CHAPTER 2_ Science of Life in the Universe.docx - CHAPTER...

CHAPTER 2: Science of Life in the Universe
Ancient Roots of Astronomy
○ sun rises in east & sets in west
○ stars move through sky in regular fashion - constellations in dif seasons
○ moon goes thru monthly series of phases
● ancients observed all of this - constructed observatories (Stonehenge, Mayans)
Planets Known in Ancient Times
● Mercury
○ difficult to see; always close to the Sun
● Venus
○ very bright when visible - morning or evening “star”
● Mars
○ noticeably red
● Jupiter
○ very bright
● Saturn
○ moderately bright
The Greeks
● Thayles
○ first natural explanation of the universe
● Plato & Aristotle
○ systemization of scientific thought
● Greeks laid foundation for modern science ~ trying to understand nature without
resorting to supernatural explanations (eg: sun moves bc of Apollo…)
● debate & test ideas - created models of nature
Geocentic Model
● Anaximander
○ stars move in circles around polar star
○ Haven isa spare around the Earth
○ Earth is not flat (his model: cylinder)
● Aristotle
○ shadow of Earth on the Moon - spherical earth
● Eratosthenes
○ measured circumference of the earth
○ stadia = 24901 miles
Ptolemy’s Geocentric Model
● earth is at the center
● sun orbits earth
● plants orbit on small circles whose centers orbit Earth on larger circles ~ small circles
around the planet while orbiting

○ the smaller circles = epicycles
● model was standard from AD 100 - 1500’s
~ most of the time we think earth is center of the universe
Retrograde Motion
● very difficult to explain in geocentric model
● easy to explain in heliocentric model
● like the sun, planets move eastwards towards sun
● but as we pass by them in our orbit, they move west relative to the stars for a few weeks
or months
● / noticeable over many nights; on a single night, a planet rises i east & sets in west…
Spread of Modern Science
● Hellenistic World
○ established by Alexander the Great tutored by Aristotle, who conquered the
largest empire of the time
○ Alexandria library: preeminent center of research for 700 years
■ founded by Ptolemy I
■ destroyed in later Roman Empire & finally by the Moslems
● Middle Ages & Modern Era
○ Islamic renaissance: -> Baghdad -> Cairo
○ European renaissance: -> Byzantine -> Italy -> Western Europe
○