Wegener had published an extensive mathematical treatment of mirages in 1918 and wanted to extend this kind of treatment to the phenomenon of halos. These “halos” are white or colored rings around the Sun or Moon, 22° away from the center of the object, and are connected with other associated but more rare phenomena: tangent arcs, sun pillars, and sun dogs (parhelia), all of which are complicated series of reflections and refractions of incident sunlight (or moonlight), dependent on the geometry of ice crystals in cirrus clouds in the very high atmosphere. The mathematics involved is not calculus but trigonometry, and the best way to present the results simply and clearly is not obvious. The basic theory was available in Pernter–Exner, but they were wrong about the geometry of ice crystals involved in some of these phenomena, and Wegener had worked it out correctly. Wegener deduced that a very rare arc, touching the 22° upper tangent arc above the Sun, was the result of a rare orientation of hexagonal, pencil-shaped ice crystals where the light refracted by a prism face was internally reflected by the prism base and then refracted again out of another face. These phenomena are known today as “Wegener arcs.”35
The success of his work on halos was one of the first fruits of the Institutstee that Wegener regularly attended. He would produce the trigonometric formulas he had chosen to represent the phenomena and then show them to the assembled group. He got quite significant help from Radakovic, but the interest in and the grasp of the problems by the “assistants”—physicists on staff without professorial appointments—and even the graduate students, was a source of great surprise and pleasure to him, accustomed as he was to struggling alone with such problems. He made great progress with his theory of halos in the fall of 1924; the resulting work is still actively cited.36
His success in the work on optics, in which he felt supported and secure, encouraged him to pursue his more extensive plans for an atmospheric physics. The other problem that he had tackled during and immediately after the war, besides the high-altitude reflection and refraction of light by the ice crystals in cirrus clouds, was a matter of atmospheric acoustics: the problem of so-called outer zones of audibility, also known as “shadow zones.” The phenomenon was well documented but poorly understood. Why was it that very loud noises—large explosions, meteor detonations, gunfire—could be heard a certain distance away from the source, then not heard for some tens of kilometers, and then heard again by others farther away? The concentric character of the zones was often complex, not a matter of a single incident zone, a shadow, and a reflected zone, but of alternate rings of silence and of transmitted sound.
Here again Wegener found support, although the problem was much more difficult than the question of the halos—even if that was difficult enough. For the halos, once one understood the geometry of the ice crystals (known from physical inspection) and understood the laws of reflection and refraction, the solution was foreordained if one had sufficient geometric imagination, persistence, and help. Pernter and Exner had gotten most of the answer correct, but not all of it. Wegener had finished the treatment of the topic, and the support of his group at Graz had been essential.
For the acoustical problem of the outer zone of audibility, the phenomenon was well documented, but the cause was much more difficult to discover. Something happened in the lower stratosphere, a phenomenon of the reflection and refraction of sound waves, but since pressure and density and temperature are all related, which of the three phenomena was causing this intermittent audibility? Was it the density of the atmosphere or its temperature? Was it a matter of the wind field and the shift from the turbulent troposphere to the laminar flow of the stratosphere? Here Wegener benefited again from his colleagues at the Institutstee. Wegener presented the problem several times, and the consensus answer was that, for the time being, no definitive solution was possible.
There was still some dispute about whether the reflection and refraction of sound, whatever the cause, happened at the boundary of the stratosphere (the tropopause) or within it. Wegener undertook a very clever study in which he showed that the distance from an explosion to the aüßere Horbarkeitszone (outer zone of audibility, as it was known) was different at different seasons of the year. Back in 1910 he had demonstrated that the stratosphere boundary was lower in winter and higher in summer. He demonstrated the same thing here using the same technique, suggesting that, indeed, whatever the cause (density or temperature or wind), the location of the deflecting surface was the tropopause.37
Thinking about temperature led him also to produce an interesting paper on the temperature of the atmosphere in the area beyond the stratosphere, what we would now call the mesosphere, and which Wegener took to be the boundary between the nitrogen atmosphere and the hydrogen atmosphere; it was also the level at which “noctilucent clouds” appeared, a phenomenon that had been studied intensively since Krakatoa. He extrapolated temperature curves from the decay of the temperature inversion within the stratosphere to argue that the temperature at 80 kilometers (50 miles) would be between −100°C (−148°F) and −110°C (−166°F), values that correspond to current estimates.38
Happy to be at home in his original career as an atmospheric physicist, a more expansive sense of having found a home persisted through the Christmas vacation of 1924, with concerts and parties with university colleagues. Alfred and Else found these events sufficiently jovial and informal to overcome Alfred’s innate resistance to social life in almost any form beyond the sphere of family, close friends, and the exchange of work and ideas with colleagues.
