University of Maryland - Fall 2004
HIST 401
Study Questions for Topic 4
The Astronomical Revolution

For instructions see previous lists of study questions.

Note: "cosmic" means pertaining to the heliocentric/geocentric debate.

1. What is a nova (in astronomy)? How would you prove that it has no parallax? What was the cosmic significance of the fact that the novae of 1572 and 1604 had no parallax?
2. Summarize Galileo's discoveries about the Moon (presented in The Starry Messenger, 1610) and their cosmic significance.
3. How did Galileo's telescopic observations of planets and stars provide a response to the no-parallax critique of the heliocentric system? How did the discovery of "Medicean stars" tend to undermine the geocentric theory while answering an objection to Earth's motion?
4. How did Galileo's telescopic observations of Venus provide a "most decisive blow against the Ptolemaic system" (Cohen)?  Explain using diagrams.
5. * According to Cohen, Galileo's procedure in establishing the principle of uniformly accelerated motion for falling bodies differs from "the scientific method" which requires collecting many observations or performing a series of experiments, classifying the results, generalizing them, searching for a mathematical relation, and finding a law. Find 3 science textbooks (any science, any level) that include a statement about the method(s) used by scientists. Summarize those statements (with page references). Based on this limited sample, discuss whether Galileo's procedure or Cohen's "scientific method" is closer to the views of modern textbook writers.
6. Identify: Andreas Osiander. What is his significance in the philosophy of science?
7. In Two New Sciences Galileo says that the result of his experiment, rolling a ball down an inclined plane to test the hypothesis of uniformly accelerated motion, confirmed the hypothesis within "a tenth of a pulse beat." What independent evidence do we have that his account is reliable?
8. How did Galileo prove that a falling body is uniformly accelerated, at a time when scientific instruments were not available to make precise measurements of instantaneous speed and acceleration? What are two objections (one physical, one logical) that could be made in the 17th century to his proof?
9. Identify Stillman Drake. What was the discovery that Cohen calls one of the greatest historical discoveries about science in the 20th century, and what was its significance for our understanding of Galileo's work?
10. Discuss Galileo's work in physics, including the question of whether he obtained his results by accurate experiments or by logical reasoning, and his views on atomism and force.
11. Cohen devotes more than 15 pages to Galileo's work on uniformly accelerated motion (and its relation to the work of his predecessors). Why is this detailed analysis justified?
12. * According to Galileo, if a stone is dropped from a tower (whose height is very small compared to the radius of the Earth) its motion with respect to the fixed stars will be a parabola. Explain why this is correct, using two of his laws of motion.
13. What is Kepler's Second Law? How does it help to explain the unequal length of the seasons?
14. What is the cause of the motion of planets around the Sun, according to Kepler? How does this cause explain (qualitatively) both his 2nd and 3rd Laws?
15. How did Galileo refute the argument that "the Earth is at rest because if it were moving a stone dropped from a tower would not land at the base of the tower but some distance away, contrary to our observation that it always does fall at the base"? Did his argument prove that the Earth does move?
16. What are two reasons why Galileo ignored or rejected Kepler's work?
17. Why are there 6 planets, according to Kepler? How did he explain the relative sizes of their orbits? (It is not necessary to give the details of his theory.)
18. What is the Tychonic [or "Tychonian"] system? What are its advantages and disadvantages?
19. What reason did Copernicus give, in his Commentariolus, for rejecting the Ptolemaic theory?
20. * In Commentariolus Copernicus says the earth "revolves annually in a great circle about the sun in the order of the signs." What are these "signs" and what is their order? In which sign is the sun, as seen from the earth, at the Vernal Equinox in the year 1950? In which sign will it be seen in the year 2300? What is the reason for this change, and how does it undermine the validity of astrology?
21. One of Copernicus' assumptions in Commentiarolus is "... the distance from the earth to the sun is imperceptible in comparison with the height of the firmament." Explain why this assumption is necessary to avoid the theory being immediately refuted by observation.
22. In his description of the "third motion" of the earth in Commentariolus, Copernicus assumes that the poles of the earth would be expected to move in a circle around the axis of the plane of the ecliptic, during a period of "not quite a year," but states that this motion is counteracted by a "motion in declination" whose period is about the same. Because of the slight difference in periods of these two motions, over a long time the "inclination of the earth to the firmament" gradually changes. What is the name of this gradual effect, and how it is explained in the modern heliocentric theory? How is it related to the "coming of the Age of Aquarius"?
23. In his dedication of Revolutions to Pope Paul III, what did Copernicus give as his primary reason for developing a heliocentric theory?
24. Identify and explain two examples of Aristotelian concepts in Galileo's Assayer.
25. Was Galileo a philosopher as well as a scientist? Was he a "natural philosopher" as well as a mathematician? Discuss the views of Matthews, Dear, and Drake and defend your own view, using specific examples.
26. Try Galileo's "titillation" experiment. If it is true, as he claims, that you "feel almost intolerable titillation" when touched by a piece of paper or feather between the eyes, on the top of the nose, or under the nostrils, but not when touched somewhere else, how does this experience support the distinction between primary and secondary qualities?
27. What is heat, according to Galileo? Is it a primary or secondary quality? What evidence does he present to support this view?
