Two situations where we can do this involve Potassium-40 atoms and Carbon-14 atoms.
All radioactive atoms decay to become a more stable kind of atom.
Scientists at the Lamont-Doherty Geological Laboratory of Columbia University at Palisades, N.
Y., reported today in the British journal Nature that some estimates of age based on carbon analyses were wrong by as much as 3,500 years.
Some of the different kinds of radioactive atoms used to date objects are shown in the following table: Potassium-Argon Dating Potassium atoms are used to date rocks that have formed from molten rock. Argon is an inert gasit does not chemically bond to other atoms.
Argon in molten rock can just bubble out and escape.
That causes a dating problem with any animal that eats seafood. After about ten half-lives, there's very little C14 left.
So, anything more than about 50,000 years old probably can't be dated at all.
In some cases, the latter ratio appears to be a much more accurate gauge of age than the customary method of carbon dating, the scientists said.
It is produced in the upper atmosphere by radiation from the sun.
(Specifically, neutrons hit nitrogen-14 atoms and transmute them to carbon.) Land plants, such as trees, get their carbon from carbon dioxide in the air. The same is true of any creature that gets its carbon by eating such plants. Suppose such a creature dies, and the body is preserved.
Radiometric dating is possible because the radioactive decay of large numbers of radioactive atoms follows a predictable pattern.
This predictability allows scientists to measure the age of an object if they can work out how many radioactive atoms were originally present.