Radioactive carbon dating formula
When an organism dies, the amount of 12C present remains unchanged, but the 14C decays at a rate proportional to the amount present with a half-life of approximately 5700 years.
This change in the amount of 14C relative to the amount of 12C makes it possible to estimate the time at which the organism lived.
The method of carbon dating makes use of the fact that all living organisms contain two isotopes of carbon, carbon-12, denoted 12C (a stable isotope), and carbon-14, denoted 14C (a radioactive isotope).
The ratio of the amount of 14C to the amount of 12C is essentially constant (approximately 1/10,000).
Other corrections must be made to account for the proportion of throughout the biosphere (reservoir effects).
Additional complications come from the burning of fossil fuels such as coal and oil, and from the above-ground nuclear tests done in the 1950s and 1960s.
The fossil fuel effect was eliminated from the standard value by measuring wood from 1890, and using the radioactive decay equations to determine what the activity would have been at the year of growth.The resulting standard value, A The first standard, Oxalic Acid SRM 4990B, also referred to as HOx I, was a 1,000 lb batch of oxalic acid created in 1955 by the National Institute of Standards and Technology (NIST).Since it was created after the start of atomic testing, it incorporates bomb carbon, so measured activity is higher than the desired standard. The method was developed by Willard Libby in the late 1940s and soon became a standard tool for archaeologists.Libby received the Nobel Prize in Chemistry for his work in 1960.