Radioactive dating uses
Using this technique, called radiometric dating, scientists are able to "see" back in time.Radiometric dating (often called radioactive dating) is a technique used to date materials such as rocks or carbon, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.Scientists discovered that rocks could be timepieces -- literally.Many chemical elements in rock exist in a number of slightly different forms, known as isotopes.Geologist Ralph Harvey and historian Mott Greene explain the principles of radiometric dating and its application in determining the age of Earth.
Segment from A Science Odyssey: "Origins."Geologists have calculated the age of Earth at 4.6 billion years.The probability of a parent atom decaying in a fixed period of time is always the same for all atoms of that type regardless of temperature, pressure, or chemical conditions. The time required for one-half of any original number of parent atoms to decay is the half-life, which is related to the decay constant by a simple mathematical formula.All rocks and minerals contain long-lived radioactive elements that were incorporated into Earth when the Solar System formed.The age of the planet, though, was important to Charles Darwin and other evolutionary theorists: The biological evidence they were collecting showed that nature needed vastly more time than previously thought to sculpt the world.A breakthrough came with the discovery of radioactivity at the beginning of the 1900s.
Carbon dating is used by archeologists to date trees, plants, and animal remains; as well as human artifacts made from wood and leather; because these items are generally younger than 50,000 years.