Department of History
University of California, Irvine
Instructor: Dr. Barbara J. Becker
Week 3. The Three Chief World Systems.
excerpts from
The Dream, or Posthumous Work on Lunar Astronomy
of Johannes Kepler, Late Imperial Mathematician (1634)
by Johannes Kepler (1571-1630)
| ...It happened one night that after watching the stars and the moon, I went to bed and fell into a very deep sleep. In my sleep I seemed to be reading a book brought from the fair. Its contents were as follows. |
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My name is Duracotus. My country is Iceland, which the ancients called Thule. My mother was Fiolxhilde. Her recent death freed me to write, as I had long wished to do. While she lived, she carefully kept me from writing. For, she said, the arts are loathed by many vicious people who malign what their dull minds fail to understand, and make laws harmful to mankind.... In the earliest years of my boyhood my mother, leading me by the hand and sometimes hoisting me up on her shoulders, often used to take me up to the lower slopes of Mt. Hekla. These excursions were made especially around St. John's Day [June 24], when the sun is visible all twenty-four hours, and there is no night. Gathering some herbs with many rites, she cooked them at home. She made little bags out of goatskin, which she filled and carried to a nearby port to sell to the ship captains. This is how she earned her living. Once, out of curiosity, I cut a bag open. Suspecting nothing, my mother was about to sell it when out fell the herbs and linen cloth embroidered with various symbols. Because I had deprived her of this little income, she angrily made me, instead of the bag, the property of the skipper in order to keep the money. On the next day he unexpectedly sailed out of the harbor, and with a favorable wind steered approximately toward Bergen in Norway. After a few days a north wind sprang up and drove the ship between Norway and England. He headed for Denmark and passed through the straight, since he had to deliver a letter from a bishop in Iceland to the Dane, Tycho Brahe [(1546-1601) astronomer whom Kepler served as mathematician], who lived on the island of Hven. The tossing of the boat and the unaccustomed warmth of the air made me violently sick, for I was a youth of fourteen. When the boat reached shore, he put me and the letter in the hands of an island fisherman.... 
Tycho's Island of Hveen, Denmark |
Learning Danish and Astronomy When I delivered the letter, Brahe was quite delighted and began to ask me many questions. These I did not understand, since I was unacquainted with the language except for a few words. He therefore instructed his students, whom he supported in great numbers, to talk to me frequently. So it came about, through Brahe's generosity and a few weeks' practice, that I spoke Danish tolerably well. I was no less ready to talk than they were to ask. For I marveled at many unfamiliar things, and they wondered about the many novelties I related about my country.... I was delighted beyond measure by the astronomical activities, for Brahe and his students watched the moon and the stars all night with marvelous instruments. This practice reminded me of my mother, because she, too, used to commune with the moon constantly. Through this opportunity, then, I, who had come from an entirely destitute background in a half-savage country, acquired knowledge of the most divine science, and this knowledge paved my way to greater things. |
[A]fter spending several years on this island, I was finally overcome by a desire to see my country again. I considered that it would not be hard for me, with the knowledge I had acquired, to rise to some position of importance among my backward people. Hence, having paid my respects to my patron, who gave me his permission to depart, I went to Copenhagen. I found traveling companions, who gladly took me under their protection because of my familiarity with the language and the region. Five years after I had left, I returned to my native land. What delighted me first on my return was to find my mother still active and engaged in the very same pursuits as before. The fact that I was alive and important put an end to her prolonged grief over the son she had lost through her impetuosity.... Sometimes she asked about the countries which I had visited, and sometimes about the heavens. She was deliriously happy that I had become acquainted with that science. Comparing what she had learned with my remarks, she exclaimed that now she was ready to die, since she was leaving behind a son who would inherit her knowledge, the only thing she possessed. Since I am by nature most eager to acquire new knowledge, I, in turn, questioned her about her arts and her teachers of those arts among a people so remote from all the others. Then one day ... she went over the whole story from the very beginning, about as follows: Advantages have been conferred, Duracotus my son, not only on all those other regions to which you went but also on our country, too. To be sure, we are burdened with cold and darkness and other discomforts, which I feel only now, after I have learned from you about the salubriousness of the other lands. But we have plenty of clever persons. |
