Astronomy in World History

Neolithic period

Period: 10,000 BCE to 2200 BCE

• moved from nomadic to agrarian societies, increased importance of the solar year
• large scale observation sites often appear with settlements
• religion and astronomy brought together in rituals

Sumer

Period: 5500 BCE to 1800 BCE

Goseck circle

Period: 4900 BCE to 4700 BCE

Stonehenge

Period: 3100 BCE to 1600 BCE

• stones exist for billions of years and transcend humanity
• trees tend to live longer than us, but stones (and stars) appear to live forever
• may have been many “treehenges” around stonehenge
• stones are used to transcend current life/generations
• thus stonehenge may have been primarily a place to connect with the dead
• likely that it had multiple purposes

alignments:
- confirmation bias
- same alignments in multiple sites in the same culture/area
- some kind of functional purpose

First/Old Babylonian Empire

Period: 1894 BCE to 1595 BCE

• early civilisations marked by the development of social structures
• ramifications of making astronomical observations central
• establishing and maintaining order, calendars and timekeeping
• expertise framed within religious context
• celestial bodies divine in nature
  • thus celestial movements seen as movements of deities
• ‘cosmological congruence’ between astronomical and religious thought
• social functions of belief systems (e.g. controlling market price by predicting market price)

Nebra Sky Disc

Period: 1800 BCE to 1600 BCE

• features a crescent moon, a full moon or sun, pliedies
  • definitely features stars - therefore earliest known depiction of stars
  • curves that match the difference between solstice sunsets at its latitude
• three layers of the disk
  • had been manipulated a few times
• disk found in central Germany
  • copper and tin from Austria
  • gold from mine in Cornwall (or Romania)
  • this distribution of materials suggests a complex trading network

Pre-Socratic Greek philosophy

Period: 600 BCE to 400 BCE

'young, wild days'

Confucius

Period: 551 BCE to 479 BCE

Greek classical period

Period: 510 BCE to 323 BCE

Plato and Aristotle, Athens based

Plato

Period: 425 BCE to 348 BCE

• ideas/forms & phenomena
  • what is reality?
  • true reality vs what we see as a reflection of it
  • world of forms vs world of phenomena
• ‘saving the phenomena’ - attributing appearances to underlying causes
• the “harmony of the spheres” - celestial motion circular
• in order to have time, planets must move in different circles to create differentiation in time
• astronomy important as the one place where forms can be observed
  • celestial motion followed perfect, circular forms

Aristotle

Period: 384 BCE to 322 BCE

• task of explaining the causes of everything
  • astronomy to be incorporated into that philosophical system, not final end to be explained
• motion understood as change or transformation from potential to actual state
• either straight line or circular motion
• all motion must be directed to/from/around the centre of the universe
  • earth: up and down (gravity)
  • sky: in circles
• prime mover: being that can produce & thus initiates all motion in the universe without being moved itself

Timaeus published (Plato)

360 BCE

Greek Helenistic/Alexandrian period

Period: 323 BCE to 31 BCE

• Euclid to Ptolemy
• Alexandria based (with other contributions)
• major developments of greek astronomy

Aristarchus

Period: 310 BCE to 230 BCE

• calculated relative distances between earth, sun and moon
• calculated relative size of sun and earth
• proposed a heliocentric system (was laughed at)
• greek astronomy focused on geocentrial models of the universe
• Aristarchus’s heliocentric theories apparently not taken seriously
  • when you move the earth out the centre of the universe, you have to explain things like gravity/why things fall down
  • his only real evidence was that the sun is bigger than the Earth

Euclid's Elements published

300 BCE

• Euclid
  • wrote a book called the elements
    • very influential
    • used until the 20th century (?) as a maths textbook
• geometry important before Euclid
• with Euclid central role in greek understanding of the world
  • spatial thinking in Euclidean terms
• development of new mathematical methods
  • proofs and techniques

