Unit 3

Astronomy and Ancient Civilizations

Agriculture is the key…

�Agriculture is the key to modern civilization

�Without agriculture

�Still hunting and gathering

�No large societies

�No governments

�No cities, factories, technology…

Astronomy allowed prediction of seasons

�People noticed that the sun rose in certain star

patterns at certain times of the year

Astronomy is the key to agriculture

�Astronomy allowed for the prediction of seasons

�Ability to predict seasons allowed agriculture to replace hunting and gathering

Astronomy

Therefore

�Astronomy is the key to modern civilization

Astronomy and ancient cultures

�Ancient cultures had commonalities with astronomy

�Religion

�Navigation

�Time-keeping

Time keeping

�Determining the dates of the solstices and equinoxes was key to early agriculture

�Allowed prediction of seasons

�Allowed for planning of planting and harvesting

�Could determine holidays

Solstices and Equinoxes

Ancient calendars

�Were big structures to monitor the path of the sun and other bodies

Stonehenge

�Ancient stone structure in England

�Used to

�Determine exact day of summer and winter

solstice

�Track path of sun throughout the year

Machu Pichu

� Incan city, believed to be estate of the emperor

�Solar observatory / Sun temple

Stone Calendars

�These sites were built to track the date (calendars)

�Why stone?

�Permanence

�Accuracy

Later calendars…

�By the time of the Greeks, mechanical calendars and calculators were being built

�Used for navigation and astrology

Antikythera Mechanism�Discovered in 1901in an ancient shipwreck

�Built around 150-100 BCE

�Could calculate position of moon, planets and stars for a given date

Chinese contributions�Left detailed records of stellar observations

�Still studied today

�More complete than Western records

Star Catalogs

�An ordered listing of astronomical objects

�Chinese and other ancient civilizations

Babylonian Contributions

�Named many zodiac constellations

Greek Contributions

�Models of the solar system

�Names of many constellations

�Use of mathematics in astronomy

Orbits of the planets

� Planets closer to

Sun than Earth:

� Inferior orbits

� Planets further from

Sun than Earth:

�Superior orbits

Figuring out that Earth is round

�Things going away disappear from bottom up

�Observing shadow of Earth eclipsing the moon

�Stars in North were more overhead when travelling North, less overhead when travelling South

Eratosthenes

�Determined the size of the Earth

Calculating the Earth's Circumference

Heliocentric system

�Sun centered

�First proposed by Aristarchus

Geocentric system

�Earth centered

�Proposed by Aristotle

Prograde Motion

�moving in the same direction as everything else

Retrograde Motion

�moving in the opposite direction to something else

The motion of Mars

Ptolemy

�Proposed a workable geocentric solar system

The Ptolemaic Solar System

Defferents

Epicycles

Why was Ptolemy accepted

�Could prove it mathematically

�Church said it was so