Assumptions used in carbon dating

Radiocarbon dating is a key tool archaeologists use to determine the age of plants and objects made with organic material.

But new research shows that commonly accepted radiocarbon dating standards can miss the mark -- calling into question historical timelines.

Careful astronomical observations show that the constants have not changed significantly in billions of years—spectral lines from distant galaxies would have shifted perceptibly if these constants had changed.

There are a number of assumptions involved in radiometric dating with respect to long time periods.

One key assumption is that the initial quantity of the parent element can be determined.

With uranium-lead dating, for example, the process assumes the original proportion of uranium in the sample is known with reasonable accuracy.

One assumption that can be made is that all the lead in the sample was once uranium, but if there was lead there to start with, this assumption is not valid, and any date based on that assumption will be incorrect (too old). In the case of carbon dating, it is not the initial quantity that is important, but the initial ratio of C, but the same principle otherwise applies.

So we wondered whether the radiocarbon levels relevant to dating organic material might also vary for different areas and whether this might affect archaeological dating." The authors measured a series of carbon-14 ages in southern Jordan tree rings, with established calendar dates between 16 A. They found that contemporary plant material growing in the southern Levant shows an average offset in radiocarbon age of about 19 years compared the current Northern Hemisphere standard calibration curve.