Clockwork Universe

The Clockwork Universe (CCU)

Unit 2: The Cosmic Order and the Clockwork Universe (weeks 4-5)

Learning Objectives:

  • Describe the difference between a sun-centered model and an earth-centered.
  • List the assumptions and arguments that Copernicus used to support his model and refute the Ptolemaic one.
  • Evaluate the strengths and weaknesses of the Copernican model compared to the Ptolemaic one.
  • Describe the important geometric properties of ellipses and apply these to planetary orbits.
  • State Kepler’s three laws of planetary motion and apply them to appropriate astronomical situations.


Heliocentric Solar System Model

  • Copernicus’ model
  • Observations made by Tycho Brahe

Kepler’s Cosmic Harmonies (Basis of orbital mechanics)

  • Law of Ellipses
  • Law of equal areas
  • Harmonic Law

Galileo’s Cosmology

  • Classical mechanics
  • Observational astronomy with a telescope


  • 1st Law: Law of motion
  • 2nd Law: Force Law (F=ma)
  • 3rd Law: Reaction Law
  • Law of Gravity: F= G(m1m2)/rand escape velocity: v=SQRT(2GM/r)

Class Notes

Clockwork Universe

Newtonian Mechanics

Read Zeilik: Chapters 3 & 4

Unit 2 Exam Study Guide: Clockwork Universe

  1. Review all presentations.
  2. Review  the assigned reading: Chapters 3 & 4 in textbook  – or – online reading assignment.
  3. Be able to compare Geocentric and Heliocentric models for our solar system.
  4. What contributions did Ptolemy, Copernicus, Galileo, Newton, Tycho, and Kepler play in the determining how our solar system works.
  5. Understand what Newton’s Laws of Motion are and how they pertain to Astronomy.
  6. Understand what Kepler’s Laws of Planetary Motion and their ramifications.
  7. Describe Satellite Motion.
  8. Describe Parallax.
  9. Calculations for Newton’s 2nd Law, Kepler’s 2nd Law, Newton Law of Gravity, and Escape Velocity.

Online Homework

Useful websites: 

Star Chart of the Month

Sky at a Glance

In the Sky this Month

Scale of the Universe

Online Astronomy:

How to choose a good telescope