He was learning that it was not enough to bring a new idea into the world; for a hypothesis to survive and grow, one must tend it and defend it. The contest is not between ideas; it is between scientists who hold them. Wegener had imagined he could defend his ideas by making them better on their own: a new edition, a better presentation. It was Köppen, above everyone else, who was teaching him not only what to do but how to do it. From Köppen he was learning not just to produce the work but also to present it; the most effective way to do this was to position it as an improvement in a promising line of advance, rather than as something entirely novel. This gave the audience a greater sense of participation in a collective enterprise and made them players rather than mere spectators.
Lunar Craters
There was nothing Wegener could do, immediately, to advance the cause of his book. To write an article, or summarize it in too great detail, could risk hurting the sales; his first wish for the book was that people should buy it and read it. He fetched about for something to do and decided to apply the lessons he was learning from Köppen, about tending and advancing hypotheses, instead to his work on the origin of lunar craters. He had published a paper (dedicated to Richarz) in the Acta of the Academy of Sciences earlier that year, as well as a companion piece in the popular astronomy journal Sirius.30 Neither of these efforts had been more than seven or eight pages long; they were the extremely condensed “physics style” papers he had greatest experience in writing.
Therefore, in the fall of 1920, he contracted with Vieweg for a short book on lunar craters, to be published in the “Sammlung Vieweg” series, in which he had first published his book on continental displacements in 1915. Vieweg was happy to do this; the 1915 volume had sold out, and it appeared that the 1920 volume would as well. Wegener was a good author, was meticulous, made few changes in the final proof, and was scrupulous about deadlines.
Wegener, in this work, made no alterations to his hypothesis of lunar craters and conducted no new experiments. He added a few supplementary line drawings comparing the profile of lunar craters with the profile of his experimental craters and also with the profile of Earth volcanoes, to show how different they were in elevation and form.31 He also drew a figure stacking the largest lunar craters on top of one another, showing that though they were identical in profile to much smaller lunar craters, their diameters ranged from 300 to 1,000 kilometers (186–621 miles); the point here was to reemphasize the difference between crater size on the Moon and volcanoes on Earth, the largest of which were only tens of kilometers across.32 He produced a chart showing the latitude and longitude on the Moon of the largest craters and showed that they were uniformly distributed over the surface, whereas Earth’s volcanoes exist only in certain zones.
Wegener’s supplementary diagrams from his short book on the origin of lunar craters showing the very different morphology of lunar craters and terrestrial volcanoes (top) and the range of the largest crater sizes on the Moon (bottom), indicating how much larger these are than any volcanoes on Earth. From Alfred Wegener, Die Entstehung der Mondkrater (Braunschweig: Friedrich Vieweg & Sohn, 1921).
More significant than his few novel illustrations was the way he inserted himself historically into a tradition of research. He went deeply into the details of every one of the predecessor theories: earlier infall (impact) theories, the bubble theory, the tidal theory, and the volcano theory, showing how they had developed over time, stressing the care his predecessors had put into the work, and noting the physical and morphological problems they faced, including the issue of scaling. He reduced his sarcasms, though he could not restrain himself from repeating that the bubble hypothesis was an “egregious fallacy.”33 He greatly expanded his historical coverage of the volcano hypothesis and went on a hunt for every conceivable predecessor of the impact hypothesis. He may have solved the problem, but he was part of a great tradition of research, not a rebel against it.34
He also chose a new title. He had originally used the term Aufsturz-Theorie, but the word Aufsturz (infall) is so unusual that it does not occur today even in very large German-English dictionaries. He entitled his new book Die Entstehung der Mondkrater, emphasizing its focus on a single genetic principle that explained all the craters on the Moon. This tied the work to his second edition of Die Entstehung der Kontinente und Ozeane and stressed that Earth and the Moon, so different in appearance, were so because of the very different origins of their surface features.35
He better understood now the need to “tend” his hypotheses. He prepared the way for this book (under the new title) by writing a three-page note, “Die Entstehung der Mondkrater,” for the scientific weekly Die Naturwissenschaften. He also wrote a four-page summary of the book for Die Umschau (a scientific monthly very much like Scientific American) and titled it “Das Antlitz des Mondes” (The face of the Moon), clearly a reference to Eduard Sueß’s great work Das Antlitz der Erde. In both of these he presented his work as a new solution to an old problem, succeeding through a new approach, but depending on a tradition of research.36
The Berlin Symposium on Continental Displacements, 1921
Wegener may well have planned an even longer book about the Moon; as published, it was less a book than a pamphlet of about fifty pages. He had received in late November or early December 1920 an invitation to present his hypothesis of continental displacements to the Geographical Society in Berlin in February 1921. He was to give a formal lecture outlining his theory, and there would be three commentators, Franz Koßmat (1871–1938), Albrecht Penck (1858–1945), and Ernst Schweydar (1877–1959). Wegener would then be given the opportunity to respond; all the papers would be published together in the society’s journal. The invitation probably came directly from Gustav Hellmann (1854–1922), the head of the Prussian Meteorological Institute and professor of meteorology in Berlin; he had worked with Wegener throughout the war, had helped him with his book on tornadoes and waterspouts, and was a close colleague of Köppen. Hellmann was, in 1921, president of the Geographical Society.
