Radiometric dating and astronomical dating
Radioactive dating is the procedure of calculating an age for an artifact by determining how much of the radioactive material has decayed and calculating how long that would take given the half-life (how long it takes for half the material to decay) of the material being tested.Several dozen methods exist, using different radioactive isotopes and decay products, with varied dating ranges and precision.Carbon-14 for example is considered accurate by its supporters on ages from 2 to 50 thousand years.Modern methods can detect essentially any Carbon-14, and therefore produce dates up to about 100,000 years.This provides a calendar date with an error margin.This form of dating measures the decay of uranium within igneous zircon over a scale of tens of millions to billions of years.
Yet few people know how radiometric dating works or bother to ask what assumptions drive the conclusions. This figure wasn’t established by radiometric dating of the earth itself. Radiohalos shouldn’t exist, according to conventional wisdom!
For example, the geological formations and dates from surrounding features may suggest that the "true" date can only lie within a certain range.
As another example, a date that is obviously wrong would confirm a strong belief in the fundamental unreliability of radioactive dating.
In either case, there will be a subjective tendency to accept the result, rather than performing additional checks that might reveal unsuspected problems.
Anyone using these methods should be well aware of the conditions for validity, the known confounding factors, and the sources of error.