The Book Nobody Read

by Owen Gingerich

  As I sat with his De revolutionibus in the Schaffhausen library, I marveled at the multiple layers of annotations in the copy that demonstrated the lengthiest active use by a single owner. Inside the front cover was a hand-colored bookplate with a coat of arms, dating from 1584, when he had been recalled to Tubingen. But on the title page was an earlier inscription, "Ex libris M Michaelis Maestlini Goeppingensis Anno Domini 1570," and inside the back cover was a note saying that he had obtained the book from the widow of Victorin Strigel for one and a half florins. Strigel had been a student at Wittenberg, had founded the school that later became the University of Jena, and had gone on to become professor of theology at Leipzig, where he wrote an astronomy textbook. Elsewhere in the volume Maestlin's notes cite the third edition of De revolutionibus, which was published in 1617, and furthermore, the places censored or altered in 1620 by the Vatican Congregation of the Index were indicated with red emphasis marks. From 1570 to 1620—fifty years of annotating!

  In the margins near the beginning of the book Maesdin penned a unique appreciation of what Copernicus had accomplished. No other copy of De revolutionibus contains anything comparable. Maestlin pointed out that "the arrangement presented in this book is the sort of structure in which all the sidereal motions and phenomena are explained very exactly. Therefore this hypothesis recommends itself to the intellect." Maestlin went on to comment that he thought many others would also agree with Copernicus' ideas if they hadn't been convinced long before that the Earth didn't move. Copernicus wasn't just playing a clever game, he wrote.

  The heavenly motions were at the point of collapse, and so he concluded that appropriate hypotheses were needed to explain these motions. When he noticed that the common hypotheses were insufficient, he eventually accepted the idea of the Earth's mobility, since indeed, it not only satisfied the phenomena very well but it didn't lead to anything absurd.

  In fact, if anyone would straighten out the common hypotheses so that they would agree with the phenomena and allow no inconsistencies, then I would gratefully trust him; clearly he would bring very many to his views. But I see that some, even very outstanding mathematicians, have labored on this, yet, in the end, without results. Therefore, I think that unless the common hypotheses are reformed (a task that I am not up to because of my inadequate abilities), I will accept the hypotheses and opinion of Copernicus—after Ptolemy, the prince of all Astronomers.

  Because in his elementary astronomy textbook Maestlin presented only the geocentric arrangement, his complete commitment to the Copernican system has always seemed somewhat problematic. The statement near the beginning of his copy of Copernicus' book would dispel any doubts except for his repeated use of the word hypothesis. Today when the word hypothesis is used to describe a scientific concept (such as evolution), many people tend to mentally add the word mere, to make a pejorative mere hypothesis. Sixteenth-century astronomers, working in a very different intellectual framework, used the word in a very different way. They generally viewed astronomy as a geometric (rather than physical) science, and the hypotheses were the geometric devices or arrangements used to explain celestial motions. Later on Maestlin would scold his student Kepler for dragging physics into astronomy, which he believed was inappropriate. So Maestlin may well have harbored reservations about the physical reality of the Copernican arrangement even while accepting that it was the best explanation for the planetary phenomena.

  Toward the back of the book long notes in Maestlin's microscopic hand revealed that he tried to pursue a fiercely technical question that Copernicus had left hanging and which could potentially serve as another convincing (but subtle) argument for the heliocentric arrangement. Copernicus had referred all of the planetary motions not to a fixed Sun but to the center of the Earth's orbit. This would have made little difference except that Copernicus had noticed that the distance between the Sun and the center of the Earth's orbit had diminished since Ptolemy's day. If the center of the Earth's orbit were the true center of the universe, then it wouldn't make any difference with the planets' orbits if the Sun bobbled back and forth with respect to Earth's orbit. On the other hand, if the Sun was the truly fixed reference point for the planets' orbits, then their own centerings would change over time as seen from the hobbling center of the Earth's orbit. So Maestlin set out to see if he could establish this effect. Had he been able to find it, there would have been one further connection between the Sun and the planets, a fine argument for the centrality of the Sun in understanding the planetary arrangement. But he failed, not for any shortcoming with his mathematical technique but because Ptolemy's observations were not accurate enough for the required comparison.

