Measuring Contemporary Displacements
Wegener’s estimates for the rates at which the continents were moving apart are enormous by current standards. He estimated that the westward separation of Greenland from Scandinavia, in 1912, was proceeding at a rate between 14 and 28 meters (46–92 feet) per year. He obtained this astonishing rate by assuming the separation of the two continental blocks from one another to have taken place between 50,000 and 100,000 years ago. This would have been after the “great” ice age but before the last ice age, according to the geochronology of his time, and was an estimate based jointly on preliminary radiometric dates and paleontological data supplied by Arldt and others. The distance of 1,400 kilometers (870 miles) between Scandinavia and Greenland in 1912 and the assumption that they had been separating for between 50,000 and 100,000 years accounted for the spreading rate of 14–28 meters per year.
Wegener did not obtain this number by any geophysical calculation having to do with any quantity concerning plasticity, fracture and flow, isostatic adjustments, or any other geophysical considerations. He got his spreading rates the way we get ours: he took the total distance and the total time and divided the distance in meters by the time in years, to get meters (or fractions of meters) per year. In spite of a general impression to the contrary, our current plate tectonic spreading rates have yet to be unambiguously measured. Scientists, since the 1990s, using very long baseline interferometry, satellite laser ranging, and GPS systems, continue to claim to have demonstrated such motions. Without exception, their claims repeatedly confuse the precision of their measurements with the accuracy of their results, which have uncertainties of 40 percent and greater. The uncertainties are largely driven by the need to incorporate into their calculations a theory of Earth’s nutation and a crucial term for atmospheric refraction, the latter depending on the amount of water vapor in the atmosphere, a quantity that changes hour by hour. The measurement results agree with models, and no one doubts that the plates are moving, but accurate measurements of plate motions are still, at this writing, beyond the limits of resolution of the best technologies, regardless of many strident claims to the contrary.
With the current estimate of the end of the Cretaceous as the time for the beginning of the opening of the Atlantic (this was also Wegener’s timing of this event, again following Keilhack), this gives a time of around 57 million years ago for the original separation. Current estimates for the opening of the Atlantic are on the order of 2 centimeters (0.8 inches) per year, with the notion that earlier spreading rates may have been as high as 5 centimeters (2.0 inches) per year. The spreading rate is obtained by the ratio of the distance (3,500 kilometers [2,175 miles]) and the time. This is identical to Wegener’s method, with his much-attenuated time span producing a reciprocally increased spreading rate.
Wegener wanted to test his estimate against measurements of the longitude of East Greenland, but he had only three sets of measurements with which to deal. There were those made by Edward Sabine in 1823, those made by Börgen and Copeland on the Germania Expedition in 1869/1870, and finally those made by Koch (and Wegener) on the Danmark Expedition in 1907–1908. The technique of measurement was an old one, that of the observation of the Moon against the background of the fixed stars. Each of these three expeditions used a different version of this technique. Sabine used lunar distances (distance between the Moon and a fixed star), Börgen and Copeland used lunar culminations and stellar occultations, and Koch and Wegener had used lunar azimuths. None of these observations were taken at exactly the same place, and all were subject to very taxing and minute corrections to yield any accuracy at all. In spite of the possibility of errors in the range of hundreds of meters for the location of these observing stations, Wegener insisted that the difference between Sabine’s measurements and those of Koch and himself, after a lot of calculating, showed a westward drift of Greenland of 950 meters (3,117 feet) over the span of eighty-four years. This gave a rate of drift of 11 meters (36 feet) per year, within his predicted range, and he chose to believe that this figure was not the summation of large individual errors.
