the earth in universe 1

7/28/2019 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



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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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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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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