The second difficulty arises from the extremely low abundance of C, making it incredibly difficult to measure and extremely sensitive to contamination.
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.
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.
This means that although they are very similar chemically, they have different masses.In this way large domed tombs (known as tholos or beehive tombs) in Greece were thought to predate similar structures in the Scottish Island of Maeshowe.This supported the idea that the classical worlds of Greece and Rome were at the centre of all innovations.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.