8. Astonomy Comparison Documents
Arab & Islamic Astronomy
“During the period when Western civilization was experiencing the dark ages, between 700-1200 A.D., an Islamic empire stretched from Central Asia to southern Europe. Scholarly learning was highly prized by the people, and they contributed greatly to science and mathematics. Many classical Greek and Roman works were translated into Arabic, and scientists expanded on the ideas. For instance, Ptolemy's model of an earth-centered universe formed the basis of Arab and Islamic astronomy, but several Islamic astronomers made observations and calculations which were considerably more accurate than Ptolemy's. Perhaps the most fascinating aspect of Islamic astronomy is the fact that it built on the sciences of two great cultures, the Greek and the Indian. Blending and expanding these often different ideas led to a new science which later profoundly influenced Western scientific exploration beginning in the Renaissance.
Perhaps the most vital reason that the Muslims studied the sky in so much detail was for the purpose of time-keeping. The Islamic religion requires believers to pray five times a day at specified positions of the sun. Astronomical time-keeping was the most accurate way to determine when to pray, and was also used to pin-point religious festivals. The Muslim holy book, the Koran, makes frequent reference to astronomical patterns visible in the sky, and is a major source of the traditions associated with Islamic astronomy.
Another important religious use for astronomy was for the determination of latitude and longitude. Using the stars, particularly the pole star, as guides, several tables were compiled which calculated the latitude and longitude of important cities in the Islamic world. Using this information, Muslims could be assured that they were praying in the direction of Mecca, as specified in the Koran.
Aside from religious uses, astronomy was used as a tool for navigation. The astrolabe, an instrument which calculated the positions of certain stars in order to determine direction, was invented by the Greeks and adopted and perfected by the Arabs (see picture below).
The sextant was developed by the Arabs to be a more sophisticated version of the astrolabe. This piece of technology ultimately became the cornerstone of navigation for European exploration.”
SOURCE:
Gharaibeh, Mohammad. Arab & Islamic Astronomy. From StarTeach Astronomy Education. 2007. Web.
11 Jul. 2014. ˂
Copernicus's heliocentric model, 1543
Copernicus's heliocentric model, diagram published in 1543 by Nicolaus Copernicus (1473-1543) in his book De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres). This model revolutionised astronomy, replacing the previous Earth-centred (geocentric) model. The diagram (labelled in Latin), shows concentric spheres around the Sun (centre). The outer, fixed sphere (I, the stars) surrounds rotating spheres (II-VII) for Saturn, Jupiter, Mars, Earth (and the Moon), Venus, and Mercury. Some of the planets have their orbital periods lebelled. This model still used the heavenly spheres of the Ancient Greeks. Later work showed the stars were much further away and that planetary orbits are ellipses, not circles.
[CREDIT: ROYAL ASTRONOMICAL SOCIETY/SCIENCE PHOTO LIBRARY / Universal Images Group, Rights Managed / For Education Use Only]
Ptolemaic cosmology
Historical artwork of the Earth-centred (geocentric) Ptolemaic cosmological model. This system is known through the Almagest of the Egyptian-Greek astronomer Ptolemy who lived in the 2nd century. This work summarized 500 years of Greek astronomy and this model of the heavens owes much to work by Hipparchus. The Moon, the Sun and the five known planets inhabited a series of perfect, Earth-centred, rotating spheres, ending in a sphere of stars. Later astronomers added more spheres to improve the model. However, inaccurate predictions led to it being overthrown by the 1543 Sun-centred (heliocentric) model of Copernicus. From Bilder Atlas by Johann Georg Heck, 1860.
[CREDIT: SHEILA TERRY/SCIENCE PHOTO LIBRARY / Universal Images Group, Rights Managed / For Education Use Only]
“How Islamic inventors changed the world”
…By the 9th century, many Muslim scholars took it for granted that the Earth was a sphere. The proof, said astronomer Ibn Hazm, "is that the Sun is always vertical to a particular spot on Earth". It was 500 years before that realisation dawned on Galileo. The calculations of Muslim astronomers were so accurate that in the 9th century they reckoned the Earth's circumference to be 40,253.4km - less than 200km out. The scholar al-Idrisi took a globe depicting the world to the court of King Roger of Sicily in 1139.
SOURCE:
Vallely, Paul. “How Islamic inventors changed the world.”The Independent,Sat. 11 Mar. 2006