Wegener was Bezold’s student, and Bezold’s collected papers (to the year 1900), published in 1906, were mostly in the area of atmospheric thermodynamics. Yet so much had been learned in the period 1900–1908 that Wegener had argued (in his inaugural lecture at Marburg in March 1909) that a full-length book would be required to do justice to this new material; this included a huge bulk of ideas concerning atmospheric temperature distributions. Wegener had further argued in that lecture that the principal function of thermodynamics, applied to the study of atmospheric structure, was to demonstrate the unintelligibility of all existing theories of cyclonic and anticyclonic storms. Wegener had also said that the mean thickness of the various layers of the atmosphere, their variation with altitude, and the associated changes in the meteorological elements within them all had to be understood before one could determine how cyclones and anticyclones would behave, especially since these turbulent disturbances were associated with breaches in the integrity of atmospheric layers.3 Thus, from Wegener’s standpoint, the updating of the presentation of basic thermodynamic concepts applied to the atmosphere (to reflect the results of the new aerology) was a fundamental precondition for the understanding of dynamic meteorology.
Bezold had extended his notion of atmospheric thermodynamics to include studies of föhn winds, of water vapor in the atmosphere, of the formation of precipitation, of atmospheric dust, of cloud forms and the macrophysics of clouds, and of cloud elements—the microphysics of clouds. To this he had also added the study of the formation of raindrops and snow crystals. This broad version of the thermodynamics of the atmosphere was pursued by everyone at Berlin: Helmholtz, Hertz, Aßmann, Berson, and Bezold himself, over the span of a half century, had combined theoretical development, laboratory experiment, and field observation to this end.
So it could hardly count as a surprise that Wegener, fetching about for a way to approach the physics of the atmosphere, decided to begin his course of lectures with the material most assiduously pursued by his own graduate school professor. As an added impetus to this very obvious course of action, the pursuit of this material would require some exciting and significant modifications. Bezold’s collected papers did not address the profound consequences of the discovery of the tropopause and the stratosphere. These phenomena, which everyone was learning to call by these new names (since Teisserenc de Bort had announced them the previous September), had changed almost everything in theoretical meteorology.
If Wegener’s approach to the physics of the atmosphere was, as the theorists say, “overdetermined” by Wegener’s graduate education, it was further reinforced by his very powerful physical and intellectual experience of Greenland. Greenland in winter was a purely thermodynamic universe, the full realization in physical form of theoretical principles. When the ocean was frozen and the shore covered with snow, the world was nothing but the pressure, density, temperature, and volumes of water, with all of water’s phases simultaneously present and covering the entire world—ice, water, water vapor, flowing and changing, ascending and descending, transforming one into another, condensing, vaporizing, sublimating, all this physics constantly before one’s eyes. What the Tower of Pisa was to Galileo, the Greenland ice cap was to Wegener: the physical embodiment of universal law in action.
There is an important reservation here in referring to thermodynamics as composed of “laws,” a reservation of which Wegener was well aware and in full agreement. These “laws” (as we noted earlier) are descriptions, not explanations, and are expressed in “system and boundary” equations. The “laws” of thermodynamics are not derived; they are just written down. This distinction is better observed in German than in English. In Helmholtz’s and Planck’s writings, as well as in Wegener’s, what are referred to in English as “laws” are described as Hauptsatz: fundamental principles. “Laws” are something found in nature, whereas “principles” are something found in science. The philosophical sophistication of German university education worked together constantly to remind Alfred Wegener and all other Berlin physics graduates that science was a human construct, not a direct apperception of the natural world.
Wegener’s approach through this sort of thermodynamic thinking reflected a desire to bring simplification and conceptual clarity to an atmospheric science that had become enormously complex. In much the spirit of Planck at Berlin, he wished to sever the fundamentals of atmospheric thermodynamics from their applications to theories of atmospheric motion.
The question at issue here was the theoretical turmoil concerning the formation of midlatitude cyclonic storms. Meteorologists in both Europe and North America, from the 1860s on, had worked diligently to adapt physical theory, and especially thermodynamics, to meet meteorological problems.4 Foremost among all the problems of meteorology was the understanding of the formation and propagation of storm systems.
The complexity and conceptual confusion that Wegener hoped to avoid in his own teaching of thermodynamics came out of the evolution of the thermal theory (also called the “convective theory”) of cyclones in the latter part of the nineteenth century. The idea of the conservation of energy had brought much benefit to atmospheric physics in the 1860s and 1870s as an explanation of adiabatic processes. A good deal of work in the 1870s led to the conclusion that the primary source of kinetic energy in storms came from the release of latent heat of condensation in rising air.
The fundamental idea was that a rising column of moist air released heat, and then localized heating and vertical expansion caused the lowering of pressure at the ground center of a storm and potentiated the inflow of air from all sides. Cyclonic motion was the result of the deflection of these winds by Earth’s rotation. Constant low pressure at the surface (it was assumed) was maintained by divergence and outflow of air at the top of the cyclone, which would therefore move in the direction of greatest moisture, that is, in the direction of the heat source.
