Schmidt, Johann Friedrich Julius
Born Eutin, (Schleswig-Holstein, Germany), 26 October 1825
Died Athens, Greece, 7 February 1884
German observer Julius Schmidt compiled the most complete maps of the Moon of his generation and reported changes in the appearance of one crater that were widely accepted at the time. In an era when study of the Moon had become increasingly specialized and knowledge of its topography so comprehensive that it led to the formation of a committee of British observers to further its mapping, Schmidt worked unaided and alone. It was plausibly suggested by Harvard College Observatory astronomer William Pickering that Schmidt “perhaps devoted more of his life than any other man to the study of the Moon.”
Schmidt was the son of Carl Friedrich Schmidt, a glazier by profession, and Maria Elisabeth Quirling. At the age of 14, young Schmidt chanced upon a copy of Johann Schröter ’s Selenotopographische Fragmente. He was so fascinated by its pictures of mountains and craters that the future direction of his life was determined then and there. Schmidt immediately began to study the Moon himself, using a small telescope made with lenses ground by his father.
Schmidt’s first view of the Moon through a good telescope came in July 1841, when A. C. Petersen, director of the Altona Observatory near Hamburg, showed him the imposing craters Bullialdus and Gassendi. He also saw for the first time a copy of the great 1837 map of the Moon prepared by Wilhelm Beer and Johann von Mädler . Soon afterward, Schmidt moved to Hamburg and for several years made frequent observations with the telescopes of the Altona Observatory.
A strange interlude followed in 1845, when Schmidt accepted a position in the private observatory of Johann Benzenberg at Bilk, near Düsseldorf. Benzenberg was preoccupied with the search for a possible intra-Mercurial planet and did not allow Schmidt to use his large refractor, apparently for no better reason than that “its outward good looks and polish might not suffer by handling.” Instead, he gave Schmidt access only to a “wretched instrument.” After a few months, Schmidt left Bilk in disgust and took a position under Friedrich Argelander at the Bonn Observatory. Although most of his time was taken up with entering meridian circle observations of stars for Argelander’s great catalog, the Bonner Durchmusterung (Bonn Survey), he made as many lunar observations as he could.
In 1853, Schmidt left Bonn for E. von Unkrechtsberg’s observatory at Olmütz (now Olomouc), in Moravia, where he made some 3,000 measurements of the heights of lunar mountains with a filar micrometer. This work was published in an 1856 treatise, entitled Der Mond (The Moon), in which Schmidt attempted to provide a quantitative comparison of lunar and terrestrial features. He prudently warned against taking the apparent similarities between the Moon and Earth too seriously.
On 2 December 1858, Schmidt assumed the directorship of the Athens Observatory in Greece, where he would remain for the rest of his life. When he set foot on Greek soil at Piraeus, Schmidt was still a comparatively young man, full of energy. Arriving at the observatory, he found it in a state of disrepair and neglect. Within only a year, however, Schmidt was able to restore to working order a fine 6.2-in. refractor by the Viennese optician Georg S. Plössl, which served as the main instrument for his lunar work over the next quarter of a century.
By 1865, Schmidt had assembled so many lunar observations that he began laying down his surveys of selected regions on a 6-ft diameter map. The next year, he began to construct a 1-m map based on Wilhelm Lohrmann ’s observations, which had been entrusted to Schmidt by Lohrmann’s publisher.
At first, Schmidt planned to enter details from his own observations onto Lohrmann’s map, but he soon abandoned this approach in favor of something far more ambitious – nothing less than a fresh topographic map of the Moon roughly 2-m diameter, which, like Lohrmann’s original design, was to be divided into 25 sections. Schmidt hoped to record all of the details of the lunar surface visible through his 6.2-in. refractor, but gradually came to the realization that such a feat would require “more powers of endurance and a longer lifetime than are allotted to mortals.”
It was while Schmidt was involved in this lengthy series of observations that he came across something startling but not entirely unexpected. In 1866, he announced that the tiny crater Linné in Mare Serenitatis had undergone a profound change. He maintained that, prior to 1866, Linné had always been recorded as a crater about 6 miles in diameter and “very deep,” but had been suddenly reduced to a diffuse white patch. As a recent eyewitness of volcanic eruptions on the Aegean island of Santorini, Schmidt proposed that Linné had been filled in by a similar “eruption of fluid or powdery material.”
Given the daunting complexity of lunar detail, the variable effects of shadow, foreshortening, and libration as well as the inevitable deficiencies of the selenographic record, the surprising fact is that Schmidt’s claim of a definite change was widely and uncritically accepted. Despite the fact that the evidence of change was always weak, the alleged alteration of Linné would not be thoroughly discredited for more than a century.
In July 1874, Schmidt presented his lunar map to the Berlin Observatory, where it excited admiration as a performance highly creditable to “Teutonic intellect and perseverance.” Before long, it was being touted as a uniquely Prussian achievement. Its 25 sections were photographed at the General Staff Office under the direction of Count von Moltke; its publication as the Charte der Gebirge des Mondes (Map of the Mountains on the Moon) was sponsored by the Crown Prince of Prussia himself.
In even a cursory examination of Schmidt’s map its completion by a single observer must seem almost incomprehensible …; but it requires protracted study to well realize the extent of the work. Any person who tries with the aid of a 6-inch telescope to give a closely detailed delineation of even a small area of the Moon, will soon conclude that the period of 33 years was comparatively a very short one for the accomplishment of Dr. Schmidt’s great task.
To give some idea of Schmidt’s amazing industry in lunar researches, it may be mentioned that in 6 years he made nearly 57,000 individual settings of his micrometer in the measurement of lunar altitudes. His great chart of the mountains in the Moon is based on no less than 2,731 drawings.
According to Schmidt’s own rather compulsive analysis, Lohrmann had charted 7,177 craters and Mädler 7,735; his own map recorded no less than 32,856. The superiority of Schmidt’s map was also apparent in his record of rilles – the 71 on Mädler’s map paled in comparison with his own 348.
Schmidt also had a keen interest in seismology. At the age of 20, he began to collect materials for a global earthquake catalog, and he contributed to Johann J. Noeggerath’s study of the 1846 Rhineland earthquake by calculating the propagation speed of the seismic wave. In 1874, he published a study of four volcanoes: Santorini, Etna, Vesuvius, and Stromboli. Schmidt’s Studien über Erdbeben (Studies on earthquakes), a comprehensive catalog of earthquakes recorded in southeastern Europe since ancient times, was issued the following year.
Schmidt reorganized the meteorological service of the Athens Observatory. He made meteorological observations from locations throughout Greece and regularly submitted data to the Paris Observatory. These results were presented in his 1864 work, Beiträge zur Physikalischen von Griechenland. Schmidt also dabbled in archeology and made a concerted effort to find the site of ancient Troy.
Schmidt was awarded an honorary doctorate from the University of Bonn in 1868. Fittingly, a crater on the Moon is named for him.
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