Chapter%20Three

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Chapter Three
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Questions of the Day

• What is a Scientific Model?
• Who developed the Geocentric Model?

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What is a Scientific Model?

• An attempt to explain observations made of a
  system.
• Usually using physical law to constrain the
  model.
• One must test the model and see if it fits the
  data.

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Understanding a Model.

• State the aesthetic, geometric, and physical
  bases of the model.
• State clearly the assumption behind the model and
  evaluate how well they are supported.
• State the key observations the model attempts to
  explain and evaluate how well it succeeds.

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Understanding a Model

• Postdictions Describe the relative importance of
  various aspects of the model, making clear the
  connections between parts.
• Predictions Indicate how the model deals with
  new observations and suggests new actions for
  the system.

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Who developed the geocentric model?

• Pythagoras
• Socrates
• Plato
• Aristotle
• Hipparchus
• Ptolemy

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Pythagoras

• 6th Century B.C.
• Created the Pythagorean Theorem
• Believed beauty and harmony ruled nature.

www.zoence.co.uk/about/ about_win.htm
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Pythagorean Theorem
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Pythagorean Model

• Simple Spherical Shells
• Geocentric
• Explained the motion of stars.
• But failed to explain retrograde motion.
• Wanted harmony and symmetry.

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Socrates

• Introduced logos natural law.
• Produced a school of several different
  philosophers.

www.wpunj.edu/cohss/philosophy/
LOVERS/ancient.htm
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Plato

• 427 347 B.C.
• Student of Socrates.
• Father of modern democracy in the Republic.

www.mysteriousworld.com/Journal/
2002/Spring/Atlantis/
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Platonic Model

• Demanded the aesthetic of spherical shells.
• Influenced the models of astronomers until
  Kepler.

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Aristotle

• 365 232 B.C.
• Main court philosopher of Alexander the Great.
• Taught the Emperor the ways of science and
  thought.

ring.mithec.com/side/ aristotle.html
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Aristotelian Model

• Wanted symmetry and used 56 shells centered on
  Earth.
• Best physical model for the times.
• Thought Earth was 5,100 k.m. in diameter.

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Aristotles Motivations

• Believed in two types of Action
• Natural motion of planets, stars
• Forced caused by man
• Earth did not rotate because items would be
  thrown up due to natural action.
• No stellar parallax

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Stellar Parallax
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Aristarchus

• 365 323 B.C.
• Work lost with the fire of the library at
  Alexandria
• Eratosthenes, Hypatia

http//www.perseus.tufts.edu/GreekScience/Students
/Kristen/Aristarchus.html
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Aristarchus Model

• First to propose a Heliocentric model
• Moon receives light from the sun.
• But his model was rejected due the lack of
  observations of stellar parallax.

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Eratosthenes

• Noticed a shadow differences between Alexandria
  and Syrene.
• Found the Earth to be 43,000 km, only 3,000 km
  over the modern value.

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Eratosthenes Method
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Modern Value of Earths Circumference
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Hipparchus

• 160 127 B.C.
• Worked at an observatory on Rhodes

www.belmontnc.4dw.net/ AstroBio.htm
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Hippocratic Model
http//www.opencourse.info/astronomy/introduction/
05.motion_planets/geocentric_cosmology.gif
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Ptolemy

• 127 A.D. his first astronomy text was produced
• His model was used for 1,400 years
• Good for optical observations up to 5
• Universe 20,000 Earth Radii

www.pbs.org/wgbh/nova/longitude/ secrets.html
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Ptolemaic Model
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Homework 3

• If Eratosthenes had measured the shadow
  difference to be 8, instead of the 7 he did
  measure, what is the Earths circumference? How
  far off is this measurement from the modern value
  of the Earths circumference? (Hint Find the
  difference between the modern value and the 8?
  value. In other words, subtract the modern value
  from the 8? value.)
• Page 54, CQ 3,4,7,8