Parameterizing the Age of the Universe

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

2. WARNING! Cosmologist talking about Cosmology!

3. Last Time: The Expanding Universe Today Past

4. The Scale Factor Today Past a = 0.5 a = 1

5. Scale Factor from Redshifts Time 1 Time 2 Time 3

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

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

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

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

10. A closer look at the expanding universe Present Past

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

12. Predictions for a Universe with only Matter Scale Factor Larger Expansion Rate Slower Matter Only Scale Factor Smaller Expansion Rate Faster Present Past

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

14. Predictions for a Universe with only Dark Energy Scale Factor Larger Expansion Rate Faster Scale Factor Larger Expansion Rate Slower Scale Factor Smaller Expansion Rate Slower Dark Energy Only Matter Only Scale Factor Smaller Expansion Rate Faster Present Past

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

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

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

18. What is the Cosmic Microwave Background? Microwaves are Electromagnetic Radiation with Wavelengths between 1 mm and 10 cm Wavelength 1 pm 1 nm 1  m 1 mm 1 m 1 km Visible 600 nm 700 nm 400 nm 500 nm

19. What is the CosmicMicrowave Background ? Telescopes sensitive to microwaves detect a signal from space Penzias and Wilson, discoverers of the CMB 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

20. What is the Cosmic MicrowaveBackground? Decoupling Wavelength 1 pm 1 nm 1  m 1 mm 1 m 1 km

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

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

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

24. Curvature Energy Density Lower Density Higher Density Critical Density Negative Curvature Positive Curvature Zero Curvature

25. Curvature and the Apparent Size of Objects Energy Density Lower Density Higher Density Critical Density Negative Curvature Positive Curvature Zero Curvature From Observer’s Viewpoint Object Appears Smaller Object Appears Larger

26. Curvature and the Apparent Distance to Objects Energy Density Lower Density Higher Density Critical Density Negative Curvature Positive Curvature Zero Curvature Object is Closer Object is Farther Away Object appears to be the same size

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

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

29. Distance and Time Energy Density Lower Density Higher Density Critical Density Negative Curvature Positive Curvature Zero Curvature Object is Closer Object is Farther Away Expansion Rate Faster Expansion Rate Slower Longer Time Shorter Time

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

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

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

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

34. 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!

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