Trees undergo spurts in growth in the spring and summer months while becoming somewhat dormant in the fall and winter months.When a tree is cut down, these periods are exhibited in a cross section of the trunk in the form of rings.Free 5-day trial Radiometric dating is used to estimate the age of rocks and other objects based on the fixed decay rate of radioactive isotopes.

Radioactive elements are unstable; they breakdown spontaneously into more stable atoms over time, a process known as radioactive decay.

Radioactive decay occurs at a constant rate, specific to each radioactive isotope.

Plants and animals assimilate carbon 14 from carbon dioxide throughout their lifetimes.

When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.

American physical chemist Willard Libby led a team of scientists in the post World War II era to develop a method that measures radiocarbon activity.

He is credited to be the first scientist to suggest that the unstable carbon isotope called radiocarbon or carbon 14 might exist in living matter. Libby and his team of scientists were able to publish a paper summarizing the first detection of radiocarbon in an organic sample. Libby who first measured radiocarbon’s rate of decay and established 5568 years ± 30 years as the half-life. Libby was awarded the Nobel Prize in Chemistry in recognition of his efforts to develop radiocarbon dating.

Since the 1950s, geologists have used radioactive elements as natural "clocks" for determining numerical ages of certain types of rocks. "Forms" means the moment an igneous rock solidifies from magma, a sedimentary rock layer is deposited, or a rock heated by metamorphism cools off.

It's this resetting process that gives us the ability to date rocks that formed at different times in earth history.

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.

Different methods of radiometric dating can be used to estimate the age of a variety of natural and even man-made materials.

Simply counting the number of rings will give one a fairly good idea of the age of the tree.