Alfred Wegener

by Mott T. Greene

  Planck instead proceeded to develop a general framework for physics out of thermodynamics by the formal deduction of a variety of physical and chemical laws beginning from a few empirical facts, foremost among them the two fundamental principles of thermodynamics: the principle of the conservation of energy, and the principle of increasing entropy.45 These principles, often called “laws,” are not explanations, but rather descriptions. When we talk about energy in thermodynamics and thermochemistry, we are actually only applying an accounting system to nature. The science has an empirical feel because we are always patching and doctoring the equations of state which describe the systems we analyze, in order to make them work. Classical thermodynamics is a scheme, a set of rules to show the changes in energy in a system.

  That being said, thermodynamics is still the most powerful and general theory in physics. It covers everything from the very small to the very large, it applies over any time interval, it covers both living and dead things, and it applies equally to classical physics, quantum mechanics, and relativity—precisely because, as Planck saw so clearly, it is not dependent on any microscopic model of reality for its accuracy.46 Rather, it serves as a check on the accuracy of microphysical models, which, when scaled up to macroscopic size, must give results consistent with thermodynamics.47

  Thermodynamics led one to meditate on the measurable bulk properties of things—their mass, temperature, pressure, and volume—and the transformations of these variables through time. In Planck’s treatment, one studied moving systems (machines or gases or chemicals in solution) as things passing through a variety of states of equilibrium, on their way to a state of maximum stability.48

  It is perhaps notable for Alfred Wegener’s impressions of the subject that Planck introduced thermodynamics via a variety of real atmospheric processes and mixtures of gases. Planck was also extremely careful about definitions, constantly reminding the students that to define the state of a substance (and therefore its energy), one needed to know not only its mass and chemical nature but also its pressure and temperature.49

  Planck explained to his students that this streamlined—and what we would now call “phenomenological”—approach to thermodynamics corresponded best to the actual state of the science. It was appropriate to what was known; it did not overreach or deceive. The caution and intrinsic modesty of this physical theory, with its professed indifference to causal mechanisms (always treated as subsidiary hypotheses), would stay with Wegener for the rest of his life and characterize all his work. It would also have important implications for the later consideration of his work in the English-speaking world. In British and American physics there was in the late nineteenth century and first part of the twentieth century a fascination with and a commitment to mechanisms and mechanical analogies: some force or some process had to be named as the cause, or the theory was incomplete; not so in Germany.

  Albert Einstein’s insistence on physics as, first of all, acts of measurement by human observers was a part of the cautious phenomenological strategy he learned in his university years, no more uniquely his own than his conviction that science is something freely created by human minds. So it was for Wegener and every other physics student at Berlin. To do physics in this fashion, one had principally to overcome, as Erwin Schrödinger later remarked, the custom, inherited over thousands of years, of thinking causally.

  Wegener took away from Planck’s teaching a strong commitment to brevity in the service of clarity. He adopted a caution, bordering on aloofness, in offering mechanical models and causal explanations, especially of the sort that only confirmed what one knew from experience without adding anything to the facts. He became convinced that the best avenue of approach in presenting a theory to an audience was to begin with some facts of experience and then deduce some physical and chemical laws governing the system from these facts—pushing the formal derivation of consequences from the facts as far as possible, testing by applications, and looking for (and expecting) exceptions. Most importantly, he heeded Planck’s injunction never to consider any form of a theory as final, and to think of “good theory” simply as that mode of treating phenomena that corresponded to the actual state of a science at that moment—and never to one’s aspirations for it.

  Cosmic Physics

  It is clear from the selection of courses in his third year of graduate study that even as Wegener returned to the technical training in astronomy, his focus had begun to shift from the observational astronomy that had brought him to the university to topics in physics, geodesy, and meteorology. There is nothing very remarkable about this. Students generally know at an early age that they want to be scientists (this was certainly true for him), but their initial choice of a science is controlled by what they see in secondary school. Most biochemists and geneticists turn out to have had, in high school, some idea of medical school, and they only found their actual vocation while taking “premed” courses in college. Very few geologists know they are going to be geologists or even scientists until they get to the university. For subspecialties the process repeats itself, and a typical scientific education goes through several apparent changes of field before the student finds the proper mix of talent, opportunity, and inclination.

  The Berlin curriculum in astronomy and physics allowed one to stitch together a program in what was then called “cosmic physics.” There was no such degree, nor any university professorships in the subject: “cosmic physics” was not a field so much as a point of view. When we talk of cosmic physics today, we mean astrophysics or space physics—the study of processes and substances with no counterparts on Earth because of the extremities of temperature, pressure, and radiation required to manifest them. The cosmic physics of 1902 was something rather different and, perhaps surprisingly, something more ambitious. It was an attempt to bring the study of the heavens together with the study of Earth, including its oceans, its atmosphere, and the intense and hostile regions of severe temperature and pressure below its surface. To this it added geology, geography, and biology, the latter existing in a fragile envelope extending a few hundred meters above the surface and a few meters below it—the biosphere. It was a physicist’s counterpart to the Kosmos of Alexander von Humboldt (1769–1859), with its grand vision of the unity of nature and of mankind’s place in it.