It is well known that in the measurement of longitude with the help of the moon, the attainable accuracy is poor. One may estimate the probable error of a single series of measurements as quite easily several, and perhaps many hundreds of meters. The difference of 950 meters, however, that has here become apparent over the course of time, seems to me to be somewhat too great already to be justifiably set aside as merely an unfortunate summation of individual errors. It might rather be quite considerably more likely that it has been caused by an actual displacement of the continents of the order of magnitude given.32
Understanding (and then discounting!) the fragility of the inferences from such measurements, Wegener then offered as evidence of continental displacements a series of measurements made between 1866 and 1892 comparing the longitudes of positions in North America with those at points in England and France. These measurements used the (then) recently laid submarine telegraph cables to exchange exact time signals of the culmination of celestial bodies above established observatories. At the precise instant of culmination the observer struck a telegraph key that sent a telegraph time signal across the Atlantic, to be recorded on a revolving drum on an instrument at the other observatory. The difference in the times of culmination of the same celestial body between two stations on opposite sides of the Atlantic represented the difference in longitude between the stations.
Such measurements strove for great accuracy, and observers traveled back and forth across the Atlantic carrying their recording equipment, so that the U.S. observer and his telegraphic equipment would then be used in England, and the English observer and his telegraph equipment would be used in the United States. The resulting difference in longitude as measured was 0.23 seconds of longitude over twenty-six years, or somewhere around 1/100 of a second of time per year, equivalent to a continental displacement of about 0.27 meters (0.89 feet) per year.33
These measurements were, of course, not carried out to measure continental displacement but were part of an ongoing international program to correct the accuracy of geodetic networks and also of stellar ephemerides. The possibility of exchanging instantaneous time signals was something that Wegener was familiar with through his own astronomical work at the Berlin and Potsdam observatories, and of course something in which he was keenly interested as a student and author of tables of planetary and lunar positions. At the very time Wegener was working on his article on continental displacements, an international conference was preparing to convene (in Paris) to establish a system of universal time, to be based on time signals transmitted telegraphically from the Royal Greenwich Observatory in Great Britain. Thus, the 0° of longitude would also become the home of the reference time signal and make highly accurate determinations possible according to a single international standard.
Wegener had to admit, however, that with regard to measurements of continental displacement “these numbers are not only for the time being still completely uncertain, but also that they are, up to now, scarcely to be regarded as at all sufficient to establish the reality of displacement. The observed time difference amounts to only 0.23 s and is thus still so small, that it, if need be, could be explained by the greater imprecision of the earlier measurements. If however some new longitude measurement—twenty years have now already passed since the last—again should likewise yield to change, the reality of the displacements could no longer be doubted.”34
Wegener also considered that latitude measurements could be employed to measure displacement, both to measure the displacement of India and Australia, which he believed to be moving northward, and through measurements of the position of the North Pole, by the International Latitude Service. This international organization, established in 1899, with six observatories located at latitude 39°08″ north, was a joint effort of the U.S. Coast and Geodetic Survey, the Prussian Geodetic Service, and other organizations. These were a co
ntinuation, using zenith telescopes, of the observations initiated by the Potsdam Observatory in Germany, under the direction of Wegener’s professor, Friedrich Helmert, and the observations of Chandler himself in the United States, to measure the wobble of Earth’s axis of rotation. Wegener was again intimately familiar with these measurements; indeed, they were the inspiration for his doctoral dissertation.
While no such measurements had yet detected a permanent offset of the pole of rotation such as might be produced by a displacement of the pole of inertia, Wegener believed that a longer time series would also soon show this displacement and thus serve as an argument for the displacement of the continents as a cause of the displacement of the poles. “Naturally, these views will be considered correct only when it will have been possible to support them through an exact mathematical treatment. At present I do not have time to undertake such an investigation. Perhaps this brief note has, however, succeeded in calling attention to this problem, which through its connection with the hypothesis of the horizontal displacement of continents, seems to me, in a manner undreamed of previously, to be thrust into the foreground of interest.”35
With this laconic observation, Alfred Wegener brought to an end his first extensive presentation of his theory of continental displacements. The abrupt termination of the argument, without summation or conclusion, reminds one of the last lines of Wegener’s Thermodynamik der Atmosphäre, published the year before. As in that case, there was more to say but no time to say it: the publishing deadline loomed, and other tasks were at hand.
