So this was the deed demanded of Wegener, his scientific task, and the riddle for him to undo—to understand the layered structure of the atmosphere, and to understand the physics that made it and moved it. This was why he had come to Lindenberg, where, in Aßmann’s words, “the tasks of the observatory are primarily scientific, and directed to the investigation of the physical relationships and processes in the upper layers of the atmosphere.”23 Not upper reaches, but upper layers.
Alfred and Kurt set to work on this task immediately after they took up their positions. At Kurt’s request, he was permitted to occupy and use the mountain observatory at the summit of the Brocken, outside Berlin, from 1 January until 8 February 1905 to carry out a program of kite ascents, as well as to examine the appearance and behavior of the upper surface of the cloud layers. Since the cloud layer that blanketed Berlin in January was usually lower than the summit of the Brocken, he should be able to observe motions and patterns in the upper surface of the overcast. While Kurt worked there, Alfred would take part in the daily round of observations at Lindenberg.
The problem that Alfred and Kurt had in mind—hazily at first—was based on an often-repeated opinion of Bezold’s: that one had to think of the upper surface of the cloud layer at any given time as a sort of “second surface of the earth” and think of the atmosphere between Earth’s surface and the top of the clouds as a region with its own dynamics.24 The discovery of the boundary layer at 11 kilometers (7 miles) intensified the search for dynamic layers elsewhere in the atmosphere, and cloud layers were the most visible evidence of such layering. The bottoms of clouds are typically flat, as they are the thermal signatures of the altitude(s) at which the atmosphere becomes saturated with moisture and the excess condenses into clouds. The upper surfaces of clouds may be similarly flat but are often billowy—reflecting the presence of vertical (convective) motions in the atmosphere. Sometimes, however, the upper surfaces of extensive cloud layers (and, less frequently, their lower surfaces) show a regular up-and-down billowing, resulting in long rows of peaks and troughs that look like frozen waves. They are indeed waves—and in Wegener’s time they were known as Helmholtzschen Luftwogen, “Helmholtz air waves.”
Their interest in the problem of air billows, or Helmholtz air waves, or, as they are known today in the English-speaking world, “Kelvin-Helmholtz instabilities,” grew out of their quotidian observational work for Lindenberg Observatory in the first months there. The Wegener brothers were responsible for working up, out of the records of the individual balloon and kite flights, a monthly summary and map of the temperatures at various altitudes above Lindenberg. These appeared in the meteorological journal Das Wetter, edited and controlled by Aßmann. Alfred and Kurt were allowed to publish the data for April 1905 under their own names—their first real scientific publication.25 In working up the data from individual kite flights, Alfred occasionally noted (as had his colleagues) a pattern of slight temperature oscillations in the record of kites flying on a fixed length of cable, and he wondered about their cause.26 He asked the other observers and assistants about the phenomenon and collected their comments.
The course of his investigation of these temperature oscillations followed a pattern often repeated later in his career, when a question brought forth by a small but interesting anomaly led to another, and then another, and soon the investigation of some phenomenon was pulling him along willy-nilly into a deep and broad search, though his original idea had been a mere technical note. In his own words, “I originally only had the idea of bringing together and drawing attention to the observations of my aeronautical colleagues (to whom the phenomenon had appeared) on the cause of these small temperature oscillations; in working them up, however, I stumbled on a number of issues that made a wider investigation necessary, and their discussion did not seem to be completely without interest; consequently the investigations have far outgrown my original plan.”27
As he studied the problem of the temperature swings, the daily work of the observatory continued. He became an expert in the rigging and flying of kites and balloons, with their special lashings, knots, clips, and cable ends, and in the daily rhythm of observing and recording meteorological data—calibrating the thermographs against the station records, keeping the logbook in the Windenhaus, and standing watches day and night while the instruments were aloft. It really was very like being at sea, an impression not lessened by the rippling of the surrounding wheat and barley as the prevailing northwesterly wind passed across the plain, or by the creak of the cable against the winch drum, or, as often as not, the drumming of rain on the roof of the Windenhaus—in this and many respects like the wheelhouse of a merchant steamer.
