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From the Dynamic Earth at the University of Leeds, a cross-linked series of static diagrams illustrates the underlying principle of radioactive decay, the concept of a decay constant, and isochron plots. Inscriptions, distinctive markings, and historical documents can all offer clues to an artifact's age.Play a game that tests your ability to match the percentage of the dating element that remains to the age of the object.We’re going to see what 'half-life' means and why radioactivity changes with time. It doesn’t depend on the size of the sample and it doesn’t change with time. So we imagine going in forward one half-life at a time from ZERO years: 10 years, 20 years, 30 years, etc.Carbon-14 is produced all the time but it also decays all the time back into nitrogen-14.
An equilibrium is reached whereby about one in a trillion carbon atoms in the atmosphere is carbon-14.
If you have a wooden box, carbon dating can tell you when the tree to make it was cut down but not when the box was made. Carbon dioxide is made into simple sugars and it is these that are the building blocks that make up wood, bark and leaves.
Carbon dating can be used to date things up to about 60 000 years old. Many people think that plants grow by taking food from the soil through their roots but this is not true. Animals eat plants (or other animals that eat plants) so animals are also mostly rearranged carbon dioxide.
It is mostly carbon-12 with tiny amounts of the radioactive carbon-14. For example, a sample with a count of only 25% of atmospheric carbon dioxide must be two half-lives old: 100% - 50% takes 1 half-life 50% - 25% takes a second half-life If the half-life is 5600 years then the sample must be 5600 x 2 = 11 200 years old.
We measure the radioactivity of the carbon dioxide in a special chamber to shield it from background radiation. You can use a much smaller sample of the material you want to test if you count the carbon-14 atoms directly rather than having to wait for them to decay.
This section provides access to a number of visualizations and supporting material illustrating the concept of radioactive decay and its central role in radiometric dating.