Lesson 1

• eclipse occurs when one heavenly body such as moon or planet moves into the shadow of other heavenly body.
• during lunar eclipse, earth blocks sunlight from reaching the moon. Earth casts a shadow onto the moon.
• during a solar eclipse, the moon blocks the sunlight to earth. the moon also casts a shadow onto earth.
• Greeks are the first to realize that earth is round by the three observations

  • Ship
  • Star and Constellations
  • Shadow of Earth during eclipse
• Oblate Spheroid is the shape of the earth.
• Phytagoras proposed a spherical earth, mainly on Aesthetic Grounds rather than any physcial evidence.
• Sphere was the most perfect shape.
• By just looking at the moon, Aristotle concluded that all heavenly objects including earth must be sphere.
• Aristotle observed that there were starts in Egypt that can't be seen in Cyprus.
• Aristotle's Argument 1 states that sphere was a perfect solid and heavens were regions of perfections because they were symmetrical.
• Geocentric is when heavenly objects all orbiting the earth inside of Eudoxus' spheres.
• Heavens represented a higher state of being and were therefore made perfect more than the earth.
• Heavens are perfect and made up of fifth element, that is Ether.
• Sphere had the center of all directions.
• In Aristotle's Argument 2, Earths' component pieces are falling naturally towards the center, would later press into a round form.
• If enough material were accumulated on the surface of the earth, it would begin to curve and form a sphere due to Gravitational Attraction towards the center.
• In Aristotle's Argument 3, an eclipse of the moon, Earth's shadow is always circular— a flat disc would cast an Oval Shadow.
• In Aristotle's Argument 4, the polestar is higher in the sky.
• In Aristotle's Argument 4, the polestar is higher in the sky.
• Greeks observed changes in the attitude of stars and even new stars appearing in the local horizon which were not visible from their homeland.
• Aristotle argued that earth could not be flat since all observers on a flat earth have exactly the same local horizon.
• The first person to discover the Earth's Circumference was Eratosthenis.
• Erathosthenis combined geometrical calculations with physical observations.
• Astronomy is a science that studies determination of the positions dimensions and movements of the celestial bodies.
• Astronomy is the oldest of the natural sciences