On this “expedition,” as on any other, the interruptions, snafus, and assorted emergencies provided much of the interest and excitement. Kites snapped their cables and sped off and away with alarming frequency, occasionally cutting telegraph lines, but more commonly making a mess of farm fences. These truants had to be pursued, the cables and equipment salvaged, and the instruments recovered. Once, during a kite flight on which Alfred was standing watch, a lightning strike incinerated the kite aloft and sent 9 kilometers (6 miles) of wire into an incandescent meltdown, creating a beautifully spiraling smoke trail across the sky and causing an impressive brush fire when the incinerated apparatus crashed to the ground. It was a harrowing escape at the tether end: had the cable not parted aloft, he might easily have been electrocuted, becoming not a subject for a biography but a grim footnote to Ben Franklin’s injunctions about flying kites in bad weather without a lightning rod. Thereafter, on days with a danger of lightning, the scientist rigging the kites and clipping on the “helper-kites” (as needed) stood inside yet another Aßmann invention—the Blitzschutzbügel—a rectangular lightning-rod enclosure attached and grounded to the Windenhaus.28
Aßmann liked Alfred, not least because he found in him a kindred spirit in the matter of instrument design and tinkering. From the time he arrived at Lindenberg, Alfred gravitated more and more toward work that involved the theodolites used to track the free balloons. He had enjoyed his work in navigation and position finding with Marcuse at Berlin, and his doctoral thesis had led him to study the forerunners of these astronomical instruments. He had become proficient in both plane and geodetic surveying, and in the latter he had employed zenith telescopes (a form of astronomical theodolite) to locate the terminal points of the geodetic baselines, by fixing the positions of stars directly overhead. These were extremely fine measurements, and the accuracy of an entire triangulation network depended on the accuracy with which the baselines were anchored. Alfred was familiar with these instruments and their design, but he was pleased that the work at Lindenberg offered a different set of design problems—aimed at instruments that could be swiveled easily and read off rapidly; he spent much time in studying ways to improve the combination of speed and accuracy for these specialized tools.
Only surviving photograph of Wegener at Lindenberg, here rigging a kite tether from within a Blitzschutzbügel, a rectangular lightning rod designed to prevent electrocution in a lightning strike to a kite (a common occurrence). Note the “Hargrave” box kite on the ground behind him: Wegener is preparing to send it aloft. From Aßmann, Das Königlich Preußische Aeronautische Observatorium Lindenberg.
Aßmann put Alfred to work testing new instruments as they came to the station, and one of these was a theodolite for following free balloons, designed by Swiss meteorologist and geophysicist Alfred de Quervain (1879–1927). De Quervain, though only a year older than Wegener, had already been on a polar expedition, participating in Drygalski’s “Gauss” Expedition in 1901–1903 and making meteorological observations on the island of Kerguelen in the far South Atlantic.29 Wegener’s review of de Quervain’s instrument is a nice demonstration of how tinkering and experimentation can go on while still providing a scientific result, and it gives some of the flavor of daily life at Lindenberg and of Wegener’s earnest enthusiasm for his work.
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The test took place on a beautiful, clear January morning, with a light surface wind from the south, a temperature of −8°C (18°F), and unlimited visibility—perfect conditions. The morning kite flight was already aloft and registering when the balloon was released at 8:00 a.m. from the Windenhaus. Wegener manned the theodolite, while his assistant called out at thirty-second intervals for him to mark the altitude and azimuth. To accomplish this, he had to take his eye from the telescope and read the vernier scales, but he succeeded in keeping track of the balloon—mostly. At an altitude just over 1,000 meters (3,281 feet), the balloon, which had been traveling almost due north, suddenly veered 90° to the east “and disappeared, behind the Windenhaus, from the view of the completely unprepared observer [himself]. The theodolite had to be set up again, but we were lucky to find the balloon and thereafter the observations could be carried on without further disruption.”30 He followed the balloon for eighty-five minutes in its ascent and descent, collecting 134 observations: a few were lost in moving the theodolite, and for most of the last kilometer of descent the parachute on the packet of instruments was invisible—though Wegener guessed its trajectory and caught it again 150 meters (492 feet) above the ground to fix the landing site.31
The flight aimed to test the theodolite, but also to compare two thermographs aloft simultaneously on a single balloon—one of these was a modified design of Hergesell’s, the other an instrument built by Teisserenc de Bort. Moreover, Aßmann had decided that they might as well experiment with a new method of plotting balloon tracks (de Quervain’s), in which the balloon’s altitude was plotted along a vertical axis and the time along a horizontal axis, the latter also scaled in kilometers. One could in this way get a picture of the flight path in both its vertical and horizontal dimensions in a single view and, from the plot and the distance between the points, calculate the wind velocity (as well as the direction) at every altitude. The test chart also featured a compass rosette centered on the Windenhaus, so that one could read the direction of flight readily. This sort of planning and economy of effort, this packing in of information and results, was typical of Aßmann, who had ample resources but stretched them to the limit at all times—a valuable lesson for an apprentice aerologist to learn.