When we examine the lines of geophysical and geological evidence he brought to bear in hypothesizing continental displacement, it is astonishing how many of the principal authors he employed in his arguments were either his professors (like Helmert) or senior colleagues with whom he was closely associated (like Wiechert and Kayser). He had firsthand knowledge and training in astronomical position fixing, geodesy, gravity measurement, solid mechanics, thermodynamics, and physical chemistry. In this regard, his work in continental displacements was similar to his work on atmospheric physics, where his confidence to handle the material stemmed not least from his personal contact with the leading practitioners of that science and his direct training and experience in what appears, in retrospect, to be an astonishingly broad range of subfields of physical science.
In consequence, one should not be misled by later characterizations of Wegener as a rebel, an outsider, a loner, a maverick, or an isolated genius figure. Wegener was a well-trained, experienced, highly competent physicist who saw all his work, continental displacements included, as legitimate extensions of solid and well-accepted conclusions concerning the physics of Earth. He was professionally well placed, well known, and widely published.
Alfred Wegener in a photo taken in 1911 or 1912. His demeanor suggests the confident and expansive mood that characterized his work on the origin of continents and oceans and the thermodynamics of the atmosphere. Photo courtesy of the Heimatmuseum, Neuruppin.
It may, nevertheless, seem a great overreaching for a theorist of the atmosphere to develop and advance publicly (within months of its first formulation) a comprehensive theory of the origin of continents and oceans. Perhaps it was. From Wegener’s standpoint, however, the unification of material parted out to different disciplines within Germany—geology, oceanography, meteorology, geophysics, geography, and astronomy—was precisely the task of cosmic physics, already recognized as a discipline meriting professors and professorships in Scandinavia and as a subject matter in German secondary schools. Wegener made no secret of his ambition, expressed to his brother, his parents, his wife-to-be, his future father-in-law and collaborator Wladimir Köppen, and his superiors at Marburg, Richarz and Kayser, that he should become one of the first university professors of cosmic physics in Germany. His confidence that he would achieve this was as absolute as his confidence that he would mathematically confirm continental displacements within a few years. In both cases it was merely a matter of time.
Greenland
When he had learned in early February 1912 that his Greenland expedition—his and Koch’s—was now imminent, Wegener knew he had to raise 15,000 marks in a little less than two months and additionally had to face another difficult truth: almost everyone he knew and loved opposed the trip. Köppen thought it an unnecessary diversion from the opportunity, offered by the Carnegie grant, for Wegener to move to Hamburg and begin their closer collaboration. Else was unhappy with the prospect of the danger and the postponement of the marriage. Wegener’s parents, Richard and Anna, were aghast that at this critical juncture in his professional life, on the cusp of being a candidate for a real professorship, he would venture off on another one of his vagabond larks.
The timing was certainly inconvenient for him professionally as well. It would force him into hurrying and compressing his revisions to the paper on continental displacements, which so obviously showed its unevenness and the haste of its composition, especially in the final section. Clearly, however, he wanted to go back to Greenland. There was his private ambition to be known as a polar explorer. Moreover, with his work on the Danmark Expedition science complete, he had consequently run out of any data of his own which he might offer as an original scientific contribution. He could certainly make his mark as a theorist, but it was also necessary to do field science if one wished to be listened to in a world as data driven as that of meteorology and geophysics.
There was another significant dimension to this expedition plan. Wegener had a score to settle with the way that the Danmark Expedition had been run. It had been sprawling, wasteful, and disorganized and had sacrificed science to everything else, from Mylius-Erichsen’s unquenchable ambition to the insistence that all the scientific staff perform the work of ordinary deckhands. The motorcar that was the only source of power for the kite winch, the loss of which cost him so many hours of painful labor, had been sacrificed in a joyride. This and dozens of other irritations he painstakingly recorded in his expedition diaries from those years. While his loyalty to and friendship with Koch might have carried him again to Greenland anyway, this expedition was very much the fruit of their many conversations about how things should have been done in 1906–1908; it was a chance to do things “the right way.”
