well, uh, yeah, i guess discussing KNOWN problems would be helpful.
quote the particular passage of my source you have a problem with, or drop the matter entirely.

Really? PLEASE! Just what part of "it is what he does not explain" that is the problem do you not understand? The entire presentation does nothing more than to describe problems that may or may not be encountered with radiometric dating methods. By leaving out the very important part of how those problems are detected, solved and/or avoided, is the problem. The whole purpose of Dr. Pitmans presentation is to cast doubt on radiometric dating methods. In doing this he engages in intellectual dishonesty.
Intellectual dishonesty is the act of presenting only information that appears to support one's position while deliberately ignoring all credible information that does not support that position.
As for the specific example you ask for, review my post #122, where I describe how the Ar/Ar method accounts and corrects for any excess or diffused daughter material. The only discussion Pitman actually makes concerning the Ar/Ar method is to refer back to the list of assumptions, which is by the way, circular reasoning.
Now lets visit those assumptions. From your source:
- Beginning Conditions Known
- Beginning Ratio of Daughter to Parent Isotope Known (zero date problem)
- Constant Decay Rate
- No Leaching or Addition of Parent or Daughter Isotopes
- All Assumptions Valid for Billions of Years
- There is also a difficulty in measuring precisely very small amounts of the various isotopes
"Beginning Conditions Known": For those trained in Petrology and Geochemistry, no problem.
"Beginning Ratio of Daughter to Parent Isotope Known": That is not really assumed. If it were, then why are there specific methods that detect and correct for any excess daughter isotope.
"Constant decay rate": Again, not really assumed. Decay rates are constantly measured by scientists who work with them. There are a few "cosmogenic" isotopes that do vary their rate by an extremely small amount which are well within any margin of error, thus they really have no effect. And those are actually rate changes, rather oscillations. Furthermore, none of them are even used in radiometric dating. And how do we know over time that rates have not changed? There are two specific criteria there. First is basic physics and chemistry, it doesn't change. Second, decay rates have been detected and measured from from supernova emitting gamma rays that are hundreds of thousands and even millions of light years distant. Those measured decay rates are the same as those we measure on earth today.
"No Leaching or Addition of Parent or Daughter Isotopes": Again, that is not assumed. As I mentioned before, there are specific methods for detecting and accounting for this.
"All Assumptions Valid for Billions of Years": Previously described above under the constant rate assumption.
"There is also a difficulty in measuring precisely very small amounts of the various isotopes". That simply is not true. With today's methods and technology, samples weighing only a few milligrams can be dated very precisely.
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