ASTR 001 Lecture Notes - Lecture 27: Ancient Greek Philosophy, Semi-Major And Semi-Minor Axes, Moe Williams
15 Jul 2020
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Kepler"s first law: the orbit of each planet around the sun is an ellipse with the sun at one focus. Kepler"s second law: as a planet moves around its orbit, it sweeps out equal areas in equal times. Kepler"s third law: more distant planets orbit the sun at slower average speeds, obeying the relationship. A= average distance from sun in au (semi-major axis) If you have a planet that is further away, it moves slower (slower at larger distances) Farther planets have more distance to cover. Three key objections rooted in ancient greek philosophy were: Earth could not be moving because objects in air would be left behind. Non-circular (elliptical) orbits are not perfect , as heavens should be. If earth were really orbiting sun, we"d detect stellar parallax. Galileo"s experiments showed that object in air would stay witha moving earth. Aristotle thought that all objects naturally come to rest.
