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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Almagest | 1/4 | https://en.wikipedia.org/wiki/Almagest | reference | science, encyclopedia | 2026-05-05T08:32:30.906530+00:00 | kb-cron |
The Almagest ( AL-mə-jest) is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths, written by Claudius Ptolemy (c. AD 100 – c. 170) in Koine Greek. One of the most influential scientific texts in history, it canonized a geocentric model of the Universe that was accepted for more than 1,200 years from its origin in ancient Greece, through to the medieval Byzantine and Islamic worlds, and in Western Europe through the Middle Ages and early Renaissance until the Scientific Revolution. It is also a key source of information about ancient Greek astronomy. Ptolemy set up a public inscription at Canopus, Egypt, in 147 or 148. Norman T. Hamilton found that the version of Ptolemy's models set out in the Canopic Inscription was earlier than the version in the Almagest. Hence the Almagest could not have been completed before about 150, a quarter-century after Ptolemy began observing.
== Names == The name comes from Arabic اَلْمَجِسْطِيّ al-majisṭī, with اَلـ al- meaning 'the' and majisṭī being a corruption of Greek μεγίστη megístē 'greatest'. The Arabic name was popularized by a Latin translation known as Almagestum made in the 12th century from an Arabic translation, which would endure until original Greek copies resurfaced in the 15th century. The work was originally called Μαθηματικὴ Σύνταξις (Mathēmatikḕ Sýntaxis) in Koine Greek, as also in Modern Greek (primarily), and was known as Syntaxis Mathematica in Latin. The treatise was later called Ἡ Μεγάλη Σύνταξις (Hē Megálē Sýntaxis), "The Great Treatise" (Latin: Magna Syntaxis), and the superlative form of this (Greek: μεγίστη megístē, 'greatest') lies behind the Arabic name from which the English name Almagest derives. In the study of medieval Hebrew texts, the Almagest is sometimes referred to as "Ptolemy's Book of Elections", to emphasize parallelism with Abraham ibn Ezra's manuscript of the same name.
== History == Written possibly around 150 CE, the text survives as copies, the oldest being from the 9th century when Arabic scholars started to translate the text, which in turn have survived in copies from the 11th and 13th centuries.
== Contents ==
=== The Syntaxis Mathematica books ===
The Syntaxis Mathematica consists of thirteen sections, called books. As with many medieval manuscripts that were handcopied or, particularly, printed in the early years of printing, there were considerable differences between various editions of the same text, as the process of transcription was highly personal. An example illustrating how the Syntaxis was organized is given below; it is a Latin edition printed in 1515 at Venice by Petrus Lichtenstein.
Book I contains an outline of Aristotle's cosmology: on the spherical form of the heavens, with the spherical Earth lying motionless as the center, with the fixed stars and the various planets revolving around the Earth. Then follows an explanation of chords with table of chords; observations of the obliquity of the ecliptic (the apparent path of the Sun through the stars); and an introduction to spherical trigonometry. Book II covers problems associated with the daily motion attributed to the heavens, namely risings and settings of celestial objects, the length of daylight, the determination of latitude, the points at which the Sun is vertical, the shadows of the gnomon at the equinoxes and solstices, and other observations that change with the observer's position. There is also a study of the angles made by the ecliptic with the vertical, with tables. Book III covers the length of the year, and the motion of the Sun. Ptolemy explains Hipparchus' discovery of the precession of the equinoxes and begins explaining the theory of epicycles. Books IV and V cover the motion of the Moon, lunar parallax, the motion of the lunar apogee, and the sizes and distances of the Sun and Moon relative to the Earth. Book VI covers solar and lunar eclipses. Books VII and VIII cover the motions of the fixed stars, including precession of the equinoxes. They also contain a star catalogue of 1022 stars, described by their positions in the constellations, together with ecliptic longitude and latitude. Book IX addresses general issues associated with creating models for the five naked eye planets, and the motion of Mercury. Book X covers the motions of Venus and Mars. Book XI covers the motions of Jupiter and Saturn. Book XII covers stations and retrograde motion, which occurs when planets appear to pause, then briefly reverse their motion against the background of the zodiac. Ptolemy understood these terms to apply to Mercury and Venus as well as the outer planets. Book XIII covers motion in latitude, that is, the deviation of planets from the ecliptic. The final topic of this chapter also covers how to determine when a planet first becomes visible after being hidden by the glare of the sun, as well as the last time it is seen before being hidden by the sun's glare.
=== Ptolemy's cosmos === The cosmology of the Syntaxis includes five main points, each of which is the subject of a chapter in Book I. What follows is a close paraphrase of Ptolemy's own words from Toomer's translation.
The celestial realm is spherical, and moves as a sphere. The Earth is a sphere. The Earth is at the center of the cosmos. The Earth, in relation to the distance of the fixed stars, has no appreciable size and must be treated as a mathematical point. The Earth does not move.
=== The star catalogue ===