Range of carbon dating
The radiocarbon age must then be calibrated to determine the sample's age in calendar years.
Modern radiocarbon dating uses tree-ring chronologies to produce the calibration curve.
Thus it is possible in some instances for two samples from a few decades apart to have the same radiocarbon concentration today, and hence the same apparent radiocarbon age.
The technology involved is fascinating and impressive.
Measurements can be made with a high degree of precision. Aardsma submitted a sample from a reed mat known to be over 5,000 years old.
The potassium-argon age of some meteorites is as old as 4,500,000,000 years, and volcanic rocks as young as 20,000 years old have been measured by this method.
A common misconception about radiocarbon dating is that it gives a precise date---3577 B. In actual practice radiocarbon dating can only give a range of dates for a given sample---3650 to 3410 B.