Alfred Wegener

by Mott T. Greene

  Wegener wrote on 21 January to Köppen that he was making progress on lunar tides, although he said, “It is moving in a somewhat different direction than I had planned.”96 He had analyzed the Moon’s motion in relation to atmospheric tides in a series of published measurements from the 1870s and 1880s, taken at both high and low latitudes. He considered carefully the relationship of the atmospheric tides to the oceanic tides and the variations brought about when the Moon was closest to Earth (perigee) and when it was farthest from Earth (apogee). None of these details completely resolved the anomalous offsets.

  The answer, he found, lay in the question of the Moon’s declination. This refers to the altitude above the horizon of the Moon when it reaches its culmination, its highest point in the sky. Because of the tilt of Earth’s axis at 23.5°, the Moon will reach a maximum and minimum altitude above the local horizon two weeks apart. But because the Moon’s axis is also tilted at 5° away from the orbital plane of Earth around the Sun, in a long and complicated cycle this variation in declination can be as small as 18.5° or as large as 28.5°. Wegener observed that the long-term variation in the Moon’s declination could explain the apparent anomalies at high latitudes and the absence of such apparent variation at very low latitudes.97 He was extremely pleased with this result, and it was an outstanding version of his ability to find in published data the signature of some physical phenomenon not noticed by the authors. By late February he had checked his result by extending the time series back into the middle of the nineteenth century, and he put the paper into publishable form.98

  As if this were not enough, he was working on another problem as well. Wegener’s old boss and his constant champion, Richard Aßmann, at seventy not in the best of health, had retired from Lindenberg in 1914. His students and colleagues had quickly organized a celebratory volume to be published as a supplement to Das Wetter, a journal he had helped to found. Everyone from “the Berlin school” was to be in it, including Köppen, Richarz, Kurt, Hergesell, and Berson. This, of course, meant that Wegener had to produce something, and he turned to a topic he had taken up in his review of recent work in meteorology and geophysics, the attempt to verify the chemical differentiation of the upper atmosphere at different altitudes by the change in color of large meteors.

  He wrote to Köppen in late February that he had finished his contribution and gotten a nice result although “it had not cost much work.”99 Once again Wegener was mining data available in the meteorological literature of the nineteenth century and applying it to a novel aim. Observations of the color of large meteors taken in the nineteenth century had not been directed at the spectroscopic analysis of the layers of the upper atmosphere but were clearly useful for such purposes. Where the meteor and its color had been observed by more than one observer at distant points from one another, there was a possibility of determining the altitude by knowing the time. Wegener’s interpretation of this phenomenon was that the color of the meteor trail was determined not by the composition of the meteor itself but by the atmospheric gases through which it was passing and which it was igniting in its passage. We may recall that Wegener believed the atmosphere to be chemically differentiated with sharp boundaries between an oxygen atmosphere, a nitrogen atmosphere, a hydrogen atmosphere, and eventually a geocoronium atmosphere.100

  All this writing and thinking in the spring of 1915 transpired in Marburg, in Alfred and Else’s apartment, with their new child, Hilde, and, fortunately for them, the assistance of a hired girl, their first household help. Money was a problem as always. Wegener had no announced lectures and thus no lecture fees, although these were never a large part of their income. In October 1914 his stipend of 1,500 marks per year had been discontinued.101 Now that he was back in Marburg, the stipend was to be renewed, on the condition that he fill the role of “assistant” in the Physical Institute. This was something arranged for him by Richarz, knowing his financial difficulties. Wegener begrudged the time, 9:00 a.m. to 1:00 p.m. and 3:00 to 6:00 p.m. each day, but had not been able to say no to Richarz, who had lost both of his actual assistants to military service.102 The institute work turned out not to be nearly as burdensome as he had imagined, and in early April there was a visit from Vilhelm and Honoria Bjerknes.103 While technically a neutral (Norwegian), Bjerknes could not help but be involved in war work. The German navy had always been deeply involved in meteorology, but now there was an air service, and with the army preparing for large-scale use of poison gas, knowledge of prevailing winds would be a matter of life and death. Indeed, Germany would make its first major gas attack on Allied positions later that month, in the Battle of Ypres. Leipzig’s (and Bjerknes’s) meteorological institute became a center of military meteorology.104

  However different their work, Bjerknes and Wegener saw eye to eye: both considered dynamics and thermodynamics parallel but separate disciplines within meteorology. Both were deeply focused on surfaces of discontinuity: Wegener in the vertical, Bjerknes in the horizontal. During the Marburg visit, they discussed the “squall line theory” (Böentheorie) of Wilhelm Schmidt (1883–1936). A squall line refers to what we would now call a cold front, and Schmidt had done laboratory experiments on the behavior of adjacent masses of different temperatures, with the idea that the thermal difference was a cause of the instability. Wegener had seen in Greenland squalls without thermal difference, as well as huge thermal differences that did not produce squalls. If there was a relationship, it was not causal. Bjerknes was grateful for Wegener’s critique and for knowledge of Schmidt’s work, for which Wegener provided references.105 During the visit, Else was not feeling well. Hilde had been feverish for more than a week, and Else became feverish herself and ultimately suffered a miscarriage—she was in the first or second month of her second pregnancy. The Bjerkneses moved to a hotel and came over for meals—Honoria Bjerknes was able to provide advice and solace for Else, as she herself had miscarried earlier in her marriage.106 While Honoria spent time with Else, Alfred and Vilhelm went for walks or retired to Alfred’s study.

