Learn more: Radiocarbon Dating is an "Archae Interactive" module from North Carolina State University. A calibrated radiocarbon date is one that has been calibrated to the tree-ring record to adjust for variations in the concentration of atmospheric C-14 over time. This discovery meant that there are three naturally occurring isotopes of carbon: Whereas carbon-12 and carbon-13 are stable isotopes, carbon-14 is unstable or radioactive.Carbon-14 is produced in the upper atmosphere when cosmic rays bombard nitrogen atoms. Along with hydrogen, nitrogen, oxygen, phosphorus, and sulfur, carbon is a building block of biochemical molecules ranging from fats, proteins, and carbohydrates to active substances such as hormones.
Testing two pieces each at two different facilities should provide consistent results – and indeed it did. The proportion of C-14 in the atmosphere, and hence in living things, is not constant but varies over the centuries, and it also varies between the atmosphere and the oceans.The ensuing atomic interactions create a steady supply of c14 that rapidly diffuses throughout the atmosphere.Plants take up c14 along with other carbon isotopes during photosynthesis in the proportions that occur in the atmosphere; animals acquire c14 by eating the plants (or other animals).Calibrated C-14 dates correspond to true calendar years; standard C-14 dates do not. In the scientific literature, calibrated dates are usually reported as cal A.
Search for radiocarbon dating:
Since carbon is fundamental to life, occurring along with hydrogen in all organic compounds, the detection of such an isotope might form the basis for a method to establish the age of ancient materials.