## Tools & Beliefs

- AstrolabeFrom
*The Columbia Encyclopedia*

Instrument probably used originally for measuring the altitudes of heavenly bodies and for determining their positions and movements. - Copernican systemFrom
*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. - Heliocentric theoryFrom
*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. - Kepler's Laws of Planetary MotionFrom
*The Columbia Encyclopedia*

Three mathematical statements formulated by the German astronomer Johannes Kepler that accurately describe the revolutions of the planets around the sun. - Mural quadrantFrom
*Astronomy Encyclopedia*

Early instrument used for measuring declination. It consists of a graduated circle fixed to a wall (in Latin, murus) orientated north-south. - Newtonian telescopeFrom
*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. - Refracting telescopeFrom
*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. - Sextant: Topic PageInstrument 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.
- Universal Law of GravitationFrom
*Dictionary of Astronomy*

The law of gravitation set out by Newton and applying to every object in the universe. It states that every body in the universe exerts an attraction on every other, proportional to the product of their masses (their masses multiplied together) divided by the square of the distance between them.

Comments (0)

## Astronomers

- Ulugh Beg (1393 - 1449)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. - Tycho Brahe (1546 - 1601): Topic PageDanish 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.
- Giovanni Cassini (1625 - 1712): Topic PageFrench 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.
- Nicolaus Copernicus (1473 - 1543): Topic PagePolish astronomer who promulgated the now accepted theory that the earth and the planets move about the sun (the Copernican system).
- Galileo Galilei (1564 - 1642): Topic PageGreat Italian astronomer, mathematician, and physicist.
- Edmond Halley (1656 - 1742): Topic PageEnglish 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.
- William Herschel (1738 - 1822): Topic PageGerman-born English astronomer and musician. He took up astronomy in the 1770s, making his own telescopes and mirrors.
- Christiaan Huygens (1629 - 1695): Topic PageDutch physicist and astronomer who discovered Saturn's rings (1655), pioneered the use of pendulums in clocks (1657), and formulated Huygens' principle.
- Johannes Kepler (1571 - 1630): Topic PageGerman astronomer who combined great mathematical skills with patience and an almost mystical sense of universal harmony.
- Charles Messier (1730 - 1817)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. - Sir Isaac Newton (1642 - 1727): Topic PageEnglish mathematician and scientist who invented differential calculus and formulated the theory of universal gravitation.
- Johannes Sacrobosco (1195 - 1256)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. - Sylvester II (945 - 1003)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.