The Works of Galileo

Foundations of Mathematical Physics

Astronomy: Copernicus

The second of the 3 most important astronomical works of the 16th century is by Nicholas Copernicus (Figure 1) , On the Revolutions of the Heavenly Spheres, published in 1543 (Figure 2) . The De Revolutionibus begins with an unsigned preface "To the Reader, on the Hypotheses of this Work." The preface says that one should read the book, and instead of taking offense, interpret it hypothetically (Figure 3) . Mathematical works were often regarded as hypothetical, because one could save the phenomena with various mathematical devices, even with false ones. It was unsigned because this was the middle of the Reformation and the preface was written by Andreas Osiander, a leading Lutheran theologian. Copernicus was a Catholic who worked in a cathedral in what is now Frombork, Poland.

In a second preface, Nicolaus Schoenberg, a Cardinal, states that Copernicus wrote this book because he asked him to. In other words, "Don’t bother him" (Figure 4) . Finally, Copernicus himself dedicated the book to none other than the pope. In his preface, Copernicus said that astronomy is a work of mathematics, for mathematicians. Theologians should understand, before they criticize, that the current system was mathematically inelegant, and no credit to the deity. (Figure 5)

In Book I Copernicus laid out his basic assumptions, such as that the universe is spherical and that the Earth is spherical (Figure 6) . Ptolemy began the Almagest in the same way. But Copernicus departed from Ptolemy by switching the positions of the Sun and the Earth (Figure 7) . One chapter heading (Figure 8) is on the triple motion of the Earth. First, the Earth rotates around its axis once each day. Second, it revolves in orbit around the Sun once each year. Third, because Copernicus accepted the reality of the solid spheres, he had to postulate another motion of the Earth’s axis (which we don’t need today, of course), to keep from tilting the north pole toward the Sun throughout the year.

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Copernicus, portrait.

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Figure 2 Figure 2 - Return to Text

Copernicus, 1543. Title page.

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Figure 3 Figure 3 - Return to Text

Copernicus, 1543. Osiander’s Preface.

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Figure 4 Figure 4 - Return to Text

Copernicus, 1543. Schonberg dedication.

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Figure 5 Figure 5 - Return to Text

Copernicus, 1543. Dedication.

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Figure 6 Figure 6 - Return to Text

Copernicus, 1543. Book I.

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Figure 7 Figure 7 - Return to Text

Copernicus, 1543. Cosmic section.

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Figure 8 Figure 8 - Return to Text

Copernicus, 1543. Triple motion.

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Exhibit credit: Kerry Magruder, with the assistance of , Marilyn B. Ogilvie, Duane H. D. Roller.

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