In the 1890s aerological observations challenged this simple view, and by the early 1900s it was evident that both thermodynamic and hydrodynamic considerations would have to be deployed to avoid gross oversimplification. In spite of this, many meteorological theoreticians continue to think of storm systems as thermal entities, and of the thermodynamics of the atmosphere as something that should include consideration of the energetics of storms.5
In addition to his desire to untangle atmospheric thermodynamics from the theory of midlatitude cyclonic storms, Wegener wanted to counter a trend, going back to Carnot and Poisson, of developing the subject with great mathematical complexity and elegance, on a foundation of integral calculus. Wegener’s strong preference was for the statement of concepts in ordinary language, without reference, whenever possible, to mathematical formalism. In 1911 he wrote to Köppen and referenced approvingly the following quotation from the German edition of Sir George Darwin’s book Tides and Kindred Phenomena in the Solar System (1898):
A mathematical argument is, viewed in this light, only a means to organize ordinary human understanding, and it is good when scientific men rather than constantly wrapping their scientific work in a veil of technical terminology such that it is available only to the few, rather from time to time uncover and expose to a broader public the train of thought concealed beneath their mathematical formulas. (From Darwin: Ebb and Flow).…6
I myself hold the crass and probably exaggerated point of view that such mathematical treatises as I cannot understand (for instance in those works where one can no longer see the train of thought glimmering through the mathematics—it’s often still possible to follow the train of thought without working through the formulas) are either wrong or incomprehensible. It is not necessary always to think that one bears the entire responsibility when one does not understand the printed or written word: “for just when ideas fail, a word comes in to save the situation” so it is that where the logic of an argument falters one can usually fill the gap with a few formulas.7
The quoted reference within the above passage is from Goet
he’s Faust, where Mephistopheles is telling a student not to think about what he’s learning but just to memorize the words: Wegener means this as a critique of memorized, copied, and repeated formulas.
Wegener found complex mathematical presentations in physics distasteful not because he couldn’t do the math but because of the tendency of a fully mathematical presentation to make physical subject matters more difficult than they needed to be, and because he considered the superfluous, as opposed to the essential, use of advanced mathematics as a kind of veil, thrown by an author over a subject to cover gaps in his understanding. Wegener’s objections in this regard appear to be well founded, as diagrams in nineteenth-century theoretical treatments of paths of airflow in cyclonic storms often appear to owe more to the graphical form (with a particular fondness for hyperbolae) of sequences of partial differential equations than they do to the flow of real air within a real storm. Wegener was insistent that purely theoretical laws had to be modified in favor of the empirical results obtained, in the actual atmosphere, with real and well-calibrated physical instruments.
In addition to his principled opposition to the use of more mathematics than absolutely necessary for the doing of physics, Wegener had another reason for wanting a plain, clear, and straightforward treatment of the subject of thermodynamics, as he prepared his lectures for the summer semester in Marburg. Most of his students, never very numerous, were training to be not university professors but Oberlehrer, high school teachers, who would have to re-present even simpler versions of this material to students in their late teens.
Wegener’s clear presentation of atmospheric physics in his first course of lectures at Marburg received an enthusiastic testimonial from one of his first students, Johannes Georgi (1888–1972), later himself an atmospheric physicist who did notable work on the jet stream and in the scientific investigation of Greenland.8 Georgi, then twenty-one and in his last year of university study, arrived in Marburg to complete his physics degree in April 1910 and recalled finding “a notice on the board of the Physical Institute, in a clear and attractive handwriting, announcing that Privatdozent Dr. Wegener was to give some meteorological lectures and demonstrations.” Georgi remembered Wegener as firm but modest and reserved: “only here and there could we catch a glimpse of the lion behind the lamb-like manner.”9
His lecture on the thermodynamics of the atmosphere was remarkable for the ease of his delivery, which was in complete contrast to the difficulty of the subject. Numerous examples were taken from his recent observations in Greenland; and here for the first time the attempt was made to relate the bulk of measurements from the free atmosphere during the last dozen years to general physical rules for the explanation of the manifold phenomena such as the different atmospheric layers (only eight years had passed since the discovery of the stratosphere!) and the various types of cloud formation. Whoever in those days had the opportunity of following the lectures and practical work of famous scholars would have had to admit that Dr. Wegener’s lectures bore no professorial stamp at all. On the contrary, the tutor came down to the level of his audience and developed with them the theme which he had just set down.… It is true that the final result still had to be formulated mathematically, but neither before nor since have I had the experience of hearing a tutor state quite simply: “this derivation is not mine; you will find it in the physics textbook by … on page.…” … He always took the greatest pains even in his most specialized work to be as intelligible as possible and not write only for his fellow experts … an outstanding trait of his character was his frankness even towards his students. He had an unusually high degree of integrity in such a natural and unpretentious way that one had the impression that he was exempt from the common human temptation of occasionally making oneself appear a little more important than one actually is.
