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Parameterizing the Age of the Universe The Age of Things: Sticks, Stones and the Universe http://cfcp.uchicago.edu/~mmhedman/compton1.html

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WARNING! Cosmologist talking about Cosmology !

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Today Past Last Time: The Expanding Universe

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Expansion is NOT due to movement of Galaxies through space Expansion is due to changes in geometry caused by the presence of matter WRONG!

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Today Past The Scale Factor a = 1 a = 0.5

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Today Past The Scale Factor a = 1 a = 0.5 The Big Bang happens when a = 0

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(Coutesy of E. Sheldon) Hydrogen Oxygen Wavelengths measured in Laboratory

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Scale Factor from Redshifts Time 1 Time 2 Time 3

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Galaxy Distances: Type Ia Supernova Luminosity Days Supernova 1994D

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Based on Data from Riess et. al. astro-ph/0402512 The Scale Factor Over Time Supernova 1994D PastPresent

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The Scale Factor Over Time Supernova 1994D PastPresent

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a = 1 a = 0.5 a = 0 The Scale Factor The Big Bang Past Present

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The Expansion History and Material Content of the Universe General Relativity Distribution of Matter and Energy Geometry of Space and Time Energy Density (Amount of Energy contained in a unit volume) Expansion Rate (How fast the Scale Factor changes with Time)

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The Expansion History and Material Content of the Universe General Relativity Distribution of Matter and Energy Geometry of Space and Time Energy Density (Amount of Energy contained in a unit volume) Expansion Rate (How fast the Scale Factor changes with Time) Higher Energy DensityFaster Expansion Rate

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The Expansion History and Material Content of the Universe General Relativity Distribution of Matter and Energy Geometry of Space and Time Energy Density (Amount of Energy contained in a unit volume) Expansion Rate (How fast the Scale Factor changes with Time) Higher Energy DensityFaster Expansion Rate Slower Expansion RateLower Energy Density

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The Expansion History and Material Content of the Universe General Relativity Distribution of Matter and Energy Geometry of Space and Time Scale Factor (Average Distance between particles) Energy Density (Amount of Energy contained in a unit volume) Expansion Rate (How fast the Scale Factor changes with Time) Equation of State (How Energy Density changes with Scale factor)

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A closer look at the expanding universe PastPresent

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Types of Energy: Matter Scale Factor Increases Energy Density Falls Expansion Rate Slows

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Types of Energy Scale Factor Increases Energy Density Falls Expansion Rate Slows Matter

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Matter Only PastPresent Predictions for a Universe with only Matter Scale Factor Increases Energy Density Falls Expansion Rate Slows Matter

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Matter Only PastPresent Predictions for a Universe with only Matter Scale Factor Smaller Energy Density Larger Expansion Rate Faster Scale Factor Larger Energy Density Lower Expansion Rate Slower

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Matter Only PastPresent Predictions for a Universe with only Matter Scale Factor Smaller Expansion Rate Faster Scale Factor Larger Expansion Rate Slower

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Types of Energy Scale Factor Increases Energy Density Falls Expansion Rate Slows Matter Dark Energy Scale Factor Increases Energy Density Stays Constant Expansion Rate Grows

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Types of Energy: Dark Energy

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Dark Energy Only Matter Only PastPresent Predictions for a Universe with only Dark Energy Scale Factor Smaller Energy Density Larger Expansion Rate Faster Scale Factor Larger Energy Density Lower Expansion Rate Slower Scale Factor Smaller Energy Density Same Expansion Rate Slower Scale Factor Larger Energy Density Same Expansion Rate Faster

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Dark Energy Only Matter Only PastPresent Predictions for a Universe with only Dark Energy Scale Factor Smaller Expansion Rate Faster Scale Factor Larger Expansion Rate Slower Scale Factor Smaller Expansion Rate Slower Scale Factor Larger Expansion Rate Faster

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Dark Energy Only Matter Only PastPresent Predictions for a Universe with only Dark Energy Scale Factor Increases Energy Density Stays Constant Expansion Rate Grows Scale Factor Increases Energy Density Falls Expansion Rate Slows Matter Dark Energy

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Dark Energy Only Matter Only 25% Matter, 75% Dark Energy 75% Matter, 25% Dark Energy PastPresent 50% Matter, 50% Dark Energy Predictions for a Universe with mixtures of matter and D.E. Best Fit is about 3 Parts Dark Energy for every 1 part Matter Note Fractions only valid today

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The Expansion History and Material Content of the Universe General Relativity Distribution of Matter and Energy Geometry of Space and Time Scale Factor (Average Distance between particles) Energy Density (Amount of Energy contained in a unit volume) Expansion Rate (How fast the Scale Factor changes with Time) Equation of State (How Energy Density changes with Scale factor)

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Predictions for Universes with different total Energy Densities Energy Density Today = Critical Density Energy Density Today = 1.5 x Critical Density Dark Energy Only Matter Only Dark Energy Only Matter Only 25% Matter, 75% Dark Energy 75% Matter, 25% Dark Energy 50% Matter, 50% Dark Energy

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400 nm500 nm 600 nm700 nm Visible What is the Cosmic Microwave Background? Wavelength 1 m1 km1 mm 1 m 1 nm1 pm Microwaves are Electromagnetic Radiation with Wavelengths between 1 mm and 10 cm

