PHY 102 1st Edition Lecture 3 Outline of Last Lecture I Celestial Motions A Sun Patterns a Daytime sky b Rotation of the earth B Equinoxes C Moon Patterns Outline of Current Lecture I Yearly Solar Motions a Position of the sun in the sky b North to South motion of the sun II General Planetary Motion a Inferior Planets b Superior Planets III Zodiac IV Theories of Heliocentrism and others a Philolaus Cosmology b Earthshine c Homocentric Spheres of Eudoxus d Unacceptance Current Lecture I Yearly Solar Motions a Why does the sun change position in the sky These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute i Sun changes its path every day 1 Moves west to east among the stars like the moon 2 About 1 degree eastward each day ii Possible explanations 1 Sun moon stars could all move at different rates around the earth 2 Earth is the one rotating iii The sun has an apparent motion among the background stars b Why does the sun have a North to South motion i The ecliptic s motion on the horizon mimics the sun s motion along the horizon 1 Winter 2 Summer II III IV ii Summer north polar axis points toward the sun iii Winter north polar axis points away from the sun iv 23 degree tilt causes the seasons and the apparent pathway of the sun General Planetary Motions a Inferior planets i Closer to the sun always within a few degrees ii Mercury venus can ONLY see during sunrise and sunset b Superior planets i Can be viewed opposite the sun ii Jupiter moves eastward among the stars then westward then back eastward looping over its own path ZODIAC a Series of constellations along which the sun and the planets move b Planets and stars were all considered living things in ancient society c Signs of the Zodiac are when the sun is in line with a certain constellation d Astrology how the parts of the sky affect things on the earth i Stars used to tell stories ii Stars sometimes called the cathedral of the heavens iii Mostly BUNK Theories of Heliocentrism and others a Philolaus s Cosmology b c d e i central fire was the center of the universe light we could never see Explanation of earth shine i The moon is still partially illuminated but not from the sun 1 Due to the sun s rays bouncing off the earth hitting the moon and bouncing back to the earth Homocentric Spheres of Eudoxus i Nested spheres show the retrograde motion of the planets ii Each sphere has its own axis which rotates at a different speed iii Multiple spheres for each planet s rotation Aristarchus i Showed relative sizes of earth moon from the eclipse shadow ii Studied the shadow of the earth on the moon at a lunar eclipse iii MISCONCEPTION phases of the moon are NOT caused by the earth s shadow iv Concludes that the moon is 1 3 earth s diameter Unacceptance i Heliocentrism not accepted because of lack of evidence 1 Parallax 1 a Angle of the earth to the stars would be different at different positions around the sun assuming that the stars are at equal distances from the sun 2 Parallax 2 a Visibility of the stars would differ based on the position of the earth around the sun