AST101H5 Lecture Notes - Lecture 7: Atomic Nucleus, Move, Continental Drift
Document Summary
Astronomy studies earth in a general way o o. To use earth"s general properties to guide our investigation of other planets- particularly other terrestrial planets. The most primitive meteorites also have the same age o o. Note: the age of the universe is about 13. 7 billion years solar system formed when the universe was already 9 billion year old. Recall: chemical elements occur as different isotopes o. Radioactive isotopes are unstable, they change/decay spontaneously into isotopes of other elements, emitting particles. The rate of decay does not depend on the environment the atomic nucleus. The rate of decay depends only on the properties of. The decay is expressed as the half-life= time for half the isotopes present to convert. Carbon-14 nitrogen-14 with a half-life of 2730 years. This is used to date items for archeology but the half- life is too short to find earth"s age. Potassium-40 argon-40 (a gas) with a half-life of 1. 25 billion (1. 25 x 109) years.
