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# Aristole

In 330BC Aristole's Book Physics II was published. It consisted of his ideas and thoughs as to why objects fall on earth and it also talked about motion in general. He believed that the Earth was a sphere shape and that it was the center of the universe.Since Earth was the center of the universe all objects would have the tendency to fall towards it.
Source:http://www-history.mcs.st-and.ac.uk/PrintHT/Gravitation.html>
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Aristole still had some information missing like exactly how the planets or bodies moved around the earth, weither they stop, slow down, or go fast and etc.In his book Almagest written in 150AD he presented a complete system of mathematical construction that was successfully used to find out the orbital motions of the rest of the bodies around the earth. He used epicycles and added to them.
source: http://galileo.rice.edu/sci/theories/ptolemaic_system.html
• # Newton

Legend has at that what influenced Newton to think about gravity was an apple falling from a tree and hitting him on the head.The reason for the apple's acceleration was because of gravity (2nd law). He explained that gravity is when an object falls onto earth using with his cannon experiment.He believed that gravity was all around and not just on earth and came up with the law of universal gravitation.
source:http://farside.ph.utexas.edu/teaching/301/lectures/node152.html
• # Cavendish

In 1798 Henry Cavendish came up withthe gravitational constant for Newton's law of Universal gravitation. His experiement consited of a dumbell from a fine string. He placed two large lead weights below the dumbell, and was able to see a small twisting in the string. From the small twist in the string he was able to measure the force between the objects. After measuring the force, masses, and distance, he was able to calculate the gravitational constant. Source: http://www.juliantrubin.com/bi
• # Einstein

He violated Newton's theory with his theory defining gravity which was created by bending space and time around it. Everything in space was bent even ray lights. To prove his theory an expidition was launch in1919 by the Royal Astronomical Society to a West African Island Principe to observe the a total solar eclipse.
souce: http://www.juliantrubin.com/einsteininvent.html, http://www.sciencedaily.com/releases/2009/05/090528204402.htm