Chemistry laureate Willard Libby realized that a radioactive isotope called carbon-14 can act like a clock and be put to use to solve archaeological mysteries.
In 1949, he developed radiocarbon dating or carbon-14 dating, a method that harnesses radioactive decay to determine the age of organic materials that has helped experts re-write history books by shedding light on “the wilderness of prehistory” and more accurately dating at the center of historical mysteries. For example, it determined that Ötzi the Iceman, whose remarkable remains were found in the Alps, was frozen for 5,300 years and that the last North American ice age ended about 10,000 years ago, not 25,000 years ago as previously believed by geologists.
Carbon-14 forms in the atmosphere when acted upon by cosmic radiation and then deteriorates. Living organisms absorb carbon-14. When an organism dies and the supply of carbon from the atmosphere ceases, the content of carbon-14 declines through radioactive decay at a fixed rate. Experts can accurately determine the age of organic materials up to 60,000 years old by counting carbon-14 atoms left in the materials.
Libby initially tested his dating method on charred bread from Pompeii and a fragment of an ancient chest from Ancient Egypt, but his discovery that carbon atoms act as a marker of time of death has not only revolutionized the field of archaeology but has also helped scientists understand Earth’s geology and changing climate, as well as revealing how our bodies work.
In nominating Libby for the Nobel Prize (which he was awarded in 1960), one scientist said: “Seldom has a single discovery in chemistry had such an impact on the thinking in so many fields of human endeavor. Seldom has a single discovery generated such wide public interest.”
