ASTRON 1010 Study Guide - Midterm Guide: Retrograde And Prograde Motion, Copernican Revolution, Celestial Sphere
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Review session notes amount of time it takes for half of whatever is left to decay. The half-life of a large group of unstable atoms of the same type is the. Number of half lives (cid:883) fraction (cid:883)/(cid:883) percentage remaining (cid:883)(cid:882)(cid:882) (cid:884), , 5(cid:882)% A half-life is the time for half the nuclei in a substance to decay. Suppose you find a rock originally made of potassium-40, half of which decays into argon-40 every 1. 25 billion years. You open the rock and find 15 atoms of argon-40 for every atom of potassium-40. The study ago of the earth was based on minerals that naturally occur in rocks and have half-lives of 700 million to 100 billion years. How big is the universe: roughly 100 billion galaxies with 100 billion stars, nearest star is 4 light years away. Local sky- zenith (straight up), meridian (moves with you), altitude of north in east set in west) star=latitude (degrees above horizon)
