Note that, contrary to a popular misconception, carbon dating is not used to date rocks at millions of years old.Before we get into the details of how radiometric dating methods are used, we need to review some preliminary concepts from chemistry.So, we have a “clock” which starts ticking the moment something dies.Obviously, this works only for things which were once living.By measuring the ratio of the radio isotope to non-radioactive carbon, the amount of carbon-14 decay can be worked out, thereby giving an age for the specimen in question.But that assumes that the amount of carbon-14 in the atmosphere was constant — any variation would speed up or slow down the clock.
Carbon dating is used to work out the age of organic material — in effect, any living thing.
Recall that atoms are the basic building blocks of matter.
Atoms are made up of much smaller particles called protons, neutrons, and electrons.
The clock was initially calibrated by dating objects of known age such as Egyptian mummies and bread from Pompeii; work that won Willard Libby the 1960 Nobel Prize in Chemistry.
But even he “realized that there probably would be variation”, says Christopher Bronk Ramsey, a geochronologist at the University of Oxford, UK, who led the latest work, published today in Science.