Spring 2010

One must decide at the outset whether bodies have a natural movement or not, whether there is no natural but only constrained movement.

- Aristotle

Reading Assignment

Aristotle. 2003. The Physical Foundation for the Geocentric Universe. In The Tests of Time, edited by Lisa M. Dolling, Arthur F. Gianelli and Glenn N. Statile, 13-26. Princeton and Oxford: Prince-ton University Press. From Aristotle’s On the Heavens.

Instructor information

Kerry Kuehn, Ph.D. URL: http://faculty.wlc.edu/kuehnOff. (S133): 414.443.8850 Email: kerry.kuehn@wlc.eduLab. (S132): 414.443.8663 Office Hours: See online calendar.

Vocabulary Words

1. magnitude2. locomotion3. substance4. natural 5. eternal6. subsequent7. rectilinear8. curvilinear9. contiguous

10. lentiform11. oviform12. cogent13. acceleration14. retardation15. incorporeal16. perpetual17. contrary18. unequivocal

Preliminary comments

Aristotle has a strong interest in classification: he likes to classify types of objects, types of motion, and types shapes. For this reason, many beginners find reading Aristotle to be somewhat diffi-cult. Try not to get overwhelmed; the difficulty is largely because his classification schemes are often unlike the ones we use today. For instance, he classifies all types of motion as either (i) straight, (ii) circular, or (iii) a combination of the two. Although scientists don’t usually classify motion like this today, there are good reasons for doing so. Try to enter Aristotle’s world. See if his arguments are reasonable; try to find weaknesses in his arguments. Is he right or wrong in his conclusions? Are you sure? If he is wrong, why is he wrong? Is it because of a wrong assumption that he is making, or is it because he has reasoned incorrectly from his assumptions? Studying Aristotle’s On the Heavens has two main benefits.

1. It will give you practice in analyzing both simple and complex arguments.

2. It will provide a framework for understanding subsequent theories of the universe. Ptolemy, Copernicus and Kepler created their planetary theories largely in response to Aristotle’s ideas. The better understanding you have of Aristotle, the more clearly you will understand their ideas.

Week 1: The heavens and the earth

Concepts in Physics - Spring 2010 1

Spring 2010

Questions

The following are discussion questions which we will be addressing in class this week. You should answer each of these, in essay format, for this week’s homework assignment. Each general question is followed by a number of sub-questions which you should consider so as to focus your essay.

1. According to Aristotle, out of what type of material are the heavenly objects made?

1.1. How does he classify types of motion?

1.2. How does he classify types of bodies?

1.3. What is the relationship between the type of body and its type motion? In particular, you should distinguish between natural motion and constrained motion.

1.4. What are the four types of bodily substances? On what grounds does he suggest the existence of a hitherto unknown type of bodily substance?

1.5. What type of motion is natural to this new substance? Why so?

1.6. On what grounds does he argue that the four substances are not eternal? How does he rely upon opposites, or contraries, in this argument?

2. What, according to Aristotle, is the shape of the heavens?

2.1. How does he classify plane figures?

2.2. What shape does he rank as the first, or of the highest priority? Why?

2.3. What is the relationship between the motion of the heavens and its shape?

2.4. Why does he say it cannot be egg shaped or lens shaped?

2.5. What does the shape of the earth have to do with the shape of the heavens?

3. Why, according to Aristotle, do the heavens move in the way that they do?

3.1. Are the motions of the heavens regular or irregular? Why?

3.2. What evidence does he provide that the heavens are unchangeable?

3.3. What reason does he provide for why animals decay, but the heavens do not?

3.4. Does Aristotle adopt a “that’s just the way it is” explanation for the motion of the heav-ens? Or does he seek a deeper explanation?

4. What, according to Aristotle, is the composition, shape and movement of the stars?

4.1. Of what are the stars made? Why does Aristotle believe this?

4.2. Why does Aristotle reject the possibility that both the stars and the sphere of the heav-ens are at rest?

Week 1: The Heavens and the Earth

Concepts in Physics - Spring 2010 2

Spring 2010

4.3. Why does he claim that the stars are fixed to the heavenly spheres, which in turn are in motion?

5. What, according to Aristotle, is the position, shape and motion of the earth?

5.1. What were the views of the Pythagoreans on the position of the earth? Does Aristotle agree with them?

5.2. What were the views of Xenophanes, of Thales and of Anaxagoras on the shape of the earth? Does Aristotle agree with any of them?

5.3. What is the “indifference theory” of Anaximander as to why the earth is motionless and at the center (of the world/universe)? Does Aristotle agree with Anaximander?

Week 1: The Heavens and the Earth

Concepts in Physics - Spring 2010 3