AS101 Lecture Notes - Lecture 2: Orbital Period, Validity, Ellipse
Document Summary
Kepler published his three laws of planetary motion in the early 1600s: kepler"s first law: the orbit of each planet around the sun is an ellipse with the sun at one focus. All planets move around sun in elliptical orbits with sun as focus. Radius vector joining any planet to sun takes out equal areas in equal lengths of time. When a planet is closer to the sun (around its perihelion) it moves faster along its orbit than when close to the aphelion (further point from the sun) Galileo introduced the telescope to the world in the early 1600s and proved the earth was not the centre of the universe and in fact the sun-centred model was correct. Newton"s universal law of gravitation: if the mass of either object is doubled, the force doubles. Also, if the distance between the masses doubles, the force diminishes by a factor of 4 (two squared)
