Hubble parameter is hdlnadt hubble constant is h0ht0

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Unformatted text preview: /13 UW, ASTR 323, SP13, Eric Agol ©2013 3 Hubble’s law, revisited •  a(t) is the ____ ______: a(t0)=1; in the past a(t)<1; in the future a(t)>1. Redshi\ is a(t)=1/ (1+z). •  Hubble’s law w/ isotropy & homogeneity implies a(t) is the _____ throughout Universe. Hubble parameter is H=d(lna)/dt; Hubble constant is H0=H(t0) •  Hubble distance = rH = c/H0 ≈ furthest we can see ≈ cosmic horizon 5/21/13 UW, ASTR 323, SP13, Eric Agol ©2013 4 Olbers’ paradox •  Why isn’t night sky as bright as Sun? •  If Universe were ∞ in size & age, we would see surface of a star in any direc8on: the night sky should be as bright as ___ _____ •  Possible resolu8ons: –  Universe has a _____ ____ –  Universe has a _____ ____ –  Light is...
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