CoursesCourse 3
The cosmos before Newton
For two thousand years, educated people lived in a small, snug universe: the earth at the center, perfect heavens turning around it, everything in its natural place. This course traces how people climbed from myth to that cosmos, and how careful measurement finally broke it apart.
Start lesson 1Lessons
- 1 What physics wantsFrom a flood myth to a flood found in the rocks: what makes an explanation scientific, and why physicists keep hunting for simpler laws.
- 2 Everything in its placeThe first philosophers traded gods for causes. Aristotle built from them a cosmos so complete, and so close to everyday experience, that it lasted two thousand years.
- 3 Moving the sun to the centerWhy the planets seem to loop backward, how Ptolemy explained it with circles on circles, and what Copernicus changed, and didn’t.
- 4 Eight minutes of arcA tiny error in the best measurements ever made forced Kepler to give up the perfect circle, and the classical cosmos fell with it.
You’ll be able to
- Explain what makes an explanation scientific by this course’s three-part test: it explains, it can be repeated, and above all it predicts.
- Describe Aristotle’s cosmos, from the four elements and their natural places to the perfect circles of the heavens, and why it felt right for two thousand years.
- Compare how Ptolemy and Copernicus accounted for the planets’ backward loops, and what each was really arguing about.
- Show how Tycho Brahe’s measurements, Galileo’s telescope, and Kepler’s ellipses ended the classical cosmos.
About this course
This course follows 古典宇宙观 (The Classical View of the Cosmos), from the first myths about the sky to the ellipses that ended the classical cosmos. It is the first of four courses on physics, and the story continues in Courses 4 to 6.
The central argument and examples lead. Around them we add background for readers outside China, the views of historians where they differ, and hands-on activities. Where a reading is interpretive or contested, we say so.