Euclid

Period: 300 BCE to 270 BCE

Eratosthenes

Period: 276 BCE to 195 BCE

• used the difference in height of the sun at the summer solstice at different latitudes to determine the size of the Earth
  • calculated 20,000 - 16,000 km, (depending on how units are converted)

Antikythera Mechanism

Period: 200 BCE to 60 BCE

Ptolemy

Period: 100 to 170

• various mathematical techniques to calculate motions that fit observations and use circles
  • epicycles
  • excenters
  • equants
• combined the different techniques and built a planetary system that worked/fit all of the observational data

Medieval period

Period: 500 to 1500

Muhammad

Period: 570 to 632

Bayt al Hikma founded (Baghdad)

820

• founded by the Caliph al-Ma’mum (9th century)
• central institution for learning in the caliphate
• collection of manuscripts from all parts of the empire and neighbouring states
• Greece, Egypt, Persia, India, Mesopotamia - translation of texts into Arabic (inc. ptolemy and aristotle)
• strong interest in ‘foreign sciences’
• knowledge of texts enabled access to higher positions in society

al-Biruni

Period: 973 to 1048

• central asian philosopher, astronomer and mathematician
• various astronomical works
• precision measurements of the size of the earth
  • correct within 1%

University of Bologna founded (first university)

1088

• right to universities of self-governance
• 4 faculties: arts (inc. science), medicine, law and theology
• First 2 years studies of the seven liberal arts:
  • Grammar, dialectic (i.e. logic), rhetoric (the ‘trivium’)
  • Arithmetic, geometry, astronomy and music (the ‘quadrivium’)
• Third year studies of philosophy
  • Focus of philosophical studies dependent on planned higher degree
• Subsequently higher degree study in theology, law or medicine
• astronomy stronger outside universities

Maimonides

Period: 1135 to 1204

Maimonides criterion
- Argument: there can be no contradiction between two truths
- scripture is always correct but we might not understand it correctly
- Criterion:
- if there is proof that "contradicts" scripture, believe proof and asses our understanding of scripture
- if there is not full proof, then believe scripture

University of Paris founded

1150

• prohibitions to teach Aristotelian philosophy in 1210, 1215, 1231, and again in 1277
• Aristotle was popular, and prohibitions did not really work
• 1277: Bishop Etienne Tempier prohibited the teaching of 219 Aristotelian ideas specifically
  • bishop of Paris was also chancellor of the university

Nasir al-Tusi

Period: 1201 to 1274

• first director of the observatory in Maragha (Persia)
• concerned with developing methods to relate all kinds of motion to circular movements
• developed the Tusi couple as a way to reduce linear motion to two circles moving in opposite directions

Observatory of Maragha founded

1259

• located in northwest Persia
• first large observatory in Islamic world
• founded in 1259 by Mongolian ruler Hulagu Khan (related to Genghis Khan)
• First director Nasir al-Tusi
• Participation of Chinese astronomers and Indian astronomers
• first large scale observatory in islamic world
  • too many different observations - needed a consistent model/method

Renaissance period

Period: 1300 to 1800

• a different culture of learning
  • urban centres and societies
  • focussed around the wealthy elites
  • self-fashioning and rhetoric
    • expectations to praise oneself extravagantly
• the focus on the ancient world
  • renaissance thought of the medieval world as worthless, rather valued the ancient world and aimed to refashion the ancient world to make it better
• the rise of critical thinking
  • edited/revised ancient texts
  • aim to review and make better

Jean Buridan

Period: 1301 to 1358

• 14th century philosopher and theologian based at the uni of paris
• work on the Aristotelian concept of motion, cosmological studies in this concept
• Combined Ptolematic system and Aristotelian cosmology

On the rotation of the Earth:
- no solution by observation as motion is always relative
- analogy of two moving ships
- theological arguments in favour of rotating earth
- physical arguments in favour of rotating celestial sphere:
- falling stones are not dragged towards one side

