but the ratios are not dates or ages.The dates must be inferred based on assumptions about the ratios.The claimed “fact” that decay rates have always been constant is actually an inference based on a uniformitarian assumption.

It is true that radioisotope decay rates are stable today and are not largely affected by external conditions like change in temperature and pressure, but that does not mean that the rate has always been constant.

If any of these three conditions is not accurately known, the hourglass will give an inaccurate measure of time.