Their exquisitely sensitive instrumentation was originally developed for studies in entirely different fields including nuclear physics, biomedicine, and detecting fallout from bomb tests.(1) Much of the initial interest in carbon-14 came from archeology, for the isotope could assign dates to Egyptian mummies and the like.
Some of the carbon-14 might find its way into living creatures.
After a creature's death the isotope would slowly decay away over millennia at a fixed rate.
Tricks also spread through visits between laboratories and at meetings, and sometimes even through publications.
Any contamination of a sample by outside carbon (even from the researcher's fingerprints) had to be fanatically excluded, of course, but that was only the beginning.
However, at the moment of death, the amount of carbon-14 begins to decrease because it is unstable, while the amount of carbon-12 remains constant in the sample.
Half of the carbon-14 degrades every 5,730 years as indicated by its half-life.
Libby and coworkers, and it has provided a way to determine the ages of different materials in archeology, geology, geophysics, and other branches of science.
Some examples of the types of material that radiocarbon can determine the ages of are wood, charcoal, marine and freshwater shell, bone and antler, and peat and organic-bearing sediments.
From its origins in Chicago, carbon-14 dating spread rapidly to other centers, for example the grandly named Geochronometric Laboratory at Yale University.
The best way to transfer the exacting techniques was in the heads of the scientists themselves, as they moved to a new job.
For other examples, see the essays on Temperatures from Fossil Shells and Arakawa's Computation Device.