Plants take in atmospheric carbon dioxide by photosynthesis, and are ingested by animals.So, every living thing is constantly exchanging carbon-14 with its environment as long as it lives. The carbon in its body will remain until it decomposes or fossilizes.They have masses of 13 and 14 respectively and are referred to as "carbon-13" and "carbon-14." If two atoms have equal numbers of protons but differing numbers of neutrons, one is said to be an "isotope" of the other.Carbon-13 and carbon-14 are thus isotopes of carbon-12.
Radiocarbon dating is only effective for objects and fossils that are less than 50,000 years old.
The amount of carbon-14 gradually decreases through radioactive beta decay with a half-life of 5,730 years.
So, scientists can estimate the age of the fossil by looking at the level of decay in its radioactive carbon.
Libby calculated the half-life of carbon-14 as 5568, a figure now known as the Libby half-life.
Following a conference at the University of Cambridge in 1962, a more accurate figure of 5730 years was agreed upon and this figure is now known as the Cambridge half-life.