Carbon has an atomic number of 6, an atomic weight of 12.011, and has three isotopes: carbon-12, carbon-13, and carbon-14.
Radiocarbon dating—also known as carbon-14 dating—is a technique used by archaeologists and historians to determine the age of organic material.
It can theoretically be used to date anything that was alive any time during the last 60,000 years or so, including charcoal from ancient fires, wood used in construction or tools, cloth, bones, seeds, and leather.
It cannot be applied to inorganic material such as stone tools or ceramic pottery.
The technique is based on measuring the ratio of two isotopes of carbon.
The theory behind radiocarbon dating is as follows: Why doesn't the carbon-14 in the air decay along with terrestrial carbon? The trick is that radioactive carbon-14 is continually replenished in a complex reaction that involves high-energy cosmic rays striking the upper atmosphere.
In this process, nitrogen-14 (7 protons and 7 neutrons) gains a neutron and loses a proton, producing carbon-14 (6 protons and 8 neutrons).
The proportion of carbon-14 to carbon-12 in the atmosphere therefore remains relatively stable at about 1.5 parts per billion.
One of the implied assumptions in radiocarbon dating is that levels of atmospheric carbon-14 have remained constant over time.
This turns out not to be exactly true, and so there is an inherent error between a raw "radiocarbon date" and the true calendar date.