Brief History of the Center of the Universe Setting the Stage For: Any

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 Brief history of the center of the Universe

 Setting the stage for:  The Great Debate  Lovers of irony take note  Who won?  Does it matter?

 Any take home lessons?

 Today 2

1  Paid their astronomers to figure out the size of the Universe

 Fast forward 2200 years to now, guess what?

 Astronomers still busy trying to figure out the size of the Universe

 The more things change the more they stay the same?

The Universe… The Center of the Universe…

Me NOT YOU!

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 In the sky they saw: the Sun, the Moon, Planets, Stars, some small fuzzy patches, AND ONE BIG FUZZY PATCH

 Goes from horizon to horizon

 As a scientist, have to explain that big fuzzy

patch in the sky 6

3  Copernicus moves the Sun to the center of the solar system, but keeps the planets moving on circles

 Kepler finally gets it right (by exhaustion) and puts the planets moving on ellipses

 Galileo using telescope finds supporting, not conclusive, evidence  Phases of Venus  Moons of Jupiter

 Net effect: Center of the Universe moves 93 million

miles to the right from the Earth to the Sun 7

The Universe… The Center of the Universe…

The Sun NOT YOU! Me

4  Galileo also used the telescope to look at the big fuzzy patch in the sky  Turned out to be nothing but stars  So why are there a lot of stars in a band?

 Thomas Wright  Two concentric spheres  In between these spheres are all the stars & our Sun and solar system, a shell of stars  Look perpendicular to spheres see few stars  Look along shell see more stars

 Center of the Universe is on the move! 9

The Universe… The Center of the Universe…

The Sun

5  Charles Messier  French astronomer during Comet craze  Even with best telescopes of the day some fuzzy patches still fuzzy  Real annoying when want to find a comet (another type of fuzzy patch)  Came up with a catalogue of  100 fuzzy patches to ignore  So don’t look at the following

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 William Hershel  English astronomer  Surveyed the whole sky and did star counts  Saw less stars out of the plane of the Milky Way  Decrease in density of stars as got further from the Sun  Some of fuzzy patches could be resolved into stars, so assumed that was true for all objects.

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The Universe… The Center of the Universe…

The Sun NOT YOU! Me

9  William Parsons  English astronomer mid‐1800’s  72 inch telescope (He was an Earl)  Could see some spiral structure in some nebula (fuzzy patches)  No way to estimate distance to them (if know distance know size)

 Jacobus Kapteyn  Dutch astronomer at turn of century (1900’s)  Did star counts a lá Hershel and came to the same conclusions as Hershel (200 yrs no change)  Galaxy flattened disk . 10 kiloparsecs in diameter . 2 kiloparses thick . Sun near center

10  But what were those spiral nebula?  Galaxies like ours but far, far away? (Island Universes)  Or objects within our galaxy (galaxy = universe)?

 Write “before” on one side & your name

 And answer the following question:  Are science debates useful for . For Science? . For informing the public?

11  Prohibition took effect on 16 January

 Women could vote for President for the first time

 Communist party completed take over of the U.S.S.R.

 Population of the U.S. 108 million  Total graduating from High School 300,000 60% Women 40% Men  Total graduating from College 48,000 66% Men, 33% Women (U of MD enrollment 27,000)

 Nuclear Fusion unknown  This is what powers stars  Talk of “subatomic energy”

 Thought elements common in the Earth dominated the composition of the stars:  Oxygen Silicon Iron

 Stars are 90% H2 & 10% He  Thesis of Cecilia Payne in 1925  And later work by Russell on the Sun

12  George Ellery Hale (big shot):  Funded an annual lecture at the NAS  Wanted either: . The size of the universe (galaxy) . Relativity

 Secretary of the Academy wrote back  Size of universe is boring  Suggested instead: . Cause of glacial periods . Something biological

 Hale wrote back, How about relativity then?

