Learn about half-life and how it is used in different dating methods, such as uranium-lead dating and radiocarbon dating, in this video lesson. As we age, our hair turns gray, our skin wrinkles and our gait slows.
However, rocks and other objects in nature do not give off such obvious clues about how long they have been around.
In a related article on geologic ages (Ages), we presented a chart with the various geologic eras and their ages.
Students not only want to know how old a fossil is, but they want to know how that age was determined.When an organism dies it ceases to replenish carbon in its tissues and the decay of carbon 14 to nitrogen 14 changes the ratio of carbon 12 to carbon 14.Experts can compare the ratio of carbon 12 to carbon 14 in dead material to the ratio when the organism was alive to estimate the date of its death.So, we rely on radiometric dating to calculate their ages.Radiometric dating, or radioactive dating as it is sometimes called, is a method used to date rocks and other objects based on the known decay rate of radioactive isotopes.