Wegener got a good result out of this flight and was pleased. After recovering the thermographs (the balloon landed 20 kilometers [12 miles] away), he determined that there was an overnight inversion (pooling of cold air near the ground) of almost 10° at an altitude of 1 kilometer (0.6 miles). Even more exciting was his confirmation of the passage of the balloon into the permanent inversion zone. Just above 7 kilometers (4 miles) the balloon, until then traveling steadily northeast for some time, suddenly began to wander in a circle and slow its velocity, and it continued a 360° turn during its passage through an altitude of 10 kilometers (6 miles). After that, it stabilized and continued in a new direction at a lower speed. Finally, after reaching a maximum altitude of almost 11.5 kilometers (7 miles), an hour into the flight, the balloon deflated and the parachute opened. Wegener was able to track the parachute descent and observe the same 360° turn on the way down, later verifying—on both thermographs—a true inversion of 1°C (33.8°F) on the Hergesell instrument and 1.5°C (34.7°F) on Teisserenc de Bort’s, occurring in the last 500 meters (1,640 feet) of the ascent. This was, Wegener wrote, “clearly not explainable as a radiation-effect, rather, it was as it appeared.”32
Wegener’s comments confirming the presence of the inversion were of course directed to Aßmann, who was ever the confirmer more than the discoverer. The turbulent eddies just below the inversion zone, combined with a marked decrease in wind velocity, ought to have interested Aßmann, but they did not: his desire to enhance his supporting role in the discovery of the stratosphere was leading him away from another discovery—the turbulent eddies witnessed by Wegener were evidence of the lower surface of the tropopause at 7 kilometers (4 miles), not unheard of for a deep barometric depression in wintertime in temperate latitudes. The juxtaposition of low- and high-pressure areas (a deep low to the northwest and a high to the southwest) on that day indicates that the jet stream (as yet undiscovered) was probably nearby and the tropopause complexly layered. Wegener saw the unusual structure (the eddies) and could relate it to the distribution of pressure across the middle of Europe.33 What made the eddies especially interesting to Wegener was that he had seen them in clear air, rather than in cloud formations. He was, however, an apprentice, writing to his superior within his superior’s scheme of things. A deeper look could be reserved for another time.
De Quervain balloon theodolite that Wegener tested and reviewed at Lindenberg. From Alfred Wegener, “Über die Flugbahn des am 4. Januar 1906 in Lindenberg aufgesteigenen Registrierballons,” Beiträge zur Physik der freien Atmosphäre 2 (1906): 30–34.
Wegener seems to have really liked the design of the de Quervain theodolite.34 Aßmann was pleased with the work and gave Wegener permission to write it up for publication: this was his first solo scientific paper in a refereed journal, and the official beginning of his scientific career and the possibility of a scientific reputation. The journal was Beiträge zur Physik der freien Atmosphäre, founded the year before and edited by Aßmann and Hergesell as a venue to draw attention to the physics of the “free atmosphere,” the region beginning a few hundred meters above the surface of Earth. Aßmann was anxious to make a place for atmospheric physics separate from that of descriptive meteorology—a subject more suitable to Das Wetter (The weather), the journal Aßmann had edited since 1884.
