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.All carbon atoms have a nucleus containing six protons.As a result it is always undergoing natural radioactive decay while the abundances of the other isotopes are unchanged.Carbon-14 is most abundant in atmospheric carbon dioxide because it is constantly being produced by collisions between nitrogen atoms and cosmic rays at the upper limits of the atmosphere.The earliest experiments in radiocarbon dating were done on ancient material from Egypt. Libby’s team obtained acacia wood from the 3rd Dynasty Step Pyramid of Djoser to test a hypothesis they had developed.Libby reasoned that since the half-life of C years, the Djoser sample’s C14 concentration should be about 50% of the concentration found in living wood (for further details, see Arnold and Libby, 1949). Subsequent work with radiocarbon testing raised questions about the fluctuation of atmospheric C14 over time. It was perfect prey for a band of hunters, wielding spears tipped with needle-sharp points made from bone.Sensing an easy target, they closed in for the kill.
While alive, all plants and animals take C14 into their bodies.Almost 14,000 years later, there is no way to tell how many hits it took to bring the beast to the ground near the coast of present-day Washington state.But at least one struck home, plunging through hide, fat and flesh to lodge in the mastodon's rib.We wanted to use science to test the accepted historical dates of several Old Kingdom monuments.One radioactive, or unstable, carbon isotope is C14, which decays over time and therefore provides scientists with a kind of clock for measuring the age of organic material.