Alfred Wegener

by Mott T. Greene

  The exercise of interviewing ordinary people about a scientific event was highly instructive. Mixed in with sober and clear observations were all sorts of fantastic apparitions. One observer claimed to have seen a fiery cloud in which the face of the kaiser appeared.25 The most interesting phenomenon was perhaps the invention of sounds—especially whispering sounds—by those who had seen the fireball and claimed to have heard it simultaneously. This was, of course, impossible for anyone not within 500 meters (1,640 feet) of the impact site; for most observers the sound would have arrived several minutes later.26

  Rosette of meteor paths Wegener constructed from interviews in the late spring of 1916, producing a likely impact site near the village of Treysa. (The meteorite was eventually discovered just outside Wegener’s target circle.) From Alfred Wegener, Das detonierende Meteor vom 3 April 1916 3 1/2 Uhr nachmittags in Kurhessen, vol. 14, Schriften der Gesellschaft zur Beförderung der gesamten Naturwissenschaften zu Marburg (1917).

  At the other end of the spectrum from apparitions and imagined whistling and whispering sounds, there were observations of great value. One such was a newspaper account of observations by a painter named Fritz Behr, who lived in Römhild, more than 100 kilometers (62 miles) from the estimated impact site, and reported hearing an explosion about five or six minutes after the fireball passed overhead. Another observer, perhaps 10 kilometers (6 miles) distant from Behr, had also heard the explosion “some minutes” after the fireball had passed. There were no other claims of having heard the explosion outside the circle roughly 50 kilometers (31 miles) in diameter around the village of Treysa.27

  These reports of audible explosions more than 100 kilometers from the impact site indicated to Wegener that the meteor impact had created an “outer zone of audibility.” He was already attuned to this phenomenon because while at the front in Belgium in October 1914 he had heard multiple versions of the same explosions and had begun collecting accounts of such multiplications of sound. The exact nature of this phenomenon was not well understood, but it had to do with the refraction or reflection of sound from layers in the upper atmosphere. Indeed, improbable as it may seem, some residents of Marburg had reported (throughout early 1916) hearing faint artillery fire. Wegener had urged his PhD student Walther Brand, now a high school teacher in Marburg, to pursue these reports, and Brand had determined that they were hearing the furious artillery fire from the Battle of Verdun, some 360 kilometers (224 miles) to the west. “Outer zones of audibility” from Verdun had appeared at 225, 275, 325, and 360 kilometers (140, 171, 202, and 224 miles, respectively) away from the source.28

  The analysis of all this meteor data would take some time; Wegener would take his observations back with him to Mülhausen at the end of his leave. Before he left on 10 May, he was able to give an address to the Marburg Natural History Society with preliminary conclusions. Based on the observations, and using the algorithm devised by his professor at Berlin, Julius Bauschinger, he was able to determine the velocity of the meteor (37.5 kilometers [23 miles] per second) and its angle of descent (55°), the latter achieved by reducing a variety of qualitative descriptions to quantitative estimates. The calculations were extremely laborious, but he was used to it and enjoyed it.29

  One of the most interesting calculations he presented to the Natural History Society was the time of impact, which he determined by reference to railroad timetables. In Germany it was standard meteorological practice in the early twentieth century to determine the time of weather events—including tornadoes and severe thunderstorms—from observations made by passengers on trains, referenced to the train schedules. Wegener was able to calculate that the fireball had streaked across the sky at 3:25 p.m. on 3 April 1916. He knew this because a reliable account had been given by a passenger on the train between Cassel and Marburg, a train that had arrived on time in Marburg at 4:08 p.m. The observer had recorded that he saw the fireball while the train was between Neustadt and Allendorf. The train schedule showed that an on-time train would have been between these two villages at 3:25 p.m. on that day.30

