is a technique used by scientists to learn the ages of biological specimens – for example, wooden archaeological artifacts or ancient human remains – from the distant past.
It can be used on objects as old as about 62,000 years.
In 1947, picking up where Kamen and Rubin had left off, Libby first proposed the theory of radiocarbon dating, and demonstrated its effectiveness soon afterward.
In the 1930s, he was a chemistry instructor at Berkeley and a researcher with an ambitious group of radiochemists at the university’s Lawrence Radiation Laboratory. And the discoveries made during that time are still the main bulwark and substance of chemical nuclear chemistry,” Libby later recalled.
“The seminar ran the whole nine years, and we began to be major contributors to the whole field.” One of the most important outcomes of its research was the discovery of carbon-14 on February 27, 1940, by two chemists, Martin Kamen and Samuel Rubin.
They determined that the basic element of carbon had a radioactive isotope, carbon-14, which contained two additional neutrons and could be dated back thousands of years.
For example, in the The decay constant has dimensions of reciprocal seconds.
In the special case in which parent and daughter atoms are present in equal quantities, the age of the specimen is the half-life of the parent isotope: The first assumption, that the amount of the daughter isotope in the original rock is known, is the weakest assumption.
Organisms at the base of the food chain that photosynthesize – for example, plants and algae – use the carbon in Earth’s atmosphere.