 Secretary of the Academy wrote back:  “I would rather have a subject in which there would be a half dozen members of the Academy competent enough to understand at least a few words of what the speakers were saying if we had a symposium upon it”

 In the end “The Scale of the Universe” was the topic

 Harlow Shapley Vs. Heber Curtis 26

13  A young ambitious astronomer, a golden boy of astronomy

 Published a series of papers on properties of stars in binary systems or globular clusters

 Hale was his boss (and when your boss asks you to do something…)

 Very nervous  Knew Curtis was the better speaker  Position of the Director of the Harvard College Observatory had just opened up and he really, really, really wanted the job  Talk was essentially a job interview for him

14  He was a bit older, more established, the “pro”

 By far the better speaker

 Had published a series of papers on the properties of spiral nebulae.

 Hard worker usually taking the conservative view

 Frequently skeptical of anything new until proven to his exacting standards.

 Essentially read his paper: 19 typewritten pages

 Gave a very elementary general talk, Six pages in finally defines a light year.

 Focused on the scale of the Galaxy

 Final three pages are devoted to equipment he developed  Irrelevant to his main argument  But perhaps directed to those members of the audience responsible for the future development of Harvard College Observatory! 30

15  His model for the Galaxy based upon distribution of globular clusters  Globular clusters are concentrated more toward one half of the sky.  That half of the sky must be where the true center of our Galaxy is.  Got distance to clusters from RR Lyre and Cepheid variable stars

 Size of the Galaxy  Diameter of our Galaxy was 100 kiloparsecs,  10 times larger than Kapteyn’s value!  Reality more like 50 kiloparsecs

 Placement of the Sun  Sun 20 kiloparsecs from the Galactic Center  So much for being the center of the universe  Reality more like 8 kiloparsecs

16  What are (where are) the spiral nebulae then?

 Shapley thought that the Galaxy was so large it was essentially the whole universe. Therefore spiral nebulae are in the galaxy.

 Knew that the nebulae were moving away from us from spectroscopic observations (red‐shifts).

 Spiral Nebula are gaseous clouds repelled by the light pressure of our Galaxy (think solar sails) 33

 Based his size of galaxy arguments upon:  Star count analysis  Distance estimates involving the spectral types and intrinsic brightness's of different type stars.

 Size of the Galaxy  Followed Kapteyn : 10 kiloparsecs in diameter  Reality more like 50 kiloparsecs  (Note (10 + 100)/2 = 55)

 Sun close to the galactic center

17  Disagreed with Shapley that Cepheid variables were good distance indicators (or more like it that more data are needed)

 What are (where are) the spiral nebulae then?

 Knew that the nebulae were moving away from us from spectroscopic measurements  High radial velocities for the nebulae  He argued if they were in the galaxy they would be moving much more slowly relative to the sun.

 What are (where are) the spiral nebulae then?

 Novae (Stellar explosions)  Novae observed in our Galaxy were similar to novae observed in spiral nebulae  But novae in spiral nebulae very faint  Implying that the nebulae were very distant & outside the galaxy

 So the spiral nebulae are systems of stars

 Therefore our galaxy just one of potentially many galaxies 36

18  Shapley did go on to become director of Harvard’s Observatory

 Not much attention in the popular or scientific press

 Who won?  Human interest importance?  Scientific importance?

 Shapley –studied globular clusters  Better size of galaxy  Sun is off to one side  Cepheid variables are good distance indicators to globular clusters

 Curtis –studied spiral nebula  Spiral nebulae are really galaxies  Novae observed in spiral nebulae are similar to novae observed in our Galaxy

19  Here there be dust – Messes up star counts  Imagine you are in a very thick fog in a city and can see only one city block in any direction. Can you tell where are you in the city?  Explains why globular clusters can be used to find the center of the galaxy

 Edwin Hubble in 1924  Working at Mount Wilson observatory, where Shapley worked at the time of “The Great Debate”  Photographed the Andromeda nebulae & identified a Cepheid variable  Which Shapley believed could be used as distance indicators but not Curtis  Got a distance to the Andromeda Galaxy of 750 kiloparsecs and size for the Andromeda Galaxy of 70 kiloparsecs !  Showing Curtis was correct about the spiral nebulae 40

20 The Universe courtesy of Shapley The Center of the Universe (galaxy)

You are off to one side and only a small part of the Universe

The Universe courtesy of Curtis & Shapley & Hubble

Galaxy

Galaxy Galaxy

You are off to one side and only a small part of a galaxy

21  What makes you feel important?  Being the center of everything and everything turns around you?  Or being unique, there is one and only one you?