  Unable to stretch his home leave any further, Wegener returned to Field Weather Station 12 in mid-May 1916. To his surprise and pleasure he found that things had gone efficiently and productively in his absence. He had an unusually competent staff of junior officers, even if most of them were not meteorologists. In fact, the only other meteorologist on staff was Erich Kuhlbrodt (1891–1972). But among Wegener’s officers were some outstanding scientific intellectuals. For instance, there was Walter Porstmann (1886–1959), who had been an assistant to Wilhelm Ostwald before the war and was just finishing a book with the provisional title Normenlerhre, on the history and theory of fundamental measurement units and their relationship. It contained an ambitious plan to reform and reorganize the entire system of measurement and time units which Wegener much admired.31

  Also among the junior officers was Ulrich Hellmann, a specialist in German literature. Wegener had had a standard classical literary education but did not know much about modern German literature, and Hellmann was his guide here, especially to literature in a lighter vein. Hellmann procured a volume of the nonsense verse of Christian Morgenstern (1871–1914), a much-beloved author and the German counterpart of Edmund Lear, Ogden Nash, and Dr. Seuss. Else said that Alfred memorized a number of these nonsense poems (from Morgenstern’s Galgenlieder [Songs from the Gallows, 1905]) and drove her crazy with them by reciting them when they hiked together—until she screamed at him to stop.32

  Wegener was touched by the dedication of his junior officers and impressed by their ability to learn the science. It gave him a deep satisfaction that they were—in the midst of this terrible war—doing good science, and he had pleasure in his command: it was the first time he’d ever been in charge of anything. Previously, there had always been a superior in close proximity: Mylius, Aßmann, Richarz, even his good friend Koch. Now, in Mülhausen, he was actually in charge of a scientific institution, albeit a modest one. It brought him out of his shell, made him more social, less likely to retreat at every opportunity to the isolation of his study.

  Wind- und Wasserhosen

  The industriousness of his junior officers allowed Wegener to make great progress in May and June on his book on Tromben. He was in something of a quandary about terminology. Tromben was derived from the Italian tromba, which meant variously “trumpet,” “trunk” (i.e., as of an elephant), and “water pump.” It was the broadest generic designation for a rotating column of air. It was also confusing, as the word “trombe” was sometimes used to designate only waterspouts. There was the additional problem that the Americans referred to these phenomena as “cyclones” and also as “tornadoes.” What Americans said about them was important because America had many more and somewhat larger tornadoes than Europe, and tornado research in the United States was ahead of that in Europe.

  He eventually solved this problem by giving primacy to considerations of shape, scale, and size: once again he had found a morphological solution to a problem. He noted that whirling vortexes of air could be partitioned into classes by their size. It was a nice problem. Tropical cyclones and barometric depressions (we would call the latter low-pressure systems, or “lows”), he noted, were anywhere from 300 kilometers (186 miles) in diameter (in the case of tropical cyclones) to 3,000 kilometers (1,864 miles) in diameter (in the case of low-pressure systems). At the other end of the size spectrum were Staubwirbel (“dust devils”), at most 200 or 300 meters (656–984 feet) in diameter. In between were the phenomena he was actually interested in cataloging: tornadoes and waterspouts. For these he chose descriptive terms already in use: Windhose and Wasserhose. The series of whirling vortices thus fell neatly into successive orders of magnitude, with the largest of the “dust devils” 100 times smaller than tornadoes, and with the largest tornadoes 100 times smaller than the smallest tropical depressions.

  Wegener accepted Hann’s distinction between these classes and extended his discrimination into a form
al definition. Windhosen and Wasserhosen were Großtromben. They were large rotating whirlwinds with the vertical axis extending from a cumulonimbus cloud to the ground, rotating fast enough to cool and condense the air and make them visible as a cone, funnel, hose, or pillar, narrower at the bottom than at the top. These were the result of mechanical action, with thermodynamic consequences (the condensation of water vapor in the rapidly whirling column). On the other hand, Staubwirbel (dust devils) were thermally driven, not rotating fast enough in most cases to cause serious destruction, short-lived, and visible only because of the dust particles picked up at their base, since they were not able to cool the air enough to condense it; neither did they have the marked thinning of the air so characteristic in the cores of tornadoes.33 These smaller, thermally driven objects (Staubwirbel) fell into the class of Kleintromben.

