physics gravitational forces

Ptolemy (100 AD)

• Greek mathematician

• Believed in the Geocentric Universe Theory (Earth is the center of the universe)

• Believed in Circular Orbits

Copernicus (1470-1543)

• Heliocentric Universe Theory (Sun is the center of the universe)

Galileo (1564-1642)

• Used telescope to gather data to support heliocentric universe theory

• Believed in circular orbits

Brahe (1546-1601)

• Gathered precise measurements of the positions of planets

• Died before he could evaluate his data

Kepler (1571-1630)

• Founded the 3 laws of Gravitation with Brahe’s data

1st Law (Kepler)

Orbits of planets are elliptical and Sun is at one of the foci. Eccentricity = 0 → circular orbits

2nd Law (Kepler)

Planets cover the same area in the same amount of time. (changed to the closer planet is to the sun, the faster it moves)

3rd Law (Kepler)

\left(\frac{Ta}{Tb}\right)^2=\left(\frac{rA}{rB}\right)^3 (A is usually the farther planet)