Mathematician, astronomer and Alexandrian geographer, born in Egypt. Although very little is known of it, so it has come to us can be said that it was the last important scientist of antiquity. Although it owes its fame to the exposure of its ptolomaico system, his knowledge went far beyond; He collected scientific knowledge of its time, which added its observations and those of Hiparco de Nicea (who lived during the second half of the 2nd century B.c.), and formed 13 volumes which summarize five hundred years of Greek Astronomy and that dominated astronomical thinking of the West during the next fourteen centuries. This work came to Europe in a version translated to Arabic, and is known as the Almagest (Ptolemy had called it mathematical syntax).
The central theme of Almagest is the explanation of the Ptolemaic system. According to this system, the Earth is located in the center of the universe and the Sun, the Moon and the planets revolve around her swept away by a large sphere called "primum mobile", while the Earth is spherical and stationary. The stars are located in fixed positions on the surface of the sphere. Also, and according to the theory of Ptolemy, the Sun, the Moon and the planets they are gifted in addition to additional own movements that add to the of the Primum Mobile. Ptolemy says that the planets describe circular orbits called epicycles around central points that in turn orbit eccentrically around the Earth. Therefore all celestial bodies describe perfectly circular orbits, although apparent trajectories are justified by the above mentioned eccentricities. In addition, in this work he offered measures of the Sun and the Moon and a catalogue of 1,028 stars.
The Ptolemaic theory is unsustainable because it is based on the adoption of false assumptions; It is however consistent with itself from the mathematical point of view. However, his astronomical work had great influence in the middle ages, compared with Aristotle's philosophy.
Ptolemy, also worked in other areas of science. In optics he exhibited toward the 150 year a treaty, in which explained that eye emits high speed straight Visual rays continuously; due to this issue the eye Gets the sense of distance. In this work he also explained the laws of reflection, saying that visual incident Ray and the reflected are in the same plane, the angle of incidence equals the angle of reflection, and the image is seen at the intersection of extended incident ray with the perpendicular drawn from the object to the plane tangent to the mirror or plane of reflection. Also talk about the atmospheric refraction and the errors of observation that may result in practice this phenomenon. Finally, Ptolemy presented in this work three tables of refraction for steps air-water, aire-vidrio and chemists.
In cartography stressed because it bequeathed an eight-volume work called "Geographia" in which are catalogued 8,000 populations through the indication of your latitude and longitude in degrees; This was based on the journeys of traders, official Roman and shot marine observations. Also described in the same some landforms. Apparently, Colon taking as a reference the sphericity of the Earth and the sizing so great that Ptolemy predicted for Asia to the East, to encourage its claim to reach this continent by sailing West.
It estimated the numerical value of p as 377/120; It created new mathematical formulas, although some of its achievements attributed in this field were due to Hipparchus, including trigonometry, and researched in the field of acoustics.
He died in CANopen near his hometown of Alexandria at the age of nearly 70 years.
See: scientific revolution.