PHYS 190 Lecture Notes - Lecture 20: Anisotropy, Microwave Oven, Smoking Gun
27 Mar 2018
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Our intuition suggests that universe ought to . Look the same from all locations ( be homogeneous ) (on cosmological scales) Look the same in all directions ( be isotropic ) ( have no privileged locations . An analogy: the universe is like a forest. And has existed forever (so that light reaches you from infinitely far away) Then everywhere you look you will see a tree. Then sky should be blazing with light - but not the case. Notice that it is okay for universe to be lumpy (inhomogeneous and anisotropic) on small scales. Individual stars - farther away, fainter it appears, but more stars visible. Universe, regardless of how big it is, has not existed forever. We"ve known since hubble that universe had a beginning foreshadowed centuries before olbers" paradox. 250 million light years - cosmological principles applied. When universe gets larger, distance b/w galaxies gets larger as well.
