Quiz 2 Answers (Chapters 2 and 3)

1. How did Copernicus, Tycho, and Kepler challenge the Earth centered model?
2. What are Kepler's three laws of planetary motion?
3. How did Galileo solidify the Copernican revolution?
4. How can we distinguish science from nonscience?
5. What is a scientific theory?
6. What does the universe look like from Earth?
7. Why was planetary motion so hard to explain?
8. Why did the ancient Greeks reject the real explanation for planetary motion?
9. In what ways do all humans use scientific thinking?
10. How did astronomical observations benefit ancient societies?

1. Copernicus created a Sun-centered model; Tycho provided the data needed to improve this model; Kepler found a model that fits Tycho's data.

2.  1. The orbit of each planet is an ellipse with the Sun at one focus.

     2. As a planet moves around its orbit it sweeps out equal areas in equal times.

     3. More distant planets orbit the Sun at slower average speed: 

3. His experiments and observations overcame the remaining objections to the Sun-centered solar system.

4.  Science: seeks explanations that rely solely on natural causes; progresses through the creation and testing of models of nature; models must make testable predictions

5.  A model that explains a wide variety of observations in terms of a few general principles and that has survived repeated and varied testing.

6. -- We can see over 2000 stars and the Milky Way with our naked eyes, and each position in the sky belongs to one of 88 constellations.

  -- We can specify the position of an object in the local sky by its altitude above the horizon and its direction along the horizon.

7. Like the Sun and Moon, planets usually drift eastward relative to the stars from night to night; but sometimes, for a few weeks or few months, a planet turns westward in its apparent retrograde motion.

8. Most Greeks concluded that Earth must be stationary, because they thought the stars could not be so far away as to make parallax undetectable.

9. Scientific thinking involves the same type of trial-and-error thinking that we use in our every day lives, but in a carefully organized way.

10. Keeping track of time and seasons; navigation.