This new expedition would be a study in contrast to the previous one. It would be well organized, well planned, compact (if 20,000 kilograms [44,092 pounds] of equipment and supplies can be called compact), and, best of all, collaborative on an equal footing. Wegener, Koch, and the botanist Andreas Lundager would be equal scientific partners; Vigfus Sigurdsson would see to the horses. Lundager had been their companion in the “Villa” on the Danmark Expedition, along with the painter Aage Bertelsen, and was a proven quantity, as was Vigfus, well known to Koch. There would be none of the personal struggles and petty squabbles of the Danmark years.
Wegener had to make the case to his family, friends, allies, and colleagues that he should, instead of pursuing his career, finding a professorial post, defending his radical theoretical claims in both meteorology and geophysics, getting married, settling down, and entering into some stable and long-term professional relationships, take off on an expedition to traverse the middle of Greenland, simply because it had never yet been done. The expedition had a scientific program, but it was not extensive, and neither the time they would spend in winter quarters on the east coast of Greenland nor the pace they would set in order to make it across the ice cap in the summer months would permit a concentrated program of scientific work anything like what had been accomplished between 1906 and 1908. In polar science, the sheer physical challenges to survival were immense, and the chances of failure in every scientific undertaking were very high. For anyone who knew anything about Arctic science, this was “a long shot.”
Persuasive help in making his case arrived from an unlikely quarter. Wegener’s Thermodynamik had been rapidly reviewed and received positive notices in the Physikalische Zeitschrift and elsewhere. In
December of 1911, however, it had received a terse and dismissive review in the one place it could hurt most: Meteorologische Zeitschrift.36 The reviewer was Felix Maria Exner (1876–1930), who was only four years Wegener’s senior but professionally very highly placed. He had been, since 1907, the secretary of the Central Institute for Meteorology and Geomagnetism in Vienna. As a scion of the Exner family’s academic dynasty, extending back into the nineteenth century, he had been named professor of cosmic physics at the University of Innsbruck in 1910. His uncle, Franz Serafin Exner (1849–1926), a celebrated physicist, had become rector of the University of Vienna in 1908.37
In February of 1912, shortly after Alfred broke the news to his parents that Koch had obtained the money from the Carlsberg Foundation and that he would therefore be leaving for Greenland in a few months, Kurt Wegener wrote to Richard and Anna to explain the situation. The context makes it clear that Wegener’s parents had asked Kurt to intercede with Alfred and to induce him to abandon the Greenland plans. Here is what Kurt wrote:
The [Greenland] plan is scientifically significant … the possibility of Alfred suddenly becoming a professor has, in consequence of the extremely unfriendly review of his beautiful book (Thermodynamics) by Exner in the Meteorologische Zeitschrift, for the time being completely vanished, since externally or to all appearances the opinion of the Meteorologische Zeitschrift passes as the standard measure for the profession, though the true professional opinion which one has heard everywhere speaks of Exner’s careless and cursory review, and this must be given time to slowly penetrate. So that the expedition year signifies thus from this viewpoint no loss, especially since in that year the first reviews of Alfred’s many completed papers (including those concerning his “Urkontinent”) will appear and have time to work. Finally, it seems to me for his later finding a permanent situation, it will be advantageous for him to actually carry through an already announced expedition so that he doesn’t develop a reputation as a blowhard and puffer. You will probably be very angry with me but I can’t for all the above reasons fail to believe that this is true and above all for the good of the expedition cannot dissuade Alfred from this undertaking. And also his health makes me think that a “sport year” seems to be desirable. This constant bent-over sitting makes him seem like he’ll become just as slight as I am.38
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