by John Traveler

Created on: November 10, 2009   Last Updated: November 16, 2009

In the first half of the sixteenth century, Nicolas Copernicus's heliocentric revelations modified mans understanding of the cosmos, taking the Earth out of the center of the universe and making it just one of 6 planets (those know in the day) it obit of the Sun. Copernicus meticulously describe his theory and geometric proofs of it in his book On the Revolutions of the Heavenly Orbs, but would not allow publication of the book until he was on his deathbed.

Those who read Copernicus' book and subscribed to his theory, began to wonder what force or power held the planets in their orbits. One such Copernican convert was Johannes Kepler, who in his own book Harmonies of the World refers to the existence of a mysterious force exerted by the sun on the planets and by planets on their moons. While Kepler himself would never understand Gravity he was the first to realize its existence.

Isaac Newton was born in 1643, a hundred years after the death of Copernicus and 13 years after Kepler died, but during his education would read the books these men had written as well as others investigating the new heliocentric reality. Newton took particular interest in the mysterious force Kepler had pointed to and focused his attention on solving the enigma. Experimenting with gravity here on Earth, Newton gained a unique understanding of the properties of gravitational attraction and in the process discovered a few other things about the motion of objects, claiming that he was able to see further than others by standing on the shoulders of giants.

In 1876, Sir Isaac Newton published his own book called Principia, and in it described his universal law of gravity along with his three laws of motion. Newton's law of universal gravity would later be modified by Albert Einstein's own theory of General Relativity, but his three laws of motion remain intact and true, and are fundamental precepts of modern physics.

FIRST LAW:

A body continues in a state of rest or uniform motion unless acted upon by an external force.

Newton's 1st law of motion is today more commonly referred to as the law of inertia. It basically states, that if an object is standing still, it will continue to stand still until some external force is applied to cause it to move. Conversely, if an object is in motion, it will continue to travel in the same direction and at the same velocity until some other external force acts upon it to change its direction or velocity.

SECOND LAW:

Acceleration of a body is proportional

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