"The Harmony of the Worlds"

(from Cosmos)

Video Pre-questions with Sample Answers

What is astrology? What do astronomers think of it?

According to Dr. Sagan, astrology (in this program presented as "modern" western newspaper-horoscope style astrology) is a superstition that where the planets are in the sky when you were born has strong influence on all aspects of your life. Astronomers think that this is completely wrong at best, and deceitful fraud at worst.

Why did ancient cultures "go to so much trouble to teach themselves astronomy"?

Timekeeping (daily, monthly, yearly and beyond) and ceremonial purposes are two very important aspects of most cultures' astronomical traditions and applications.

What did European religious leaders think of Copernicus's ideas?

The two dominant religions in Europe then were Roman Catholicism and Protestantism. Leaders of both Christian sects, believing in their own interpretations of the Bible's account of the origin of the world, believed that Copernicus's ideas were foolish.

What motivated Kepler to formulate his laws of planetary motion?

Kepler was educated in religious schools, and the very strong desire "to read the mind of God" that he developed as a child remained with him throughout his life. Also, he was fascinated with the precision and logic of geometry, which he viewed as a form of "God Himself". So what motivated all of Kepler's work (not just the pieces we call his laws of planetary motion) was an obsession with theology and geometry.

Why did Kepler need the data gathered by Tycho Brahe?

Kepler was trying to find a precise description of the changing positions of the planets as they move through the constellations. In order to do so, he needed the most precise measurements of planets' positions that he could obtain. The most accurate measurements available at the time were ones done by Tycho Brahe. In other words, Kepler needed a description of reality that was as accurate as possible in order to test his theories, and Tycho Brahe had the best stuff.

What are Kepler's laws of planetary motion?

They are descriptions of the shapes of the planets' orbits, how fast they move around the Sun at different places in their orbits, and how long they take to go around the Sun. See table 4-1 in Chapter 4 of your text for a good summary of the laws.

How did Kepler get his mother into trouble?

Kepler wrote a science fiction story called "The Dream", in which his characters travelled to the Moon. Since "rocket science" wasn't around in the early 1600's, he imagined that his characters got there by way of witches' spells. His mother was a troublesome woman, often suspected of being a witch. When Kepler's story came out, the local police used it as an excuse to arrest the old lady and throw her in jail. In other words, Kepler inadvertently caused his mother to be arrested on charges of witchcraft.