3rd century B.C. - true size of earth worked out by Eratosthenes

~1543 - Copernicus overturns the 1500 year old model of the earth being the center of the universe (by Ptolemy, an Alexandrian astronomer) and demonstrates that the sun is the center of the solar system

~1600 - Johannes Kepler, working with 35 years of observational data from Tycho Brahe, comes up with his 3 laws of planetary motion

~1700 - Isaac Newton formulates his three laws of motion and from them, his law of universal gravitation

~1900 - Einstein publishes his general theory of relativity