Symbolically, the process of radioactive decay can be expressed by the following differential equation, where N is the quantity of decaying nuclei and k is a positive number called the exponential decay constant.The meaning of this equation is that the rate of change of the number of nuclei over time is proportional only to the number of nuclei.To see how we actually use this information to date rocks, consider the following: Usually, we know the amount, N, of an isotope present today, and the amount of a daughter element produced by decay, D*.By definition, D* = N-1) (2) Now we can calculate the age if we know the number of daughter atoms produced by decay, D* and the number of parent atoms now present, N.Thus, if we start out with 1 gram of the parent isotope, after the passage of 1 half-life there will be 0.5 gram of the parent isotope left.After the passage of two half-lives only 0.25 gram will remain, and after 3 half lives only 0.125 will remain etc.Some isotopes have half lives longer than the present age of the universe, but they are still subject to the same laws of quantum physics and will eventually decay, even if doing so at a time when all remaining atoms in the universe are separated by astronomical distances.Various elements are used for dating different time periods; ones with relatively short half-lives like carbon-14 (or C) are useful for dating once-living objects (since they include atmospheric carbon from when they were alive) from about ten to fifty thousand years old. Longer-lived isotopes provide dating information for much older times.
This age is computed under the assumption that the parent substance (say, uranium) gradually decays to the daughter substance (say, lead), so the higher the ratio of lead to uranium, the older the rock must be.
At their request, physicist Dr Jim Mason, of CMI Canada, reviewed the material from the meeting and his response was published on 2 April 2015 (see Response to Geochronology: Understanding the Uncertainties, a presentation by Dr Justin Payne).
We previously reported an event organized by the Adelaide, Australia, Chapter of Reasonable Faith where Dr Justin Payne, a lecturer within the School of Earth and Environmental Sciences at the University of Adelaide, sought to ‘disprove’ objections to long-age radiometric dating.
Any age calculated is based on multiple unprovable assumptions to match the long-age worldview.
Kevin Rogers submitted a comment to that article (reproduced below, edited to focus on substantive issues), to which Dr Jim Mason replies.