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.
Ptolemy's model is different from the earlier Greek model because Ptolemy developed a compllex geocentric model of the universe and his model seemed to explain motions until the 1500s.The early Greek astronomers believed that Earth was the center of the universe.