the milky way · quiz will last 15-30 minutes and will be followed by lecture. saturday, september...

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All that is required to measure the diameter of the Earth is a person with stick and a brain.

-adapted from Big Bang, Simon Singh, p.13

Saturday, September 24, 2011

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Announcements:

Quiz #2: Monday, September 26 at beginning of class. Will cover Chp. 1-3.

Quiz will last 15-30 minutes and will be followed by lecture.


The Origin of Modern Astronomy

Chapter 4


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Several important people are introduced in Chapter 4. Name three of them and tell me about their contribution to our knowledge of the Solar System.


I. The Roots of Astronomy A. Archaeoastronomy B. The Astronomy of Greece C. Aristotle and the Nature of Earth D. The Ptolemaic Universe

II. The Copernican Revolution A. Copernicus the Revolutionary

B. De Revolutionibus C. Galileo the Defender D. The Trial of Galileo

III. The Puzzle of Planetary Motion A. Tycho the Observer B. Tycho Brahe's Legacy C. Kepler the Analyst D. Kepler's Three Laws of Planetary Motion E. The Rudolphine Tables

IV. Modern Astronomy

Outline


The Roots of Astronomy


The Roots of AstronomyMonuments dating back to ~ 3000 B.C. show

alignments with astronomical significance.

Newgrange, Ireland, built around 3200 B.C.: Sunlight shining down a passageway into the central chamber

of the mount indicates the day of winter solstice.


Stonehenge


Stonehenge

• Constructed: 3000 – 1800 B.C.


Stonehenge

• Alignments with locations of sunset, sunrise, moonset and moonrise at summer and winter solstices



Stonehenge



•Probably used as calendar


Stonehenge


Summer solstice




Stonehenge


Summer solstice

Heelstone




Other Examples All Around the World

Chaco Canyon, New Mexico


Other Examples All Around the World

Chaco Canyon, New Mexico

Slit in the rock formation produces a sunlit “dagger” shape, indicating the day

of summer solstice


Other Examples All Around the World (2)

Mammoth tusk found at Gontzi, Ukraine: Inscriptions probably describing

astronomical events


Ancient Greek Astronomers

- Earth’s shape- Earth’s size- Earth’s position- Scale of the Solar System



Ancient Greek’s tried to explain the Universe using mathematical models.

- Earth’s shape- Earth’s size- Earth’s position- Scale of the Solar System


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You’ve just met a member of The Flat Earth Society who believes all NASA images are fake. You want to provide evidence that the Earth is spherical. What might you say/do?


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You’ve just met a member of The Flat Earth Society who believes all NASA images are fake. You want to provide evidence that the Earth is spherical. What might you say/do?

1. Watch a ship sail away.

2. Make a long-distance phone call and compare relative position of Sun and/or stars.

3. Observe a lunar eclipse.and look at the stars.


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Earth’s shadow is round as seen during an eclipse


Scale of the Solar System

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Aswan Dam, Egypt

Second largest city of Egypt; main port

Eratosthenes (~ 200 B.C.):Calculation of the Earth’s radius


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• Sun at noon on summer solstice in Syene is straight overhead.

• Sun at noon on summer solstice in Alexandria is 7 degrees off the zenith.



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7°

7°



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Suppose you were an alien living on the fictitious warlike planet Myrmidon and you wanted to measure its size. The planet’s “sun” is shining directly down a missile silo 1000 miles to your south, while at your location, it is 36 degrees from straight overhead. What is the circumference of Myrmidon?

a. 36,000 mib. 3,600 mic. 10,000 mid. 6,280 mie. 1,590 mi



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Size of the Earth + Lunar Eclipse Observations

Size of Moon!!!


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Size of the Moon + Angular Size in Sky

Distance to Moon!!!


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Distance to the Moon + Sun/Moon Angle

Distance to Sun!!!


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Distance to the Sun + Angular Size in Sky

Distance to Sun!!!


Structure of the Solar System

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Geocentric Models


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Geocentric Models• Eudoxus (409 – 356 B.C.):

Model of 27 nested spheres


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• Aristotle (384 – 322 B.C.),

major authority of philosophy until the late middle ages: Universe can be divided in 2 parts:


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• Aristotle (384 – 322 B.C.),


1. Imperfect, changeable Earth,


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• Aristotle (384 – 322 B.C.),


1. Imperfect, changeable Earth,

2. Perfect Heavens (described by spheres)


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The WanderersPlanet: from Greek πλανήτης αστήρ planētēs astēr "wandering star"


http://en.wikipedia.org/wiki/Ancient_Greek


http://en.wiktionary.org/wiki/%CF%80%CE%BB%CE%B1%CE%BD%CE%AE%CF%84%CE%B7%CF%82


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Retrograde (westward) motion of a planet occurs when the Earth passes the planet.

The Wanderers

Motion of the planets across the sky is markedly different than the motion of the stars.

Planet: from Greek πλανήτης αστήρ planētēs astēr "wandering star"






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Refinements to Geocentric Models

Ptolemy’s epicycles(150 AD)

Model survived until Copernican Revolution of 1500’s.

Publication: Syntaxis (the greatest)


the milky way · quiz will last 15-30 minutes and will be followed by lecture. saturday, september...

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