[The Month's Sky]
[History of Astronomy]
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[Astro History: Asian and Greek]
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A Brief History of AstronomyIndian and Arabic Astronomy(500 to 1200) |
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He also championed the use of the Indian number system working out the rules of arithmetic that would simplify calculation. His numbers arrived in Europe where they became known as Arabic Numerals.
Al-Battani also updates the figures for the Precession of the Equinoxes (54.5'' per year) and the tilt of the Earth's axis (23° 35').
His observations show that the Earth's distance to the Sun varies, putting a doubt on the idea of perfect circular orbits.
This is the first written mention of the object that would later be known as the Andromeda Galaxy.
His surveying techniques using triangulation allow him to measure the radius of the Earth as 6339.6 km, a value that would not be improved for 500 years.
He suggests that the velocity of light is immense compared to that of sound. He theorises that the appearance of the Milky Way is due to it being made up of countless stars, an assertion that would not be verified until the invention of the telescope 500 years later.
The (Christian) Catholic Church adopts Aristotle's cosmology. In the coming centuries, disagreement with this cosmology would become a heresy.
The model enlarges Aristotle's ideas of the corrupt Earth and the perfect heavens. The most corrupt part of the Universe is Hell which is situated in the centre of the Earth. Both Earth and Hell are imperfect and both are subject to change, corruption and decay. Man's Sin causes the corruption of the Earth. Above the Earth is the atmosphere. This is less subject to change but changes enough to produce the weather. Aurora, meteors and comets are also considered to be atmospheric phenomena.
The Moon being further from the Earth, changes less. It changes its phases and has a blotchy appearance but has the perfect circular motion of a celestial object. The Sun and planets come next. They don't change and also move in circles around the Earth. Most distant is the crystal sphere containing the stars. The stars are unchanging and eternal. God (the most perfect part of the Universe) is on the outside of this final crystal sphere. All heavenly motion is in circles (a perfect shape) or 'circles within circles'.
Dante, would later write about descending the nine circles to Hell and ascending the celestial spheres to God.
Based on Biblical chronologies, the Earth and the Universe were considered to be only a few thousand years old.
History of Science A large collection of resources looking at the history of astronomy, physics, chemistry and mathematics.