Back at work in early 1925, Wegener received a request from Eduard Brückner (1862–1927), professor of geography in Vienna, to come and give “his lecture” on the climates of the past to the Geographical Institute in Vienna. Brückner had coauthored Die Alpen im Eiszeitalter with Penck in 1909, and before that he had been a colleague of Köppen at the old German Marine Observatory in the 1880s. He was extremely excited by what he saw to be the confirmation of his and Penck’s dating of the ice ages through Milankovich’s calculations, and he was willing to pay Wegener a handsome honorarium to come. These sorts of invitations were becoming frequent; some could be refused, but this one could not.39
The invitation is notable more for political reasons than for scientific; Wegener had made a splash at Innsbruck the previous September, and his lecture in Vienna in March apparently went off well, thus strengthening the geographers in Vienna against the geologists. The Innsbruck meeting had been a plenary congress of “naturalists,” and the lecture in Vienna was before geographers; Wegener had yet to come into contact directly with Austria’s leading geologists.
Finally, on 15 May 1925 the Geological Society (Vienna) held a symposium, of sorts, on Wegener’s displacement theory. Otto Ampferer spoke on the subject of Wegener’s displacement theory. The president of the society, Fritz Kerner (von Marilaun) (1866–1944), then spoke on the subject of Wegener and Köppen’s book on the climates of the past. Wegener was quite conspicuously not invited to this session.
Wegener had depended since 1912 on Ampferer’s (1906) idea of flow or “under-streaming” in a fluid (if extraordinarily viscous) subcrust. Where Ampferer had imagined such flowing currents acting locally as the mechanism for mountain formation, Wegener had taken this idea as hypothetical support for large-scale streaming of the Sima and as a possible mechanism for continental displacement. He had stressed this especially in the 1920 edition of Die Entstehung der Kontinente und Ozeane. In 1922 he had used such “streaming” again as a hypothesis subsidiary to Polflucht and Westwanderung to explain the displacement of India to the northeast (i.e., against the rotation of the globe), where it had collided with the Eurasian landmass.
The Vienna session of 15 May 1925 was attended, among others, by Felix Exner, Carl Diener (who had just become the Rektor of the University of Vienna), Lukas Waagen, Eduard Brückner, and Anton Handlirsch (1865–1935), all of whom spoke after the papers. Brückner, Exner, and Waagen gave support; Diener and Handlirsch (a famous insect paleontologi
st) spoke in opposition. Waagen added a manuscript to the reports of the session, which included his reflections on continental displacement as “an idea which shows up in minor publications by senior Austrian scientists” from the previous generation, and he added some cautiously supportive comments about Wegener’s geophysics.40
Fritz von Kerner (1866–1944), the organizer, was a paleoclimatologist and son of the famous Austrian botanist Anton Kerner von Marilaun (1831–1898)—professorship in Austria was very much “going into the family business.” Kerner had long been an advocate of temperature differences in different periods of Earth based on the distribution of land and water and had argued in 1895 that the Southern Hemisphere must have been warmer than the Northern Hemisphere in the Jurassic, because there was more land in the Southern Hemisphere at that time. This sort of argumentation about climate differences based on differences in temperature, given the distribution of land and water, Köppen and Wegener rejected in 1921 and again in 1924 as an unlikely cause of climate change, since it was a matter of a very few degrees of the mean annual temperature and expressed only at rather high latitudes.