  Maestlin's annotations, like Reinhold's, were thick in the technical, later sections of De revolutionibus. But unlike Reinhold, Maestlin also had some very cogent remarks about the front matter of the book; in fact, they are the most fascinating front-end comments in any extant copy. At the very beginning, above the anonymous introduction to the reader, the multiple layering of notes exhibits itself. Maestlin started off by saying, "This preface was added by someone, whoever its author may be, (for indeed, its weakness of style and choice of words reveal that it is not by Copernicus)."*

  On the top margin of the facing page Maestlin added another note.

  NB: Concerning this letter, I found the following words written somewhere among the books of Philipp Apian (which I bought from his widow); although no author was given I could recognize Apian's hand:

  On account of this letter Georg Joachim Rheticus, the Leipzig professor and disciple of Copernicus, became involved in a very bitter wrangle with the printer, who asserted that it had been turned over to him with the rest of the work. Rheticus, however, suspected that Osiander [the proofreader of Copernicus' book] had prefaced it to the work. If he knew this for certain, he declared, he would handle that fellow so that in the future he would mind his own business and not slander astronomers any more. Nevertheless [Peter] Apian told me that Osiander had openly admitted to him that he had added this all by himself.

  It took me some later detective work to sort out the origin of this confusing note—confusing because more than one Apian is mentioned. I realized that both Philipp Apian and his more famous father, Peter Apian, were involved in Maestlin's note after I discovered another copy of the quoted passage in Munich. The De revolutionibus in the Bavarian capital had been there since 1571, whereas the copy of the note that Maestlin had seen (not necessarily in a copy of Copernicus' book) was in his hands after 1589, when Philipp Apian had died. So here is how I reconstruct the story. Peter Apian, a well-known author and astronomy professor at Ingolstadt north of Munich, got the information about the anonymous introduction straight from Osiander himself and mentioned it to a colleague, who noted it in his copy of De revolutionibus. At some point the young Philipp Apian saw the note, probably after his father had died in 1552, and he made a verbatim copy of it. The original De revolutionibus containing the note was acquired by the banker Johann Jacob Fugger, who had it rebound (thereby trimming off part of the note). In 1571, when he was bankrupted by his passion for books, Fugger sold the De revolutionibus to Duke Albrecht V of Bavaria, founder of the library in Munich, where it has been ever since. Philipp Apian's copy has disappeared, but what is probably the original, as well as Maestlin's third-hand transcription, both survive.

  This was not the end of the Osiander story, however, for Maestlin wrote a third, terse comment above the anonymous introduction: "NB: I know for sure that the author of this letter was Andreas Osiander (plate 7f)." What made him so sure? The answer revolves around Maestlin's most famous student, the primary reason that Maestlin himself is remembered today.

  LIKE MAESTLIN, Johannes Kepler was born near Tubingen, studied in a preparatory school before going to the university to study for his master's degree, and then went into the theological program, fully expecting to become a Lutheran clergyman. When, instead, he was sent out to be a mathematics and astronomy teacher, he complaine
d that nothing had indicated that he had a special talent for astronomy. In evidence, he was a straight A student except in astronomy, where he got an A-.* Nevertheless, astronomy was in his background. Kepler recalled that, when he was six years old, his mother had shown him the Comet of 1577. Also, he may very well have inherited his De revolutionibus through his family, possibly from a Nuremberg bookseller named Kepner, who may have been an ancestor.

  I remember vividly the circumstances when I first saw Kepler's copy in Leipzig in 1972, the same field trip that had originally taken us to Schaffhausen. It was the first time Miriam and I had penetrated deep into East Germany beyond East Berlin. The country was a drab police state, but with scattered friendly though apprehensive persons cautiously willing to make contact with the outside world. Since we had got behind the iron curtain, I was keen to see the Wittenberg archives and to find any traces of Erasmus Reinhold, which was what made the trip particularly memorable. But first we had to attend to Leipzig.