  Both men were deeply involved in scientific aeronautics, and with the advent of war, suddenly knowledge of winds aloft was of pressing interest: in January of 1915, Germany had begun bombing raids on England, employing zeppelins—large and navigable rigid airships filled with hydrogen. In these first raids, the zeppelins encountered unexpected upper-level winds and were blown far off course. As winter turned to spring, the kaiser wished to extend and expand these raids, but he had ruled historic buildings in the heart of London off-limits, restricting the raids to the docks on the Thames.

  It is therefore not surprising that Alfred was requested, in early May 1915, to cut short his military leave and depart immediately for Brussels, where he was to make a circuit of the aerodromes for the zeppelin bombers and teach the pilots and crew aerial navigation. Night raids made it harder to shoot at the zeppelins, and Wegener’s navigation technique for astronomical position finding in balloons using the sextant that he had designed back in 1906 was the only well-known information on the subject.107 Wegener’s doctor objected strenuously to the trip, arguing that the rapid changes in elevation in an airship could affect his heart, but Wegener agreed to go. Kurt, after all, had been in the newly created air force at the outbreak of war, and in April he had suddenly been made adjutant to Hugo Hergesell (1859–1938), head of the newly created Field Weather Service; doubtless the appeal had come directly from them, and Wegener spent the month of May in and around Brussels, teaching aerial navigation to zeppelin captains.108

  Returning to Marburg in early June, he found that the doctor’s reservations had been merited, as he began to experience palpitations when reclining.109 Else’s health was also not good. It had been decided that her miscarriage had not merited “an operation,” but even before Alfred left for Brussels she had experienced chest pain diagnosed as angina. One possibility for her diagnosis is listeria, a food-borne illness and a frequent cause of miscarriage in early-term pregnancies; listeria is a bacterial infection
that proceeds in some cases to endocarditis—with fever and chest pain.

  Alfred decided that they needed a “cure” and took Else on a two-week vacation including a cruise down the Rhine and a walking tour in the Taunus, the low mountain range inside the state of Hesse; they were not far from Marburg but worlds away from their recent cares and fears.110 By mid-June, when they returned home, she was feeling fit and refreshed, but Alfred’s military physical in Berlin on 19 June (at the end of his official six-month leave) again revealed a pronounced “click” in his heart sound, which, together with the palpitations, indicated a prolapsed mitral valve. The battalion medical officer, Friedlander, declared him permanently unfit for combat but available for “temporary garrison duty.”111

  On 19 July, Alfred was reexamined by Dr. Hildebrand (his physician in Marburg), who found his symptoms diminished and pronounced him ready for full garrison duty within about four weeks.112 Even before his July medical examination, he had written to Köppen that he daily expected orders to return to his regiment in Berlin. The realization that he would return to active duty had hit him hard, and once again he had difficulty working. “The last month has been very unproductive for me scientifically.”113 He was unwilling to start work on the optical phenomena from Greenland—or anything else—only to be interrupted by military service.

  Alfred, Else, and Hilde Wegener in June 1915, shortly before Alfred’s return to active service in the German Army. Photo courtesy of the Alfred Wegener Institute, Bremerhaven.

  There was more to Wegener’s dispirited disinclination to work than just his impending return to military service. At the end of June Köppen had written him a long letter about the book on the displacement theory, having read through the proofs. Wegener was pleased, even delighted, that Köppen, who had always treated the work on displacement theory as a distracting sideline, had warmly approved it. But Wegener’s percipient guide and mentor had also raised a number of pointed questions about the manuscript, not least the inconsistent, confusing, and (finally) inconclusive treatment of oceanic deeps. Wegener had been persuaded by his discussions with Cloos to include something about these interesting features on the outside of the great island arcs of the western Pacific, even though he could not give a convincing explanation of them. Now that Köppen had asked for details, he found that he could give none. Moreover, the existence of the Peru-Chile Trench, pointed out by Köppen, 8 kilometers (5 miles) deep and 5,000 kilometers (3,107 miles) long, on the leading edge of the South American continent made nonsense of the explanation that such trenches were somehow connected with the creation of island arcs springing away from the trailing edge of a continent. Why had he not seen this before?

