However, conditions may have been different in the past and could have influenced the rate of decay or formation of radioactive elements.
Thus radioactive dating relies purely on assumptions.
We could put forward the following counter arguments to the constancy of these assumptions: a) The constancy of cosmic ray bombardment might be questioned.
This requires that only the parent isotope be initially present or that the amount of daughter isotope present at the beginning is known so that it can be subtracted.
Many examples from literature show that the zero-reset assumption is not always valid.
If the clock is not set to zero when a deposit forms, then there can be no starting point from which to calculate the age of a deposit.
It is assumed that we are dealing with a closed system—no loss of either parent or daughter elements has occurred since the study material formed.d) Even if the rate of decay is constant, without knowledge of the exact ratio of carbon-12 to carbon-14in the initial sample, the dating technique is subject to question.It's assumed that the clock was set to zero when the study material was formed.No scientist can guarantee that any sample can be considered a closed system unless it was isolated from its environment when it was formed.Elements can be transported into a sample or leach out of a sample.Scientists will reject theories about the age of the earth that do not conform to the norm.