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

12. Mapping the Neighborhood

13. Mapping the Galaxy: Not There Yet

14. 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 Mv2
What does it take to get a 1000-ton spaceship to 10% of the speed of light? (43 years to Alpha Centauri)
M=106 kg, v = 3 x 107 m/sec
KE = 1/2 x 106 x 9 x 1014 = 4.5 x 1020 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, 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  1 - v2/c2
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 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 1023 joules = U.S. energy use for 1100 years

26. Another Consequence of Relativity- Gravitational Lenses

27. What Does The Universe Look Like?

28. 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: 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
trillion years: Stars stop radiating
1015 – 1020 years: Planetary orbits decay
1032 – 1041 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