ASTR 100 Lecture Notes - Lecture 3: Ecliptic, The Moons, Stellar Parallax
26 Sep 2016
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Eclipses do not occur every 30 days since the moon"s orbit is tipped relative to the. The tipped orbit allows the shadow of the earth (moon) to miss the moon (earth). The moon"s orbit is tilted 5 degrees to ecliptic plane. So we have about two eclipse seasons each year, with a lunar eclipse at a full moon and solar eclipse at a new moon. Half the moon is lit by the sun, half is in shadow. Its appearance to us depends on the position of the moon in respect to the sun. ; aristotle presented naked eye observations for the earth"s spherical shape. Shape of earth"s shadow on the moon during an eclipse. He also noted that a traveler moving south will see stars previously hidden by the southern horizon. As ships sail away from port, the hull would disappear fast, and the tops of sails last. Early ideas: distance and size of the sun and moon.
