How do we know radiometric dating is accurate jejudating 2016 jelsoft enterprises ltd
For example, the C14 concentration in the atmosphere depends upon cosmic ray intensity.
To take this into account, a calibration curve is developed using other dating methods to establish the C14 levels over time.
Age estimates can be cross-tested by using different isotope pairs.
Results from different techniques, often measured in rival labs, continually confirm each other.
Measuring the ratio of C14 to C12 and C13 therefore dates the organic matter for periods back to about eight half-lives of the isotope, 45,000 years.
By analogy, a stop watch will not keep accurate time if it is not wound, if it is not in good repair, or if the operator forgets to press the button.
C14 is continually being created and decaying, leading to an equilibrium state in the atmosphere.
When the carbon dioxide, containing C14 as well as stable C12 and C13, is taken in by plants it is no longer exposed to the intense cosmic ray bombardment in the upper atmosphere, so the carbon 14 isotope decays without being replenished.
Since then, geologists have made many tens of thousands of radiometric age determinations, and they have refined the earlier estimates.
A key point is that it is no longer necessary simply to accept one chemical determination of a rock's age.