Topic: Models of the Universe

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Topic Models of the Universe

• Key Terms
• Geocentric Theory
• Heliocentric Theory

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Geocentric Theory
Ancient Greece
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Geocentric Model

• ___
• ___

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Problems with Geocentric Theory

1. This model does explain apparent motions of
   celestial (space) objects
2. Cannot explain Foucaults Pendulum or the
   Coriolis Effect

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Motion of the other planets
Mars Retrograde Motion
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• Geocentric Model Ptolemy (87-150 AD)
• Used epicycles to explain planetary movements

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Ptolemaic System
     
Mars
Jupiter

• Correction Added
• Epicycles added to epicycles
• Precision Timing for Venus Mercury
• Earth placed off center.

Saturn
Earth Moon
Venus
Mercury
Sun
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Retrograde Motion
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Ptolemys Prediction Future planetary positions
Observation retrograde motion of planets
Refine epicycles
Success! For 1500 years
cfa-www.harvard.edu/seuforum/mtu/MTUcosmology.ppt
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Ptolemys system provided the first framework for
all discussion of the universe for nearly 1500
years!! But there was a problem
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Heliocentric Theory
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• Copernicus (1473-1543)
• Suggests a model that the Sun was the center of
  the universe.
• Argued that the motion of the Sun planets could
  be equally described by a Sun centered
  (heliocentric) system.

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Retrograde Motion
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Outer Planet
Earth overtakes slow outer planet so the outer
planet appears to slow down, move in reverse, and
then move forward again with respect to the fixed
stars.
http//faculty.salisbury.edu/jwhoward/astro108/ht
ml/GeoHelio.ppt274,10,Slide 10
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Tycho Brahe (1546-1601) the greatest of the
pre-telescope observers in Europe. 20 years
measuring the positions of the Sun, Moon and
planets with great accuracy.
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• Johannes Kepler (1609)
• Johannes Kepler was an assistant to Tycho Brahe.
  He used Brahes observations to study the orbit
  of Mars
• Discovered three laws of planetary motion
  predict with accuracy the motions of the planets

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Copernicus Prediction Future planetary
positions
Observation No better than Ptolemy
cfa-www.harvard.edu/seuforum/mtu/MTUcosmology.ppt
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• Galileo (1564-1642) first scientist to use a
  telescope to observe the sky. He observed the
  phases of Venus and the moons of Jupiter. Both
  observations supported the heliocentric model.

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Heliocentric Model

• ___
• ___

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• Is the Sun the Center of the Universe?

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Modern Universe

• Is the Sun the center of the Universe?

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Final Question

• http//www.polleverywhere.com/multiple_choice_poll
  s/MTQzODY3NjcwMQ/web