  Wegener held onto Köppen’s letter for several weeks before replying. He expressed delight at the approval and thanked him for his comments, and he admitted his inability to explain ocean trenches in any greater detail (“the whole thing is still not clear to me”). His reflection went much deeper than this, however: “I think, by the way, that it is a weakness of all my work that I am forever going into too many side issues. I managed to cut out many of them from this book, but I should have limited myself to an even greater extent to the straightforward establishment of the displacements. Now we’ll just have to wait to see how it is received. We can scarcely expect much discussion as long as the war lasts.”114

  Wegener’s rueful self-assessment in this letter strikes home. His book on thermodynamics and now this book on continental displacements had a tendency to lose central focus in an overly meticulous treatment of peripheral issues. By the time he had sent the proofs (in 1911) of the book on thermodynamics to Köppen, he had felt the need to apologize for incorporating a large number of physical speculations that they had not discussed. It was exactly these speculations and this miscellaneous character that Exner had savaged in his review of the book. Now he could see clearly that this same tendency had come to the fore again. This motif in his work was closely tied to the source of his enthusiasm, his thirst for novelty, and his pleasure in discovery. Moreover, it could also be linked to something drummed into him by his father in childhood: that all intellectual work, all creative work should be infused with what Schiller had called Spieltrieb, the spirit of play.

  Wegener believed that theoretical work should incorporate some sense of the novel play of ideas, but he also believed in hard evidence and that novelty comes not so much from theoretical speculation as from careful empirical work. He had said so to Köppen in responding to Exner’s review, noting that he thought that Exner overvalued theory as a tool of discovery. Moreover, in his inaugural lecture in Marburg back in 1909, he had argued that in all sciences, periods of theoretical elaboration must alternate with periods of renewed empirical work and the gathering of data. Certainly his work on continental displacements was a theoretical elaboration of a great quantity of empirical data, and as certainly it was infused with the spirit of creative play of ideas, both in 1912 and to a much larger extent in 1915. It was now, perhaps, time to move to the other extreme.

  Also at work here was his sense of science as a vocation, very like a call to the clergy. This was strong, though not exaggerated, in him, and it was not uncommon in men of his generation. Two of the most famous essays by Max Weber, written at just about this time, are entitled “Politics as a Vocation” and “Science as a Vocation.” Perhaps because Wegener’s own father was a clergyman, he easily adopted clerical vocabulary to describe his intellectual life. He had already referred to the deepest part of himself as his Allerheiliges, his “inner sanctum,” and he referred to the science-interested but not professional public as Die Laien, “laymen.” This is common in English as well, as in “layman’s language,” but in German it has a somewhat stronger sense. With his overreaching and speculative forays in his work on displacements now evident to him, he felt something close to a sense of sin, and certainly a sense of remorse.

  Two weeks after his confession to Köppen, at the end of July, these strands of thought seem to have come together in the form of a plan. He wrote to Köppen that he had turned again to his work on Tromben, a generic term for whirlwinds of all kinds, but which in 1911 he had used as a synonym for “tornado,” a distinct rotating column of air usually occurring along with a thunderstorm and spinning off away from a squall line. He had not been satisfied with the work and found it poorly substantiated, and now he had turned to original descriptions of tornadoes and had come to the conclusion that “it would be very useful to write a book on this topic, perhaps in the ‘Science’ series of Vieweg [his publisher on continental displacements].” He went on to say (in a long and enthusiastic letter) that it would be very important to report all the descriptions of tornadoes “word for word” (his italics) from the original and present them together with the original illustrations. Information about tornadoes was scattered throughout the literature, often in small notes and reviews tucked away between articles. In the few collections of descriptions which existed, the descriptions had been edited and the figures adapted in ways that appeared to serve the theory of the formation of tornadoes which went with that book.115

  Köppen feared a repetition of the same sort of theoretical excursion as that on continental displacements, a work that would run off in all directions at once, as Wegener’s work so often did. Therefore, he urged Wegener to consider instead a theoretical article or supplement to a scholarly journal like Meteorologische Zeitschrift, and Wegener immediately replied that he did not want to write something narrow for meteorologists or something theoretical. This was to be just a compilation and not an investigation. While professional meteorologists would certainly find it interesting, the audience he had in mind was a lay audience—for the general reader, for meteorological observers (who manned weather stations and sent data as part of meteorological networks), and especially for sailors—and his aim was not just to inform them of what was known but to give them, as it were, a template to encourage new descriptions.116

  So Wegener’s book would
be limited to descriptions, not theoretical speculation, and further limited to description of these phenomena only in Europe. He would consolidate the descriptions into lists of various kinds, try to clarify terminology, and for each verifiable occurrence of a tornado or waterspout give the year, day, hour, and place. In addition to these lists, he would organize the material in other ways: the direction and speed of travel, descriptions of the origin, and descriptions of the disappearance.

  He would analyze meteorological elements: cloud conditions, precipitation, the direction of rotation, the diameter, the height, and further specification of its effect on trees, crops, buildings, and ships, the better to assess the energy involved. As he wrote to Köppen at the end of August, “I have come with much more clarity to the ways in which I will limit my work on tornadoes.”117 These limitations—scrupulously avoiding all theorizing, not even paraphrasing, not even redrawing original illustrations—would be one of those efforts he described as necessary in 1909 in his inaugural lecture at Marburg: the accumulation of data preparatory to theory. At that time he had spoken of meteorology as a science that alternated accumulation and assimilation as creative moments. It also underlined his feeling, in this case in some sense a remorseful feeling, that empirical description should be kept separate from theory, and both of these separate from advocacy.