1. The Golden age was from 600 B.C. - 150 A.D. It was known as the golden age because it was centered in Greece which was the origin of geometry and trigonometry. 2.The great Greek philosopher Aristotle (384 - 322 B.C.) concluded that the Earth was round because it always casts a curved shadow on the moon when passing between the sun. 3.Aristarchus (312-230 B.C.) was the first to believe in a sun-centered, also known as heliocentric universe. In this model, every planet orbits around the sun. Aristarchus used geometry to calculate the relative distances from earth to he sun and from Earth to the moon. He was right that the sun is much larger than the earth and farther away than the moon, but his measurements were too small. 4.Eratosthenes was the first to successfully establish the size of the earth (he lived from 276-194 B.C.) He observed the angles of the noonday sun in two Egyptian cities that were roughly north and south of each other. Finding that the angles differed by 7 degrees, or 1/50 of a complete circle concluded that the circumference of Earth must be 50 times the distance between these two cities. 5.Hipparchus was likely the greatest of early greek astronomers, he was best known for his star catalog. He determined the location of almost 850 stars, which he divided into six groups according to their brightness. He measured the length of the year to within minutes of the modern year and developed a method for predicting the times of lunar eclipses to within a few hours. 6.In a 13 volume work published by Ptolemy in 141 AD. Ptolemy presented a model of the universe that was called the Ptolemaic system. It accounted for the movements of the planets. The precision with which his model was able to predict the motion of the planets allowed it to go unchallenged for nearly 13 centuries. 7. 13 8.Came up with the geocentric model (earth centered), perfect circles for orbits but was incorrect because they are actually elliptical. 9.Tycho Brahe (1546-1601), He persuaded King Frederick 2 to build an observatory. Be built the angle-measuring device, His observations of mars were far more precise than any made previously. 10. Johannes Kepler The path of each planet around the sun is an ellipse with the sun at one focus. Each planet revolves so that an imaginary line connecting it to the sun sweeps over equal areas in equal time intervals. The square of the the length of time it takes a planet to orbit the sun is proportional to the cube of its mean distance from the sun. 11.Galileo Galilei (1564-1642) His most important contributions were his descriptions of the behavior of moving objects. He used a telescope. His five discoveries were: The discovery of 4 satellites or moons orbiting jupiter, the discovery that planets were circular discs as opposed to points of light as was previously thought, the discovery that venus had phases like the moon, the discovery that the moons surface was not smooth, the discovery that the sun had sun spots. 12. Sir issac newton, He formulated the universal law of gravitation, (1642-1727), according to newton every body in the universe attracts every other body with a force that is directly proportional to their masses and inversely proportional to the square of the distance between the centers of mass.