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.
The Copernican Model: A Sun-Centered Solar System. The Earth-centered Universe of Aristotle and Ptolemy held sway on Western thinking for almost 2000 years. Then, in the 16th century a new (but remember Aristarchus) idea was proposed by the Polish astronomer Nicolai Copernicus (1473-1543).