And carbon dating
Rachel Wood does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.Australian National University provides funding as a member of The Conversation AU.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.
Australia has two machines dedicated to radiocarbon analysis, and they are out of reach for much of the developing world.
Luckily, we can measure these fluctuations in samples that are dated by other methods.
Tree rings can be counted and their radiocarbon content measured.
If 1% of the carbon in a 50,000 year old sample is from a modern contaminant, the sample will be dated to around 40,000 years.
Because of this, radiocarbon chemists are continually developing new methods to more effectively clean materials.
In 2008 we could only calibrate radiocarbon dates until 26,000 years.