11 - Lecture 5 1/26/11 The History of the Universe The Big...

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Lecture 5 1/26/11 The History of the Universe The Big Bang When the universe was born there was no carbon or oxygen in existence Temperature was too hot and matter was in a form of “atomic parts”: protons and neutrons As the universe expanded the initial soup began to cool and formed simple atoms mostly H and He About 1 minute after the birth of universe Next? Fluctuations in primordial soup The dark ages: gravity slowly wins: forming giant clouds of hydrogen gass The age of illumination: first stars Galaxy Formation: islands of stars How Do We Know This? Recall-- observing more distant objects means we are looking back in time! In every direction we look we see radiation that has a characteristic temperature: 2.7 K Found by accident by Penzias and Wilson in 1970 Nearly every galaxy is moving away from us More distant ones appear to be moving faster Temperature and motion predicted in Big Bang Theory How Can We Tell This? The Doppler Effect The universe has no center and no edge as far as we can tell
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How do we know the age of the Universe? Radioactive dating of elements Very precise measurement, but requires knowledge of galaxy evolution, so its uncertain age is 11.5- 17.7 Byr Ages of the oldest stars 10-15 Byr Looking for the most distant objects (oldest) we can detect in the universe
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11 - Lecture 5 1/26/11 The History of the Universe The Big...

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