  Edition Leipzig was a major East German publishing house eager to bring in hard currency through splendidly printed art books and reproductions of library treasures. One of the great typographical triumphs of the sixteenth century, printed just three years before De revolutionibus, was Peter Apian's Astronomicum Caesareum—literally, "Astronomy for the Emperor," and the princely book Tycho had glowingly inscribed to Wittich. It was a giant folio with astronomical diagrams full of rotating parts, brilliantly hand colored. The most complex set of volvelles, seven layers deep, served as an analog computer to simulate the Ptolemaic epicyclic theory for finding the longitude of the planet Mercury. Edition Leipzig used a disassembled copy from the library in Gotha to make a spectacular facsimile. Unfortunately, while its facsimile was a typographical tour de force, the actual assembly of the moving parts was thoroughly botched, with some volvelles on the wrong pages and others pasted down so they wouldn't turn properly. On the pages of the Journal for the History of Astronomy I had called attention to this misassembly, and subsequently Edition Leipzig had invited me for a consultation.

  I explained to my hosts that in addition to trying to figure out what to do about the faulty facsimile,* I hoped to explore the Wittenberg University archive. In response they broke the news that the famous old University of Wittenberg no longer existed. It had long since been combined with the university in Halle. And there was another problem. As the editors pointed out, our East German visa was good only for the Leipzig circle, and if we drove over to Halle, we would be dangerously conspicuous. They offered instead to send us over to Halle the following day by train with one of their assistants, thinking that no one would then notice.

  The assistant was enormously pleased to accompany us to Halle. On that particular day the radical American activist Angela Davis was in Leipzig for a rally, and each company had a quota of employees obliged to turn out for the demonstration. The young assistant who accompanied us to Halle had been assigned as a "volunteer" to attend the rally, something she did not relish, so she was delighted to be escorting us instead. We were surprised at how freely she made her sentiments known, in English, on the train.

  In Halle we got a warm welcome. The university library's copy of Copernicus' book had been missing for some time, but the librarian was eager to show us some of their other rarities. The crown jewel was the dean's book from sixteenth-century Wittenberg. I immediately recognized the clear, neat hand of Erasmus Reinhold. The deanship had been a bureaucratic office passed quickly around from one teacher to another, but because Reinhold's handwriting was so legible, some of the other deans asked him to do the honors. A pair of special lectures recorded in Reinhold's hand jumped out, one by Reinhold himself on astronomical hypotheses, and the other "Against the Anabaptists." Since I come from a long line of Anabaptists, this topic particularly resonated with me. I had brought along my Nikon, but I had only color film. This was the only time I've made a microfilm on Ektachrome.

  Back in Leipzig I naturally went to see both the Astronomicum Cae­sareum and the first-edition De revolutionibus in the university library. I was especially thrilled to see Kepler's Copernicus, but in retrospect I missed several of the most important points. Since Edition Leipzig had already issued a facsimile of the book, I wasn't surprised to see on the flyleaf Kepler's Latin translation of a long Greek poem by the Leipzig humanist Joachim Camerarius, nor did I have a sudden burst of insight when I saw Osian­der's name written above the anonymous introduction, the Ad lectorem. What Edition Leipzig had not included in its facsimile, quite rightly as it turned out, was an old inscription concerning the earliest copy of Copernicus' book acquired by the university. It had been clipped out of the original copy when it was sent out for auction as a duplicate, and hence it was an important document for the history of De revolutionibus in general, and so I was keen to see it even though it was totally irrelevant to Kepler's copy in particular.

  What I failed to photograph were two annotations that attracted my attention only after I began to understand the layering of the annotations in the book. Most, but not all, of the marginal annotations are in Kepler's hand. Many small interlinear corrections are in the hand of its original owner, Jerome Schreiber, who had received the book as a gift from the printer, as he noted in a corner of the title page. Schreiber was from Nuremberg but studied at Wittenberg and was for a while a mathematics teacher there. He was an insider, so to say. That turned out to be quite important, because when I eventually examined those corrections more carefully in my copy of the facsimile, I discovered something curious. Where as the corrections in the first three-quarters of the book came directly from the printed errata leaf that accompanied some copies, the corrections continued to the very end, well beyond where the errata leaf left off. After I discovered this same extended errata set in a few more copies, I realized that the insiders had access to a more complete list than the printer Petreius had supplied to his customers.

