History of Astronomy

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History of Astronomy
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Todays theme
We inherit the ideas of those who have gone
before us
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Observations and Questions

• What the Ancients saw
• Stars have a fixed pattern, but move at night and
  with the seasons
  
• Some stars wander (the planets)
• Changes of the seasons
• Every morning the Sun appears
• The Moon goes through phases

What are the stars Where are they located? Why a
re they there?
What role humans have in all this?
How did all this begin?
What makes the sun rise? Where does the Sun go at
night?
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Mythology

• Universe Models
• Related to human hopes, desires, and culture.
• Anthropomorphic
• Anthropocentric
• Genesis (creation) stories
• Often related to astronomy (sun, moon, stars)
• Many cultures made detailed observations of the
  sky

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The Universe

• Some contemporary questions
• How did the Big Bang Begin and why?
• Is the universe open or closed?
• What are space and time?
• Why is there an arrow of time?
• What are black holes?
• Are we alone in the universe?
• What is Gravity?
• Is there a TOE (Theory of Everything)?

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Astronomy in Ancient Egypt

• NABTA PLAYA - 5000 BC Egyptian Stonehenge
• Stellar alignments of Temples such as AMEN-RA
• From ancient Egyptian tombsides
• Timekeeping, seasons by the rising of Sirius
• Clocks showing nights divided by 12 parts
• Shadow clocks, and water clocks
• Stars on tomb ceilings
• Tomb of Senmet (1472 BC) depicts
• Orion, Sirius and the planets
• Temple of HATHOR at Dendera (700 BC)
• Circular Dendera Zodiac (now in the Louvre)

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Egyptian StonehengeJuly 1998, Discover Magazine
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Temple of Dendera Zodiac
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Stonehenge
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Babylonian Genesis

• Cosmos began with CHAOS and WATER
• From these, two Gods were created
• Marduk protector of Babylon
• Tiamat sea goddess of chaos
• Marduk killed Tiamat and created the earth from
  her body

Marduk bade the moon come forth
Entrusted night to her, Made her creature of the
dark, to measure time And every month, unfailing
ly, adorned her with a crown.
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Greek Genesis

• The cosmos began from the God Chaos, who had
  children who created Other Titan Gods.
  
• Zeus governed the sky
• Poseidon governed the sea
• Athena Goddess of wisdom
• Apollo God of light and music
• Aphrodite Goddess of beauty and love
• Ares God of war
• Dionysos God of wine

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Chinese Genesis

• In the beginning the cosmos was a great EGG.
• The God Pan Gu slept in the egg. It awoke and
  broke free from the egg, the heavy material
  became the earth, and the light the air.

His breath became the wind His voice the thunder
His left eye the Sun His right eye the Moon
Heaven and earth are large, and in the whole of
empty space they are but as a small grain of
rice
(Bo Ya Qin)
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Chinese Star Chart. 940 AD. British Library
Dunhuang Collection.
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• The Hebrew Old Testament Genesis
• Let there be light, and there was light
• God created the universe in six days and rested
  during the seventh day.
  
• God created man in his own image.
• God gave free will to man.
• Tanzanian Genesis
• At the beginning there was a tree and ants lived
  in it. One day the wind blew away a leaf with
  some ants. The ants ate the leaf and themselves
  and grew into a huge ball that became the earth.

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Aztec Mesoamerican Genesis

• At the beginning when everything was mixed up and
  confused (chaos), there was Ometeotl, God of
  Duality
  
• Ometeotl created himself.
• When it pleased Ometeotl, he blew and separated
  the water from heaven and the earth.
  
• When everything was darkness, the Gods gathered.
  They lit a fire on which the one who would become
  the Sun would be sacrificed.
  
• The God Namahuatl jumped into the fire and was
  consumed. He became the Sun. The God
  Tecciztecatl jumped after him, but the fire was
  weaker, and he became the Moon.
• The Milky Way was Tamoanchar Paradise, from
  which the gods and humans had been expelled.

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Native American Cosmologies

• Walam Olum
• A chronicle of the Delaware (the Lenni Lenape)
  Indians
  
• There at the edge of the water where the land
  ends, the fog over the earth was plentiful, and
  this was where the Great Spirit stayed.
  
• He created much land here as well as land on the
  other side of the water. He created the sun and
  the stars at night. All these he created so they
  might move.

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The Geocentric Model
Plato Aristotle believed in the perfection of
the
heavens
Perfect circles Perfect spheres
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Aristarchus of Samos(310 230 BC)

• The First Heliocentric System
• The Moon reflects light from the Sun
• Estimates of the distances to the Moon and Sun

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Eratosthenes(276 195 BC)

• Head of the famous Alexandria Library
• Geographer, astronomer, philosopher
• Scientific measurement of the size of the earth
• Assumed that Alexandria and Syene (Aswan) were on
  the same meridian.
  
• On the longest day of the year (Summer Solstice)
  when the sun was at its highest point, he had
  reports that at Syene there were no shadows ( the
  sun would shine down deep into a well).
• But at the same time (same day, sun at highest
  elevation), there were shadows in Alexandria,
  making an angle of about 1/50 of a circle (7
  degrees)
• Eratosthenes knew the distance between Alexandria
  and Syene to be about 5000 stades (500 miles).
  He deduced a circumference of the earth of 25000
  miles (7 degrees for 500 miles, hence 360
  degrees 25000 miles).

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Measuring the size of the Earth
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Ptolemy of Alexandria (c. 150 AD)

• Mathematically described motion of planets
  stars
  
• Megale Syntaxis
• Almagest (al Magisti) translated into Arabic
• All of Astronomy
• Constellations
• Star catalogue
• Planetary motions
• One of the great books of science, comparable
  to
  
• Elements by Euclid
• Principia by Newton
• Origin of Species by Darwin

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Geocentric Model
Everything orbits the earth
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Retrograde motion
Difficult to explain in geocentric model
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Epicycles and Deferents
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Explaining retrograde motion with epicycles
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Hypatia of Alexandria

• About 3rd century A.D.
• Astronomer and Mathematician with contributions
  to geometry and the Astrolabe
  
• Reserve the right to think, for even to think
  wrongly is better than not to think at all.
  
• To teach superstitions as truth is a most
  terrible thing.

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The Astrolabe
position of celestial objects
measure the time of the night (or of the day)
measure the time of the year
compute what part of the sky is visible at any
time determine the altitude of any object over
the horizon determine the current latitude
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Greek contributions a summary
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Nicolaus Copernicus
The first giant of modern astronomy
Portrait from Torun - beginning of the 16th
century.
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Copernicus

• Born in Poland family had Church ties
• First modern proponent of heliocentric model
• Did not make new observations, but created a more
  consistent, simple, and satisfying explanation
  
• Still believed in perfect circular orbits

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De Revolutionibus On the Revolution of the
Heavenly Spheres
Published 13 years after he wrote it
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Retrograde Motion according to Copernicus
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Tycho Brahe
Tycho Brahes cosmological model. Earth remained
at the center of the cosmos, and the Sun circled
the Earth, but the other planets orbited the Sun.
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Tycho Brahe
the first to try to measure the parallax of a
new star
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Brahe saw NO parallax
The new star must then Be part of the firmament
Aristotle was wrong. (shocking!!)
Brahe became famous and The king gave him money
To build a fancy observatory
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The Observatory Island of Hven
Brahe saw NO parallax
The new star must then Be part of the firmament
Aristotle was wrong. (shocking!!)
Brahe became famous and The king gave him money
To build a fancy observatory