It was a tremendous opportunity for Wegener, and his commentators were major figures. Koßmat had been one of the first to comment on Wegener’s hypothesis, and while finding “tectonic difficulties” in Wegener’s rearrangement of the southern continents, he had referred to the “kühne Hypothese von Wegener” (Wegener’s bold hypothesis).37 Koßmat was a mineralogist, geologist, and paleogeographer, head of the Geological Survey of Saxony, and director of the Geological-Paleontological Institute at Leipzig. In 1920 he had published the first gravity map of Central Europe; he was thus expert in several of the areas drawn together by Wegener’s hypothesis. Albrecht Penck was even more famous and was the head of the Berlin Oceanographic Institute. He had written a classic work on the ice ages, Die Alpen im Eiszeitalter, and was a world leader in the study of geomorphology and climatology; he had been one of the original supporters of the plan to test continental displacements with telegraph time signals in 1914. The third commentator, Ernst Schweydar, was somewhat less well known, but he was an expert on Earth’s gravity field, astronomical position finding, and Earth tides, and he had been an assistant at the Geodetic Institute in Potsdam since 1897; he was now a professor as well.
The Berlin session was scheduled for 21 February 1921 and would be chaired by Ernst Kohlschütter, the undersecretary of the navy who had insisted on having Wegener to replace Köppen at Hamburg; he was also one of Germany’s leading experts on Earth’s gravity field. It would be a Fachsitzung (technical session) rather than a meeting aimed at the general public.
The panel favored Wegener’s chances of a good hearing. Kohlschütter and Koßmat were ten years older than Wegener, and Schweydar only three years older. Penck, twenty-two years his senior, was on the other side of a generational divide that Wegener understood very well. Along such lines Wegener could expect the most support from Schweydar. Kohlschütter would not speak but could be expected to be sympathetic and to show it. Koßmat was more traditional and geological but ha
d published geophysical work and understood the arguments. Penck would be the problem. With the exception of Penck, everyone on the panel had published detailed work in geophysics. Penck was not hostile to geophysics, and where he moved away from it he moved in the direction of a morphological-empirical approach, which Wegener also championed. Schweydar would be generous and favorable, Penck opposed but probably not dismissive, and Koßmat somewhere in between. Whatever the speakers said, the most important thing that would come out of the meeting would be that Wegener’s ideas were important enough to merit a symposium. It is generally true that in science, as in other areas of endeavor, “the only thing worse than being talked about is not being talked about.”
Things appeared to be going his way. Shortly after hearing that he was to take part in the symposium on 21 February, he wrote to the German Meteorological Society and offered to give a lecture on “Climates of the Past,” a theoretical approach to paleoclimatology, evaluating the different classes of evidence. They accepted with alacrity, and he and Else traveled to Berlin on the eighteenth to be ready for these two appearances.38
The larger challenge was the symposium at the Geographical Society. Wegener knew that for his opening remarks he would have perhaps an hour, and he would not have time for details. Details would be a trap in any case, because his opponents could pounce on any specific detail at the expense of the whole argument. So rather than talk about individual pieces of evidence, Wegener chose to talk about classes of evidence, groups of arguments collected by many scientists working independently of one another over a long time, none of whom had had the idea of continental displacements in mind. He chose to describe these sets of data as each having a sign, pointing either toward his ideas being likely or away from them. The idea was that if the general tendency or preponderance of evidence in some realm of the study of Earth made room for his hypothesis, he could count it as potentially on his side. The more independent classes of evidence he could count as being on his side, the stronger the plausibility of his overall argument, and the greater the likelihood of it being true.
On the day of the event, he began briefly and diffidently, remarking what an odd picture he had drawn of Earth, with all the continents far away from their accustomed positions and all clustered together. Then, through time, there was the spectacle of their moving away from one another, some to the south, some to the north, and some to the west. He said that he had done the best he could to give the foundations for this strange idea in the second edition of his book, and that in a venue like the symposium he could only give a few of the pertinent facts, briefly presented.39
He then went through the geophysical evidence we have seen him rehearse before, beginning with the bimodal elevation of Earth’s surface: this could not be a matter of chance, but one of necessity, of structure. He quickly indicated the gravity data that suggested that the continents and oceans were made of different stuff, and how the study of geomagnetism supported this idea, as did the study of the propagation of earthquake waves and the dredging up of samples from the ocean bottom; all elements pointed in the same direction: the continents and oceans were two different layers made of different materials. He pointed to the generally accepted notion that Earth’s outer layer floated on the layer below it: isostasy. So, Wegener said, you have to admit that most of the geophysical evidence is on my side. “In fact,” he continued, “I have never met, or even heard of a geophysicist who disagrees with anything that I’ve just told you.”40
Then he turned to geology. Here again Wegener ran through the classes of evidence: he pointed to the huge overfolds in the Alps and other great mountain ranges that almost all geologists accepted, and the impossibility that they should be caused by Earth contraction—not his own conclusion but that of a variety of experts. There was the correspondence between the coast of South America and the coast of Africa, both in the contours of the coastline and in the continuity of geological formations across them; together these suggested that they were once connected. His critics, he allowed, have made much of his failure to exactly specify in his reconstructions of the continents where some mountain range in South America connects with another in Africa, but with the distances involved, he mused, did it really matter if it were 100 kilometers (62 miles) south or 100 kilometers north of where he put it on his map across a distance of 6,000 kilometers (3,728 miles) of open ocean? The geological evidence, he judged, ran heavily in his favor.41
He then moved on to talk about a completely separate universe of material, from biology and paleontology. This had nothing to do, he said, with geophysics and had nothing to do with mountain ranges or other geological structures. Then he introduced the compilation by Arldt, about former connections between all the continents at different times, inferred by paleontologists to explain the unity or disparity of flora and fauna. Wegener had known he could not possibly present this material in a lecture by showing a table with all the pluses and minuses of twenty different thinkers for thirty different periods of time concerning thirteen different land bridges—as he had published it in his book—so he came up with a graph for the four most important land connections for his theory. These showed, in a way that was immediately visible, where expert opinion judged that various continental segments began to lose connection, and how the timing of these breaks fit with his own reconstructions.42 Thus, he argued, paleontology and biology count in his favor as well.