In October 1905, there came a milestone of sorts: it was Alfred’s first October in twenty years without being registered somewhere as a student. Still, with the fall, after a summer of vigorous activity, he had a desire to do some real physics, in addition to his observational work. Anyone close to academic life feels a tug at this time of year: in the university and scientific world it is much more the New Year than the first of January. The stimulus of fall weather was reinforced for Alfred and Kurt in midmonth by the arrival at Lindenberg of Arthur Coym (b. 1875), transferring from the Meteorological Institute in Berlin, as the aerological operations there were finally shut down in favor of Lindenberg.35
Their new colleague was a Berlin physicist turned meteorologist (PhD in 1903) and had been helping Bezold (by then seriously ill) finish editing his collected scientific papers for publication; Coym was still editing these and reading proof in Lindenberg during the fall of 1905.36 Coym had a sweeping view of what needed doing in meteorology, and Kurt and Alfred welcomed his company and conversation and evidently benefited from it as well.37 The three of them were the only scientists on staff other than Berson and Aßmann, who were much their seniors. With Aßmann as the captain and Berson as executive officer, the three were more or less the lieutenants of Lindenberg, and they lived, worked, and stood watch together.
There was one difference, subtle but fateful, between Coym and the Wegener brothers: Coym arrived with the rank of ständigen Mitarbeiter (permanent staff member), whereas they were only Technische Hifsarbeiter (technical assistants); thus, he outranked them. With Coym’s arrival, Berson could be promoted to Observator, and this compact shifting of chairs foreclosed permanent, salaried, and pensioned employment for either Kurt or Alfred at Lindenberg, as long as Coym wanted to stay: there was room for only one Mitarbeiter, and it was to be Coym. The arrival of Coym was perhaps more a blow to Kurt than to Alfred. Alfred had elected a path leading to academic employment early on; Kurt had rejected it in favor of a technical degree likely to lead to a career as a government staff scientist somewhere, whereas Alfred’s degree had prepared him for immediate academic employment, were he to seek it.
It was clearly time for both the Wegeners to look to their resumes. They both had to get out as many publications as possible, and to get as much practice in every part of aerology as they could, if they were to have a chance at jobs where they could pursue meteorology. One area of expertise they could develop, by far t
he most exciting and exhilarating, was flying aloft themselves—in the great observation balloons made available for meteorological research to Aßmann and his staff by the German army. Flying anything at all was a rare and dangerous skill and immensely popular with the public; manned flight was as miraculous and exotic then as is manned spaceflight today: in 1905 balloon and zeppelin pilots had something of the status of astronauts. That may have been part of the allure for Kurt and Alfred; they were, after all, experienced and devoted sailors and athletic outdoorsmen who enjoyed alpine mountaineering, and they were not afraid to take risks. Ballooning was the perfect job for them—a complete fusion of science and sport.
Ballooning
The opportunity to go ballooning had been from the beginning one of the main attractions that brought Alfred and Kurt Wegener to Lindenberg. Bezold had been for many years a great exponent and urged his students to enroll in the Luftschiffahrtsverein (Aeronautical Society). Berlin flattered itself a world center for aviation under the lavish patronage of the kaiser and the army, and Kurt and Alfred had, many times in their childhood, looked up to see the great balloons soaring over the city.
In 1905 heavier-than-air flight was only two years old, and the maximum times aloft for these primitive and rickety craft were still measured in minutes; the altitudes were negligible, often only 10 or 20 meters (33–66 feet) above the ground. Ballooning, on the other hand, offered time aloft measured in hours, altitude measured in kilometers, and the prospect of serious scientific work in flight. Airplanes were loud, were cramped, and required constant use of both hands and both feet to steer and propel; they vibrated madly and were in every way unsuitable as research platforms. Balloons were nearly perfect platforms for studying the vertical structure of the atmosphere: they were silent, they went easily and directly up and down, and they were able to hover as conditions permitted; they were roomy enough to move around in, were made of nonconducting materials, and could be flown “no hands.” They were also tremendously exciting to fly in. The only drawback (besides the danger of the flights themselves) was the immense expense involved.
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