Kepler's laws of planetary motion

From Conservapedia
Jump to: navigation, search
Illustration of Kepler's three laws
(1) The orbits are ellipses, with focal points ƒ1 and ƒ2 for the first planet and ƒ1 and ƒ3 for the second planet. The Sun is placed in focal point ƒ1.

(2) The two shaded sectors A1 and A2 have the same surface area and the time for planet 1 to cover segment A1 is equal to the time to cover segment A2.

(3) The total orbit times for planet 1 and planet 2 have a ratio a13/2 : a23/2.

Kepler's three laws of planetary motion were developed in the early 17th century by Johannes Kepler. Kepler developed the laws after studying the astronomical observations of Tycho Brahe for several years. Kepler realized that the movement of the celestial bodies whose data Brahe had recorded did not fit a circular orbit, as was believed at the time.

Kepler's three laws of planetary motion are:
1. Planets orbit the sun on elliptical orbits with the sun occupying one of the foci of the ellipse.

2. A line connecting the sun to the orbiting body sweeps out an equal area in an equal amount of time regardless of position in the orbit. In other words, the body moves faster when it is closer to the sun and moves slower when it is further away. This law was much later shown to be true because of conservation of angular momentum.

3. The square of the period of the orbit of a body is proportional to the cube of the semimajor axis of that orbit.