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The Copernican Principle, Part I

Page history last edited by Rashaad Barnett 15 years, 7 months ago

Summary of Today's Topic

 Influence of Scientific Revolution: The "Scientific Revolution" occurred between 1500 and 1700. It started with Copernicus and his ideas about removing the Earth from the center of the universe and instead placing the sun in the center and have the Earth revolve around it (among other things) and ended with Newton. The Scientific Revolution can be split into two halves. One being from 1500-1600 where there took place a "Renaissance Science". The other from 1600-1700 where there took place the deliberate effort to overturn all ancient scientific notions.

General Characteristics of Scientific Revolution:

  • Rejection of "common sense" theories of the world
  • Renewed emphasis of quantitative (mathematical) properties
  • Nature is equated with a Machine, made of atoms which produced natural phenomenons.
  • Appearance of new data (telescope, microscope, vacuum pump, the Americas)
  • Development of a new experimental method (the manipulation of nature, not just observations)
  • Abandonment of the search for demonstrative knowledge and ultimate causes


Implications of Copernicanism:

  • The universe is much larger than perviously thought
  • The Earth is simply a planet
  • Stars are suns, possibly with planets circling them
  • A new version of Principle of Plenitude (distinctly theological)- it was a waste of God's power if he didn't fill the big universe with something
  • The "Copernican Principle"- all areas of space are more or less like all other areas of space- they are all roughly equal, and the universe operates in a heliocentric system.



  • Came up with "new physics," that were compatible with a moving earth
  • One of the first to use a high resolution telescope
  • Looked at moon discovering "mountains and valleys," and looked at the sun discovering sunspots and realized that they moved, and as such, the sun moved.
  • Discovered 4 moons of Jupiter which allowed him to say that the universe could have multiple centers: the Earth could be a center with it's moon, Jupiter with it's moons and the Sun with the encircling plants.
  • Even upon his deathbed, Galileo refused to truly renounce his beliefs, despite pressures from the Catholic church to do otherwise.



  • Advocate for Copernican system
  • Universe is infinite
  • Earth is simple just one of the planets
  • The fixed stars are actually suns like our sun
    • They have motion but are so far away that they appear "fixed"  
  • Denies Aristotle's hierarchy of elements
  • If you accept the idea that the sun has motion then you deny that the stars are "fixed"     


Johannes Kepler:

  • Wrote a letter to Galileo about primarily the moons of Jupiter, in favor of life on Jupiter    
  • Disagrees with Bruno that there are infinite worlds; Believes there is a center of the universe (the sun)
  • Interested in purpose (teleology) of why Jupiter has four moons and why Earth is the third rock from the sun

Primary Sources



Key Terms, Definitions, and People


Aristotle - believer in geocentrism and the fifth element (quintessence).


Ptolemy - developed the mathmatical application of the geocentric idea. He also used an eliptical model to show the retrogradation of the planets.

             - eccentric circle - explained various motions of the sun


Copernicus - rewrites Ptolemy, swapping the earth and the sun (heliocentrism). His method was similar to those of ancient astronomers like Ptolemy in that his evidence for a heliocentric universe was entirely mathematical, with no observational evidence to support it. 


Copernicanism- ideas based on a copernican system


Tycho Brahe- One of the most prominent naked-eye observational astronomers, espoused a form of geocentricism which placed the sun orbiting the earth, but the rest of the planets orbiting the sun


Johannes Kepler-  The successor to Brahe, claimed that God was a geometrist because of the way that all of the planets fit into the solar system. Kepler also developed the idea of planets traveling in elipses rather than the commonly believed circular orbits as his first law of motion.


Epicycles- A concept invented by Ancient Greeks astronomers to explain retrograde motion, a phenomenon in which the planets appear to be rotating irregularly and sometimes "backward" around the Earth, instead of in a predictable circular motion. Epicycles are smaller circular orbits a planet makes around a center, while simulaneously moving in a larger orbit around the Earth, thus explaining why sometimes planets seem to be moving in the opposite direction.



Relevant Links


The First Telescopes


The Start of Scientific Cosmology - Galileo, Tycho Brahe, Kepler


The Copernican Model: A Sun-Centered Solar System

Comments (1)

Peter Ramberg said

at 8:26 am on Sep 4, 2008

It's okay to use bullet points occasionally, but most of this should be written out like an essay.

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