lect 21 part 1

lect 21 part 1 - Exploring the Early Universe Chapter 27...

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1 Exploring the Early Universe Chapter 27 The Isotropy Problem: Why is the Microwave Background so uniform? The Flatness Problem: Why is 0 =1? • In order for the universe to be as flat as is today, the value of right after the Big Bang must have been equal to 1 with more than 50 decimal places! How can it be fine-tuned so precisely? • If > 1 => would have collapsed rapidly! • If < 1 => would have expanded so rapidly that matter could never have clumped together to form galaxies! • Either case, we would not be here…
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2 The newborn universe may have undergone a brief period of vigorous expansion • A brief period of rapid expansion, called inflation , is thought to have occurred immediately after the Big Bang • During a tiny fraction of a second, the universe ddt i t i l th i t expanded to a size many times larger than it would have reached through its normal expansion rate • Do not mistake inflation for the expansion of the universe. Inflation only lasted ~ 10 -32 sec, shortly after the Planck time. Inflation explains why the universe is nearly flat and the 2.725 K microwave background is almost perfectly isotropic Isotropy Problem solution : During inflation, material concentrated in a small region was moved out to tremendous distances. So, regions of the universe that cannot be connected today, were connected right before inflation Flatness Problem solution : The diagram shows how inflation : The diagram shows how inflation can produce a locally flat geometry
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3 The Fundamental Forces of Nature Strong Strong Weak Electro- magnetic Four basic forces: strong, electromagnetic, weak, and gravitational , explain all the interactions observed in the universe (hypothetical particle) GUT SGUT Grand unified theories ( GUTs ) are attempts to explain three of the forces in terms of a single consistent set of physical laws •A Supergrand unified theory ( SGUT ) would explain all four forces • GUTs suggest that all four physical forces were equivalent just after the Big Bang • However, because we have no satisfactory supergrand unified theory, we can as yet say nothing about the nature of the universe during this period before the Planck time ( t = 10 –43 s after the Big Bang) • At the Planck time, gravity froze out to become a distinctive force in a spontaneous symmetry breaking Di d t t b k i t h
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This note was uploaded on 02/06/2011 for the course ASTR 113 taught by Professor Geller during the Spring '08 term at George Mason.

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lect 21 part 1 - Exploring the Early Universe Chapter 27...

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