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.
Heraclides Ponticus (387â312 BCE) proposed that the Earth rotates on its axis. Aristarchus of Samos (310 BCE â c. 230 BCE) identified the central fire with the Sun, around which he had the Earth orbiting. And Copernicus formulated.