| It was already spring. The moon, becoming a crescent, began to shine as soon as the sun set below the horizon, and was in conjunction with the planet Saturn in the sign of the Bull [the constellation Taurus]. My mother went away from me to the nearest crossroads. Raising a shout, she pronounced just a few words in which she couched her request. Having completed the ceremonies, she returned. With the outstretched palm of her right hand she commanded silence, and sat down beside me. Hardly had we covered our heads with our clothing (in accordance with our covenant) when the rasping of an indistinct and unclear voice became audible. It began at once as follows, albeit in the Icelandic tongue. |
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Fifty thousand German miles up in the ether lies the island of Levania. The road to it from here or from it to this earth is seldom open. When it is open, it is easy for our kind, but for transporting men it is assuredly most difficult and fraught with the greatest danger to life.... Great as the distance is, the entire trip is consummated in four hours at the most. For we are always very busy, and agree not to start until the moon begins to be eclipsed on its eastern side [the start of a total lunar eclipse on earth]. Should it regain its full light while we are still in transit, our departure becomes futile. Because the opportunity is so fleeting, we take few human beings along, and only those who are most devoted to us. Some man of this kind, then, we seize as a group and all of us, pushing from underneath, lift him up into the heavens. In every instance the take-off hits him as a severe shock, for he is hurled just as though he had been shot aloft by gunpowder to sail over mountains and seas. For this reason at the outset he must be lulled to sleep immediately with narcotics and opiates. His limbs must be arranged in such a way that his torso will not be torn away from his buttocks nor his head from his body, but the shock will be distributed among his individual limbs. Then a new difficulty follows: extreme cold and impeded breathing. The cold is relieved by a power which we are born with; the breathing, by applying damp sponges to the nostrils. After the first stage of the trip is finished, the passage becomes easier. At that time we expose their bodies to the open air and remove our hands. Their bodies roll themselves up, like spiders, into balls which we carry along almost entirely by our will alone, so that finally the bodily mass proceeds toward its destination of its own accord. But this onward drive is of very little use to us, because it is too late.... [W]e forge ahead of it from now on lest it suffer any harm by colliding very hard with the moon. When the humans wake up, they usually complain about an indescribable weariness of all their limbs, from which they later recover well enough to walk. Many additional difficulties arise which it would be tedious to enumerate. On the other hand, we suffer no harm at all. For as a group we inhabit the earth's shadows, whatever their length. When they reach Levania, there we are as though disembarking from a ship and going ashore. Up there we quickly withdraw into caves and dark places, lest after a short while the sun overpower us in the open, and drive us out of the living quarters we had chosen, and force us to follow the retreating shadow. Up there we are granted leisure to exercise our minds in accordance with our inclinations.... [When the moon's shadow] touches the earth with its apex [during a solar eclipse on earth], we rush toward the earth with our allied forces. This we are permitted to do only when mankind sees the sun in eclipse. Hence it happens that solar eclipses are feared so much.... |
The fixed stars look the same to all Levania as to us. But its view of the movements and sizes of the planets is very different from what we observe here, so that its entire system of astronomy is quite diverse. Just as our geographers divide up the sphere of the earth into five zones on the basis of celestial phenomena, so Levania consists of two hemispheres. One of these, the Subvolva [the Earth-facing side of the moon], always enjoys its Volva [Earth], which among them takes the place of our moon. The other one, the Privolva [the far side of the moon], is deprived forever of the sight of Volva. The circle which separates the hemispheres passes through the celestial poles ... is called the divisor. In the first place I shall explain what is common to both hemispheres. All Levania experiences the succession of day and night as we do, but they lack the variation that goes on all year among us. For throughout the whole of Levania the days are almost exactly equal to the nights, except that each day is uniformly shorter than its night for the Privolvans, and for the Subvolvans longer.... Levania seems to its inhabitants to remain just as motionless among the moving stars as does our earth to us humans. A night and a day, taken together, equal one of our months, since at sunrise in the morning almost an entire additional sign of the zodiac appears on any day as compared with the previous day. For us in one year there are 365 revolutions of the sun, and 366 of the sphere of the fixed stars.... Similarly, for them the sun revolves 12 times in one year and the sphere of the fixed stars 13 times.... [Duracotus goes on to compare other Levanian observations (seasonal changes, observed motions of planets, for example) to those of Earth.] |
