The Ordered Universe

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The Ordered Universe

• The Birth of Modern Astronomy
• (Trefil Hazen, The Sciences, Ch 2)

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Homers Bear that never bathes
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Stonehenge

• one of several old time-reckoning machines.
  Its moving parts are in the sky.
• Ancient astronomy

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Great Pyramid of Giza

• was aligned to the pole star, and it was
  possible to read the seasons from the position of
  the pyramids shadow.

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The Mayans of Yucatan

• inscribed stone monuments with formulae for
  predicting solar eclipses

6
Plains Indians

• Recorded the rising points of the bright stars,
  to record seasonal grazing patterns.

7
Political Power

• Columbus influenced native people to provide
  food for his crew by warning of an inflamed and
  angry moon.

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Brief Overview of Early Science

• Greece, 4th C B.C.
• Roman Empire Fell, 5th C A.D.
• Chinese, Polynesians, Arabs
• Islamic influences in Spain 10-12th C

• Universities emerge in Europe, 13th C
• Printing press, 15th C
• Copernican hypothesis heliocentrism 15th C
• Galileo and scientific method 17th C

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The Ordered Universe

• Part 1
• Ancient Astronomers

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Ancient China

• Working calendar 13th Century B.C.!
• Star Catalog with 800 entries, 350 B.C.!
• Observed comets and supernovas

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Babylonian Astronomy

• Oldest scientific documents
• 800 B.C.
• Record eclipses, positions of planets and
  rise/setting of the Moon

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Greek Astronomy600 B.C. to 200 A.D.

• Thales introduced geometrical ideas into
  astronomy.
• Pythagorus universe as a series of concentric
  spheres
• Eudoxus the idea of rotating spheres to account
  for the observed complexities of planetary
  motions.
• Aristotle correct explanation of lunar eclipses
  sound argument for the spherical shape of the
  earth.

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Astronomy at Alexandria 3rd Century B.C.

• Aristarchus
• Determined size and distance of Sun and Moon rel
  to Earth
• Developed 1st heliocentric model

• Eratosthenes
• Made accurate calculation of the size of the Earth

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Claudius Ptolemy

• Greek astronomer from 2nd Century, proposed first
  enduring theory of the universe, an
  Earth-centered or Geo-centric model.

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Occams Razorand interpreting oddities

• 14th Century English Philosopher
• Given a choice, the simplest solution to a
  problem is most likely to be right.

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Stonehenge
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The Ordered Universe

• Part 2
• Birth of Modern Astronomy
• The Fab. Four
• Copernicus, Brahe, Kepler, Galileo

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(a)
(b)
Figure 2-5 The Ptolemaic (a) and Copernican (b)
systems both assumed that all orbits are
circular. The fundamental difference is that
Copernicus placed the Sun at the center.
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Mikolai Kopernik, 1473

• Copernicus outlined a theory for a sun-centered
  or heliocentric universe
• 1543,
• On the Revolutions of the Spheres

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Tycho Brahe,1546-1601
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Johannes Kepler, 1571-1630
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Keplers Laws

• Planets orbit the sun in an ellipse.
• planets move more rapidly when close to the sun
  and more slowly when distant from the sun
• The cube of the mean distance of each planet from
  the sun is proportional to the square of the time
  it takes to complete one orbit

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Check your neighbor

• Summarize key ideas of our attempt to make sense
  of the universe
• Ancients of China, Egypt, Greece
• Aristarchus
• Eratosthenes
• Ptolemy
• Copernicus
• Brahe
• Kepler