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What is the Cosmic Microwave Background ? Penzias and Wilson, discoverers of the CMB Telescopes sensitive to microwaves detect a signal from space This signal is nearly the same from every point on the sky (it is nearly isotropic) This radiation has a spectrum characteristic of heavily redshifted thermal radiation

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The Spectrum of the Cosmic Microwave Background Points= Data Line= 2.7 K Blackbody Thermal Radiation

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The Thermal Spectra of Stars and the CMB Wavelength Brightness 2.7 K 0.0004 mm0.0005 mm 40,000 K10,000 K7,000 K4,000 K 0.0004 mm0.0005 mm0.0004 mm0.0005 mm0.0004 mm0.0005 mm

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The Thermal Spectra of Stars and the CMB Wavelength (millimeters) Brightness 2.7 K 10,000 K 0.00040.00050.00060.0007 Star CMB

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Interactions between light and matter ProtonElectron Plasma: Free Charged Particles Strong coupling to Electromagnetic Waves Produces Blackbody Radiation Typically exists at High Temperatures Gas: Neutral Atoms Generally does not couple strongly with Electromagnetic Waves Does not produce Blackbody Radiation Typically exists at lower Temperatures

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Radiation in an expanding Universe Scale Factor Increases Radiation Density Decreases Photon Wavelength Increases Effective Temperature Decreases

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Radiation in an Expanding Universe Scale Factor Increases Radiation Density Falls Photon Wavelength Increases Effective Temperature Drops Radiation The CMB had a higher effective temperature in the past when the scale factor was smaller

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What is the Cosmic Microwave Background? Decoupling Wavelength 1 m1 km1 mm 1 m 1 nm1 pm

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Brightness Variations in the Cosmic Microwave Background Data from the WMAP Satellite, processed by Tegmark et. al.

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The Size of features in the CMB Angular Size of Features ~ 1/2 o Decoupling

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The Size of features in the CMB Angular Size of Features ~ 1/2 o Actual Size of Features ~ 400,000 Light Years Decoupling

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Curvature Energy Density Critical Density Lower DensityHigher Density Zero Curvature Positive CurvatureNegative Curvature

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Curvature and the Apparent Size of Objects Energy Density Critical Density Lower DensityHigher Density Zero Curvature Positive CurvatureNegative Curvature Object Appears LargerObject Appears Smaller From Observer’s Viewpoint

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Curvature and the Apparent Distance to Objects Energy Density Critical Density Lower DensityHigher Density Zero Curvature Positive CurvatureNegative Curvature Object is Farther Away Object is Closer Object appears to be the same size

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The CMB and the total energy density of the Universe Angular Size of Features ~ 1/2 o Actual Size of Features ~ 400,000 Light Years The distance the light has to travel depends on the curvature

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The CMB and the total energy density of the Universe Angular Size of Features ~ 1/2 o Actual Size of Features ~ 400,000 Light Years The Scale Factor increases by a factor of 1000 between decoupling and Today The distance the light has to travel depends on the curvature The amount of time this takes depends on the total energy density Decoupling, radiation mostly in visible: wavelength ~ 500 nm Today, radiation mostly in microwaves wavelength ~ 1 mm

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Distance and Time Energy Density Critical Density Lower DensityHigher Density Zero Curvature Positive CurvatureNegative Curvature Object is Farther Away Object is Closer Expansion Rate Slower Expansion Rate Faster Longer TimeShorter Time

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The CMB and the total energy density of the Universe Angular Size of Features ~ 1/2 o Actual Size of Features ~ 400,000 Light Years The Scale Factor increases by a factor of 1000 between decoupling and Today The distance the light has to travel depends on the curvature The amount of time this takes depends on the total energy density Decoupling, radiation mostly in visible: wavelength ~ 500 nm Today, radiation mostly in microwaves wavelength ~ 1 mm

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Apparent Size of CMB Features is only consistent with Zero Curvature Energy Density Critical Density Lower DensityHigher Density Zero Curvature Positive CurvatureNegative Curvature Object is Farther Away Object is Closer Expansion Rate Slower Expansion Rate Faster Longer TimeShorter Time Only in this case can light travel the required distance in the allowed time

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Negative CurvatureZero CurvaturePositive Curvature Negative CurvatureZero CurvaturePositive Curvature Curvature and the Apparent Distance to Objects

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The Expansion History and Material Content of the Universe General Relativity Distribution of Matter and Energy Geometry of Space and Time Scale Factor (Average Distance between particles) Energy Density (Amount of Energy contained in a unit volume) Expansion Rate (How fast the Scale Factor changes with Time) Equation of State (How Energy Density changes with Scale factor)

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Matter Density Dark Energy Density Cosmological Consistency The Age of the Universe is 13.6 billion years, Give or take a few hundred million years The Concordance Model

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Thanks to: James Pilcher Bruce Winstein, Dorothea Samtleben and the whole CAPMAP group Nanci Carrothers, Charlene Neal, and Dennis Gordon The Chicago Maya Society, K.E. Spence, John C. Whittaker, Wen-Hsiung Li, Robert Clayton, Stephen Simon, Andrey Kravstov, James Truran, Stephan Meyer, Erin Sheldon, Wayne Hu And all the people who attend and support these lectures!

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So Long, Enjoy the Luncheon! Next Lecture Series: Origin of Mass: A Challenge for Experimental Particle Physics By Ambreesh Gupta

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