This process is broken down into seven layers; Application Layer, Presentation Layer, Session Layer, Transport Layer, Network Layer, Data Link Layer, and Physical Layer. When a person communicates to another person on a network the information passes through these layers.
Ptolemy was an astronomer and mathematician. He believed that the Earth was the center of the Universe. The word for earth in Greek is geo, so we call this idea a geocentric theory.
Galileo's Work. When Galileo first turned his telescope to the moon, he had no idea that he was about to see something that would cast doubt upon centuries-old beliefs. At the time of Galileo, science was based upon the teachings of Aristotle. According to Aristotle, the Earth was the center of the universe.