How Does Carbon Dating Work?

Carbon 14 dating, also known as radiocarbon dating, determines the age of organic objects by measuring the amounts of different isotopes of carbon they contain. Since the different isotopes age, or decay, at different rates, scientists can use this technique to date materials.

About Carbon 14
Nitrogen and carbon are abundant elements in the earth's atmosphere. Normally, a nitrogen atom has seven protons and seven neutrons, giving it an atomic weight of 14; carbon has six protons and six neutrons, giving it an atomic weight of 12.

In the upper atmosphere, cosmic radiation converts very small amounts of nitrogen into an unstable type of carbon atom with six protons and eight neutrons, called carbon 14, which slowly decays into nitrogen 14.

In the air around us, the rate of decay of carbon 14 is balanced by its ongoing production in the upper atmosphere, resulting in a stable concentration.

Living organisms continually exchange carbon with the environment, and their carbon 14 content thus reflects the equilibrium concentration in the air. When an organism dies, however, its carbon 14 levels cease to be replenished and begin to decrease at a slow, steady rate. Because carbon 14 decays at a known rate, scientists can estimate the age of organic material based on how much carbon 14 remains (see diagram).

Dating the Getty Cabinet
At the Getty, conservators drilled small holes in inconspicuous locations on the cabinet's walnut surface to collect sawdust for analysis. They also took tiny clippings from the edges of a tear in the green silk and linen lining the drawer.

The results of the analyses were calibrated against reference standards to yield a probable date range for the walnut and the fabric of 1585, plus or minus 34 years.