  So his book would be about the Großtromben, and since this was a classification he himself was inventing or reinventing, he eventually settled on the book title Wind- und Wasserhosen in Europa. The book he produced in these months is exactly what he set out to make: a historical and descriptive catalogue of all known tornadoes in Europe since the sixteenth century, in which these were analyzed and characterized by their size, shape, duration, velocity, speed of rotation, altitude, frequency, length of destructive path and extent of destruction, seasonality, characteristic geographic location, mode of formation and dissipation, relationship to squall lines and to individual large cumulonimbus clouds, and other weather phenomena. Each of the items in the above list had a full chapter of its own in the finished book.

  Wegener worked steadily on the book in late May and all of June. By the end of the first week in July he estimated that he had only a week’s worth of writing left.34 Things were going well for him and seemed to be going well for Germany. He wrote proudly to Köppen that he had been promoted to captain, something so unexpected that he found himself without the appropriate uniform, and he had had to write to his student and friend Brand in Marburg and borrow one from him; Brand was a captain in the home guard. The promotion came with a very substantial raise, which embarrassed him, and he expressed to Köppen his hope “that the war will end before I become a millionaire.”35

  In early July, in spite of Wegener’s hopes for an early end to the war, things suddenly took a turn for the worse. The British offensive on the Somme River had begun on 1 July. The beginning of this battle is notorious for the terrifying casualties taken by the British: 60,000 killed and wounded on the first day. In the English-speaking world this catastrophe tends to overshadow what was happening on the German side. The Germans had been caught unawares by the attack and took terrible casualties all during July, even though they managed to stop Allied advance after only about 10 kilometers. Kurt Wegener wrote Alfred that since 3 July things had gone very badly. He had been shot down and was in no-man’s-land for several days before being rescued. Returning to his aerodrome, he found that it had been bombed by the British. In anticipation of further Allied advances, Wegener’s entire staff had been ordered to a staging area closer to the front, should they be needed to shore up the line. Wegener hoped they would get no further toward the action, but he was worried.36

  Things at home were little better. Else had money, but prices for food were inflating wildly, and there was little to buy in the market in Marburg. Indeed, that summer there was rioting in Vienna over the price of bread, and serious unrest and unease gripped the home front in Germany and Austria. Mail was slowing down between his forward station and home, and he was having difficulty finding out any news. He asked Köppen to find out some information. Else had help and support from the Brands, as well as from Cloos and his wife, but they had no more access to food than she. That summer and autumn she and Hilde would travel to Hamburg and to Zechlinerhütte; food and fruit were plentiful in the older Wegeners’ garden.37

  By the third week in July the British and French advances had been definitively stopped, although the cost was horrifying. Stabilization of the front lines allowed Wegener to return to Mülhausen and resume his routine. With a full staff and complement of officers, he could once again proceed with his scientific work, and within a few days he was able to send the manuscript of his book to Köppen to look through, before he sent it along to the press.38

  The completed book was just over 300 pages long. There are several things worth noting about it. The first of these is the meticulous, even exhaustive, detail. Every description is worked over again and again to extract every piece of information. Wegener had numbered each of the tornado descriptions and referred to them by number whenever he needed them in a specific context. They seem almost to emerge as individual personalities, so repeatedly are they named and discussed.

