History of Astronomy Notes

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History of Astronomy Notes
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Four Periods of Astronomy

• Prehistoric before 500 BC
• Classical 500 BC to 1400 AD
• Renaissance 1400 to 1650
• Modern 1650 to present

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Prehistoric Period

• People observed daily and seasonal motions of
  sun, moon stars
• Used stellar motion to keep time and determine
  distance
• Able to predict events like sunrise and sunset
• Developed constellations
• Stonehenge
• Built by ancient Britons on Salisbury Plains
• Marks seasonal rising setting points of the sun
• Worlds first clock and first observatory

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Classical Period

• Scientists Philosophers began to make
  measurements of the heavens.
• Constructed models to account for motions of
  heavenly bodies with the help of geometry
• First real scientists
• Ancient Greeks were first to try to explain the
  workings of the heavens using models and
  observations
• Limited to naked-eye observations.
• Numerous famous scientists from this period

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Classical Period Famous Scientists

• Pythagoras (560-489 BC)
• First to teach that the Earth was spherical
• Believed that the sphere was a perfect shape
• Gods would have used this shape to create Earth
• Aristotle (384 322 BC)
• Helped to prove Earth was a sphere
• Proved based on observations of lunar eclipses

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Classical Period Famous Scientists

• Eratosthenes (276 195 BC)
• Made first measurements of Earths size
• Obtained a value of 25,000 miles circumference
• True circumference 24,901.55
• Ptolemy
• Researched planetary motions
• Thought that each planet moved on one small
  circle, which moved on a larger one like a
  frisbee spinning on a bicycle wheel called
  epicycles
• Idea survived until the 1500s

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Reniassance Period

• Models re-assessed
• New models that took into account data-based
  observations
• Invention of telescope
• Heliocentric Model introduced

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Copernicus (1743-1543)

• Developed taught Heliocentric Model
• Described retrograde motion of the planets
• Calculated distance to planets
• Ideas werent accepted by the Catholic Church
  forced to stop teaching Heliocentric views

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Tycho Brahe (1546-1601)

• Born into nobility (Duke)
• Believed God placed planets in heavens to be used
  as signs to mankind of events on Earth
• Built tools to measure planetary motions
• In his model, all planets except Earth went
  around the Sun the Sun circled the Earth
• Last great astronomer to believe that Earth was
  center of universe

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Johannes Kepler (1571-1630)

• Brahes assistant
• Used precise info to show that Mars moved in an
  elliptical orbit
• Developed 3 Laws of Planetary Motion
• Planets move in elliptical orbits
• Planets speed always covers equal areas in equal
  time
• p2 a3 (p is the period of orbit and a is the
  longest distance from the Sun to the planet)
• Kepler is credited with coming up with the word
  satellite when he saw the moons of Jupiter.

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Galileo Galilei (1564-1642)

• Invented the telescope
• Believed taught Heliocentric theory
• Developed the scientific method
• Discovered craters mountains on moon, sunspots,
  4 moons of Jupiter, Saturns rings, phases of
  Venus
• Brought before the Holy Roman Inquisition and
  ordered to stop teaching his Heliocentric view
• Finally stopped teaching his views after being
  threatened with death
• Spent last 13 years of his life under house arrest

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Modern Period

• Scientists began to search for physical laws
  (like gravity)
• Major advanced in technology optics,
  electronics, computers
• Better mathematic techniques
• Astrophysics uses physical laws to understand
  the structure and workings of heavenly bodies

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Sir Isaac Newton (1642-1727)

• Greatest scientist of all time math, physics,
  astronomy
• Pioneered studies in motion, optics, and gravity
• Religious man wrote on theology as well as
  scientific matters
• 3 Laws of Motion

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