History of Astronomy Review

• Universe in 2 parts: imperfect Earth and perfect heavens – 55 spheres

• Believed that the heavens were perfect; motion & shapes circles and spheres

• Epicycles used to explain retrograde motion

• Made repeated observations; believed the heliocentric model where sun and moon orbit earth, but all other planets orbit the sun

• Aligned sunset, sunrise and moonset at solstices

• Measured Earth’s radius using shadows

• Celestial bodies are spheres moving around a central fire that is blocked out by a counter Earth

• Planets move on elliptical paths at non-uniform velocities

• f=ma

• Discovered moons of Jupiter, rings of Saturn, phases of Venus, sunspots

• P2/A3

• Heliocentric universe

• Every two particles of matter attract each other with a force dependent on mass and inverse square of distance

• Planets orbit the sun in elliptical orbits

• An object remains in motion or at rest unless acted upon by an outside force

• A planet sweeps out equal areas in equal amounts of time

• The extent to which an ellipse is stretched

• Amount of light reflected from the surface of a planet