Such uncertainties are usually glossed over, especially when radioactive dates are communicated to the public and, more importantly, to students.
Generally, we are told that scientists have ways to analyze the object they are dating so as to eliminate the uncertainties due to unknown processes that occurred in the past. Hayes has pointed out a problem with isochrons that has, until now, not been considered.
The amount of Sr-87 that was already in the rock when it formed, for example, should be proportional to the amount of Sr-86 that is currently there.
Since the data are divided by the amount of Sr-86, the initial amount of Sr-87 is cancelled out in the analysis.
That’s just over half a percent error in something that is supposedly multiple billions of years old.
Of course, that error estimate is complete nonsense.
If a consistent isochron is generated, however, we can be “certain” that no process interfered with the relative amounts of Rb-87 and Sr-87, so the radioactive date is a good one. Atoms and molecules naturally move around, and they do so in such as way as to even out their concentrations.
Was Rb-87 or Sr-87 added to the rock by some unknown process?
Was one of them removed from the rock by some unknown process?
The isochron is supposed to take care of such issues.
Essentially, rather than looking at the amounts of Rb-87 and Sr-87, we look at their compared to Sr-86.