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.
Heliocentric Universe. A heliocentric universe is a universe in which the sun is the center and the planets orbit around it. Copernicus was the first person to formulate this idea. The idea of a heliocentric universe was rejected by the Church because God's prized creation, Earth, should be at the center. geocentric universe is the model of the universe created by Ptolemy, in which everything in the universe (sun, stars, other planets, etc.) orbits around the Earth.