Toward the end of the chapter on displacements, Wegener ventured very gingerly into a way out of this difficult series of contradictions. The one way out appeared to be occasional but large excursions of Earth’s pole of rotation relative to the fixed stars. Wegener was quite aware of the effect of such variations on Earth’s climate system, but he then noted quite tentatively that from the Triassic through the early Tertiary there was no ice anywhere on Earth, although at least one of the poles was on land or near land most of the time, so that there would have been an opportunity to form ice sheets.56 During this period, there was a marked advance of both animal and plant life toward the poles. “These variations in polar climate can be accounted for quite well by the assumption that the mean value of the 40,000 year fluctuation [of the angle of the axis, one of Milankovich’s three parameters, that shifted between 21.5° and 24.5°] underwent significant changes during the course of Earth history, such that in periods when there was inland ice the oscillations were small and in the periods without ice—those periods in which organisms spread widely—the oscillations were large.”57 Wegener does not say how large, but his descriptions make it clear that these might be as high as 20° or more of tilt.
Wegener and Kepler
In the following chapter, “The Displacing Forces,” Wegener began his discussion by pointing out that the “Newton of the displacement theory has not yet appeared.”58 Wegener characterized his arguments concerning the “ascertainment and establishment of relative continental displacements” as a purely empirical matter, arrived at by a consideration of an ensemble of evidence, without adopting any position on the causes. He then remarked that the formulation of the law of falling bodies and of planetary orbits had also been determined purely inductively, and only later did Newton arrive and show how to derive all of these from the single law of universal gravitation; this was the proper sequence: induction, then deduction.59
The law of falling bodies had been determined by Galileo, albeit purely kinematically, and the laws of planetary orbits, also kinematic, were the work of Johannes Kepler. Among Wegener’s books left behind in Graz is a copy of Kepler’s Traum von Mond (Dream of the Moon), the Latin title of which is Somnium. Wegener’s version was an annotated edition produced by Ludwig Günther in 1898.60 In this manuscript, not published until after Kepler’s death, the protagonist is transported to a point halfway between Earth and the Moon where he can see their relationship and compare their surface features. It also contains remarks on the formation of lunar craters by impact, astronomical position fixing, geomagnetism, the effects of solar and lunar tides on the surface of Earth, and other matters. Wegener’s copy is heavily underlined and marked in the kind of blue pencil he used to correct proof.61
Kepler (1571–1630) had been a professor at Graz, and he had been a mathematician, physicist, and astronomer. He had produced a set of planetary tables, he had done fundamental work in optics and on the geometry of snowflakes, but above all he had solved the problem of the orbits of the planets and generated several empirical laws governing their motion. Kepler, in order to solve the problem of the motion of the planets around the Sun and to make his discovery that they moved in elliptical orbits with the Sun at one focus, used the observational data of his colleague and sometime employer, the Danish astronomer Tycho Brahe (1546–1601), after the latter’s death.
Here was Wegener, 300 years later, in Graz, a mathematician, physicist, and astronomer, who had done work on optics and on ice crystals, who had written a book on the Moon and its craters, who had studied the lunar tides on Earth, and who had just spent a full year working up the data of his deceased Danish colleague, friend, and sometime employer, the geodetic astronomer and glaciologist Johan Koch. Among the many marked passages of Wegener’s copy of Kepler’s Traum von Mond is one pointing out the extent to which Kepler’s work was the absolutely necessary foundation for that of Newton. The passage is in Günther’s commentary, following his discussion of Kepler’s notion that the seas on the Moon must be attracted by the gravitational power of Earth just as those on Earth are attracted by the gravitational power of the Moon, and that the Sun, Moon, and Earth all work together: “I have treated the subject at some length to show how large a part Kepler played in the discovery of the gravitational law: he was Newton’s teacher, and as Humboldt said, to call the laws ‘Newton’s’ almost contains an injustice to the memory of this great man.”62
Hence, Wegener was to play the part of Kepler and prepare the way for the Newton who would follow. To turn the motion of continents from a kinematic theory (showing the motions) to a dynamic theory (specifying the unifying forces) would be the work of another. The problem was not many problems but one: “It is clear from the outset that for this question of forces, the entire complex of continental displacements, crustal wandering, polar wandering, internal and astronomical axial displacements form a single problem.”63
Wegener’s consideration of these forces in the fourth edition was brief and mostly directed toward the clarification of the Polflucht, on which an interesting experiment had recently been done by a Dutch physicist, U. Ph. Lely; Wegener had repeated the experiment with Letzmann, who was then in Graz.64 It was a simple lecture-demonstration using a cylindrical vessel placed on a turntable, with a flat cork with a nail driven into it used as a “continent.” The vessel was then set in motion, and depending on whether the nail was up or down, the float either approached the upper margin of the fluid (the equator) or drifted toward the bottom of the vessel (the pole).65 This was the effect of the distance in the “continent” between the center of mass and the center of buoyancy which Wegener had earlier investigated in detail.
