Feb_12 - Dark Matter Dark Energy Tuesday February 12 Recap...

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Dark Matter, Dark Energy Dark Matter, Dark Energy Tuesday, February 12
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Recap of the history of cosmology: Version 1.0: “Superdome” model
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Version 2.0: Geocentric model spherical Earth at center
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Version 3.0: Heliocentric model Sun at center
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v. 3.1: Infinite Infinite heliocentric model
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v. 4.0: Big Bang model
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v. 4.1: Hot Hot Big Bang model Cosmic Cosmic Microwave Microwave Background Background
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v. 4.1.1: Hot Big Bang model with space-time curvature space-time curvature . Mass & energy cause space to curve. This curvature causes an observed observed bending of the path of light.
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Gravitational lensing” by a massive Gravitational lensing” by a massive cluster of galaxies cluster of galaxies
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Observation: Observation: on large scales, space is close to flat flat . Implication: Implication: density is close to the critical density critical density .
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Flat & negatively curved spaces are infinite infinite (unless you add a boundary). Positively curved spaces are finite finite , but without a boundary.
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Suggestion: Suggestion: space is positively positively curved, but with a radius of curvature much larger than the Hubble distance (4300 Mpc). This gives the universe a huge (but finite finite ) volume. The part I can see looks flat!
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The critical density required for space to be flat is E = mc E = mc 2 2 implies m = E/c m = E/c 2 2 : this critical density can be contributed by mass mass or by energy energy . 3 27 crit kg/m 10 9 - × = ρ
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the electrons, protons, neutrons, neutrinos, photons, etc. in the universe must sum to (nearly) the critical density. 1 m
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This note was uploaded on 07/17/2008 for the course ASTRO 294 taught by Professor Ryden during the Winter '08 term at Ohio State.

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Feb_12 - Dark Matter Dark Energy Tuesday February 12 Recap...

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