Radiometric dating wikianswers
Knowing that the carbon 14 has a half life of 5,730 years allows the estimation of the age of the object based on the fraction of carbon 14 remaining.
Uranium-lead dating is an established radiometric dating technique.
Very old rocks have been dated by measuring the amount of lead in the mineral zircon (Zr Si O4) which forms with radioactive uranium that takes more than 4 billion years to decay.
By this method, the age of the Earth has been estimated to be about 4.6 billion years.
This figure is in good agreement with the age of meteorites and the age of the Moon as determined independently. Carbon 14 dating is the best known example of radiometric dating, but there are many others.