Ibn al-Shatir

Period: 1304 to 1375

• redefinition of celestial spheres
• parts of the sphere of fixed stars shine, other parts don’t
  • celestial spheres must have an internal structure, possibly caused by different elements
• criteria what could be part of such an internal structure
  • Epicycles and Tusi couples could, eccentrics and equants could not
• development of a planetary system according to these criteria
  • many of his ideas adopted by Copernicus (however unlikely that Copernicus knew about all of his work)

Nicole Oresme

Period: 1325 to 1382

• 14th century philosopher and theologian at the uni of Paris

Extrapolation/response to Buridan:
- ‘falling stone’ argument not valid: air could be dragged along the rotating earth
- ships cabin vs deck
- theological argument still in favour of rotating earth
- physical function for precession of the equinoxes
- final verdict
- rotation of earth probably, but not proven
- Maimonides criterion:
- if not proven, believe the scripture

Ming Dynasty

Period: 1368 to 1644

• celestial/divine influence basic premise of astrological thinking
• chinese emperor as 'son of heaven'
• astronomy as a bureaucratic exercise done by bureaucrats, who monitored and recorded the sky looking for changes
• meticulous record keeping
• clear tasks to be fulfilled (calendar making, observing abnormalities, etc.)
• production of star catalogues and star maps central task (ensure heavens are as predicted)
• importance of “guest stars” (comets, supernovae)

Printing press invented

1436

• allowed texts to be reproduced
• allowed astronomers to gain knowledge of data
  • e.g. Copernicus was able to buy the data he used in a way that he would not have been able to do fifty years prior

Nicolaus Copernicus

Period: 1473 to 1543

copernician system
- sun in the centre
- all planets including the earth revolve around the sun
- in detailed system epicycles and eccentric motion still exist
- each planet with its own centre of eccentric cycles arguments for:
- Slightly simpler (23 instead of 27 epicycles)
- No larger epicycles
- No equant
- Intrinsic harmony arguments against:
- Contradicted Aristotelian philosophy
- No explanation for gravity
- and didn’t care about this

Copernicus's Commentariolus (Nicolai Copernici de hypothesibus motuum coelestium a se constitutis commentariolus)

1514

outline of heliocentric theory, published anonymously
- no one centre of all celestial circles and spheres
- Earth's centre is not the centre of the universe, but only of gravity and of the moon’s orbit.
- planets revolve around the sun, the centre of the universe.
- earth-sun distance imperceptible compared to earth-star distance
- rotation of Earth -> daily rotation of stars
- earth revolving around the sun -> annual cycle of movements of the sun
- motion of earth (pov) -> retrograde motion

'On the Revolutions of the Heavenly Spheres' published (Copernicus)

1543

Tycho Brahe

Period: 1546 to 1601

• Danish nobleman with astronomical interest
  • Use of astronomy for political and career purposes
• built an observatory and used the highest precision possible to get the best possible measurements

tycho’s system
- Sun, moon and fixed stars rotate around the earth
- All planets rotate around the Sun
- fixed stars ‘don’t move’ relative to us, therefore we don’t move either
- Earth as centre of universe

• first discovery of a new star in Europe
• Difficult to explain in classical theories

Galileo Galilei

Period: 1564 to 1642

• Mathematical philosopher
• became and remained supportive of the original Copernican system
• catholic
• heliocentric view, but no proof
• convicted of heresy

Johannes Kepler

Period: 1571 to 1630

• First and foremost an astronomer
• Early commitment to heliocentric system, grew stronger over the years
• Rejection of Copernican system in favour of ‘proper’ heliocentric astronomy
• Rejection of all three systems (ptolemaic, copernican, and tycho)
  • Copernican system the only one that Kepler could accept as true in principle
• proposed elliptical orbits (a last resort)

Rene Descartes

Period: 1596 to 1650

Issac Newton

Period: 1643 to 1727