An archaeologist working at Villaricos located 5f km east of Mula in Murcia (Spain), to study first hand the model of rural settlement in Roman times known as Villae. Image credit to Capture The Uncapturable.

What is the carbon 14 method?

It’s a method often used by scientists to determine the age of archaeological objects, remains from humans, animals, and plants.

Schematic of 14C production and decay in the atmosphere. Credit to Australian National University.

How does it work?

A stable variant of carbon has been denoted 12C, C-12 or carbon-12. But besides this molecule of carbon, there is also another version called carbon-14, containing 6 protons and 8 neutrons.

C-14 is present in the air and is therefore absorbed by all living organisms, plants and animals alike. The proportion of C-12 to C-14 is the same in the atmosphere as long as the organism lives.

But when the organism dies, it ceases to absorb carbon dioxide and since C-14 is unstable it starts to dissolve. The half-life of C-14 is approximately 5,700 years. So after 5,700 years, the amount of C-14 is half.

Therefore, by measuring the ratio of C-12 to C-14 in a sample from the organism, it is possible to determine how many years have passed since the organism died.

Estimating a more exact age is harder the older the specimen is, and uncertainty is therefore expressed by using a range of age statement.

The method was invented in 1948 by Willard Libby of the University of California. He received a Nobel Prize in Chemistry for his discovery in 1960.