1. The Big Bang etc getting Time off to a good start 1 Origins

2. Part II why is the night sky dark? atomic spectra measuring recessional velocity measuring distance: parallax cepheid variables, and supernovae Origins 2

3. Why Is The Night Sky Dark? Heinrich Wilhelm Matthias Olbers (1758- 1840) Origins 3

4. Night Sky Paradox Origins 4

5. Georges Lemaitre (1894-1966) Belgian astronomer proposed a version of the Big Bang (1927) Ante-dated Hubble by two years Explosive expansion permits permits a finite universe Origins 5

6. Edwin Hubble (1889-1953) Observations showed that distant galaxies were red-shifted. Presumed to be receding. Requires measurements of recession speed and distance. Origins 6

7. Measuring Recession Speed Figure 02-02

8. Absorption Lines in Solar Spectrum Figure 02-03

9. Figure 02-04 How to Build a Habitable Planet Copyright © Princeton University Press 2012

10. Figure 02-05 How to Build a Habitable Planet Copyright © Princeton University Press 2012

11. Measuring Distance

12. Figure 02-07 How to Build a Habitable Planet Copyright © Princeton University Press 2012

13. Parsec Astronomical distances outside the solar system are usually expressed in parsecs. A parsec is the distance to a star with a parallax of one arcsecond. One parsec is 3.26 light years. Origins 13

14. Figure 02-06 How to Build a Habitable Planet Copyright © Princeton University Press 2012 Parallax Measurement of Distance

15. Hipparcos Origins 15

16. Parallax Limits Origins 16

17. Extending Beyond Parallax Standard Candle Methods (I) Cepheid Variables Large variables with periods of days to months Due to ionized He layer around the star Origins 17

18. Figure 02-08 How to Build a Habitable Planet Copyright © Princeton University Press 2012

19. Extending Beyond Parallax Standard Candle Methods (II) Type Ia supernovae Characteristic brightness curve One or two per century per galaxy Origins 19

20. Type Ia Supernova Origins 20

21. SN 1987a Origins 21

22. Origins 22

23. How to Build a Habitable Planet Copyright © Princeton University Press 2012 Methods Based on Galaxy Sizes

24. Distance Toolkit Origins 24

25. Figure 02-10 How to Build a Habitable Planet Copyright © Princeton University Press 2012

26. Origin Time Origins 26

27. Additional Big Bang Evidence Origins 27

28. Accelerating Expansion Origins 28

29. Expansion Timeline Origins 29

30. Figure 02-15 How to Build a Habitable Planet Copyright © Princeton University Press 2012 Dark matter: 23%

31. Earliest Stars Had No Rocky Planets No heavy elements in the Universe at that time Origins 31