Everything a Christian Should Know About the Torah

Appendix 5

Radiological Dating

For a quick overview of some of the problems using radiological methods for determining age of an object, here is an excerpt from Dr. Andrew A. Snelling’s book, “Earth’s Catastrophic Past: Geology, Creation and The Flood^[1]” pointing out some of the assumptions of radioactive dating. 

The measurement of time by radioactive decay of a parent isotope is often compared to the measurement of time as sand grains fall in an hourglass. The sand in the upper chamber of an hourglass represents a radioactive parent isotope, while the sand in the lower chamber is analogous to the respective daughter isotope. The sand grains fall from the upper chamber at a constant rate, said to be analogous to radioactive decay. If all the sand grains started in the upper chamber and then the number of sand grains were measured in the two chambers after some time elapsed, provided the rate at which the sand grains fall has been measured, simple mathematics can be used to calculate how long the hourglass has been in operation, and thus, the time when the process started. When applied to the radioactive decay “clock,” this starting time is when the rock formed and is, therefore, its calculated age.

From this description of the analogy of the hourglass to radioactive decay of isotopes in rocks and minerals, it should be evident that the calculation of the “age” of a rock or mineral, based on the measurements of the quantities of the parent and daughter isotopes, and of the decay rate for the particular parent-daughter isotope pair, requires three assumptions:

1. The number of atoms of the daughter isotope originally in the rock or mineral when it crystallized can be known. In other words, it is assumed that we can know the initial conditions when the rock or mineral formed. In the potassium-argon method it is usually assumed that there was originally no daughter argon; therefore, all the argon measured in the rock or mineral was derived by radioactive decay from in situ parent potassium.
2. The number of atoms of the parent and daughter isotopes have not been altered since the rock or mineral crystallized, except by radioactive decay. In other words, it is assumed that the rock or mineral remained closed to loss of gain of parent and/or daughter isotopes since crystallization.
3. The rate of decay of the parent isotope is known accurately, and has not changed during the existence of the rock or mineral since it crystallized.

These assumptions require careful evaluation for each rock or mineral being dated, and obviously impose certain restraints in the interpretation of the resultant calculated “ages.” Indeed, these assumptions simply cannot be proven, because when most rocks and minerals crystallized, no human observers were present to determine the original number of atoms of the daughter isotopes. Nor were human observers present throughout the histories of most rocks and minerals to determine whether the rocks and minerals have remained closed to loss or gain of parent and/or daughter isotopes, and if the rates of radioactive decay of the parent isotopes have not changed. Thus, it logically follows that these assumptions are, strictly speaking, not provable. It is often claimed that it is obvious where assumption two has failed, because anomalous results are obtained, that is, results not in agreement with the expected “ages.” Otherwise, the calculated “ages” are often what are expected, and so the methods are confidently accepted as valid. Of course, this is uniformitarianism in the extreme, because it is assumed that decay rates measured in the present (over the past century) have been constant for millions and billions of years, an extrapolation of up to seven orders of magnitude!

⇐Previous Chapter (Introduction/Index) Next Chapter⇒

[1] Snelling, Dr. Andrew A. (2009). Earth’s Catastrophic Past: Geology, Creation and The Flood (pp. 800-801). Institute for Creation Research.