  This cosmic physics, for which Wegener felt a growing affinity, was fueled by a number of intellectual tendencies and discoveries since the middle of the nineteenth century: it seemed to combine, in its vitality, the fundamental ideas of both thermodynamics and evolution. Among the discoveries that advanced this viewpoint was the spectroscopic study of light coming to Earth from planets and stars, and the determination that the stars and planets are made of the same elemental substances as those found on Earth. Cosmic physics was equally propelled by the study of organic chemistry, biochemistry, and physiology, which pressed the conclusion that we (and all life) are made of the same elements that we see present in the most distant stars and nebulae. Svante Arrhenius’s (1859–1927) textbook Lehrbuch der Kosmischen Physik (1903) was only the most popular and widely read of many thick treatises attempting a unified presentation of the physics of nature.50

  Wegener was now being pulled, albeit gently, in conflicting directions. He had still to complete the course work required for his astronomy degree, his emerging interests notwithstanding. He had not completely relinquished the ambition to work as an astronomer, nor was he yet committed to a scientific vocation in the terrestrial side of cosmic physics, though he found it highly stimulating. Therefore, as a test of vocation, in spring and summer of 1903 he pushed his work in astronomy beyond the solar system and, under Bauschinger’s direction, extended his studies to celestial mechanics, double-star systems, and calculation of stellar ephemerides—tables of star positions. With Förster, he studied the history of Greek astronomy, theory of chronometry, and selected topics in the theory of errors, continuing his work at the Urania observatory.

  Förster’s historical
emphasis was congenial to Wegener, who enjoyed contextual work that was classical in motive. Physics education in Germany trained students to see themselves and their work in historical context, and as part of a large enterprise, though not often to the extent that characterized the curriculum of Berlin astronomy. On Förster’s part it was a way to make scientific study integral to the ideals of classical education in Greek and Latin, and it was in this way a holdover from Förster’s struggle to establish astronomy and science generally in Germany as part of Bildung. His first course of lectures in Berlin, forty-five years earlier in 1858, had been on Copernicus, Kepler, and Tycho.51

  Förster’s history of science attested the close connection between advances in astronomy and the debut of novel instruments and methods of calculation. Historical study, when it contained detailed excursions into the technical details, was not a triumphalist exercise in celebrating progress but a chronological record of the evolution of thinking about the universe and about the intricate relationship of perceptions and concepts.

  Wegener made sure in the summer of 1903 that there was room in his schedule for his new interests, though he was again assigned to the Urania observatory. He enrolled in Wilhelm von Bezold’s course in theoretical meteorology, that year concerned with the thermodynamics of the atmosphere. Bezold was in 1903–1904 preparing for retirement and was summing up his work from the previous twenty years and preparing it for publication, including his extensive work on atmospheric thermodynamics. The contrast between Planck’s approach to thermodynamics and Bezold’s was striking. Planck’s presentation of the science cut to the bone, seeking elegance and simplicity after the mode of theoretical physics. Bezold, on the other hand, had a narrative loquacity and anecdotal approach characteristic of his role as an experimenter and observer, and his writings preserved the signs of the strenuous activity that had produced the results. He had completed much of this research in the later 1870s and early 1880s and had published it (long since) in the proceedings of the Berlin Academy of Sciences between 1880 and 1892.52

  Bezold’s thermodynamics of the atmosphere was a pathbreaking effort, but he knew better than anyone that it begged to be redone and modernized in many respects, not least of which was the pressing need to get more information about the “free air”—the atmosphere kilometers above Earth—away from mountains and their self-created weather. A serious application of physical theory to weather data was also needed, to integrate the rapidly changing picture of the vertical structure of the atmosphere and of the energetics of storm systems, in terms relevant to research that was appearing in print, for the first time, even as Wegener took this course.

  In his final—and most intense—year of study in Berlin (fall of 1903 through October of 1904), Wegener’s work was almost entirely given over to detailed studies of measurement: history, theory, and technique. In the fall and winter he continued his work with Bauschinger—a history of celestial mechanics, and a seminar on the design and use of planetary tables. With Förster, he took the second half of the two survey courses he had begun in 1903—following the history of Greek astronomy with a history of Arabic and Medieval (European) astronomy, and following the course on chronometry with one on the theory of stereometry (i.e., volumetric as opposed to planimetric measurements).

  Wegener also took a course in fall 1903 entitled “The Method of Least Squares,” given by Friedrich Helmert (1843–1917), professor of advanced geodesy at Berlin and head of the Prussian Geodetic Institute. In tandem with this course Wegener studied “Topographical Surveying” with Helmert’s student Hermann Eggert (1874–1944). In 1903–1904 Helmert was at work on means of correcting measurements of gravity and on studies of the movement of Earth’s rotation axis (given by Helmert as the explanation of measured latitude changes at German gravity stations).

