A Brief History of Time

Ptolemy (Second Century A.D.)

AD 90 - c. 168) was a Greco-Egyptian writer of Alexandria, known as a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in the city of Alexandria in the Roman province of Egypt, wrote in Greek, and held Roman citizenship. Beyond that, few reliable details of his life are known. His birthplace has been given as Ptolemais Hermiou in the Thebaid in an uncorroborated statement by the 14th century astronomer Theodore Meliteniotes.This is a very late attestation, however, and there is no other reason to suppose that he ever lived anywhere else than Alexandria, where he died around AD 168 AD.

Almagest Book 1

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.

Almagest Book 2

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 spectator's position. There is also a study of the angles made by the ecliptic with the vertical, with tables.

Almagest Book 3

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.

Almagest 9, 10, 11

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.

Almagest Book 12

Book XII covers stations and retrograde motion, which occurs when the 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.

Almagest Book 13

Book XIII covers motion in latitude, that is, the deviation of planets from the ecliptic.

Almagest Book 4, 5 and 6

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.

Almagest Book 7

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. The brightest stars were marked first magnitude (m = 1), while the faintest visible to the naked eye were sixth magnitude (m = 6). Each numerical magnitude was twice the brightness of the following one, which is a logarithmic scale. This system is believed to have originated with Hipparchus. The stellar positions too are of Hipparchan origin, despite Ptolemy's claim to the contrary.

Aristotle- On the Heavens (340 B.C.)

Provided two arguments for the Earth being round. - The eclipses of the moon were caused by the earth going between the sun and the moon. The shadow on the moon is always round. - The North Star appeared lower in the sky when viewed from lower latitudes than at higher ones. Aristotle also believed in a geocentric model of the universe because he "felt" for mystical reasons that the earth was the center of the universe and circular motion was the most perfect.

Ptolemy (2)

Ptolemy was the author of three main scientific treaties. -The first is now known as the Almagest, although it was originally entitled the "Mathematical Treatise" and then known as the "Great Treatise" -The second is the Geography, which is a thorough discussion of the geographic knowledge of the Greco-Roman world. -The third is the astrological treatise in which he attempted to adapt horoscopic astrology to the Aristotelian natural philosophy of his day. This is sometimes known as the Apotelesmatika but more commonly known as the Tetrabiblos from the Greek meaning "Four Books" or by the Latin Quadripartitum.

Almagest

The Almagest is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Written in Greek by Claudius Ptolemy, a Roman era scholar of Egypt, it is one of the most influential scientific texts of all time, with its geocentric model accepted for more than twelve hundred 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 Copernicus. The treatise is broken down into 13 books