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Olber’s Paradox. Uniform Expansion. Cosmological Redshift. Expansion Redshift. Cosmological Principle. Universality – The laws of nature are the same everywhere Homogeneity – The distribution of matter and energy is uniform at the largest scales
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Cosmological Principle • Universality – The laws of nature are the same everywhere • Homogeneity – The distribution of matter and energy is uniform at the largest scales • Isotropy – The distribution of matter and energy is the same in every direction
Dark Matter • Whether our universe is closed, open or flat is determined by the density of matter and energy. • Supercritical Density – Closed Universe • Critical Density – Flat Universe • Subcritical Density – Open Universe • Universe appears close to flat but density of luminous matter is no where near critical
Dark Matter Candidates • MACHO – Massive And Compact Halo Objects – lots of mini black holes everywhere • WIMP – Weakly Interacting Massive Particles – massive neutrinos or undiscovered particles