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

2. WARNING! Cosmologist talking about Cosmology !

3. Last Time: Globular Clusters M68M92M30 M13 NGC362NGC6752 11.5  1.3 billion years 12  1 billion years 11.8  1.2 billion years 14.0  1.2 billion years 12  1 billion years 12.2  1.8 billion years Multiple analyses yield ages of 12-13 billion years, and an uncertainty of about 1 or 2 billion years

4. 400 nm500 nm 600 nm700 nm Visible Colors and Spectra Wavelength 1 m1 km1 mm 1  m 1 nm1 pm Alberio

5. Galaxies M87 Andromeda Whirlpool

6. Galaxy Redshifts (Coutesy of E. Sheldon)

7. The Spectra of different atoms 400 500600700 Wavelength (nanometers) Sodium Hydrogen Calcium Mercury Neon

8. Galaxy Redshifts (Coutesy of E. Sheldon) Hydrogen

9. Galaxy Redshifts (Coutesy of E. Sheldon) Hydrogen Oxygen

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

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

12. The Doppler Effect

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

14. Measuring the distance to the stars using Parallax Earth Sun Background Stars Nearby Stars

15. Estimating distance with brightness Pollux Castor Sirius Sirius B Luminosity = Total power emitted by star in the form of light.

16. Galaxy Distances: Cepheids Large Magellanic Cloud

17. The Period-Luminosity Relation of Cepheids More Luminous Less Luminous Based on Data from Udalski et. al. In Acta Astronomica Vol 49 (1999) pg 223

18. The Period-Luminosity Relation of Cepheids More Luminous Less Luminous Cepheid in Galaxy: Period = 10 days Magnitude = 24 Cepheid in LMC: Period = 10 days Magnitude = 14

19. The Period-Luminosity Relation of Cepheids More Luminous Less Luminous Cepheid in Galaxy: Period = 10 days Magnitude = 24 Cepheid in LMC: Period = 10 days Magnitude = 14 10,000 times fainter Same Luminosity

20. The Period-Luminosity Relation of Cepheids More Luminous Less Luminous Cepheid in Galaxy: Period = 10 days Magnitude = 24 Cepheid in LMC: Period = 10 days Magnitude = 14 10,000 times fainter Same Luminosity 100 times farther away

21. More Luminous Less Luminous The Period-Luminosity Relation of Cepheids Cepheid in Galaxy: Period = 10 days Magnitude = 24 Cepheid in LMC: Period = 10 days Magnitude = 14 10,000 times fainter Same Luminosity 100 times farther away 150,000 light years away 15 million light years away

22. Galaxy Distances: Type Ia Supernova Luminosity Days Supernova 1994D

23. The Hubble Diagram Based on Data from Tonry et. al. astro-ph/0305008

25. Now Then

28. Hubble Diagram

29. A special point in space implies anisotropies

30. Large scale anisotropies are not observed Distribution of galaxies from the Sloan Digital Sky Survey

31. General Relativity

32. An object travels in a straight line at a constant speed unless acted upon by an outside force A force changes the motion of an object by an amount that depends on its mass Classical Mechanics

33. + - + + + + + + + Objects move differently due to their composition Unless the force is gravity

35. Gravity in Classical Mechanics The more massive object feels a sronger force The more massive object requires more force to accelerate it by the same amount

36. Gravity in Classical Mechanics A B A B With no outside forces, all particles take the path with the shortest distance between two points The presence of a massive object exerts a force that causes all objects to deviate from this path by the same amount

37. Gravity in General Relativity A B A B With no outside forces, all particles take the path with the shortest distance between two points The presence of a massive object changes which path is the “shortest” distance between the two points

38. General Relativity Works It explains irregularites in Mercury’s orbit It predicted the gravitational lensing of starlight

40. The Expanding Universe Then Now

41. Re-interpreting the Hubble Diagram Based on Data from Tonry et. al. astro-ph/0305008

42. Redshifts in an Expanding Universe Time 1 Time 2 Time 3

43. Scale Factor a = 1 a = 0.5

44. Re-interpreting the Hubble Diagram Based on Data from Tonry et. al. astro-ph/0305008

45. Re-interpreting the Hubble Diagram

46. Based on Data from Riess et. al. astro-ph/0402512 Re-interpreting the Hubble Diagram

47. Based on Data from Riess et. al. astro-ph/0402512

48. Re-interpreting the Hubble Diagram

49. Extraopolating back to the Big Bang

50. a = 1 a = 0.5 a = 0 The Big Bang

51. Extraopolating back to the Big Bang

52. We need more information to do an accurate extrapolation

53. No Talk Next Week June 5: Parametrizing the Age of the Universe