Now as for what concerns the individual hemispheres separately, there is an enormous contrast between them. By its presence and absence Volva gives rise to quite different spectacles. Not only that, but the common phenomena themselves produce very divergent effects on the two sides. As a result, the Privolvans' hemisphere may perhaps more properly be called non-temperate, and the Subvolvans', temperate. For among the Privolvans night lasts fifteen or sixteen of our natural days. It is made frightful by as deep an uninterrupted darkness as we have on a moonless night, since it never receives any light even from Volva's rays. Consequently everything turns stiff with ice and frost, abetted by very sharp and very strong winds. Day follows, as long as fourteen of our days or a little less. During this time the sun is quite large, and moves slowly with respect to the fixed stars. There are no winds. The result is immense heat. And thus, in the interval of our month or the Levanian day, one and the same place is exposed both to heat fifteen times hotter than our African, and to cold more unbearable than the Quiviran.... |
[T]he most beautiful of all the sights on Levania is the view of its Volva.... From the perennial presence of this Volva this region is termed the Subvolvan, just as from the absence of Volva the other region is called the Privolvan, because they are deprived the sight of Volva. To us who inhabit the earth, our moon, when it is full and rising and climbing above distant houses, seems equal to the rim of a keg; when it mounts to mid-heaven, it hardly matches the width of the human face. But to the Subvolvans, their Volva in mid-heaven (a position which it occupies for those who live in the center or navel of this hemisphere) looks a little less than four times longer in diameter than our moon does to us. Hence, if the disks are compared, their Volva is fifteen times larger than our moon. However, to those for whom Volva always clings to the horizon, it presents the appearance of a mountain on fire far away.... Volva stands directly over the heads of some of them; in other places it is seen low down near the horizon; and for the rest its altitude varies from the zenith to the horizon, while remaining forever constant in any given area....
A gibbous Volva above the Levanian horizon. Their Volva remains fixed in place, then, as though it were attached to the heavens with a nail. Above it the other heavenly bodies, including the sun, move from east to west. There is never a night in which some of the fixed stars in the zodiac do not pass behind this Volva and emerge again on the other side....
A crescent Volva above the Levanian horizon. Their Volva waxes and wanes no less than our moon does. In both cases the cause is the same: the presence of the sun or its departure. The length of time involved is also the same, if you look to nature. But they measure it in one way, and we in another. They consider a day and a night the interval in which their Volva passes through all its waxings and wanings. This is the interval which we call a month. On account of its size and brilliance Volva is practically never, not even at new Volva, hidden from the Subvolvans.... [I]n general ... new Volva is the sign of noon; the first quarter, of evening; full Volva, of midnight; the last quarter, of returning sunlight.... But at night, which regularly lasts as long as fourteen of our days and nights, they are much better equipped to measure time than we are. For besides that series of Volva's phases, of which we said that full Volva is the sign of midnight at the mid-Volvan circle, Volva itself also distinguishes the hours for them. For even though it does not seem to have any motion in space, nevertheless, unlike our moon, it rotates in its place and displays in turn a wonderful variety of spots, as these spots move constantly from east to west. One such revolution, in which the same spots return, is regarded by the Subvolvans as one hour of time; it is equal, however, to a little more than one of our days added to one of our nights. This is the only uniform measure of time.... Besides distinguishing the hours of the day for them in this manner, Volva also furnishes no obscure indication of the seasons of the year to anyone who is observant, or who is unaware of the arrangement of the fixed stars. [W]hen the sun is in the sign of the Crab [Cancer--summer], Volva clearly displays the north pole of its rotation.... But when the sun is in the sign of the Goat [Capricorn--winter], this spot is nowhere to be seen since the entire circle with its pole disappears behind the body of Volva.... These facts show us that, while the center of the body of Volva remains stationary, the poles of this rotation revolve on an arctic circle once a year around the pole of the moon-dwellers.... |
What shall I say now about the eclipses of the sun and of Volva? Eclipses occur on Levania too, and they occur at the same moments as solar and lunar eclipses here on the globe of the earth, although obviously for the opposite reasons. For when a total eclipse of the sun is visible to us, for them Volva is eclipsed. In turn, when our moon is eclipsed for us, the sun is eclipsed for them. Nevertheless, the correspondence is not complete. For they often see partial eclipses of the sun when no part of the moon is blacked out for us. On the other hand, they not infrequently miss eclipses of Volva when we have partial eclipses of the sun. Volva is eclipsed for them when it is full, just as the moon for us when it is full; but the sun is eclipsed at new Volva, as it is for us at new moon.... They never see a total eclipse of Volva. However, for them the body of Volva is traversed by a certain small spot [the moon's shadow] which is reddish around the rim and black in the middle. Entering the eastern side