It is understood in our day and age that Earth, as well as the other planets, revolve around the sun. Also, we are aware that the universe is much bigger than the Milky Way galaxy. However, those who were apart of the early study of the cosmos were unaware of these facts. Early astronomers believed that the sun, and everything else, revolved around the Earth. By use of the scientific method, evidence began to emerge that led us to the knowledge we have today. There are three main pieces of evidence that led scientists to the conclusion of a sun-centered cosmos: the discovery of moons orbiting Jupiter, the ability to see the phases of Venus, and Newton’s introduction of his theory of gravity.
The first piece of evidence came about when Galileo Galilei used a telescope in order to make more concrete observations of our solar system. He was able to see that there were moons orbiting the planet Jupiter. This was a major discovery because at that time it was believed that everything orbited Earth. The fact that there were moons orbiting Jupiter simply proved that it was possible for items to orbit a body other than the Earth. However, this was not the only useful observation that came across because of the telescope.
The second piece of evidence, which is also tied to the use of the telescope, was Galileo’s observation of the phases of Venus. As Venus and the Earth both orbit the sun, the sunlight that reflects off of Venus is perceived differently here on Earth. The different “phases” of Venus would only be explainable if the Earth and other planets orbited the sun. If one stuck to the idea of an Earth-centered solar system, then there was no explanation for the varying appearance of Venus. Only drawing the conclusion that Venus orbited the sun and thus different parts of it became visible and not visible could rationalize the observations.
The third and final piece of convincing evidence was Newton’s introduction of his theory of gravity. This was extremely...