Download Ancient Astronomy: Geocentric to Heliocentric and more Study notes Astronomy in PDF only on Docsity! 1 Gravity and Motion The Early History of Astronomy 2 Topics Introduction Geocentric Astronomy Summary 5 Geocentric Astronomy 4000 BC – 700 AD 6 Origins of Astronomy 4000 – 500 BC Chaldean, Babylonian, Egyptian, Chinese, Indian, ... Grouped stars into constellations. Babylonians divided circumference into 360 degrees; 1 degree into 60 minutes; 1 minute into 60 seconds. Believed stars controlled human destiny. 7 10 Greek Astronomy – II 560 – 480 BC Pythagoras of Samos Discovered relationship between rational numbers and musical intervals. The goal of the Philosophos, the Lover of Wisdom, was to discover rules of Nature through deep reflection. Decided upon spiritual grounds that the Earth was spherical – the perfect shape. 11 Greek Astronomy – III 428 – 348 BC Plato Space is infinite and contains a finite, spherical, universe at the center of which lies the Earth. The visible world is but a distorted copy of the real world of Ideas. Pythagorean program abandoned. The shape of the Earth must be a sphere and all heavenly motion must be circular. 12 Greek Astronomy – IV 384 - 322 BC Aristotle Joined Plato's Academy in 367 BC. Tutored young prince who would become Alexander the Great, the founder of the city of Alexandria in 332 BC. Like Pythagoras, Aristotle believed that mathematics was the key to a true understanding of Nature. Promoted idea of circular motion into a dogma of astronomy along with geocentrism. 15 Greek Astronomy – VI 276 - 194 BC Eratosthenes of Alexandria Determined circumference of the Earth. At the Summer Solstice the Sun is vertical at Syene but at Alexandria it is 7.25 degrees south of the vertical. Alexandria N S Syene Paraetonium 0
300 KM ~ 500 MO
map prepared by Ed Stephan
17 The Circumference of the Earth A A Sunlight Alexandria Syene A = 7.5o D = 500 miles C = Circumference D C / D = 360 / A C = D * 360 / A = 500*360 / 7.5 = 24,000 miles Center of the Earth Shadow Planets: The Vagabond Stars
© 2004 Thomson/Brooks Cole
Retrograde Motion
Prograde Motion
The Ptolemaic System
Epicycle _- Deferent L\ “
) em,
’ Path of the planet
x Planet
“ ee ERY
Earth € 4 ¢ — ® Equant Center >
of
~» Center of (|
deferent | 1)
Epicycle / Ks
Deferent MY
lA B
© 2004 Thomson/Brooks Cole.
deferent
21
22 Descent into Darkness 642 AD Fall of Alexandria After a 14-month siege by Arabian troops, Alexandria was all but destroyed. The great library was razed to the ground. Dark Ages (700 AD – 1400 AD) The West enters a period of stagnation. Greek astronomy passed on to the Arabs, via India. This knowledge is preserved and extended by Islamic scholars in Baghdad.
