All Annotations of [Preview]

saved byJames Linzel on 2008-01-29

• Our view of the history of astronomy will now skip almost 1500 years to the next
  major advances in astronomy
• They had preserved and translated the
  Greek writings and adopted the Greek ideals of logic and rational inquiry. Islamic
  astronomers were careful observers of the sky and created accurate star catalogs
  and tables of planet motions. Many of the names of the bright stars in our sky
  have Arabic names (e.g., Deneb, Alberio, Aldebaran, Rigel to name a few).
• However,
  advances in the explanations of the motions of the stars and planets were
  made by astronomers in Europe starting in the 16th century.
• By the 16th century the following paradigm had developed: Man is God's
  special creation of the physical
  universe; the Earth is the center of a mathematically-planned universe and we
  are given the gift of reading this harmony.
• Scientists use a guiding principle called Occam's Razor to
  choose between two or more models that accurately explain the observations. This
  principle, named after the English philosopher, William
  of Occam, who stated this principle in the mid-1300's, says:
  the best model is the simplest one---the one requiring the fewest
  assumptions and modifications
  in order to fit the observations. Guided by Occam's Razor some scientists
  
  began to have serious doubts about Ptolemy's geocentric model in the early days
  of the Renaissance.
• During the years between Ptolemy and Copernicus, many small epicycles
  had been added to the main epicycles to make Ptolemy's model agree with the
  observations. By Copernicus' time, the numerous sub-epicycles and offsets had
  made the Ptolemaic model very complicated
• He
  adopted Aristarchus' heliocentric (Sun-centered) model because he felt that
  God should be at the center of the universe. Copernicus' model had the
  same accuracy as the revised Ptolemaic one but was more elegant.
• He found that the
  planets farther from the Sun move slower. The different speeds of the planets
  around the Sun provided a very simple explanation for the observed retrograde
  motion.

• 
  Retrograde motion is the projected position of a planet on the
  background stars as the Earth overtakes it (or is passed by, in the case of the
  inner planets). The figure below illustrates this. Retrograde motion is just an
  optical illusion! You see the
  same sort of effect when you pass a slower-moving truck on the highway. As you
  pass the truck, it appears to move backward with respect to the background
  trees and mountains. If you continue observing the truck, you will eventually see
  that the truck is moving forward with respect to the background scenery. The
  relative geometry of you and the other object determines what you see projected
  against some background.
  

  
  
• 
• Though Tycho's beliefs of the universe did not have that much of an effect on
  those who followed him, his exquisite observations came to play a key role in
  determining the true motion of the planets by Johannes Kepler. Tycho was
  one of the best observational astronomers who ever lived. Without using a
  telescope, Tycho was able to
  measure the positions of the planets to within a few arc minutes---a
  level of precision and accuracy that was at least ten times better than anyone
  had obtained before!