of Volva, it leaves by the western edge, following the same course as the natural spots of Volva, while surpassing them in speed. It lasts one-sixth of a Levanian hour or four of our hours. A solar eclipse is caused for them by their Volva, just as it is for us by our moon. This phenomenon is inevitable since Volva has a diameter four times bigger than the sun's.... Even though an occultation of the sun's entire body is frequent, it is nevertheless quite remarkable because it lasts several of our hours, while the light of both the sun and Volva is extinguished at the same time. This is a grand spectacle for the Subvolvans.... Hardly has the sun disappeared behind the body of Volva than, as happens quite frequently, bright light arises on the opposite side. It is as though the sun expanded and embraced the entire body of Volva.... |
From these phenomena, even without my saying anything, it is not difficult to infer how much the Subvolvans differ from the Privolvans in all other respects. For although the Subvolvan night lasts as long as fourteen of our days and nights, nevertheless by its presence Volva lights up the land and protects it from the cold.... On the other hand, even though a day among the Subvolvans has the sun irksomely present for fifteen or sixteen of our days and nights, nevertheless it is a smaller sun, whose strength is not so dangerous. The luminaries, being joined, pull all the water to that hemisphere, where the land is submerged so that only a tiny quantity of it protrudes. By contrast the Privolvan hemisphere is dry and cold because all the water has been drawn off. However, when night begins for the Subvolvans and day for the Privolvans, the hemispheres divide the luminaries between them, and therefore the water is divided too; the fields of the Subvolvans are drained, whereas the moisture provides the Privolvans with some slight relief from the heat. The whole of Levania does not exceed fourteen hundred German miles in circumference, that is, only a quarter of our earth. Nevertheless, it has very high mountains as well as very deep and wide valleys; to this extent it is much less of a perfect sphere than our earth is. Yet it is all porous and, so to say, perforated with caves and grottoes everywhere, especially in the Privolvan region; these recesses are the inhabitants' principal protection from heat and cold. |
Whatever is born on the land or moves about on the land attains a monstrous size. Growth is very rapid. Everything has a short life, since it develops such an immensely massive body. The Privolvans have no fixed abode, no established domicile. In the course of one of their days they roam in crowds over their whole sphere, each according to his own nature; some use their legs, which far surpass those of our camels; some resort to wings; and some follow the receding water in boats; or if a delay of several more days is necessary, then they crawl into caves. Most of them are divers; all of them, since they live naturally, draw their breath very slowly; hence under water they stay down on the bottom, helping nature with art. For in those very deep layers of the water, they say, the cold persists while the waves on top are heated up by the sun; whatever clings to the surface is boiled out by the sun at noon, and becomes food for the advancing hordes of wandering inhabitants. For in general the Subvolvan hemisphere is comparable to our cantons, towns, and gardens; the Privolvan, to our open country, forests, and deserts. Those for whom breathing is more essential introduce the hot water into the caves through a narrow channel in order that it may flow a long time to reach the interior and gradually cool off. There they shut themselves up for the greater part of the day, using the water for drink; when evening comes, they go out looking for food. In plants, the rind; in animals, the skin, or whatever replaces it, takes up the major portion of their bodily mass; it is spongy and porous. If anything is exposed during the day, it becomes hard on the top and scorched; when evening comes, its husk drops off. Things born in the ground -- they are sparse on the ridges of the mountains--generally begin and end their lives on the same day, with new generations springing up daily. In general, the serpentine nature is predominant. For in a wonderful manner they expose themselves to the sun at noon as if for pleasure; yet they do so nowhere but behind the mouths of the caves to make sure that they may retreat safely and swiftly. To certain of them the breath they exhaust and the life they lose on account of the heat of the day return at night; the pattern is the opposite of that governing flies among us. Scattered everywhere on the ground are objects having the shape of pine cones. Their shells are roasted during the day. In the evening when, so to say, they disclose their secrets, they beget living creatures. Relief from the heat in the Subvolvan hemisphere is provided chiefly by the constant cloud cover and rain, which sometimes prevail over half the region or more. |
When I had reached this point in my dream, a wind arose with the rattle of rain, disturbing my sleep and at the same time wiping out the end of the book acquired at Frankfurt. Therefore, leaving behind the Dæmon narrator and her auditors, Duracotus the son with his mother, Fiolxhilde, as they were with their heads covered up, I returned to myself and found my head really covered with the pillow and my body with the blankets.
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