Greek

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Greek Roman Calendars

• Constructions of Time in the Classical World
• By Robert Hannah

Ashley DeFlumere 12/11/2007
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Hipparchus

• 190 - 120 BC
• Greek Astronomer
• First to accurately record the motion of the sun
  and moon

http//en.wikipedia.org/wiki/ImageHipparchos_1.jp
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Ptolemy

• 83 - 161 AD
• Greek Astronomer
• Built upon the work of Aristotle
• Treatise on Astronomy Almegast

http//en.wikipedia.org/wiki/ImagePtolemaeus.jpg
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Astronomical Instruments

• Gnomon - part of a sundial
• Astrolabe - predicts positions of heavenly bodies
• Armillary Sphere - model of celestial sphere

http//en.wikipedia.org/wiki/ImageArmillary_spher
e.png
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Ancient Solar Observations

• Summer and Winter Solstices
• Solstice - Latin sol sun, sistere to stand
• Zodiac Constellations

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Measuring a Year

• Tropical (Solar) Year - time between spring
  equinoxes, 365.24219 solar days
• Sidereal Year - measure passage of sun across a
  point among the stars, 365.2464 solar days
• Lunar Year - 12 lunar cycles of 29.53059, for an
  average year of 354 solar days