March 26, 1997
Course Introduction

Robert Recorde's the Castle of Knowledge is part of an astronomy text from approximately 1560. When it was published, the Copernican theory had been circulating for 20 years.

... Copernicus proposed to increase the accuracy and simplicity of astronomical theory by transferring to the sun many astronomical functions previously attributed to the earth. Before this proposal the earth had been the fixed center about which astronomers computed the the motions of stars and planets. 
- The Copernican Revolution, Thomas S. Kuhn

Course introduction

Students are asked what they already know about the Copernican revolution, and about Copernicus, Galileo, and Kepler. Chances are that most will have only an elementary understanding. They will probably know that Copernicus "discovered" that the sun was the immoveable center of planetary motion and not the earth; they will know that Galileo was persecuted by the Catholic Church (which had always opposed the idea of the earth's motion) for maintaining this to be true, and forced to recant to save his life; they will know that Kepler came up with Kepler's Three Laws. Some will even know one or more of these laws, one or two might even know that they are related to elliptical planetary orbits, and a few will know that Galileo was the first to look at the heavens through a telescope and that he discovered the moons of Jupiter.

I tell the students that this rudimentary knowledge will certainly be augmented by this course, and that in fact some of the simplifications they have received previously are serious distortions. Copernicus, a mathematician, resurrected a theory that had been proposed by some ancient Greeks, most notably Aristarchus of Samos. But Copernicus also did the calculations necessary to determine orbital periods, etc., thus creating a model that was as good as any refinement of the Ptolemaic model in predicting planetary motions as seen from the Earth. However, the fact is that "as good" is far from perfect, and neither is accurate in any acceptable modern sense. The two models were equally inaccurate.

Given this fact, and that actual proof of whether the earth stood motionless at the center of the planets or spun dizzily around the sun was unavailable, what, I ask, is everyone arguing about? What possessed Copernicus to work so hard at developing a theory based on such an apparently absurd premise as terrestrial motion? What would make one subscribe to the Copernican theory and discard the familiar Ptolemaic model, when there was nothing to be gained from it in practical terms and the theory disturbed the foundations of other disciplines, creating far more problems than it solved? The idea of a heliocentric universe had been raised before and discarded, why should it take hold at this time? To quote Thomas Kuhn, from The Copernican Revolution:

Initiated as a narrowly technical, highly mathematical revision of classical astronomy, the Copernican theory became one focus for the tremendous controversies in religion, philosophy, and social theory, which... set the tenor of the modern mind.

This course is to be a look at the intersections of the Copernican controversy and these other controversies, at the way in which the discourse of science both influences, and is influenced by, other discourses. We will delve into the period, reading works of fact and fiction, speculation and imagination, by scientists, mathematicians and others, in a period where distinctions were not so boldly drawn as they are today.


From the fourth treatise of The Castle of Knowledge, by Robert Recorde


... And this may suffice for this time touching the earth and his accidents, principally appertaining to Astronomy: for although many other things are to be considered in it, they appertain rather to the philosophers, or Cosmographers, than to astronomers, and namely the doctrine of principles. As touching the distinction of the zones, I have said somewhat before, and will say more anon. But as for the quietness of the earth I need not spend any time in proving it, since that opinion is so fixed in most mens heads, that they account it mere madness to bring the question in doubt. And therefore it is as much folly to travail to prove that which no man denieth, as it were with great study to dissuade that thing, which no man cloth covet, nor any man alloweth: or to blame that which no man praiseth, nor any man liketh.


Yet sometime it chanceth, that the opinion most generally received, is not most true.


And so do some men judge of this matter, for not only Eraclides Ponticus, a great philosopher, and two great clerks of Pythagoras' school, Philolaus and Ecphantus, were of the contrary opinion, but also Nicias Syracusius, and Aristarchus Samius, seem with strong arguments to approve it: but the reasons are difficult for this Introduction, & therefore I will omit thern till another time. And so will I do the reasons of Ptolemy, Theon, & others do allege, to prove the earth to be without motion: and the rather, because those reasons do not proceed so demonstrably, but they may be answered fulIy, of him that holdeth the contrary. I mean, concerning circular motion: marry direct motion out of the center of the world, seemeth more easily confuted, and by the same reason, which being before alleged for proving the earth to be in the middle and center of the world.


I perceive it well: for as if the earth were always out of the center of the world, those former absurdities prould at all times appear: so it at any time the eatth should move out of his place, those inconveniences would then appear.


This is truly to be gathered, howbeit, Copernicus a man of great reaming, of much experience, and of wonderful diligence in observation, hath renewed the opinion of Aristarchus Samius, and affirmith that the earth not only moveth circularly about his own center, but also may be, yea and is, continually out of the precise center of the world 38 hundred thousand miles: but because the understan&g of that controversy dependeth upon profoumder knowledge than in this Introduction may be uttered conveniently, I will let it pass till some other time.


Nay sir in good faith, I desire not to hear such vain fantasies, so far against common reason, and repugnant to the consent of all the reamed multitude of Writers, and therefore let it pass forever, and a day longer.


You are too yonng to be a good judge in so great a matter: it passeth far your leatning, and theirs also that are much better learned than you, to improve [disprove] his suppositions by good arguments, and therefore you were best to condemn no thing that you do not wdl understand: but another time, as I said, I will so declare his supposition, that you shall not only wonder to hear it, but also peradventure be as eamest then to credit it as you are now to condemn it. In the mean season, let us proceed forward in our former order ...

The class is then directed to read an excerpt from Robert Recorde's Castle of Knowledge (1556) in which the Master and Scholar discuss briefly the Copernican view. A discussion follows, with these questions being raised:


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