the earth in universe 1
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18-Apr-13
IESO
The Earth in Universe
Part 1
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Galaxies and the Universe
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What Are Galaxies?
Greekgalax = 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 ofGlobular 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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TheLocal
Group
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Downtown: The Virgo Cluster: 50 m.l.y
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The
LocalSuper-
cluster
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The Coma
Cluster
350 m.l.y.
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Large-Scale
Structure ofthe 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)
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 tostop.
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Relativity
Speed of Light is Independent of Source Michelson and Morley, 1887 - Speed of Light
Independent ofObserver
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 Relativity:
E = 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 Newtonianformula
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 anythingelse 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 lotof invisible mass in
the Universe Not really missing, just non-luminous
A t A N t A U t A O
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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 onlythose 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 Designerhadto 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
10151020 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 onspecific assumptions
We are a long way from knowing the assumptions are
complete or correct
If you support your philosophy with science, beprepared for science to prove it wrong
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