Galaxies and the Universe

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Galaxies and the Universe
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What Are Galaxies?

• Greek galax milk
• William Herschel, 1783 A disk with the Sun
  slightly off-center

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What Are Galaxies?

• 19th Century Spiral Nebulae
• Nearby? Maybe Solar Systems in Formation?
• 1920 Galaxies are Stars
• 1920s Galaxies are like the Milky Way
• Biggest single increase in our mental picture of
  the Universe in human history

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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

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Galaxies and Globular Clusters
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The Milky Ways Globular Clusters
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The Milky Way As We See It
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Anatomy of a Galaxy
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Spiral Arms
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In Microwaves, We Can See the Hub of the Galaxy
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Mapping the Neighborhood
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Mapping the Neighborhood
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Mapping the Galaxy Not There Yet
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Mapping the Galaxy Not There Yet
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The Local Group
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Downtown The Virgo Cluster 50 m.l.y
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The Local Super-cluster
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The Coma Cluster350 m.l.y.
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Large-Scale Structure of the Universe to 500
m.l.y.
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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)
• M106 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.

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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

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Why the Speed of Light is a Speed Limit

• Energy of a Moving Object in RelativityE
  mc2
  --------------------------------------------
  ----------------------------------- ? 1
  - v2/c2
• One consequence as v approaches c, Energy goes
  to infinity
• Also, as we approach c, Energy goes up very fast

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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
  1023 joules U.S. energy use for 1100 years

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Another Consequence of Relativity- Gravitational
Lenses
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What Does The Universe Look Like?
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What Does The Universe Look Like?
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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

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As Far Out as We Can See - Ten Days With the
Hubble Telescope
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A New Name for the Big Bang?(Sky and
Telescope, 1995)

• The Big Boot
• Gods Log-On
• Fred Withair Day (Nobody ever named anything
  else after me, so why not?)
• What Happens If I Push This Button?
• Youre Never Going To Get It All Back In There
  Again

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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

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Astronomers Are Not As Upset As One Might Expect

• MACHOs (Massive Compact Halo Objects) faint
  stars, brown dwarfs, planets
• Cool non-luminous gas
• Massive Neutrinos?
• WIMPs (Weakly Interacting Massive Particles)
• Magnetic monopoles
• Exotic objects strings, mini-black holes

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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

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Fine Tuning the Universe

• It just came out that way
• It has to be that way for reasons we havent yet
  discovered
• Maybe there are an infinity of universes but only
  those with certain parameters develop intelligent
  life (Multiverse)
• Engineered or designed

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Fine Tuning the Universe

• Designer?
• Doesnt 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?

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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

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Where Will It All End?

• Trillions of years Star formation ends
• 10-100 trillion years Stars stop radiating
• 1015 1020 years Planetary orbits decay
• 1032 1041 years Protons decay?
• Heat Death?
• Big Crunch?
• Big Bounce?

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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

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