Copernican Revolution

• Aristarchus of Samos


  Presented the first known heliocentric model that placed the Sun at the center of the known universe.
• Aristarchus of Samos found out that the sun was very large, and this inspired him to suggest that the sun was a more likely the pivot point for a movement of the universe.
• Nicole Oresme (French Philosopher)

  • In his work, Book of the Heavens and the Earth (1377), he demonstrated the lack of real proof that the Earth was static and argued that there was no reason to think that it was not in motion.
  • From astronomical considerations, he maintained that if the Earth were moving and not the celestial spheres, all the movements that we see in the heavens that are computed by the astronomers would appear exactly the same as if the spheres were rotating around the Earth.
• Nicolaus Copernicus (The Problem of Geocentrism)


  The paths of planetary orbits, the heavens do not always appear to move in perfect, uninterrupted circles as they sometimes seem to move backwards (a.k.a. retrogradations). Astronomers account for these irregularities by adding smaller circular orbits(epicycles) that spun off the main orbits. By the 1500's, the model of the universe had some 80 epicycles attached to ten crystalline spheres (one for the moon, sun, each of the five known planets, the totality of the stars, a sphere to move the other spheres, and heaven)
• Copernicus' Solution (The Problem of Geocentrism)


  By placing the sun at the center of the universe and having the earth orbit it, he reduced the unwieldy number of epicycles from 80 to 34.
• Concerning the Revolutions of the Celestial Words (Copernicus, 1543)
• Tycho Brahe (1546 - 1601)


  (1) Danish Astronomer

  (2) Planets revolved around the sun, but the sun and the moon remained revolving around the globe, “Geo-heliocentric System” (3)using only the naked eye, tracked the entire orbits of various stars and planets.
• Johannes Kepler (1571 - 1630)


  (1) German Astronomer

  (2) He was the first to successfully use math to define the workings of the cosmos.
• The Laws of Planetary Motion

  (1) The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus. (The Law of Ellipses)

  (2) An imaginary line drawn from the center of the sun to the center of the planet sweeps out equal areas in equal intervals of time. (The Law of Equal Areas)

  3. The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun. (The Law of Harmonies)
• Galileo Galilei 


  (1) Italian scientist

  (2) saw four moons orbiting Jupiter.

  (3) The Starry Messenger (1611)
• Isaac Newton


  (1) realized that the same force pulling the apples to earth was keeping the moon in its orbit.

  (2) to prove this mathematically, Newton had to invent calculus for figuring out rates of motion and change.
• Claudius Ptolemy


  Stated that the planets, as well as the sun and the moon, moved in a circular motion around the Earth ~ “Geocentrism”.