 Does this effect how you feel about humans?  Important, special, unique?  Scopes monkey trial

 Write “after” on the other side

 Are science debates useful for . For Science? . For informing the public?

22  But wait it gets worse!

 Something similar to “Great Debate” going on today

 Or the ancient Greeks, take your pick

 But first to play with blocks

 Earth  Solar System

 Solar System  Sun  Either eight, nine, or eleven planets, with moons (some as large as Mercury)  Asteroids  Comets  Gas  Dust

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24  Earth  Solar System  Galaxy

 Our Galaxy (Milky Way)  All the stars you can see in the night sky . Single Stars with planets . Double and triple star systems (some with planets!)  Gas  Dust

 Han Solo: It's the ship that made the Kessel run in less than twelve parsecs!

 Ben reacts to Solo's stupid attempt to impress them with obvious misinformation.

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26  Only one method gives you an unambiguous start  Parallax (Geometry)  If p = 1 arc second, then d = 1 parsec (Full moon 30 arc seconds)  1 parsec = 3.26 light years  No star within 1 parsec of the Earth–Sun System

Radius = r Surface area = 4  r2

Radius = 2r Surface area = 4  4 r2

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N.B. Deceptive Log Scale in Use

28 Pioneering work done by Henrietta Leavitt 57

 Earth  Solar System  Galaxy  Galaxy groups, clusters, super clusters  Universe

 Universe  Galaxies  Clusters of galaxies  Super clusters of galaxies  Gas between galaxies

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 That is all of the visible mass

 In the 1970’s it became apparent there must be more mass in the Milky Way than what we could see.

 Most of the mass (80%) of the Milky Way is in “dark” matter

 This appears to be the case for other galaxies and galaxy clusters 60

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31  Increasing evidence that this dark matter is NOT the same type of matter that makes up you and me.

 Dark Matter only affected by the gravitational force (not light)

 Stuff up there is NOT the same as stuff down here.

 So when we thought we were looking at the Universe were only looking at 20% of the Universe mass in the Universe

 But wait it gets worse!

32  Starts really, really, really, really, small & hot

 Space expands –Universe gets bigger

 Expansion called the “Big Bang”

 If only gravity effecting this expansion what should be happening to the rate of expansion over time?

 Slow down  Could go to zero at infinite time  Could turn around and lead to a Big Crunch

 In the 1990’s observations of nova’s in distant galaxies showed the expansion has accelerated over time.

 So to go with the dark matter now have dark energy or the dark force  Acts like anti‐gravity  Only over large distances  We don’t know what it is  But there is a lot of it!

33  So how much dark energy is there?

 Mass and energy are can be thought of as equivalent via E = mc2

 So sum up the mass, dark mass, and dark energy in the universe:

Update: Dark Energy 68%, Dark Matter 27%, Normal Matter 5% 68

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 “Subatomic energy”  Nuclear Fusion

 “Dark energy”  ???

 Only one galaxy  many other galaxies

 We are observing all of the universe  HA!

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 What makes you feel important?  Being the center of everything and everything turns around you?  Or being unique, there is one and only one you?

 Does this effect how you feel about humans?  Important, special, unique?  Evolution on trial

37 http://dingo.care2.com/cards/flash/5409/galaxy.swf

 References  http://antwrp.gsfc.nasa.gov/diamond_jubilee/debat e.html  http://antwrp.gsfc.nasa.gov/diamond_jubilee/debat e20.html  The 1920 Shapley‐Curtis Discussion: Background, Issues, and Aftermath. Virginia Trimble, Astronomical Society of the Pacific, 107 1122‐1144, December 1995.  Dr. Alan Peel