What was ptolemy known for

Ptolemy contribution to astronomy
Claudius ptolemy
Ptolemy birth and death

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Ptolemy

Roman astronomer and geographer (c. 100–170)

For other uses, see Ptolemy (disambiguation).

Claudius Ptolemy (; Ancient Greek: Πτολεμαῖος, Ptolemaios; Latin: Claudius Ptolemaeus; c. 100 – 160s/170s AD)^[1] was an Alexandrian mathematician, astronomer, astrologer, geographer, and music theorist^[2] who wrote about a dozen scientific treatises, three of which were important to later Byzantine, Islamic, and Western European science. The first was his astronomical treatise now known as the Almagest, originally entitled Mathematical Treatise (Greek: Μαθηματικὴ Σύνταξις, Mathēmatikḗ Syntaxis). The second is the Geography, which is a thorough discussion on maps and the geographic knowledge of the Greco-Roman world. The third is the astrological treatise in which he attempted to adapt horoscopic astrology to the Aristoteliannatural philosophy of his day. This is sometimes known as the Apotelesmatika (Greek: Αποτελεσματικά, lit. 'On the Effects') but more commonly known as the Tetrábiblos, from the Koine Greek meaning "Four Book

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12 Claudius Ptolemy

Another ancient Greek astronomer and philosopher, Claudius Ptolemy (100-170 AD), developed a Geocentric Solar System which placed the “stellar” universe on a crystal sphere. Earth stood still (didn’t rotate) and the Sun orbited Earth, producing our day and night cycles. To account for the retrograde of the planets, Ptolemy used looping small circles called epicycles on the orbits. It was an ingenious system accepted, as Law… except a Geocentric Universe was wrong!Even though Ptolemy was Greek, he was born in Egypt. All of his observations and work was done from Alexandria, Egypt. He was also a geographer and mathematician, and Ptolemy’s“Almagest” (1515) is one of the most influential scientific texts of all times.

If Ptolemy’s Geocentric Universe is incorrect, why do we see Retrograde Motion? Each planet orbits the Sun at a different velocity; the closer the planet to the Sun, the faster it orbits. Earth catches up then passes planets further away from the Sun, giving the illusion that the planet is moving backwards for a while. The planet does retrograde

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Claudius’ finished his first major work on astronomy was he was 50 years old. It was based on the observations he had made over the previous 20 to 30 years. He called his book, The Almagest, which meant ‘The Greatest’. In his work, Claudius described the movements of objects in the night sky using maths. He believed the paths of the stars and planets were not random. He explained them by combining several circular movements.

In Claudius' model of the Solar System, the Earth was stationary. It was surrounded by a great sphere which carried the stars, planets, Sun and Moon around the Earth. This idea of a geocentric (Earth centred) Solar System became known as the Ptolemaic system.

The Almagest also contains a star catalogue. It listed 48 constellations which could be seen from the Northern Hemisphere. Claudius' later work, ‘Planetary Hypotheses’ was more mathematical than The Almagest. It set out the Universe as a series of spheres and estimated the distances to the Sun and the 'fixed stars'.