# Time Line Project

## Ptolemy

An Alexandrian Greek, who said that the solar system revolved a round the Earth. A geocentric (Earth Centered) solar system.

## Copernicus

Copernicus (A Polish cleric) said that the sun is the center of the solar system not the Earth in 1500's. Though there were many objections to this, like if the Earth is not the center and is moving round the sun at enormous speeds how come we don't feel it.

## Galileo

Later on Galileo was convinced that Copernicus was correct about the sun being the center, by observing the Sun, Venus, and moons of Jupiter using his newly - invented telescope. He was mostly motivated to understand Copernicus idea's and to understand inertia.

## Tycho Brahe

In late 1500's Tycho Brahe had to set out the most accurate measurements on planetary motion to support his ideas on it. Later on was successfully interpreted by Johannes Kepler.

## Johannes Kepler

Kepler proved the the orbital path of the planets were ellipses (not perfect circles). He proved that when a planet is closer to the sun its orbital path is faster then ones farther away from the sun and slower. His research provided a complete Kinematic observation on motion of planets .

## Isaac Newton

Isaac Newton realized that the falling motion of an apple and the motion of the moon were the same motion with the same force and gravitational force acting on it . He stated that the universal force acting between two thing/objects was gravity. The gravitational force would equal the objects weight. Where g = 9.8 m/s2. The reason the moon orbits the Earth is it gravitational force. The Universal Gravitation is often called an Inverse Square Law.

## Cavendish

Before 1800, Cavendish used human scale objects to measure the gravitational force. Was later improved by Van Jolly.