1. Galaxies and the Universe

2. What Are Galaxies? Greek galax = milk William Herschel, 1783: A disk with the Sun slightly off-center

3. What Are Galaxies? 19th Century: “Spiral Nebulae” Nearby? Maybe Solar Systems in Formation? 1920: Galaxies are Stars 1920’s: Galaxies are like the Milky Way Biggest single increase in our mental picture of the Universe in human history

4. Where Are We in our Galaxy? The visible Milky Way suggests our galaxy is a flat disk Surrounding other galaxies is a spherical halo of Globular Star Clusters

5. Galaxies and Globular Clusters

6. The Milky Way’s Globular Clusters

7. The Milky Way As We See It

8. Anatomy of a Galaxy

9. Spiral Arms

10. In Microwaves, We Can See the Hub of the Galaxy

11. Mapping the Neighborhood

13. Mapping the Galaxy: Not There Yet

15. The Local Group

16. Downtown: The Virgo Cluster: 50 m.l.y

17. The Local Super- cluster

18. The Coma Cluster 350 m.l.y.

19. Large-Scale Structure of the Universe to 500 m.l.y.

20. Travel to the Stars? Kinetic Energy = 1/2 Mv 2 What does it take to get a 1000-ton spaceship to 10% of the speed of light? (43 years to Alpha Centauri) M=10 6 kg, v = 3 x 10 7 m/sec KE = 1/2 x 10 6 x 9 x 10 14 = 4.5 x 10 20 joules Equals U.S. Energy Production for 4.5 years Once you get there, you have to stop.

22. Relativity Speed of Light is Independent of Source Michelson and Morley, 1887 - Speed of Light Independent of Observer “One of the Most Unexpected Results in the History of Science” - Isaac Asimov Conclusion: Speed of Light is the Same for All Observers Implication: Space and Time Must Change to Keep Speed of Light Constant

23. Why the Speed of Light is a Speed Limit Energy of a Moving Object in Relativity: E = mc 2 -------------------------------------------------------------------------------  1 - v 2 /c 2 One consequence: as v approaches c, Energy goes to infinity Also, as we approach c, Energy goes up very fast

25. Fuel Economy of a Starship At 0.1 c, energy is 0.7% greater than Newtonian formula At 0.5 c, 24% greater At 0.9 c, 3 x greater At 0.99 c, 12 x greater At 0.999 c, 43 x greater Each extra 9 more than triples the energy Getting our 1000 ton ship to 0.9 c takes 1.1 x 10 23 joules = U.S. energy use for 1100 years

26. Another Consequence of Relativity- Gravitational Lenses

27. What Does The Universe Look Like?

29. “The Big Bang” Edwin Hubble, Recession of Galaxies, 1929 Red-shift increases with distance Cosmic Microwave Background, 1965 Estimated Age of Universe: 12-15 b.y. “Big Bang” originally a derisive term, coined by Fred Hoyle

30. As Far Out as We Can See - Ten Days With the Hubble Telescope

31. A New Name for the “Big Bang?” (Sky and Telescope, 1995) The Big Boot God’s Log-On Fred Withair Day (“Nobody ever named anything else after me, so why not?”) What Happens If I Push This Button? You’re Never Going To Get It All Back In There Again

32. 90% of the Universe is “Missing” Outer Stars in Galaxies revolve faster than expected What holds clusters of galaxies together? Conclusion: There must be a lot of invisible mass in the Universe Not really “missing”, just non-luminous

33. Astronomers Are Not As Upset As One Might Expect MACHO’s (Massive Compact Halo Objects): faint stars, brown dwarfs, planets Cool non-luminous gas Massive Neutrinos? WIMP’s (Weakly Interacting Massive Particles) Magnetic monopoles Exotic objects: strings, mini-black holes

34. Fine Tuning the Universe Density – Much greater and the Universe would already have collapsed in on itself – Much less and stars could not have formed Nuclear Forces – Fusion impossible – Fusion too easy Anthropic Principle – Cosmology has to be able to explain why we exist

35. Fine Tuning the Universe It just came out that way It has to be that way for reasons we haven’t yet discovered Maybe there are an infinity of universes but only those with certain parameters develop intelligent life (Multiverse) Engineered or designed

36. Fine Tuning the Universe Designer? Doesn’t Explain Anything If the Designer can create a Universe, why is c = 300,000 km/sec instead of 400,000? If Designer had to have c = 300,000 km/sec, why? What (who?) dictated that, and why? Who says Designer is anything pictured by any religion?

37. Misinterpreting Relativity There are no absolutes – Speed of light is absolute – It may not be possible to be absolutely right but it is very easy to be absolutely wrong

38. Where Will It All End? Trillions of years: Star formation ends 10-100 trillion years: Stars stop radiating 10 15 – 10 20 years: Planetary orbits decay 10 32 – 10 41 years: Protons decay? Heat Death? Big Crunch? Big Bounce?

39. What Does Cosmology Imply for Philosophy? Nothing At Least, Not Yet It Is Hopelessly Premature To Try To Create A Philosophy Based on Cosmology – We can say what the fate of the Universe will be based on specific assumptions – We are a long way from knowing the assumptions are complete or correct If you support your philosophy with science, be prepared for science to prove it wrong