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.
Copernicus proposed a heliocentric model of the solar system â a model where everything orbited around the Sun. Today, with advancements in science and technology, the geocentric model seems preposterous.he geocentric model, also known as the Ptolemaic system, is a theory that was developed by philosophers in Ancient Greece and was named after the philosopher Claudius Ptolemy who lived circa 90 to 168 A.D. It was developed to explain how the planets, the Sun, and even the stars orbit around the Earth.