I am sure that young people in particular feel this immediately; and the simplicity of his lectures and demonstrations, obviously based on experience and achievement, always won him the hearts of his audience. At the end of the lectures in Marburg he used to bring out a number of photographs to illustrate the subject he had been discussing.10
Wegener seems to have often inspired this sort of loyalty, in which admiration for his scientific ability and understanding was combined with admiration for his honesty and integrity and for his strength of character. This admiration was not limited to his students but also shared by Köppen, Aßmann, Richarz, and in fact every academic supervisor and senior who ever worked directly with him.
Wegener, working without any other duties or distractions, devoted himself completely to the development of his lectures on the physics of the atmosphere. There were only four students actually registered for the course, but the audience was often much larger, depending on the topic, with the rest made up of other instructors and even some of the senior academics who had heard about the clarity and accessibility of Wegener’s presentation of these exciting new results in physics. Among his most frequent hearers was the physicist Karl Stuchtey (1880–1950), also an enthusiastic balloonist, and very interested, as was Wegener, in the physical form and characteristics of clouds.11
Atmospheric Physics in 1910
Wegener was committed to writing a thermodynamics of the atmosphere and using his preparations for this course in order to advance that project. But a course in the full physics of the atmosphere could not stop with thermodynamics, and Wegener had to go ahead and treat the rest of the physical topics within the subject. In his view, atmospheric physics divided neatly into the same subsections as physics in general: thermodynamics, mechanics, radiation, electricity, optics, and acoustics. For most of these there were textbooks available out of which he could develop his lectures, generally the older meteorological textbooks. Only in acoustics was there a lack of a general treatment.12
While Wegener had access to works that could reflect modern developments in atmospheric optics, atmospheric electricity, and radiation, mechanics was something of a problem. The last extensive treatment of the mechanics of the atmosphere (its kinematics and dynamics) had been published in 1885 by Adolf Sprung (1848–1909): Lehrbuch der Meteorologie. Sprung, who had worked with Köppen (with whom he was close friends) at the Hamburg Marine Observatory, had later moved to the Meteorological Institute in Berlin to work with Bezold.13
Even if Sprung’s treatment of the mechanics of the atmosphere grew out of the tradition in which Wegener himself had been trained at Berlin, it was, as Wegener noted, “unfortunately already quite out of date.”14 What had made it out of date more than anything else was the work of Vilhelm Bjerknes, who in 1898, while a professor of mathematical physics at the University of Stockholm, had published a paper on the general circulation of the atmosphere and the oceans, in which he argued that the application of classical hydrodynamic equations to the atmosphere could never advantage practical meteorology (weather forecasting) until the hydrodynamics had been integrated with a thermodynamic treatment. Sprung had tried to treat dynamics and thermodynamics together, but there were severe limitations to his approach. Since Bjerknes was also a product of the Berlin group, as well as a student of Heinrich Hertz, this was for Wegener a case of one Berliner replacing another.15
Bjerknes’s treatment of the subject had the additional attraction that it covered the circulation (the mechanics) of both the atmosphere and the oceans using the same hydrodynamic ideas. Science is supposed to be “the view from nowhere,” but this is rarely if ever the case. Even in theories of great scope, the practical needs of the national and local communities, the personal histories of those who make them up, and the people that they know and whom they trust often have a decisive influence on the form theory takes, especially in its early stages.
Bjerknes had been trained in Berlin and, had Hertz not died, would probably have stayed to work with Hertz in Berlin on electrodynamics. With his return to Scandinavia (a collection of fishing nations sharing a long coastline), it was not surprising that his work on the behavior of continuo
us media (fields of electromagnetic force) should find encouragement for its extension into problems of the ocean and atmosphere, and this is exactly what happened. Opposed to a vision of the atmosphere as an extension of the kinetic theory of gases, an immense aggregate of particles having elastic collisions with one another and velocities proportional to the temperature, Bjerknes approached the atmosphere as a continuum, as a fluid. We should recall that “the ether” had not yet been banished from theoretical physics, and that theories of electromagnetism were also based on just such a notion of the distribution of some quality in a continuum.
The connection between the atmosphere and the ocean also made Bjerknes’s treatment conceptually interesting. A study of the ocean currents and their tracks and the study of vertical temperature distribution in deep ocean basins had led in the mid-nineteenth century (through the work of Emil von Lenz [1804–1865], who predicted a lapse rate of temperature with depth in the oceans) to a general circulation model of the oceans. Cold water was sinking at the poles and converging and rising at the equator, with masses of warm surface water flowing back to the poles. Like George Hadley’s (1685–1768) atmospheric circulation, the idea was influential, though clearly not complex enough to account for what was known by nineteenth-century oceanographers about the nonsymmetric arrangement of water masses.
“Water masses” were surface bodies of homogeneous salinity and temperature, and these masses of water would or could sink to a particular depth and travel hundreds or thousands of miles coherently. Hence, patterns of temperature and salinity measurements could give a distribution of these masses and a rough picture of ocean circulation. In Scandinavia the desire to improve the fishery, along with the knowledge that certain species preferred water of a given temperature and salinity, led to a strong research program of “synoptic oceanography,” but a theoretical treatment was also required.16
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