1 Gravity and Motion The Early History of Astronomy.
-
Upload
angelica-holt -
Category
Documents
-
view
221 -
download
0
Transcript of 1 Gravity and Motion The Early History of Astronomy.
1
Gravity and MotionGravity and Motion
The Early History of Astronomy
2
TopicsTopics
Introduction Geocentric Astronomy Summary
3
IntroductionIntroduction
4
5
Geocentric AstronomyGeocentric Astronomy
4000 BC – 700 AD
6
Origins of AstronomyOrigins 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
8
http://plato-dialogues.org/tools/gk_wrld.htm
Ancient GreeceAncient Greece
9
Greek AstronomyGreek Astronomy
624 - 548 BC Thales Founded Ionian School of Philosophers. Declared universe is understandable in terms
of simple rules. Rejected superstition. Earth floats in a vast ocean.
610 - 547 BC Anaximander Earth isolated, and unsupported, in space.
10
Greek Astronomy – IIGreek Astronomy – II
560 – 480 BC Pythagoras of Samos Discovered relationship between rational rational
numbersnumbers and musical intervalsmusical intervals. The goal of the PhilosophosPhilosophos, 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 – IIIGreek 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 spheresphere and all heavenly motion must be circularcircular.
12
Greek Astronomy – IVGreek Astronomy – IV
384 - 322 BC Aristotle Joined Plato's Academy in 367 BC. Tutored young prince who would become
Alexander the GreatAlexander 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 motioncircular motion into a dogma of astronomy along with geocentrismgeocentrism..
13
14
Greek Astronomy – VGreek Astronomy – V
310 BC Aristarchus of Samos Last of the great Pythagoreans. Developed a heliocentric modelheliocentric model. Alas his ideas all but died with him. This model re-discovered by Copernicus 17
centuries later.
15
Greek Astronomy – VIGreek 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 degrees7.25 degrees south of the vertical.
Alexandria Syene
N S
16
http://www.geocities.com/Athens/Forum/8740/Alexander.htm
17
The Circumference of the EarthThe Circumference of the Earth
A
ASunlightSunlight
AlexandriaAlexandria
SyeneSyene
A = 7.5o
D = 500 milesC = Circumference
DC / D = 360 / A
C = D * 360 / A= 500*360 / 7.5= 24,000 miles
Center of the Earth
Shadow
18
End of Greek AstronomyEnd of Greek Astronomy
190 – 120 BC Hipparchus The greatest astronomer of antiquity. From his precise observations he became
convinced that Aristotle was wrong about circular motion.
Created a more accurate model of planetary motion in which he introduced epicyclesepicycles into the geocentricgeocentric model.
Became the accepted model of the universe for the next 1600 years1600 years!
19
The Empire of RomeThe Empire of Rome
47 BC – 30 AD Roman Empire at its height Era of Cleopatra, Julius Caesar and Mark
Anthony. Era of Jesus of Nazareth. Roman conquest of the Middle East.
100 - 170 AD Claudius Ptolemeus (Ptolemy) Wrote great textbook: The AlmagestThe Almagest
summarizing Greek astronomy and his own astronomical theories.
20
Planets: The Vagabond StarsPlanets: The Vagabond Stars
Prograde Motion
Retrograde Motion
21
The Ptolemaic SystemThe Ptolemaic System
22
Descent into DarknessDescent 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.
23
Period of Western history characterized by terror and despair, in populations oppressed, famished, and wretched to a degree almost unimaginable today. To the miseries of constant war, political and social disintegration, there was added the dreadful affliction of inescapable, mysterious, and deadly disease. Mankind stood helpless as though trapped in a world of terror and peril against which there was no defense.
The Sleepwalkers by Arthur Koestler
The Dark AgesThe Dark Ages
24
The Great Re-AwakeningThe Great Re-Awakening
760 AD Islamic leaders in Baghdad sponsored
translations of old Greek texts.
1000 AD The Islamic empire spreads to Spain. Greek-Arabian science enters the West.
1400 AD Gradually, the West awakens from its long
dark sleep.
25
SummarySummary
4000 BC ~ 500 BC The earliest ideas about astronomyastronomy grew from
astrologyastrology, the superstitious belief in the influence of stars on human affairs.
600 BC ~ 100 BC Abandonment of superstition and embrace of
reason. Golden age of ancient Greece
100 BC ~ 200 AD Consolidation of ancient Greek astronomy