Kerner no doubt had taken it very amiss that Wegener in 1922 had used him as an example of the kind of “impossible hypotheses” offered to explain away the extent of the ice cover in the Southern Hemisphere in the Carboniferous and Permian. Kerner had proposed that the widely distributed traces of ice were a question of local anomalies of the distribution of heat caused by cold currents in the ocean and “such like phenomena.”41
Kerner did not seek to publish his paper from the symposium in May, but Ampferer’s paper appeared in Die Naturwissenschaften in July 1925. In this paper, Ampferer made an attempt at a reconciliation of his earlier ideas and Wegener’s continental displacements by postulating a global Earth convection, rising at the poles and sinking at the equator, which could drive the continents away from the poles and cause compressional mountain building at the equator. It is an interesting paper of the kind that makes people want to “find an idea ahead of its time,” in this case a precursor of the mantle convection today believed by many to drive plate tectonics. Seen in context, it was an entirely speculative, hypothetical, qualitative extension of a very detailed mountain building theory he had offered and dropped eighteen years prior, unsupported by any new data or any quantitative argumentation.42
Ampferer’s attempt to hitch his ideas to Wegener’s was nevertheless significant. The well-worn expression “there is no such thing as bad ink” applies to Wegener’s career at this time. Ampferer began his Vienna paper by remarking, as so many others had in 1923 and 1924, that Wegener’s hypothesis was so well known that he need not review it to discuss it.
It is not nearly as important who (in the 1920s) supported Wegener and who opposed him as it is that Wegener’s theory of continental displacements had thoroughly penetrated scientific discussions in geology, paleontology, climatology, geography, and geophysics in these few years. Some agreed, some claimed priority, some offered modifications; some opposed mildly, others violently. Even if Wegener was (as often as not) deemed to have “given the wrong answer,” all but the most intransigent admitted that he was asking the right question. Wegener had succeeded in changing the question “Do continents move?” into the question “How, when, and where have they moved?” In the history of the sciences, many thousands of workers are busy at all times changing the answers; only a very few ever succeed, as Wegener did, in changing the questions.
Wegener’s Atmospheric Physics, 1925–1926
At the end of May 1925, during the Whitsun (Pfingsten) vacation, Alfred and Else invited Felix Exner and his wife to stay with them for a few days in Graz. Theirs was a friendly but delicate relationship. They were working in the same field and had already reviewed each other’s books in meteorology. Alfred wanted to talk to Felix Exner about his modifications to Exner’s work in optics.
Exner had just finished the second edition of his book on dynamic meteorology (Wegener had reviewed the first edition in 1917) and wanted to be sure where Wegener stood in the debate between himself and Bjerknes, knowing that the Wegener and Bjerknes families were close. Wegener had made a point not to take sides in that dispute. He had made a mild criticism of Bjerknes’s analogy between the wavelike disturbances of frontal boundaries and Helmholtz waves; on the other hand, he had studiously avoided taking sides between Exner and Bjerknes at the conference in Norway in 1919. Exner remained opposed to Bjerknes’s idea of the origin of cyclonic storms as wavelike disturbances at frontal boundaries. Wegener’s caution in not taking sides here had allowed Wegener and Exner to become friends. Recently, as a way to cement their personal goodwill, Exner had successfully nominated Wegener to be a member of the Academy of Sciences in Vienna, notably in the mathematical-physical section, not that for earth sciences.
Exner discovered, in the course of this friendly and productive visit, that the Wegeners had no plans to take a summer vacation that year because there was no extra money, given the purchase of the house. Exner immediately had a solution. There was a sanatorium on the summit of a mountain, the Stolzalpe (1,200 meters [3,937 feet]), in the Murau district of Styria. It was a tuberculosis sanatorium specializing in the treatment of children, following a treatment regimen in which it was believed that exposure to sunshine was an essential part of tuberculosis therapy.
