JOHANNES KEPLER'S

it is demonstrated to be impossible for there to be, or for one to even imagine, more than five regular bodies regular bodies|Also known as the five Platonic solids: the tetrahedron, cube, octahedron, dodecahedron, and icosahedron. These are the only three-dimensional shapes where every face is an identical regular polygon.. It is a thing worthy of wonder that, while I did not yet have proof regarding the specific privileges of each body in the sequence, I used a far from clever guess derived from the known distances of the Planets. I hit the mark so successfully in the order of these bodies that I was later unable to change anything in them, even when working with the most exquisite logic. To preserve the memory of this event, I record the thought for you exactly as it occurred, and in the words conceived at that very moment: (9) Earth is the Circle that measures all. Circumscribe a Dodecahedron around it: the Circle encompassing this will be Mars. Circumscribe a Tetrahedron around Mars: the Circle encompassing this will be Jupiter. Circumscribe a Cube around Jupiter: the Circle encompassing this will be Saturn. Now, inscribe an Icosahedron within Earth: the Circle inscribed within that will be Venus. Inscribe an Octahedron within Venus: the Circle inscribed within that will be Mercury. You now have the reason for the number of the planets.

This was the occasion and the success of this labor. See now also my purpose in this book. And indeed, I could never express in words how much pleasure I perceived from this discovery. I no longer regretted the lost time, nor was I weary of the labor; I fled from no difficulty of calculation, and I consumed days and nights in computing—until I could see whether the sentence I had conceived in words agreed with the orbits of Copernicus Kepler was one of the first outspoken supporters of Nicolaus Copernicus’s sun-centered (heliocentric) model of the universe., or whether the winds would carry my joys away. Because if I found the matter to be as I believed it was, I made a vow to God, the Best and Greatest, that I would at the first opportunity publish this admirable specimen of His wisdom for all people to see. I did this so that although these things are not perfected in every way, and perhaps some things remain which might flow from these principles (the discovery of which I could reserve for myself), nevertheless others who are gifted in intellect might bring forth as much as possible for the illustration of the Divine Name at the earliest time alongside me, and might sing the praise of the wisest Creator with one voice. Since the matter succeeded a few days later, and I perceived how aptly one body sat after another among its Planets, I reduced the whole business into the form of this present little work. And when it was approved by Maestlin Michael Maestlin, Kepler's former professor at Tübingen and a renowned mathematician., the famous mathematician, you understand, friend Reader, that I am bound by my vow. I cannot follow the custom of the Satirist, who commands that books be held back until the ninth year original: "nonum in annum" – a reference to Horace’s Ars Poetica, advising authors to wait nine years before publishing to ensure the work's quality..

This is the one cause for my haste. So that I may remove every scrap of sinister suspicion (10) from you, I gladly add a second reason, and I recite to you that saying of Archytas from Cicero: If I had ascended to heaven itself and had thoroughly perceived the Nature of the world and the beauty of the stars, that admiration would be joyless to me unless I had you, a fair, attentive, and eager Reader, to whom I could tell it. Once you have learned these things, if you are fair, you will abstain from the criticisms which I foresee—not without cause. But if you leave those things in their proper place, yet fear whether they are certain, and think that I have sung of triumph before the victory: then at last approach these pages themselves, and learn the matter we have been discussing. You will not find new and unknown Planets interposed here, as was done a little earlier Kepler likely refers to other contemporary astronomers who proposed extra planets to make their theories fit.; I do not approve of such audacity. Instead, you will find those ancient ones, only very slightly displaced, but so fortified by the intervention of the rectilinear bodies—however absurd it may seem—that you may henceforth answer any rustic who asks by what hooks the heaven is suspended so that it does not fall. Farewell.