In all, Wegener was willing to consider six different displacement forces, driving the five different kinds of movements (continental displacement, crustal wandering, polar wandering, internal axial displacement, and astronomical axial displacement). The pole-fleeing force that Wegener still believed could move the continents was (he was now convinced) not strong enough to create mountain ranges. Wegener briefly considered tidal friction (Earth tides) as a possible cause driving continents to the west, but he deemed the basis of this insufficiently established.66
He then considered a possibility offered by Schweydar which could drive the continents to the west and also depended on the attraction of the Sun and the Moon, which was that the axis of rotation with respect to the continents was different from the axis of rotation for Earth as a whole—such that the precession of the “continental axis” produced a very large force, much larger than the pole-fleeing force. He offered this only as a conjecture and said that he planned to develop it at a later time.67
In addition to these three forces, there was the possibility of the distortion of Earth’s figure away from a rotational ellipsoid by streaming in the Sima, which would, under certain conditions, force a westward motion, though Wegener considered this unlikely. He also noted that several investigators were willing to invoke the idea of radioactive heating to produce sufficient fluidity in the Sima beneath the continents to allow convection currents to form; these might drive the floating continents.68 Finally, as the sixth candidate force, Wegener considered that extensive excursions of the pole of rotation (however they were caused) would themselves become a force that, in conjunction with the pole-fleeing force, might “supply the energy required for folding.”69
It is remarkable how easy and untroubled was this brief discussion compared to the tortured attempt in the previous chapter to reformulate what he meant by continental displacement and polar wandering. Wegener was perfectly content, in his Keplerian stance, to announce that “the problem of the forces which have produced and are producing continental displacement, except for the pole-fleeing force, already thoroughly investigated, is still in its infancy.”70 There was work enough for a Newton: “Continental displacement, splitting and lateral compression, earthquakes, volcanoes, the alternations of transgression and regression of the seas, and polar wandering are beyond doubt c
ausally connected as part of a single grand ensemble. Their simultaneous intensification in certain periods of history shows this to be the case. Which of these are causes, and which of these effects, is something that only the future will reveal.”71
The reader may be interested to know that “which of these are causes, and which effects” is a question still under discussion today. In the theory of “plate tectonics,” the continents are generally believed to move laterally as they are “rafted” on lithospheric “plates” that float on a zone of weakness: an “asthenosphere.” In the last quarter of the twentieth century there was general agreement that these plates moved in a convective cycle, in which molten material welled up at mid-ocean ridges, creating new “plate” segments that were eventually “subducted” through collision with other plates and drawn back down into Earth’s interior.
