The Ptolemaic system also called the geocentric system or geocentric model, mathematical model of the universe formulated by the Alexandrian astronomer and mathematician Ptolemy about 150 CE and recorded by him in his Almagest and Planetary Hypotheses. Ptolemy made contributions to astronomy, mathematics, geography, musical theory, and optics. He compiled a star catalog and the earliest surviving table of a trigonometric function and established mathematically that an object and its mirror image must make equal angles to a mirror.
Population change, defined generally, is the difference in the size of a population between the end and the beginning of a given time period (usually one year).... Population change has two components: natural population change (the number of live births minus the number of deaths);
Increase in resources and health provide longer life expectancy in places
