lect 21 - Exploring the Early Universe Chapter 27 The...

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Unformatted text preview: Exploring the Early Universe Chapter 27 The Isotropy Problem: Why is the Microwave Background so uniform? The Flatness Problem: Why is =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 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 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 can produce a locally flat geometry 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) 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 GUT SGUT 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 During a second spontaneous symmetry breaking, the...
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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 - Exploring the Early Universe Chapter 27 The...

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