There is, he went on, still another class of data, that of the climates of the past. Here he made the case that the discrepancies in latitude zones could only partially be solved by the mobility of the pole. Especially in the Southern Hemisphere, motions of the pole were not enough: the continents needed to be in different positions. Here, he said, his hypothesis extends and completes earlier work explaining these climate shifts as shifts of latitude. Once again, this separate class of evidence pointed in his favor.
So, he asked, when we pile up all of this together into a single picture, all these independent lines of evidence gathered by different people having nothing to do with one another, all of which point to the direction of his hypothesis and none of which point away from it, and all of which, taken together as he had assembled them, seemed to fill most of the holes in most of the proceeding explanations given for them, how are we to judge? “Can a theory be wrong,” he said, “in the light of which the features of the face of the earth acquire in such a wonderful way, meaning, and life?” Even so, he said, “The displacement theory is ready to undergo one final, demanding interrogation. It is willing to prove itself true by precise astronomical position finding.” He then declared that Koch had provided unambiguous proof of the westward motion of Greenland based on his Danmark measurements.43
“Ten years ago,” he concluded, “when the theory of continental displacements was published by me for the first time, it stood facing a mountain of difficulties and questions. Today, these have turned into a glittering array of confirmations.”44 Since the publication of the second edition of his book, he continued, he had received numerous letters from scientists telling him that this work had transformed their previous negative attitude into one of acceptance—though still with reservations: “Even as we speak here, I happen to know, a range of plant and animal geographers, geologists, geographers, and geophysicists are working with this new theory with astonishing results. These developments will, I am convinced, not stop until the theory of continental displacements has become the fundamental basis [Grundannahme] of our understanding of the evolution of the face of the earth.”45
Koßmat came next to the podium and began a respectful, detailed, and professional critique of Wegener’s overall theory, speaking to him and his assertions from the following standpoint: “The idea of crustal wandering ties together facts from geophysics and Earth history, so Wegener’s work should be considered carefully from the geological standpoint.”46 Wegener’s ideas, he continued, have many problems, but they also show much promise. These ideas, Koßmat said, work better in the Southern H
emisphere than they do in the Atlantic. He agreed with Wegener that reuniting the continents alone could not solve the problem of the climate history of the Southern Hemisphere in the Permo-Carboniferous, nor could polar motions alone; whatever the eventual solution to this puzzle, it would require some lateral motion of continental surfaces.47
That he accepted the need for some motion of continents at some point in the past was not, he hastened to say, for him to accept Wegener’s theory; he did not. Like most geologists, his interest in Earth movements concentrated on the vertical, and he liked the idea that mountains were created by “magma injection.” Molten rock from deep within Earth pushing up from below elevates mountain ranges in thick sedimentary basins that were once areas of ocean.48 Continents and oceans were, he insisted, interchangeable, at least in areas like the shallower part of the Indian Ocean and the Mediterranean. Geophysicists, Koßmat said, will have to give way and admit that some amount of sinking of the land is possible, and that the oceans are deepening through time.49
Koßmat went on to disagree with a number of Wegener’s assertions. He saw the same problems that Cloos had seen: the explanations for the East African rift zone; the timing and nature of the split between Africa, Madagascar, and India; the timing of the motion of India and the compression of the Himalayas. He tried to constrain Wegener’s theory to the few places and times on Earth when it was absolutely required to make sense of the data. He denied that the theory was really in a position to unify all of the earth sciences. He was more skeptical of geophysical evidence than Wegener, but not dismissive of it (one recalls that even Rudzki thought that Wegener had overemphasized the difference between continental and ocean rock). There are many complications, Koßmat said, on the face of Earth, which take this simple picture Wegener has provided and force us—in following out the details of the manifold of appearances—to try to understand all of the forces that have brought them about.50 In other words, continental displacements were a piece of the puzzle, but not the solution to the puzzle in general.
Alfred Wegener Page 82
