Claudius Ptolemy’s
Ptolemy, Latin in full Claudius Ptolemies, (born c. 100 CE—died c. 170 CE), Egyptian Astronomer, a mathematician, and geographer of Greek descent who flourished in Alexandria during the 2nd century CE. In several fields his writings represent the culminating achievement of Greco-Roman science, particularly his geocentric model of the universe now known as the Ptolamic system.
Claudius Ptolemy’s Universe:
Earth is placed at the center. The sun is one of the bodies orbiting Earth. Ptolemy placed Earth in a privileged location, at the center of the universe. He would also have placed the Mediterranean Sea in a privileged location, at the center of the world. Mediterranean means middle of the land in Latin. The Greeks called it Mesogeios, meaning the same.
Taken from the book that started the Scientific Revolution . Nicolaus Copernicus correctly identified that Terra (the earth) is one of the planets orbiting Sol (the sun). Only the moon orbits Earth. Copernicus also shows the planets in the correct order. Compare this with Ptolemy’s system, shown previously, in which Earth is wrongly shown closer to Mercury than Venus. In Copernicus’s diagram, the outer circle represents the stars. Then moving inward, there’s Saturn, Jupiter, Mars, Earth (with the moon), Venus, Mercury and Sol.
What he is best for ?
Claudius Ptolemy was a 2nd century Greek mathematician, astronomer and geographer famous for his controversial geocentric theory of the universe, which would form the basis of our understanding of the motions of stars and planets for over than a thousand years.
discovery's
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.
How did he discover his theory?
Ptolemy accepted Aristotle's idea that the Sun and the planets revolve around a spherical Earth, a geocentric view. Ptolemy developed this idea through observation and in mathematical detail. In doing so, he rejected the hypothesis of Aristarchus of Samos, who came to Alexandria about 350 years before Ptolemy was born.
Theories of ptolamy
Ptolemy placed the Earth at the centre of his geocentric model. Using the data he had, Ptolemy thought that the universe was a set of nested spheres surrounding the Earth. He believed that the Moon was orbiting on a sphere closest to the Earth, followed by Mercury, then Venus and then the Sun.
Ptolamic system
In Ptolemy's geocentric model of the universe, the Sun, the Moon, and each planet orbit a stationary Earth. For the Greeks, heavenly bodies must move in the most perfect possible fashion hence, in perfect circles. In order to retain such motion and still explain the erratic apparent paths of the bodies, Ptolemy shifted the centre of each body's orbit from Earth accounting for the body's apogee and perigee and added a second orbital motion to explain retrograde motion. The equant is the point from which each body sweeps out equal angles along the deferent in equal times. The centre of the deferent is midway between the equant and Earth.
Map of Great Britain and Ireland derived from Ptolemy's Geographia, woodcut, 1482. It was included in a volume of Ptolemy's maps that was the first to be printed outside Italy and the first to use woodcuts.
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