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Mu'ayyad Al-Din Al-'Urdi
Al-Urdi (full name: Moayad Al-Din Al-Urdi Al-Amiri Al-Dimashqi) () (d. 1266) was a medieval Syrian Arab astronomer and geometer. Born circa 1200, presumably (from the nisba ''al‐ʿUrḍī'') in the village of ''ʿUrḍ'' in the Syrian desert between Palmyra and Resafa, he came to Damascus at some point before 1239, where he worked as an engineer and teacher of geometry, and built instruments for al-Malik al-Mansur of Hims. In 1259 he moved to Maragha in northwestern Iran, after being asked by Nasir al-Din al-Tusi to help establish the Maragha observatory under the patronage of Hulagu.PDF version Al-Urdi's most notable works are ''Risālat al-Raṣd'', a treatise on observational instruments, and ''Kitāb al-Hayʾa'' (كتاب الهيئة), a work on theoretical astronomy. His influence can be seen on Bar Hebraeus and Qutb al-Din al-Shirazi, in addition to being quoted by Ibn al-Shatir. Al-Urdi contributed to the construction of the observatory outside of the city, const ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Celestial Globe
Celestial globes show the apparent positions of the stars in the sky. They omit the Sun, Moon, and planets because the positions of these bodies vary relative to those of the stars, but the ecliptic, along which the Sun moves, is indicated. There is an issue regarding the “handedness” of celestial globes. If the globe is constructed so that the stars are in the positions they actually occupy on the imaginary celestial sphere, then the star field will appear reversed on the surface of the globe (all the constellations will appear as their mirror images). This is because the view from Earth, positioned at the centre of the celestial sphere, is of the gnomonic projection inside of the celestial sphere, whereas the celestial globe is orthographic projection as viewed from the outside. For this reason, celestial globes are often produced in mirror image, so that at least the constellations appear as viewed from earth. Some modern celestial globes address this problem by making th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maragheh Observatory
The Maragheh observatory (Persian: رصدخانه مراغه), also spelled Maragha, Maragah, Marageh, and Maraga, was an astronomical observatory established in the mid 13th century under the patronage of the Ilkhanid Hulagu and the directorship of Nasir al-Din al-Tusi, a Persian scientist and astronomer. The observatory is located on the west side of Maragheh, which is situated in today's East Azerbaijan Province of Iran.Niri, J. S. (2017). Determine the function and design of architectural and astronomical ... Determine the Function and Design of Architectural and Astronomical Observatory Discovered in the Maragheh. Retrieved November 8, 2022, from https://www.researchgate.net/publication/349064264_Determine_the_Function_and_Design_of_Architectural_and_Astronomical_Observatory_Discovered_in_the_Maragheh It was considered one of the most advanced scientific institutions in Eurasia because it was a center for many groundbreaking calculations in mathematics and astronomy, it hous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epicycle
In the Hipparchian, Ptolemaic, and Copernican systems of astronomy, the epicycle (, meaning "circle moving on another circle") was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets. In particular it explained the apparent retrograde motion of the five planets known at the time. Secondarily, it also explained changes in the apparent distances of the planets from the Earth. It was first proposed by Apollonius of Perga at the end of the 3rd century BC. It was developed by Apollonius of Perga and Hipparchus of Rhodes, who used it extensively, during the 2nd century BC, then formalized and extensively used by Ptolemy in his 2nd century AD astronomical treatise the '' Almagest''. Epicyclical motion is used in the Antikythera mechanism, an ancient Greek astronomical device for compensating for the elliptical orbit of the Moon, moving faster at perigee and slower at apogee than circular orbits would, using fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equant
Equant (or punctum aequans) is a mathematical concept developed by Claudius Ptolemy in the 2nd century AD to account for the observed motion of the planets. The equant is used to explain the observed speed change in different stages of the planetary orbit. This planetary concept allowed Ptolemy to keep the theory of uniform circular motion alive by stating that the path of heavenly bodies was uniform around one point and circular around another point. Placement The equant point (shown in the diagram by the large • ), is placed so that it is directly opposite to Earth from the deferent's center, known as the ''eccentric'' (represented by the × ). A planet or the center of an epicycle (a smaller circle carrying the planet) was conceived to move at a constant angular speed with respect to the equant. In other words, to a hypothetical observer placed at the equant point, the epicycle's center (indicated by the small · ) would appear to move at a st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apollonius' Theorem
In geometry, Apollonius's theorem is a theorem relating the length of a median of a triangle to the lengths of its sides. It states that "the sum of the squares of any two sides of any triangle equals twice the square on half the third side, together with twice the square on the median bisecting the third side". Specifically, in any triangle ABC, if AD is a median, then , AB, ^2 + , AC, ^2 = 2 \left(, AD, ^2+, BD, ^2\right). It is a special case of Stewart's theorem. For an isosceles triangle with , AB, = , AC, , the median AD is perpendicular to BC and the theorem reduces to the Pythagorean theorem for triangle ADB (or triangle ADC). From the fact that the diagonals of a parallelogram bisect each other, the theorem is equivalent to the parallelogram law. The theorem is named for the ancient Greek mathematician Apollonius of Perga. Proof The theorem can be proved as a special case of Stewart's theorem, or can be proved using vectors (see parallelogram law). The following ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Copernicus
Nicolaus Copernicus (; pl, Mikołaj Kopernik; gml, Niklas Koppernigk, german: Nikolaus Kopernikus; 19 February 1473 – 24 May 1543) was a Renaissance polymath, active as a mathematician, astronomer, and Catholic canon, who formulated a model of the universe that placed the Sun rather than Earth at its center. In all likelihood, Copernicus developed his model independently of Aristarchus of Samos, an ancient Greek astronomer who had formulated such a model some eighteen centuries earlier. The publication of Copernicus's model in his book ' (''On the Revolutions of the Celestial Spheres''), just before his death in 1543, was a major event in the history of science, triggering the Copernican Revolution and making a pioneering contribution to the Scientific Revolution. Copernicus was born and died in Royal Prussia, a region that had been part of the Kingdom of Poland since 1466. A polyglot and polymath, he obtained a doctorate in canon law and was a mathematician, astro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
