Radiocarbon Dating is the measurement of the age of dead matter by comparing the radiocarbon content with that in living matter. The method was discovered at the University of Chicago in the 1940s, but further research had to wait until the end of World War II. Radiocarbon, or radioactive carbon (C-14), is produced by the cosmic rays in the atmosphere and is assimilated only by living beings. At death, the assimilation process stops. Living matter, wherever found on earth, always has the same ratio of radioactive carbon to ordinary carbon. This ratio is enough to be measured by sensitive instruments to about 1 percent accuracy.