Age of solar system radioactive dating
Scientists determined the Earth's age using a technique called radiometric dating.
Radiometric dating is based upon the fact that some forms of chemical elements are radioactive, which was discovered in 1896 by Henri Becquerel and his assistants, Marie and Pierre Curie.
After one half-life, 50 percent of the original parents remains; after two, only 25 percent remains, and so on.
Many elements have naturally occurring isotopes, varieties of the element that have different numbers of neutrons in the nucleus.
Radiometric dating works best on igneous rocks, which are formed from the cooling of molten rock, or magma.
(The nucleus of an atom is made up of protons and neutrons.) For example, the element carbon, which always has six protons in its nucleus, has three isotopes: one with six neutrons in the nucleus, one with seven, and one with eight.
Some isotopes are stable, but some are unstable or radioactive.
Over time, radioactive isotopes change into stable isotopes by a process known as radioactive decay.
Some radioactive parent isotopes decay almost instantaneously into their stable daughter isotopes; others take billions of years.