From Astronomy Encyclopedia Astronomical treatise composed in c.AD 140 by Ptolemy. It summarizes the astronomy of the Graeco-Roman world and contains a star catalogue and rules for calculating future positions of the Moon and planets according to the Ptolemaic System.
Study of the relative position of the planets and stars in the belief that they influence events on Earth. A strongly held belief in ancient Babylon, astrology spread to the Mediterranean world, and was widely used by the Greeks and Romans.
System of reckoning time for the practical purpose of recording past events and calculating dates for future plans. The calendar is based on noting ordinary and easily observable natural events, the cycle of the sun through the seasons with equinox and solstice, and the recurrent phases of the moon.
Historically the most influential of the geocentric cosmological theories, i.e., theories that placed the earth motionless at the center of the universe with all celestial bodies revolving around it (see cosmology).
Instrument that indicates the time of day by the shadow, cast on a surface marked to show hours or fractions of hours, of an object on which the sun's rays fall.
From The Hutchinson Unabridged Encyclopedia Arabian scientist. He was the author of the Kitab al-Manazir/Book of Optics, translated into Latin as Opticae thesaurus (1572). For centuries it remained the most comprehensive and authoritative treatment of optics in both East and West.
Greek mathematician, physicist, and inventor. He is famous for his work in geometry (on the circle, sphere, cylinder, and parabola), physics, mechanics, and hydrostatics.
From The Columbia Encyclopedia
Greek astronomer and mathematician of the Alexandrian school. He is said to have been the first to propose a heliocentric or sun-centered theory of the universe. Of his writings only a treatise, The Sizes and Distances of the Sun and Moon, remains.
From Astronomy Encyclopedia Indian mathematician and astronomer who wrote three astronomical treatises, only one of which, the Āryabhatīya (AD 499), survives.
From Chamber's Biographical Dictionary Born in Wan (Nanyang), he was the astronomer royal at the court of the later Han emperors. Although none of his actual works has survived there are detailed accounts extant of several of his inventions.
From The Columbia Encyclopedia
Greek astronomer, mathematician, and physician. From the accounts of various ancient writers, he appears to have studied with Plato in Athens, spent some time in Heliopolis, Egypt, founded a school in Cyzicus, and spent his later years in Cnidus, where he had an observatory.
From Chambers Biographical Dictionary
It is reported that he was the first to propose that the Earth spins from west to east, thinking it highly improbable that the stars and planets could rotate once every 24 hours.
From Astronomy Encyclopedia Greek astronomer, geographer and mathematician who made observations from Nicea (in what is now modern Turkey), Alexandria, Egypt and the Greek island of Rhodes.
From The Columbia Encyclopedia Instrument probably used originally for measuring the altitudes of heavenly bodies and for determining their positions and movements.
From The Columbia Encyclopedia First modern European theory of planetary motion that was heliocentric, i.e., that placed the sun motionless at the center of the solar system with all the planets, including the earth, revolving around it. Copernicus developed his theory in the early 16th cent. from a study of ancient astronomical records.
Since the gravitational force is experienced by all matter in the universe, from the largest galaxies down to the smallest particles, it is often called universal gravitation.
From Astronomy Encyclopedia Model of the Solar System in which the Sun is at the centre and the planets revolve around it. A heliocentric theory was proposed by the Greek astronomer ARISTARCHUS in the 3rd century BC, but it seemed counter-intuitive at the time and was not widely adopted.
From The Columbia Encyclopedia Three mathematical statements formulated by the German astronomer Johannes Kepler that accurately describe the revolutions of the planets around the sun.
From Astronomy Encyclopedia Early instrument used for measuring declination. It consists of a graduated circle fixed to a wall (in Latin, murus) orientated north-south.
From Collins Dictionary of Astronomy The first reflecting telescope to be built, developed in about 1670 by Isaac Newton from the ideas of Zucchi and Gregory: Newton turned his attention to reflecting telescopes because he thought (wrongly) that there was no way in which the chromatic aberration of refracting telescopes could be corrected.
From Astronomy Encyclopedia Telescope that utilizes the refraction of light through lenses to form images of distant objects. In its simplest form, a refracting telescope consists of two lenses, an objective, and an eyepiece.
Instrument for measuring the altitude of the sun or another celestial body; such measurements can then be used to determine the observer's geographical position or for other navigational, surveying, or astronomical applications.
From Astronomy Encyclopedia Islamic Turkish ruler of Maverannakhr (now Uzbekistan) and astronomer, whose name means ‘great prince’; his real name was Muhammad Taragi ibn Shah-Rukh ibn-Timur. In 1420 Beg built a madrasa (university) equipped with a three-story observatory at Samarkand.
Danish astronomer, sometimes known by his first name only, who is most noted for his remarkably accurate measurements of the positions of stars and the movements of the planets.
French astronomer, born in Italy. He discovered (1675) Cassini's division, the gap that divides Saturn's rings into two parts, and four of Saturn's moons.
English mathematician, physicist, and astronomer who not only identified the comet later to be known by his name, but also compiled a star catalogue, detected stellar motion using historical records, and began a line of research that – after his death – resulted in a reasonably accurate calculation of the astronomical unit.
Dutch physicist and astronomer who discovered Saturn's rings (1655), pioneered the use of pendulums in clocks (1657), and formulated Huygens' principle.
From The Hutchinson Dictionary of Scientific Biography French astronomer whose work on the discovery of comets led to a compilation of the locations of nebulae and star clusters - the Messier catalogue - that is still of some relevance 200 years later.
From Chambers Biographical Dictionary
English mathematician. Born probably in Halifax, West Yorkshire, he is said to have studied at Oxford and taught mathematics at Paris, where he died in 1244 or 1256.
From The Columbia Encyclopedia Pope (999–1003), a Frenchman (b. Auvergne) named Gerbert; successor of Gregory V. In his youth he studied at Muslim schools in Spain and became learned in mathematics and astronomy.
Instrument for measuring the altitude of the sun or another celestial body; such measurements can then be used to determine the observer's geographical position or for other navigational, surveying, or astronomical applications.