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.
Nicolaus Copernicus (1473â1543) was a mathematician and astronomer who proposed that the sun was stationary in the center of the universe and the earth revolved around it.opernicus claimed that Werner erred in his calculation of time and his belief that before Ptolemy the movement of the fixed stars was uniform, but Copernicus's letter did not refer to his cosmological ideas.