33-8 - – Universe is accelerating – Cosmological...

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65 Supernovae tell us expansion is accelerating Farther Away Closer Distant supernovae appear farther away than they “should be”. (“Should be” represents the case where the Hubble expansion is linear , or unaccelerated . That is, redshift is strictly proportional to distance.) “Should” lie along this line. But data lie just a bit higher. Galaxies are farther away than expected. Expansion is accelerating !
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66 Putting It All Together CMB observations told us: Universe is flat parallel lines remain parallel forever Supernova studies tell us:
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Unformatted text preview: – Universe is accelerating! – Cosmological Constant Λ exists – Vacuum repulsion energy! Overlap of 2 studies (arrow) gives us best estimate to date for Ω Λ & Ω M • Clustering of galaxies already told us Ω MATTER ≈ 0.3 – Only 30% of energy content of Universe is in the form of known or hypothesized types of matter – So: What is the "dark energy"? Matter Density Density from “ Cosmological Constant ” Data from Supernova studies: Composition of our Universe 67 95% To astronomers, any element above lithium (Z=3) is “ heavy ”...
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