28. How did Aristotle (as summarized by Simplicio) prove from his theory of natural motion that the earth cannot move in a circle?
29. What is the significance of shifting from "a search for causes" to "a search for laws"? Give an example of each.
30. * According to Salviati/Galileo the strongest reason why the earth doesn't move is that if it did, a rock dropped from a high tower would fall to the West of the base of the tower. Explain why (stating your assumptions). If, as Salviati estimates, a person standing on the ground in Italy would be carried a distance of 16,000 miles in 24 hours by the earth's rotation, calculate approximately (within 10%) how far the base of the tower would move if it takes 5 seconds for the rock to fall from the top of the tower to the ground (ignore the annual motion of the earth around the sun).
31. Galileo wrote that no one can ever attain a complete understanding of a single effect in nature; but someone who has experienced complete understanding of one single thing can appreciate how little he understands of other things. Explain this apparently-inconsistent pair of statements.
32. Why did Copernicanism appeal to Galileo, according to Dear?
33. How did Galileo prove that "sun spots" are actually blemishes on the Sun's surface, not separate bodies that move around the Sun? (Use a diagram.) How does this conclusion undermine Aristotelian philosophy?
34. No question.
35. * According to Salviati/Galileo, a "very ingenious argument" against the motion of the earth is that centrifugal force would hurl buildings into the sky. Calculate this force using Newtonian physics and find out how fast the earth must rotate (to 2 significant figures), compared to its present rate, for this to happen.
36. What language was normally used for scientific and scholarly books in Galileo's time? Why did he write most of his books in Italian?
37. What observation first led Galileo to doubt the Aristotelian view that larger (more massive) objects fall faster than smaller (lighter) ones?
38. Identify: Robert Bellarmine.
39. How did Galileo prove that the "new star" (supernova) of 1604 was in the heavens, not in the earth's atmosphere? What did this imply for Aristotelian natural philosophy?
40. * Formulate a hypothetical theory of acceleration based on the assumption a = dv/dx rather than a = dv/dt, and derive a formula for the distance traveled by a body starting from rest and uniformly accelerated, using calculus. Discuss the paradox encountered in this case, and show that a body decelerated uniformly from a finite speed would never come to a stop. Discuss Galileo's attempt to prove the impossibility of this kind of acceleration (see extract in Matthews, p. 82).
41. Why did Galileo state that a theory could never be exactly in agreement with observation despite his strong belief in the importance of exact mathematical derivations?
42. Some 20th-century historians of science have argued that Galileo's opponents were justified in refusing to accept the validity of his telescopic observations (showing that the moon is not a perfect sphere, etc.) because he could not prove "that anything seen through curved glasses" (but not visible to the naked eye) "exists anywhere except in those lenses"; moreover things that are visible to the naked eye sometimes look distorted through a lens. How did Galileo respond to that argument?
43. What was Galileo's "one well-known ordinary physical phenomenon" that can be explained if the earth moves? Suggest a simple qualitative argument to support this claim, assuming a gravitational attraction between the moon and water in the oceans.
44. What was the affidavit that Galileo obtained from Bellarmine in 1616, and how did it refute the major charge against him in the Trial of 1633?
45. According to Drake, the "societal authority" that suppressed Galileo's views was not Christianity but Aristotelianism. Discuss the arguments and evidence for and against that statement.
46. How did Galileo answer the question "What is the centre of the universe, and is the earth located there?"
47. Summarize the "continuity debate" on the relation between medieval and early modern science. How is it related to the decision to focus on global or disciplinary change? How (if ever) could the issue be settled?
48. Identify: Regiomontanus.
49. Identify: Andreas Vesalius.
50. Stillman Drake at several points departs from a factual account of history to express his own opinions about what science is or should be. Synthesize these comments to write a summary of his opinions, and discuss whether (in your opinion) their insertion into the book makes it better or worse.
51. Why did Copernicus attribute the idea of the Earth's motion to ancient scientists rather than claiming it as his own discovery?
52. Who was Archimedes? How did Italian engineers use him in the 16th century?
53. * On what page in Cohen's book is Plate I? What conclusion would you draw if (a) the cannon ball comes back down into the mouth of the cannon; (b) it comes back down and hits the earth several miles away from the cannon; (c) it never comes back down?
54. Identify: William Gilbert. How did he influence Kepler?
       [Dear 55, LN. English physician, wrote book on magnet (1600). Earth is a magnet, rotating around own axis.]
       [Dear 77, LN: Kepler used magnetic force to explain motion of planets around sun.]
55. * Read the article on Pierre Duhem in the Dictionary of Scientific Biography, review the references to him in Lindberg's book, then write an essay discussing his influence on modern ideas about the history of science and the possibility that his interpretations were influenced by his own philosophical and religious views.
56. Explain Galileo's logical proof (as distinct from his experimental proof) that two iron balls of different weight dropped from a tower must hit the ground at the same time.
57. What (and when) was Humanism? How did it affect science?
58. Identify: Paracelsus.
59. Dear uses the metaphor of the cuckoo's egg to describe the relation between mathematics and physics (or natural philosophy). Explain this metaphor and how it works to make his point.
60. Compare and discuss the views of Huff and Dear on the external factors that encouraged the development of science in Europe in the 16th century.
61. How did the relation between mathematics and physics change in the 17th century?

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