Search for Life in the Universe

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Search for Life in the Universe

• Chapter 2
• Science of Life in the Universe
• (Part 1)

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Ancient Astronomy

• Ancient Roots
• Greek Setting
• Geocentric Model
• Planetary Motions
• Spread of Modern Science

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Ancient Roots

• Practical need to predict
• Sun understand seasons
• Moon understand tides
• China, Babylon, Mayans
• Descriptive astronomy
• Find regularities ? prediction
• Religious explanation astrology
• Greece
• First secular explanation

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Greek Setting

• Thayles (c. 624?546 BC)
• First natural explanation of the universe
• Plato (427?347 BC) Aristotle (384?322 BC)
• Systematization of scientific thought
• Greek Science
• Reason, debate and challenge
• Formal geometry ? scientific deduction
• Observations ? scientific induction
• Scientific model

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Geocentric Model

• Anaximander (610?c. 547 BC)
• Stars move in circles around polar star
• Heaven is a sphere around the Earth
• Earth is not flat (his model cylinder)
• Aristotle (384?322 BC)
• Shadow of the Earth on the Moon ? spherical Earth
• Eratosthenes (c. 276?c. 196 BC)
• Measured the circumference of the Earth

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Planetary Motions

• Nonuniform rotation of the planets
• Incompatible with simple geocentric model
• Retrograde motion
• Difficult to understand in geocentric model
• Easy to understand in heliocentric model
• Ptolemy (c. 100?170 AD)
• Epicycles explain retrograde motion within
  observational errors of the time

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Spread of Modern Science

• Hellenistic World
• Established by Alexander the Great (356?323 BC),
  tutored by Aristotle, who conquered the largest
  empire of the time
• Alexandria library preeminent center of research
  for 700 years
• Founded by Ptolemy I of Egypt (c. 367?c. 283 BC)
• At its peak, contained nearly 500,000 volumes, or
  rolls
• Destroyed in later Roman Empire, and finally by
  the Moslems
• Middle Ages and Modern Era
• Islamic renaissance ? Baghdad ? Cairo
• European renaissance ? Byzantium ? Italy ?
  Western Europe
• Printing revolutionized the spread of
  information
• Copernican revolution ? Modern astronomy and
  physics
• Modern physics relativity theory quantum
  mechanics ? modern technology
• Modern communications Radio, TV, Xerox, Internet