Almagestum Cl. Ptolemi, 1515 book
The Almagest is a 2nd-century Greek-language mathematical and astronomical treatise on the apparent motions of the stars and planetary paths, written by Claudius Ptolemy. It is one of the most influential scientific texts of all time, and its geocentric model was accepted for more than 1200 years from its origin in Hellenistic Alexandria, in the medieval Byzantine and Islamic worlds, and in Western Europe through the Middle Ages and early Renaissance until Copernican heliocentrism was accepted in the scientific community.
The Almagest is a comprehensive mathematical and astronomical treatise written by the ancient Greek astronomer and mathematician Claudius Ptolemy, who lived in the 2nd century AD. The full title of the work is "Mathematical Syntaxis" (Μαθηματικὴ Σύνταξις) in Greek, but it became known as the Almagest in medieval Latin translations. The Almagest is one of the most influential works in the history of astronomy and was the main reference work on the subject for many centuries. In the Almagest, Ptolemy presents a geocentric model of the universe in which the Earth is at the centre and the heavenly bodies, including the Sun, Moon, planets and stars, move in circular orbits around it. Ptolemy also introduces the concept of epicycles, which are small circles on which the planets move, while these circles in turn move on larger circles centred on the Earth. Despite the eventual acceptance of the heliocentric model proposed by Nicolaus Copernicus in the 16th century, the Almagest remained an important work in the history of astronomy and was widely studied in the Middle Ages and beyond. It contains valuable information on the positions and motions of celestial bodies, and includes detailed mathematical calculations and observational data.