While convection is considered today to be the principal driving force, it is not the only one, and all (save one) of the mechanisms proposed by Wegener in 1928—including heating from below, spreading and sliding, tidal forces, and even the pole-fleeing force—are still under active consideration as components of the forces driving the continents apart. Currently, no one considers the continents having a precessional axis of their own and different from that of Earth as a whole as a driving force, though since the later 1990s the notion of true polar wander (“inertial interchange true polar wander”), long rejected, and not a part of plate tectonic theory from the 1960s through the 1990s, has made a comeback as a companion to the convective plate motions in explaining the geological history of Earth.72
The motion of the plates in the contemporary theory also supposes the creation of new continents by the rifting and splitting of old ones in rift zones where Earth tears, suffers downfaulting, and eventually opens up enough that molten material can well up from below. These rifts can be detected by gravity anomalies, as well as by surface morphology. Twenty-first-century textbook and encyclopedia illustrations of this process look remarkably like Wegener’s conception in 1928—a great deal more like Wegener’s ideas than did such illustrations in the later part of the twentieth century.
Another hypothesis of continental motion proposed in the 1920s (which Wegener considered but to which he did not subscribe) is also still in play today. This was the idea of radioactively generated heat, trapped beneath the continents, forcing them upward and potentiating the subsequent “downhill” gravity sliding of tilted continental masses, as in the theories of R. A. Daly and John Joly. Robert Schwinner (1878–1953), Wegener’s Graz colleague, had in 1920 fleshed out an idea (first proposed by Otto Ampferer) of convection currents in a “tectonosphere” about 100–120 kilometers (62–75 miles) thick, in which radioactively heated material rose and drove “plates of crust” laterally. When two such plates collided, one dived under another and descended into a Verschluckungszone (“swallowing zone”), where it melted and was reabsorbed into the tectonosphere, while creating alpine ranges at the surface. R. A. Daly borrowed this entire conception (without attribution) for his 1926 book Our Mobile Earth.73
The point of such comparisons is not to determine “who was right” or who most thoroughly prefigures present conceptions, but to show that Wegener’s cautious agnosticism concerning actual driving forces—the “mechanism”—was in 1928 well considered. Something is moving the continents, there are a number of candidate hypotheses, and whatever force or forces explain these motions also probably explain ocean trenches, volcanism, the creation of mountain ranges, rift valleys, and the full ensemble of movements of the crust envisaged by Wegener between 1912 and 1928. What that “force” is (or those forces are) remains uncertain even today.
Expedition Planning, 1928–1929
Whatever else he felt about finishing this book—in proof by early September—Wegener also felt relief. All through the process of composition in the spring and early summer of 1928, he had been deeply involved in plans for Greenland. Nothing had diminished his fascination with the origin of continents and oceans, but dividing his energy between future and past investigations was a distraction and an obstruction. Already in the middle of June he had an expedition plan (several times revised) to send along to Peter Freuchen in Copenhagen. He had planned to travel there in mid-July to get Freuchen’s advice and to begin to obtain the necessary permissions to mount his two scientific expeditions in Greenland—one in the summer of 1929, and a second and much larger expedition in 1930 and 1931.74
Wegener wrote to Johannes Georgi in July to tell him that he would come to Hamburg on his way back from Copenhagen and discuss the expedition with him.75 Georgi was only eight years younger than Wegener, not quite his junior, but neither his contemporary. They had been close colleagues in Hamburg; their households had been side by side in Großborstel and their children playmates. We do not know what they discussed when Wegener arrived in Hamburg, though he had come principally to talk to the new director of the observatory to obtain Georgi’s release so that he might be part of the expeditions. Their relationship was delicate; Georgi had wanted Wegener’s support, but only as an endorsement for his own expedition to East Greenland. Wegener’s large plan was a major shift for both men, though certainly more for Georgi than for Wegener; Georgi would no longer be a Leiter (leader), but only a Teilnehmer (participant).
Wegener now had a definite plan to fold Georgi’s ideas together with Meinardus’s seismology, along with his own earlier plan to set up West Greenland, Mid-Ice, and East Greenland observatories at the same latitude, in order to chart the transit of weather systems. We do not know what Georgi thought about all this, but he did agree to be part of it. It was a sensible course: Wegener had the intellectual and institutional power to make this happen, and he had extensive experience on the Inland Ice of Greenland; Georgi had none, did not speak Danish, and had never pulled a sledge, mounted an ice cap, or driven a team of dogs. He could surrender, at least for the time being, to an apprenticeship, however much he wanted an expedition of his own.
