BEFORE 1940s, scientists had no accurate way of determining the age of fossils or other ancient objects. They had to rely on relative dating techniques, which were far from accurate.
In 1947, Willard Frank Libby first proposed his radiocarbon dating theories. Soon after, he presented evidence of its efficiency in various field experiments.
Libby figured that plants would absorb some of this trace carbon-14 while they absorbed ordinary carbon in photosynthesis. Once the plant died, of course, it couldn’t absorb any more carbon of any kind, and the carbon-14 it contained would decay at its usual rate without being replaced. By finding the concentration of carbon-14 left in the remains of a plant, you could calculate the amount of time since the plant had died.[ihc-hide-content ihc_mb_type=”show” ihc_mb_who=”2,3,5″ ihc_mb_template=”1″ ]
The half-life of carbon-14 is 5,730 years. However knowing how many carbon-14 atoms something had before it died can only be guessed at. The assumption is that the proportion of carbon-14 in any living organism is constant. It can be deduced then that today’s readings would be the same as those many years ago. When a particular fossil was alive, it had the same amount of carbon-14 as the same living organism today. With this technique scientists could determine the age of plant-based artifacts — wood, parchment, textiles — up to 45,000 years old. This has allowed estimates of the age of Egyptian mummies, prehistoric dwellings, and so forth.
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