Our endless journey for answers about the universe has widely expanded based upon numerous people throughout time. From believing the world was flat to realizing that it is not even perfectly round, our learning and discovering never seems to cease.
Before there was need for time to be calculated for our daily lives and set plans, the Sumerians wanted to understand the world in which they resided. They wrote down gradual changes they noticed in the sky. Mathematical theories were developed in order to understand more about the constantly changing universe. Ptolemy the astronomer from Alexandria had the most widely accepted theory that the planets revolved around the earth, which was the center of the universe. The church being the main authority at the time, of course immediately accepted this idea; for back then it made sense that god would put the earth in the middle of everything. .
Copernicus challenged the model and put the sun in the middle of the universe. His work was somewhat dismissed but gave inspiration to Johannes Kepler who discovered planetary motion. He said that the planets moved in an elliptical shape rather than a circular motion. But it was Galileo who saw with the newly invented telescope that the sun and the moon had imperfections in them disproving that they were round and flawless. The church not to keen on this theory confined Galileo to his house for heresy. He knew that the world was turning but did not understand why we did not fly off of it. Though he did not answer this question himself he did also among many other things discovered the moons of Jupiter and began publishing his own works. He was then sent to Rome during the inquisition where he was condemned. .
It took Isaac Newton to explain why the planets moved as they did. The famous apple symbolized gravity to the earth, which he believed must be a universal principle. A question still remained what is the fuzzy substance called nebulae? Immanuel Kant thought it to be a large star system like our own.