PHYS 190 Chapter Notes - Chapter 11: Raisin Bread, Night Sky, Observable Universe
1 Apr 2018
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Modern observations indicate that universe could be infinite & have no edge. If universe has no edge, cannot have a centre. Simple observation that night sky is dark is important. B/c reasonable assumptions about universe can lead us to conclude that night sky would actually glow bright. Olbers"s paradox - conflict b/w theory & evidence regarding darkness of night sky. Suppose you assume universe infinite & filled w/ stars. If you look in any direction, line of sight must eventually reach surface of a star. If you are deep in forest, every line of sight ends on tree trunk, and you cannot see out of forest. By analogy, every line of sight from earth out into space should eventually end on surface of star, so entire sky should be as bright as surface of average star. Olbers" paradox makes incorrect prediction b/c based on hidden assumption. Universe may be infinite in size, but is not eternal.