  After I saw the extended errata marked in several copies, I caught on that a marginal note on folio 96 was connected with these corrections, although it was simply a comment and not a correction. At that point in the text Copernicus was considering what was the true fixed center of the cosmos. Was it the Sun itself, or was it the center of the Earth's orbit? Because Copernicus believed that the stars were in a distant spherical shell, the question was whether the Earth's annual round, the "great orbit" as Copernicus put it, was neatly centered with respect to the stars (thereby putting the Sun slightly off-center), or whether the Sun itself was dead centered so that the Earth was closer to the starry shell in January than in June. If the Sun was the hub of the universe, Copernicus truly had a heliocentric system. If the hub was the center of the Earth's orbit, eccentrically offset from the nearby fixed Sun, it was a heliostatic system. This was an unresolved mystery in the book, for Copernicus hedged on the issue. However, the marginal note in a few of the copies indicated that Rheticus' Narratio prima said more. The one in Schreiber's hand reads (in Latin, of course), "These are in the Narratio of Joachim [Rheticus]. For in this work they are omitted." In fact, the Narratio prima did not discuss the question explicitly but simply assumed throughout that the Sun itself was the center of the universe.

  What follows is an exercise in minutiae, but one that ultimately offers a most intriguing insight into Kepler's student-teacher relationship with Michael Maestlin. Below Schreiber's note is another, looking at first glance very much like Kepler's hand, yet clearly distinct from Kepler's annotations elsewhere in the book. In fact, I believe it matches Michael Maestlin's hand more closely than Kepler's.* It is not the minuscule writing that characterizes the notes in Maestlin's own De revolutionibus, but very much like the handwriting in his letters to Kepler. The note states, "What can be accepted about this question is that from Book V they make either the sun fixed or else the centers of all the planets slightly displaced with it." Maestlin not only wrote a very similar comment at the same place in his Schaffhausen copy but also marked places in Book V corresponding to his statemen
t in Kepler's copy.

  Why do I get excited about something as esoteric as this? Because the presence of this little note tells us that Kepler showed his copy to his teacher, and that's why Maestlin was so sure it was Osiander who had written the anonymous introduction to Copernicus' book. There it was in Kepler's copy, in black and white, coming straight from Schreiber, a Wittenberg insider. More than that, Maestlin's little annotation suggests that he and Kepler specifically discussed this point, what was the hub of the universe. And on the day when Kepler went to work for Tycho Brahe in 1600, his notebook shows that the very first task in his research program was to adjust the orbit of Mars so that it referred to the Sun rather than to the empty point that happened to be the center of the Earth's orbit. This became an essential part of Kepler's physical approach, and a fundamental principle that led to his successful reworking of the heliocentric details. It was presaged by that fateful student-teacher conversation at Tubingen.

  Kepler is most famous for discovering the elliptical shape of the planetary orbits, and so another of the marginal comments also seems highly relevant. On folio 143 there appears the single Greek word — that is, ellipse—together with the same sort of emphasis marks that Schreiber used to highlight the passage on folio 96.

  Marginal annotations by Jerome Schreiber and Michael Maestlin (folio 96, left) and Johannes Kepler (folio 143, right).

  When I first saw that book in Leipzig, I assumed that it was Kepler who had written in the margin, and I hadn't made a color slide of it. Later, when I had discovered more information about the double layer of annotations and the evidence that it was likely Schreiber's handiwork, I had to worry about which one wrote it. Handwriting comparison didn't help because it was in Greek letters, not Latin. I decided I had better go back to Leipzig for a close scrutiny of the ink, only to learn that the book was away on exhibition. Eventually I obtained excellent color transparencies, which left no doubt that it was indeed Schreiber's ink in the book Kepler had inherited.