Glossary radiometric dating
Achondrite: A class of stony meteorites that crystallized from magmas. AGB stars: Cool, luminous, and pulsating red giant stars.
Most stars in the Universe that have left the main sequence will reach their final evolutionary stage as stars on the asymptotic giant branch (AGB).
any method of determining the age of earth materials or objects of organic origin based on measurement of either short-lived radioactive elements or the amount of a long-lived radioactive element plus its decay product.
Measuring the uranium-to-lead ratios in the oldest rocks on Earth gave scientists an estimated age of the planet of 4.6 billion years.But it wasn't until the late 1700s -- when Scottish geologist James Hutton, who observed sediments building up on the landscape, set out to show that rocks were time clocks -- that serious scientific interest in geological age began.Before then, the Bible had provided the only estimate for the age of the world: about 6,000 years, with Genesis as the history book.The amount of the isotope in the object is compared to the amount of the isotope's decay products.The object's approximate age can then be figured out using the known rate of decay of the isotope.
After all, the ever-changing Earth rarely left a complete geological record.