Exner had been invited there a few years before to make measurements of sunshine, as the hospital wished to keep an accurate record of the intensity of their therapeutic sunlight; he and his family had stayed for free in a fire-damaged farmhouse on the sanatorium grounds. He suggested that Wegener and his family could stay there for free, if they could “rough it” with bedrolls and could cook on a Primus stove, bringing their own food. All that Wegener would have to do is take the sunlight measurements each day; the rest of their time would be their own, and the surroundings were beautiful. Of course, Else and the Wegener girls were experienced campers, boaters, and hikers, accustomed to sleeping in tents and on the ground. Alfred and Else accepted with alacrity; they would go at the end of the summer term.43
That summer Alfred offered an “Introduction to Oceanography” course. Its title in the catalog, Einfuhrung in die Meereskunde, is an indication that it was already on the books, as the older word Meereskunde was being replaced everywhere by Ozeanographie.44 Following the tradition of Graz, Alfred, as the newest member of the faculty, in spite of his exalted rank, had to teach the service courses needed in the curriculum in preference to his own work, at least in the summer semester. He undertook no new scientific investigations during this term, as he and Else had decided to repaint all the doors and window frames of their new home and to dismount the complexly filigreed shutters and paint them as well.
They spent most of August on the Stolzalpe, and while all the girls were vigorous hikers, both Alfred and Else were astonished by the tenacity of five-year-old Lotte, who could climb to the summit with her sisters, and even help cook lunch on the trail, and was also able to make the hike the full distance from the Stolzalpe to the summit of the Frauenalpe via the mountain road.
Alfred and Else stayed in Graz in early September only long enough to see the girls safely off to school in the care of their grandparents, and they immediately left again for an Alpine tour of their own, which was to culminate in yet another anniversary of yet another mountain observatory, the Zugspitze, on the southern border of Bavaria, to be held from 4 to 7 October 1925.
One mentions this otherwise unremarkable tour only because the weather turned wintry early, and they found one of the passes they had to cross deep in snow. Else said, “Despite the fact that the pass was deep in snow, Alfred, without hesitation, went forward and again and again unerringly to scrape the snow away from the trail markers while I, and a lanky Thuringer who had joined up with us, waited helplessly above.”45
This reveals not so much what she knew about him but what she did not, in terms of what he had experienced in Greenland. Compared to the place
s he had been and what he had done, the things he did that gave her such pride and so surprised her—such as keeping food warm for a noon meal, or starting a stove on a cold morning, or finding the trail markers on a well-worn Alpine route in a foot or two of snow—were all child’s play to someone who had walked 700 kilometers (435 miles) across Greenland at −30°C (−22°F).
When they arrived at the Zugspitze with Benndorf, Ficker, and Defant, they found good weather and yet another “Alpine Summit meeting.” The meterologists had a sit-down meeting with Wegener and explained to him that in early July of that year the physicist Otto Lummer (1860–1925) had died suddenly. He was one of three general editors of the eleventh edition of Müller-Pouillets Lehrbuch der Physik, which was then undergoing a major revision. Lummer was not only one of the general editors but the editor for volume 5, part 1: Physik der Erde. That volume now had no lead editor. A few of the manuscripts had come in, but the volume was far behind schedule. The chapters were meant to be encyclopedia entries, many of them in excess of 100 pages.
Several of the authors were current or former members of the Graz faculty. Ficker was to do the main entry in meteorology, and Benndorf and Viktor Hess were to do the article on atmospheric electricity, a deceptively simple name for something that included Earth’s electrical field, the ionization of the atmosphere, and cosmic radiation. Emil Wiechert (1861–1928), who had trained a generation of German geophysicists at the University of Göttingen, was to do geodesy and the figure of Earth; seismology was to be the task of one of his young students, Beno Gutenberg (1889–1960). The rest of the roster of authors was also impressive: Alfred Nippoldt (1874–1936) would write the article on terrestrial magnetism, and Gustav Angenheister (1878–1945), head of the geophysics division at Potsdam, would do the aurora and Polarlicht.
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