  As an example of the meticulous detail, we can consider the material in chapter 9, “Rotation,” appearing as pages 176–185 of the finished book. In this chapter Wegener tried to determine one fundamental question: “is the rotation [of tornadoes and waterspouts in Europe] cyclonic or anticyclonic?” Of the 255 records of tornadoes he assembled, he determined that only 25 could, with absolute certainty, give the direction of rotation. Of these, he wrote, “18 (72%) are cyclonic and 7 (28%) give an anticyclonic rotation.”39 He then briefly listed them by number, giving a short description (two or three sentences) of each, in the form of a direct quotation from the original source. One recalls that he had committed, in the very early stages of this work, to stay with exact descriptions taken verbatim from the original texts. He then went on: “Four of these Tromben, namely number 176, 219, 198 and 205 allow us to determine the direction of travel; the first two traveled towards the SW, the last 2 towards the W since these are the same directions of travel of all Tromben generally considered there can be no ground for holding that anticyclonic rotating Tromben are governed by a particular direction of travel.”40

  This was a theoretical question of some importance, but the theoretical importance is implicit, and what is explicit is the description. At stake theoretically is whether the rotation of Earth governs the direction of rotation of these phenomena, these Großtromben, in the same way that it governs cyclonic and anticyclonic circulation. In the Northern Hemisphere, cyclones rotate counterclockwise and anticyclones clockwise; in the Southern Hemisphere, the reverse is true. Wegener makes no determination, pointing out merely that there can be no doubt that there are anticyclonic tornadoes in the Northern Hemisphere, even if the majority are cyclonic. It may be different in the Southern Hemisphere, but a determination of this would require more than the three existing descriptions from that half of the world.41

  One discovers such theoretical questions embedded throughout the text, with one or more in every chapter made evident in bold type. For instance, here is his evaluation of a description of a waterspout with a “double funnel” (a funnel descending from a cloud, getting narrower but then having its base embedded midair in a large bulge that is the top of a second funnel descending to the water surface). Wegener gave a graphical and theoretical analysis of the difference in wind speed and lines of rotation within such paired funnel clouds, as a preface to the following statement: “We will in this context suggest another question which is of fundamental significance for the explanation of Tromben, namely whether Tromben continue on further into the inside of the cloud, or whether they terminate at the cloud floor.”42 This is less a form of covert theorization than it is sagacity and understanding of the problem and of what sort of information is likely to be of interest and of use to investigators of these phenomena. It also poses a question successfully answered only late in the twentieth century: they actually do continue to the inside of the cloud as “supercells.”

  Wegener came to explicit consideration of, as he put it, “Views on the Origin of Tromben” (Ansichten über die Entstehung der Tromben) only in the final chapter of the book (chap. 15). Quickly dismissing the volcanic theory, the downpour theory, the electrical theory, and the wave theory in a few pages, he noted that “there remain then only tw
o theories, the mechanical and the thermodynamic.” In rejecting the thermodynamic theory, he had the same response that had occurred to him so many times in evaluating atmospheric turbulence: that the principal argument against a thermodynamic theory was that in rising columns of air, whether it be the smoke from a cigar, the air above a lamp, a volcanic plume, or simply a cumulus cloud, there is no rotation about a vertical axis.43

  This left only the mechanical theory, whether strictly mechanical or hydrodynamic; he included them both under the same heading. He noted that of all the theories of tornadoes this was the oldest, and he verified this with an extensive quotation from Lucretius, a description he had been happy to find some months before. This is delightful in its own way, as it links the oldest-known hypothesis for the formation of Tromben to the most recent, which Wegener considered for four or five pages at the very end of the book, before concluding with a mild comment that the phenomena required much further investigation.44

  The completeness of the catalog, the sagacity in selecting analytical categories, the clear delineation of questions arising from the descriptions themselves, the tentative endorsement of a mechanical/hydrodynamic theory as the only one consistent with the phenomena, and the demarcation of interesting points and rhetorical questions from the declarative portions of the text all contributed to the lasting power of this work. Of all Wegener’s publications, it is virtually the only one that remains actively cited in the twenty-first century, not in a historical context or as background, but as data pertinent to the investigation today of the phenomena it considers.45