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.
Who developed the idea of the solar system as a sun-centered universe? Aristarchus was the first person who brought this idea into  consideration, but he could not prove it. Later, the idea that  Earth is at the centre was official doctrine fâ¦or about 1400  years.