  Not ony did Helmert’s course function as an introduction to probabilistic techniques of estimation and error reduction, but in its concrete examples it furnished an introduction to a range of geophysical problems: the measurement of variations in gravity, the reality of latitude displacements, and displacements of Earth’s axis—or “pole wander.”

  This problem of the displacement of Earth’s axis, pursued by Friedrich Helmert, kept turning up in Alfred’s studies: it had been there from the first practicum with Adolf Marcuse in 1899–1900. The motions proposed for the pole were not large on an annual basis (several meters per year), but no one knew whether there was a secular (i.e., long-term) accumulation of these annual displacements, and since the International Latitude Service had only been up and running for about a decade, the question was unresolved.

  At some point in the 1903–1904 academic year, rather late in the game, Alfred made his final decision to switch from astronomy to cosmic physics. In an anecdote reported in 1931 by his longtime colleague Hans Benndorf (1870–1953), Wegener supposedly told student friends, “In astronomy, everything has fundamentally already been dealt with, and now only exceptional mathematical gifts and sophisticated equipment in astronomical observatories can lead to new discoveries. Besides, astronomy offers no opportunity for physical exertion.”53

  In the fall and winter of that year he found the physical activity he longed for in Bezold’s “Meteorological Practicum” accompanied by a course of lectures entitled “Wind and Weather.” There was no doubt about it: meteorology was an outdoor science, and most aspects of it required physical stamina: hiking to recording stations to retrieve records, and certainly everything connected with sending up and retrieving balloons and meteorological kites at the station in Templehof. In the spring of 1904, Alfred joined Bezold’s Meteorological Colloquium, where Bezold and the advanced students met to read and discuss current topics and literature at the research front of atmospheric physics.

  It was in Bezold’s practicum that Wegener met and befriended Walter Wundt (1883–1967), at that time finishing his degree at Berlin in physics, but with a thesis in meteorology. Wundt later recalled that Wegener told him in 1903–1904 of his ambition to join in polar science and exploration, specifically to go to Greenland and traverse the ice cap following a route to the north of that taken by Fridtjof Nansen (1861–1930) in 1888.54 This squares well with fellow student Walther Lietzmann’s memory of Wegener expressing his “polar ambitions” at this time to the members of A2 V, the astronomical fraternity at Berlin. It would not be surprising for Alfred to have had such ambitions. This was the great age of polar exploration, and neither pole had yet been reached in 1904. Moreover, Bezold had been part of the planning committee for the German South Polar Expedition (1901–1903) led by Erich von Drygalski (1865–1949), who had also led a major expedition to West Greenland. Drygalski was, in 1904, lecturing about his polar exploits to scientific groups all over Germany, and it is probable (though by no means certain) that Wegener had heard him speak.55

  Now that he was no longer considering a career in astronomy, he decided against some otherwise interesting courses: “The Three-Body Problem,” “The Temperature of the Sun,” and “Solar Physics.” Since he was in Bezold’s meteorology working group, he had no reason to attend the Astrophysical Colloquium. He retained an active interest in the history of science and elected to complete the full historical survey of astronomy with “History of Modern Astronomy since Newton.” A practical course on measurement of celestial angles by theodolite (with Förster) looked useful, and he signed up for that as well. With Bauschinger, he took up a subject that strongly complemented both his work with Bezold and that with Helmert, “Potential Theory with Applications to the Figure and Rotation of Heavenly Bodies,” and its practical counterpart, “Introduction to (the Art of) Calculation.” Since the global circulation of Earth’s atmosphere and the direction of prevailing winds in different latitudes are largely controlled by Earth’s figure and rotation, this final course in astronomy could be employed in atmospheric and cosmic physics; nearly everything in Wegener’s last semester had a direct application to his future work outside astronomy.

  The
steady march of classwork, reading, and calculation in his student life was matched by a profoundly stable and quiet home life. As a matter of finances, inclination, or both, Alfred was still residing with his parents at the orphanage on the Museum Insel, close to the university. As the student years came to an end, however, other changes were in the offing as well. After thirty years of directing the orphanage and, in Richard Wegener’s case, thirty years of teaching high school Greek, Latin, and literature, the Wegeners were retiring and moving out of the orphanage. Richard had turned sixty the previous year and was now eligible for his pension; with their own youngest child ready to finish school, it was time to leave.

  The Wegener family (Alfred too) moved at the end of the Easter term in 1904 to a house at the far western edge of Berlin, in the neighborhood called—then and now—“Halensee,” after one of the small lakes dotting this gracious, green, and quiet neighborhood. Alfred had been here before for his military training—the Queen Elisabeth Grenadier Guards Regiment was stationed at Westend, about 2 kilometers (1.2 miles) to the north. A walk or short streetcar ride of the same distance to the south and west brought one into the Grunewald—Berlin’s huge and wonderful forest tract, complete with walking trails, riding paths, and a large lake, the Grunewaldsee, on which Alfred and Kurt had skated almost every winter of their lives. The Wegener family took a house at 20 Georg Wilhelmstraße, just off the great boulevard of the Kurfurstendamm.