CHAPTER 1: THE ANCIENT TWO-SPHERE UNIVERSE
Foreword
In the Foreword, Conant claims that reading Kuhn’s text is better than taking the Harvard Case Studies. Why?
- While the Harvard Case Studies only teach a historical view of the events, Kuhn’s text offers a more complete, related, and unified version of the events and leaves space for the reader to question each part of the historical events. For example, Kuhn relates astronomy, politics, religion, and science; he sets a context, while the HCS are limited and narrow, providing fragmented knowledge.
The Two-Sphere Universe
“A star that rises due east is visible on only half of its diurnal circle.” Explain why.
- Stars farther from the poles are less visible, and in the case of a star that rises due east it also travels in a diurnal circle but part of it is hidden below the horizon.
“As an observer moves south, he sees fewer and fewer circumpolar stars.” Explain why.
- Stars toward the south move along a line more perpendicular to the horizon, so they will reach their maximum height more nearly over the observer’s head.
What is the difference between the sun’s diurnal motion and its annual motion?
- During the diurnal motion, the sun moves with the stars (westward). During the annual motion, the sun moves through the stars (eastward) and forms an ecliptic that completes in one year.
Early astronomers made similar observations. In this sense their data was “objective”. According to Kuhn, is there anything “subjective” about the work of a scientist?
- Yes, because while observations are “objective”, the theories and conceptual schemes derived from these observations are “subjective”, depending upon the imagination of each scientist.
From about the fourth century AD astronomers and philosophers had basically come to agreement on a description of the universe. Simply describe that universe.
- It was the “two-sphere universe”; the earth was at the geometric center of a larger rotating sphere, which carried the stars. The earth was stationary and the sun moved between the earth and the stars.
What is the difference between astronomy and cosmology?
- Astronomy is the systematic observation of the heavens and cosmology is the conception about the structure of the universe.
Where on earth must an observer be standing to see the full trajectory of northern hemisphere circumpolar stars traveling parallel to the horizon?
- In middle-northern latitudes.
“The sun must complete its diurnal circle slightly more slowly than the stars.” Why?
- Because as the sphere of the stars move rapidly westward, the sun moves slowly eastward with respect to it.
Is the two-sphere universe, according to Kuhn, a successful theory by today’s standards? Explain.
- No, because it only preserves its economical (logical) function, but its psychological function is no longer satisfying by today’s standards.
Does the two-sphere model of the universe “explain” the universe so that the universe can be “understood”? Explain.
- No, it does provide a “logical explanation” of the universe, but does not provide a “psychological understanding” of it unless we believe it to be true, rejecting the idea that the earth rotates.
Describe one competing theory that would have been an alternative in the fifth century BC.
- The Atomists (mainly Leucippus and Democritus) concluded that the earth is not at the center of the universe, in fact, there is no center since it’s an infinite universe with many heavenly bodies made by atoms.
Why, according to the two-sphere universe theory do things remain on the earth and not fly into space as a consequence of the earth’s movement and rotation?
- In the “two-sphere universe”, earth is stationary; it doesn’t move nor rotate, so it must be separated from other heavenly bodies. Earth is just a platform from which we view heavens.
What does Bohm’s Chapter 1 of “On Dialogue” have to do with Kuhn’s Chapter 1 of “Copernican Revolution”?
- Bohm explains the similarities of a dialogue with another person with that of the scientist and nature. It is by the differences in our thinking with what we see (nature) or hear (other person) that enables us to create something in common, something new.
- The scientist would have to modify his theory according to his observations, and in this process something is being created by the interaction of the scientist with nature, similar to what happens in a dialogue.
Vocabulary
- Heliocentric: sun-centered
- Circumpolar star: a star that never falls below the horizon, thus it is visible at any hour of the night.
- Gnomon: a measured stick that projects a shadow in order to observe the motion of the sun.
- Equinox: when the sun rises and sets most nearly due east and west (vernal) or almost due east and west (autumnal).
- Solstice: when the sun rises and sets to the south (winter) or to the north (summer).
- North star: the reference star that doesn’t change its position with respect to the others.
- Diurnal circle: cycle (usually of the stars) that happens when the sun is above the horizon.
- Helical motion: motion of the sun
- Celestial equator: