Astronomy: The First Science

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Astronomy The First Science

• Had we never seen the stars, and the sun, and
  the heaven, none of the words which we have
  spoken about the Universe would ever have been
  uttered. But now the sight of day and night, and
  the months and the revolutions of the years, have
  created number, and have given us a conceptions
  of time, and the power of enquiring about the
  nature of the Universe and from this source we
  have derived philosophy, than which no greater
  good ever was or will be given by the gods to
  mortal man.
• -Plato

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Announcements

• You can buy either edition 11 or 12 of The
  Physical Universe. Edition 12 has more math
  review.
• Homework is posted online. If you are having
  trouble check the book and if that doesnt help,
  come see one of us.

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ASTROLOGY TEST RESTS
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Moonwatcher (from 2001 A Space Odyssey)
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Good Place for Sky Information
http//www.space.com/spacewatch/sky_calendar.html
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Why Look at the Sky?
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Why Look at the Sky?

• To properly time planting, harvesting, seasonal
  migrations
• To schedule festivals rituals
• To keep track of history and important events
• Predict the future (doesnt work very well)
• Ensure good luck (doesnt work very well)
• Navigation

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Chaco Canyon Sun Dagger
The "Sun Dagger" in Chaco Canyon cuts through the
center of the spiral petroglyph on the summer
solstice. On the winter solstice two parallel
rays of light bracket the petroglyph. Two
smaller petroglyphs are illuminated during the
spring and fall equinox. The Chacoans (Anasazi)
were a farming community and likely used these
figures to determine the proper time for planting
and for festivals.
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Stonehenge and Astronomical Alignments
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Maes Howe
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Maes Howe Video
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Mayan Astronomy
El CaracolChichen-Itza
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Astronomy in the Tropics and the Overhead Sun
Chichen-Itza
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Tilt of the Earth
Remember to show reasons for the seasons
animation.
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Venus Tables (Dresden Codex)
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Important Definition
ephemeris i'fem(?)risnoun ( pl. -erides
-?r?dez) A table or data file giving the
calculated positions of a celestial object at
regular intervals throughout a period. A book or
set of such tables or files. ORIGIN early 16th
cent. from Latin, from Greek ephemeros lasting
only a day.
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Mayan Astronomical Accomplishments

• Accurate Calendar (Length of the day to 6
  significant figures, much better than Europeans
  of that time).
• Accurate ephemerides for Mars and Venus
• Accurate ephemerides for eclipses.

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Interesting Trivia
According to some (probably incorrect)
interpretations of the Mayan calendar, the
current cycle of the world will end in December
of 2012. This is only 4 years away. Get
ready. For amusement check out
http//endworld2012.com/
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Aside Significant Figures

• The year is 365 days long (3 significant figures)
• The year is 365.3 days long (4 significant
  figures)
• The year is 365.25 days long (5 significant
  figures)
• The year is 365.242 days long (6 significant
  figures). The Mayan Value!

