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.
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The ratio of Sr-87 to Sr-86 is graphed versus the ratio of Rb-87 to Sr-86 for several different parts of the rock. Sr-86 is another stable form of strontium, but it isn’t produced by radioactive decay.
Thus, it provides an independent analysis of the rock that does not depend on the radioactive decay that is being studied.
If those rocks really have been sitting around on the moon for billions of years, I suspect that the the wide range of physical and chemical processes which occurred over that time period had a much more profound effect on the uncertainty of the age determination.
This is best illustrated by the radioactive age of a sample of diamonds from Zaire.
Their age was measured to be 6.0 /- 0.3 billion years old. Those who are committed to an ancient age for the earth currently believe that it is 4.6 billion years old.
Obviously, then, the error in that measurement is 1.4 billion years, not 0.3 billion years!
If some process brought Sr-87 into the rock, it probably brought different amounts of the atom into different parts of the rock, so the ratio of Sr-87 to Sr-86 won’t stay consistent from one part of the rock to another. He says that there is one process that has been overlooked in all these isochron analyses: diffusion.
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.
When you’ve watched the documentary film and want to learn more, this is your next step.