Radiocarbon dating rocks
This radioactivity can be used for dating, since a radioactive 'parent' element decays into a stable 'daughter' element at a constant rate.The rate of decay (given the symbol λ) is the fraction of the 'parent' atoms that decay in unit time.But this sediment doesn't typically include the necessary isotopes in measurable amounts.Fossils can't form in the igneous rock that usually does contain the isotopes.In addition, the oldest known moon rocks are 4.5 billion years old.Since the moon and the Earth probably formed at the same time, this supports the current idea of the Earth's age.Dinosaur bones, on the other hand, are millions of years old -- some fossils are billions of years old.
Radiometric dating isn't the only method of determining the age of rocks.
Each of them typically exists in igneous rock, or rock made from cooled magma.
Fossils, however, form in sedimentary rock -- sediment quickly covers a dinosaur's body, and the sediment and the bones gradually turn into rock.
Other techniques include analyzing amino acids and measuring changes in an object's magnetic field.
Scientists have also made improvements to the standard radiometric measurements.
Search for radiocarbon dating rocks:
For example, by using a laser, researchers can measure parent and daughter atoms in extremely small amounts of matter, making it possible to determine the age of very small samples [source: New Scientist].