Since there doesn't seem to be any systematic error that could cause so many methods to agree with each other so often, it seems that there is no other rational conclusion than to accept these dates as accurate.
But how accurate is their model, and how scientific is their approach? An isochron is a line on an isotope ratio diagram denoting rock samples.
However, the methods must be used with care -- and one should be cautious about investing much confidence in the resulting age...
especially in absence of cross-checks by different methods, or if presented without sufficient information to judge the context in which it was obtained.
(For brevity's sake, hereafter I will refer to the parent isotope as ).
In addition, it requires that these measurements be taken from several different objects which all formed at the same time from a common pool of materials.
Both the decaying isotope and the isotope it produces (its daughter) can be compared to an isotope of the daughter’s elemental family that does not decay.