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Gregorian Calendar
Instituted by Papal Bull by Pope Gregory XIII on
24 February 1582
Every year that is exactly divisible by four is a
leap year, except for years that are exactly
divisible by 100 the centurial years that are
exactly divisible by 400 are still leap years.
For example, the year 1900 is not a leap year
the year 2000 is a leap year.
Fun Problem Calculate the length of a year in
days using the algorithm above.
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Important Word
Algorithm A step-by-step problem-solving
procedure, especially an established, recursive
computational procedure for solving a problem in
a finite number of steps.
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Solution
Consider 2000 years. There are 500 (2000?4) leap
years. 20 of these are centurial years But 5 of
these are divisible by 400 Therefore there are
500 - 20 5 485 leap years Total number of
days 2000 x 365 485 730485 in 2000
years The average length of a year 730485?2000
365.24 Note The Julian Calendar (simple leap
years) is off 15 days each 2000 years
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Babylonians (3000-300 BC)
Compiled large catalogs on the stars and planets
and their paths across the sky. These are
accurate, according to Ptolemy, from 747BC
onward No attempt to explain or model the motions
of the stars and planets.
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Babylon, 2nd millenium BC
Venus tablet of Ammisaduqa
Year 1 inferior Venus sets on Shabatu 15 and
after 3 days rises on Shabatu 18 Year 2 superior
Venus vanishes E on Arahsamnu 21 and after 1
month 25 days appears W on Tebetu 16 Year 3
inferior Venus sets on Ululu 29 and after 16 days
rises on Tashritu 15 Year 4 superior Venus
vanishes E on Dumuzi 3 and after 2 months 6 days
appears W on Ululu 9 Year 5 inferior Venus sets
on Nisan 29 and after 12 days rises on Ayar
11 Year 5 superior Venus vanishes E on Kislimu 27
and after 2 months 3 days appears W on Shabatu
30 Year 6 inferior Venus sets on Arahsamnu 28 and
after 3 days rises on Kislimu 1 Year 7 superior
Venus vanishes E on Abu 30 and after 2 months
appears W on Tashritu 30 Year 8 inferior Venus
sets on Dumuzi 9 and after 17 days rises on
Dumuzi 26
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• Contributions of Sumerians/Babylonians/Akkadians/C
  haldeans
• System for measuring time (seconds, minutes,
  hours)
• Signs of the Zodiac
• Accurate tables for rising setting of stars,
  planets, moon, eclipses
• Babylon was conquered by the Persians (Cyrus) in
  530 BC and then by Alexander the Great in 321 BC.
  The Greeks quickly incorporated Babylonian
  achievements in astronomy into their own world
  view, and then greatly extended them.

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Science as we practice it today was invented only
once and in ancient Greece. It began with the
recognition of patterns in the motion of heavenly
bodies.
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Thales of Miletus (624-547 B.C.), the first
philosopher.
Thales founded the Ionian school of thought that
maintained that rational inquiry can lead to an
understanding of the Universe. He brought
Egyptian geometry to Greece and greatly extended
it. He tried, with some success, to predict
eclipses of the Sun and moon, based on observed
periodicities, rather than the conventional
belief that the Sun god was angry.
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Pythagoras of Samos (570-500 B.C) and the
Invention of Mathematics

• Pythagoras founded a philosophical and religious
  school in Croton (Italy) that had enormous
  influence. Members of the society were known as
  mathematikoi. They lived a monk-like existence,
  had no personal possessions and were vegetarians.
  The society included both men and women. The
  beliefs that the Pythagoreans held were

• that at its deepest level, reality is
  mathematical in nature,
• that philosophy can be used for spiritual
  purification,
• that the soul can rise to union with the divine,
• that certain symbols have a mystical
  significance, and
• that all brothers of the order should observe
  strict loyalty and secrecy.

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Abstract Mathematics
2 sheep 2 sheep 4 sheep 1000 Persian Ships x
100 Persians/ship 100,000 Persians -Or 2 2
4 100 x 1000 100,000 Why bother with the
sheep and Persians?
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Anaxagoras of Clazomenae (499-428 B.C.)

• was a follower of Pythagoras but placed more
  emphasis on the material world. He brought
  philosophy from the edges of the Greek world to
  Athens. He was the first to realize that the
  moon shines by reflected sunlight. He thought
  that celestial objects were made of sensible
  materials and that the sun shone brightly because
  it was hot. This got him in a lot of trouble and
  he was banned from Athens.

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Plato (428-348 BC)

• argued for a model of the heavens that was simple
  and aesthetic.
• Believed that the Sun and Moon were perfect
  spheres that moved around the spherical Earth,
  along with the stars, in crystalline spheres.

The reality which scientific thought is seeking
must be expressible in mathematical terms,
mathematics being the most precise and definite
kind of thinking that we are capable of --
Plato