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Physics and Archaeology
Guinnessy writes: "In 1960 Willard Frank Libby won a Nobel Prize for his work on radiocarbon dating, a technique that truly revolutionize archaeology. Now Physics Today magazine has an article describing how new methods are yielding more accurate dates for our prehistoric ancestors, profoundly affecting our understanding of the past. Neat stuff."
I'm a geologist and I use some of these techniques fairly regularly (40Ar/39Ar, U-Pb, 14C, ams cosmogenic dating). Most often, anomalies in the ages you get are most readily explained by geologic uncertainty rather than gross flaws in the techniques themselves. Sloppy field work and sample collection/documentation can get you in trouble when you try and interpret the geochronology. Also, non-idealities of the materials we use to date and other factors come into play. The dating techniques are sound, the "critical assumptions" you seem to question regarding the mechanics of calculating a radiometric age and the theory behind it really come down to radioactive decay and our technical ability to measure isotopic ratios very precisely, both of which are far from dispute. The diffuculty is in interpeting the resulting ages in a meaningful way. For instance, fluid infiltration and other processes often impart "extraneous argon" to a sample that results in an anomalously old 40Ar/39Ar age. We can analyze the
isotopic data to see if the extraneous Ar is there and we can look at the minerals and the geologic context of the sample and assess the likelihood of it. But unless we do those things throughly, we can misinterpret the isotopic data and thus the age of the sample. The isotopes don't lie, but we can be fooled.