Radiometric dating technology
Over the past six decades, the amount of radiocarbon in people or their remains depends heavily on when they were born or, more precisely, when their tissues were formed.
Forensic anthropologists at The University of Arizona took advantage of this fact in a recent study funded by NIJ.
In contrast, from 1955 to 1963, atmospheric radiocarbon levels almost doubled.
Since then they have been dropping back toward natural levels.
Now, new applications for the technique are emerging in forensics, thanks to research funded by NIJ and other organizations.
In recent years, forensic scientists have started to apply carbon-14 dating to cases in which law enforcement agencies hope to find out the age of a skeleton or other unidentified human remains.
But in a dead organism, no new carbon is coming in, and its carbon 14 gradually begins to decay.
So by measuring carbon 14 levels in an organism that died long ago, researchers can figure out when it died.
Each atom has a positively charged nucleus surrounded by negatively charged electrons.Most carbon atoms have six protons and six neutrons in their nuclei and are called carbon 12. But a tiny percentage of carbon is made of carbon 14, or radiocarbon, which has six protons and eight neutrons and is not stable: half of any sample of it decays into other atoms after 5,700 years.Carbon 14 is continually being created in the Earth's atmosphere by the interaction of nitrogen and gamma rays from outer space.The activity uses the basic principle of radioactive half-life, and is a good follow-up lesson after the students have learned about half-life properties.See the background information on Students will use half-life properties of isotopes to determine the age of different "rocks" and "fossils" made out of bags of beads.