Carbon dating and the
The calibrated date is also presented, either in BC or AD or with the unit cal BP (calibrated before present - before 1950).The calibrated date is our “best estimate” of the sample’s actual age, but we need to be able to return to old dates and recalibrate them because new research is continually used to update the calibration curve.
In the early years of radiocarbon dating a product’s decay was measured, but this required huge samples (e.g. Many labs now use an Accelerator Mass Spectrometer (AMS), a machine that can detect and measure the presence of different isotopes, to count the individual C atoms in a sample.From these records a “calibration curve” can be built (see figure 2, below).A huge amount of work is currently underway to extend and improve the calibration curve.These new techniques can have a dramatic effect on chronologies.With the development of a new method of cleaning charcoal called ABOx-SC, Michael Bird helped to push back the date of arrival of the first humans in Australia by more than 10,000 years.In 2008 we could only calibrate radiocarbon dates until 26,000 years.
Now the curve extends (tentatively) to 50,000 years.
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View the full list Radiocarbon dating has transformed our understanding of the past 50,000 years.
Professor Willard Libby produced the first radiocarbon dates in 1949 and was later awarded the Nobel Prize for his efforts.
Radiocarbon dating works by comparing the three different isotopes of carbon.
In addition, samples need to be thoroughly cleaned to remove carbon contamination from glues and soil before dating.