Wegener was also in Hamburg to get another permission: that of Georgi’s wife. Georgi remembered many years later this kindness on Wegener’s part: “I shall never forget his long and friendly conversation with my wife; how Wegener explained, when naturally she asked what risk was entailed for me, how he hoped to minimize the risk by careful planning keeping in mind his own experience there; how what one usually calls bad luck is very often only a result of errors or inadequacies in preparation.”76
We have seen, in looking at the Danmark Expedition and Koch’s 1912–1913 traverse, that expeditions like these begin long before they “begin” and end long after they “end.” The total amount of labor expended on preparation before and publication after is at least as great and probably greater than one’s efforts in the field. Preparations for a summer reconnaissance expedition in 1929 had to be under way by the summer of 1928 in order to secure funding and begin to choose participants. Before either of these could happen, there needed to be a plan to ask for funds and to recruit scientists to join.
While in Copenhagen in late July, Wegener had gone over the maps of West Greenland with Freuchen, looking for possible routes onto the Inland Ice. Freuchen also called in their old expedition comrade Aage Bertelsen, the doctor from the Danmark Expedition, who had been for some years the district physician in the Umanak District of West Greenland, and who had made many photographic trips along the coast. He showed Wegener some routes he thought possible in the Umanak Fjord. Freuchen remembered having found a usable valley in Ingnerit, one of the inner branches of the Umanak Fjord.77
From July 1928 on, Wegener was completely immersed in planning for Greenland, to the exclusion of all other scientific work except his remaining experiments with Letzmann on tornadoes. His courses for the winter semester of 1929–1930 were to be a colloquium on the theory of continental displacements (two hours a week) and an introductory course on aerology. Neither of these required special preparation, and he could throw his energy into the immense task of planning a
multiyear expedition in the high Arctic.78 As of 13 July 1928, he had one expedition member besides himself: Georgi. He had promises of funds but no commitments, and he had yet to obtain approval for his plans. In spite of this slim warrant, he was in fact now the leader of what was tentatively known as the “Inland Ice Expedition to Greenland.”79
After his discussions with Freuchen and Bertelsen in Copenhagen and his meeting with Georgi in Hamburg, Wegener was ready to put together a final plan, and by 30 July he had it in shape for Freuchen to review. He asked Freuchen especially to look at the technical questions on methods of travel (Reisemethode), as he hoped to have a finished report submitted to the Notgemeinschaft (the funding agency) in Berlin by 20 August.80
The next day, 31 July, Wegener began to put together the rest of his expedition. He wrote to Fritz Loewe (1895–1974), a Berlin-trained meteorologist who had replaced Kurt Wegener as director of meteorological observations (kite and balloon flying) at Lindenberg in 1925. Kurt had great confidence in Loewe and had helped to select him; Wegener had also discovered that Loewe was an experienced and talented alpine climber. The latter skill would be an absolute prerequisite for participation in this expedition, as the only snow and ice experience (other than war service on the Russian front) young German scientists were likely to have would have been obtained in recreational climbing. Loewe was, as Wegener had been delighted to learn, an experienced radio operator; that had been his war service.
Wegener asked Loewe, whom he had yet to meet, whether he would be willing to join both the 1929 reconnaissance expedition and the 1930–1931 main expedition to Greenland. He sketched out for Loewe the scientific plan and some technical details of transport and travel. He then got directly to the point: would Loewe be willing to go climbing with him in the week of 5–11 August in the Ötztal Alps (Austria), where they would join Hans Mothes on the Hintereisferner glacier and learn from him the basics of ice thickness measurements using seismic/acoustic techniques?81 Loewe was delighted to accept, and he agreed to meet Wegener in August.
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