Problems with getting accurate dates from radiometric dating
If two or more radiometric clocks based on different elements and running at different rates give the same age, that's powerful evidence that the ages are probably correct.
Along this line, Roger Wiens, a scientist at the Los Alamos National Laboratory, asks those who are skeptical of radiometric dating to consider the following (quoted in several cases from [Wiens2002]): All of the different dating methods agree--they agree a great majority of the time over millions of years of time.
Some [skeptics] make it sound like there is a lot of disagreement, but this is not the case.
The disagreement in values needed to support the position of young-Earth proponents would require differences in age measured by orders of magnitude (e.g., factors of 10,000, 100,000, a million, or more).
As we pointed out in these two articles, radiometric dates are based on known rates of radioactivity, a phenomenon that is rooted in fundamental laws of physics and follows simple mathematical formulas.
Dating schemes based on rates of radioactivity have been refined and scrutinized for several decades.
Other objections raised by creationists are addressed in [Dalrymple2006a].
For example, creationist writer Henry Morris [Morris2000, pg.The differences actually found in the scientific literature are usually close to the margin of error, usually a few percent, not orders of magnitude!Vast amounts of data overwhelmingly favor an old Earth.Over a thousand papers on radiometric dating were published in scientifically recognized journals in the last year, and hundreds of thousands of dates have been published in the last 50 years.
Essentially all of these strongly favor an old Earth.
The isochron techniques are partly based on this principle.