Modern

• What scientific theory did Nicolaus Copernicus adapt?

  Heliocentrism
• What does the heliocentric theory state about celestial objects?

  The motions of celestial objects can be explained without putting the Earth at rest in the center of the universe.
• What was the significance of Copernicus's work "Commentariolus"?


  It laid out a general framework for a model of the solar system based on heliocentrism.
• What are the seven postulates proposed by Copernicus in his heliocentric theory?


  1. No single center of orbits for all planets.
  2. Only the moon orbits the Earth.
  3. All planets, including Earth, orbit the sun.
  4. Stars are immeasurably far away.
  5. Stars appear to move due to Earth's rotation.
  6. The sun appears to move due to Earth's revolution.
  7. Retrograde motion is an optical illusion caused by Earth's motion.
• What principle did Copernicus believe in more than Ptolemy?

  The Principle of Uniform Circular Motion
• What did Copernicus object to in Ptolemy's model?

  The invention of the equant as a violation of the Principle of Uniform Circular Motion.
• What was Tycho Brahe's contribution to astronomy regarding stellar parallax?

  He expressed the idea that the position of stars should shift if the Earth revolves around the Sun.
• What was Tycho Brahe known for in terms of astronomical observations?

  He made the most accurate naked-eye astronomical observations in history.
• What did Tycho Brahe prove about comets and supernovae?

  They are celestial bodies.
• How did Tycho Brahe's observations challenge existing astronomical models?

  He found that existing tables were inaccurate and decided to take his own data.
• What significant event occurred in 1572 that Tycho Brahe observed?


  A new star appeared in the constellation of Cassiopeia.
• What was the title of Tycho Brahe's publication about the new star?

  De Stella Nova
• What did Tycho Brahe conclude about the new star's parallax?

  There was no measurable parallax, indicating it was farther than the moon.
• What did Tycho Brahe build on the island of Hven?

  A castle/observatory called Uraniborg.
• What was the significance of Tycho Brahe's observatory Uraniborg?

  It was the largest scientific enterprise of its time.
• What did Tycho Brahe's instruments measure?

  Celestrial positions with an accuracy of a couple minutes of arc.
• What happened to Tycho Brahe in 1597 regarding his observatory?

  The new king of Denmark ended his support of Uraniborg.
• What position did Tycho Brahe hold after moving to Prague?

  Imperial Mathematician to Emperor Rudolph II.
• What did Tycho Brahe propose in 1588 regarding the solar system?

  A hybrid model combining a stationary Earth with planets orbiting the Sun.
• What are the three basic laws of planetary motion derived by Johannes Kepler?

  1. The path of planets is elliptical (Law of Ellipses).
  2. Equal areas are swept out in equal time (Law of Equal Areas).
  3. The ratio of the squares of periods is equal to the ratio of the cubes of distances (Law of Harmonies).