Prof. Dr. Klaus Hentschel

Loss of the Inner Core: Expectations and Fears for the Future of the History of Science. In this paper, I discuss the current state of history of science in Germany, a combination of strong interest in the field from various neighboring fields (including cultural history, media history, history of art, visual studies) and increasing fragmentation. Powerful institutions such as the Max Planck Institute for History of Science rather encourage this tendency to lose the inner core of the field, a kind of fluidization or vaporization.

ZusammenfassungBei der Durchsicht des Nachlasses von Rudolf Tomaschek (1895–1966) fand ich ein 30 Seiten umfassendes Typoskript seines damaligen Assistenten Hugo Watzlawek (1912–1995) aus dem Jahr 1944 mit dem Titel „Interatomare Energie“. Heute würde man eher von „inneratomarer Energie“, oder von „Kernenergie“ sprechen, da der Inhalt des Typoskripts „technische Kernphysik“ einschließlich ihrer potentiellen militärischen Anwendungen betrifft. Der Text bietet einen ungefilterten, erstaunlich kenntnisreichen, aber in vielem auch erschreckenden Einblick in die technokratische Gedankenwelt sowie den Wissensstand und Anwendungshorizont eines „technischen Kernphysikers“ im „Dritten Reich“, der unter Verweis auf konkurrierende amerikanische Forschungen 1944 nachdrücklich um weitere Mittel für kernphysikalische und -technische Forschung sowie für die Entwicklung von Kernwaffen bittet. Der vorliegende Aufsatz kommentiert und kontextualisiert das Typoskript; meine ebenfalls online gestellte annotierte Transkription des Typoskriptes bietet ungekürzten Zugang zum Originaltext samt knapper, für dessen Verständnis notwendiger historischer und technischer Erläuterungen.

In late 1912, Fritz Goos at the Hamburg Physikalisches Staatslaboratorium discovered a systematic dependency of arc-spectra wavelengths on the length of the electric arc used and on its electric parameters, such as, for instance, the current employed. In early 1913, at Heinrich Kayser's better-equipped physical laboratory in Bonn, Goos was able to confirm these effects using a large concave Rowland grating. He was able to establish that variations of between 3 mm and 10 mm in the length of the arc produced wavelength differences of up to 0.02 Å violet shift and -0.007 Å redshift respectively. Further inquiry also revealed a dependency of the wavelength on the region of the arc selected for spectrometric observation. All these surprising effects were soon collectively named ‘pole effect’.As is shown in this paper, the pole effect threatened the validity of the results of the entire research tradition of high-precision spectroscopy which, around 1910, had excelled in establishing several internally coherent systems of wavelength assignments. These wavelength catalogues had been established by spectroscopists such as Heinrich Kayser, Paul Eversheim and their co-workers in Bonn, by August Herman Pfund in Baltimore, and by Charles Fabry and Henri Buisson in Marseille under the aegis of the ‘International Union for Co-Operation in Solar Research’. They had all produced locally consistent, “homogeneous” systems of wavelengths with estimated errors sometimes smaller than 0.001 Å. However, long before 1913, strange non-local inconsistencies had emerged between these systems that were of much greater magnitude than the estimated error. The discovery of the pole effect opened up the possibility that variations in the arc parameters used in the measurements, which the different teams had hitherto not specified, were responsible for the systematic differences, in their respective sets of measurements, coming to up to 0.025 Å.This paper explores the interrelations between local knowledge production, the strategies for the establishment of local coherence, and the ways in which the community of physicists and spectroscopists handled a possible threat to this coherence after 1913. Around 1930, a general agreement was reached about the physical cause of the pole effect, namely Stark effects, caused in turn by intermolecular electric fields of ions in the arc. Much before 1930, however, the community had already succeeded in standardizing the instrumentation used in high-precision spectrometry and had conformed its research practice to such an extent that from 1917 on the pole effect could be routinely circumvented in high-precision spectrometry and interferometry. Thus, experimentation along with its instrumentation, indeed had ‘a life of its own’, independent of the many unsuccessful efforts to explain the pole effect theoretically.

To compile a comprehensive edition of the correspondence of the world-famous physicist, physiologist, philosopher, and pioneer historian of science, Ernst Mach is an urgent desideratum. An estimated 5000 letters to and from Mach are kept in public and private archives worldwide. The largest part of this correspondence was formerly kept in the Ernst Mach Institut für Kurzzeitdynamik der Fraunhofergesellschaft in Freiburg/Breisgau and is now archived at the Deutsches Museum in Munich. A smaller partial estate, based on collections by Ernst Mach’s son Ludwig has been transferred to the Staats- und Universitätsbibliothek Göttingen. Other major collections are kept in Konstanz, Vienna, Prague etc. Mach’s own letters are spread throughout Europe and North America in hundreds of archives hosting private papers or estates of his contacts.

This paper discusses facets of 19th-century scientific photography as a visual culture. The example of spectral research and documentation is particularly well suited, because prismatically diffracted light from the sun or from luminous gases was one of the most frequently examined phenomena of that century. The results were significant not only for physics but also for analytical chemistry and astrophysics. The spectrum also served as an ideal test object for checking the effectiveness of a wide array of photochemically sensitizable surfaces to the various color regions. Scientific photography became the most important experimental technique in the infrared and ultraviolet. H. A. Rowland's spectrum charts are discussed as an example of the transition from comprehensiveness in documentation to fetishism. The discussion of the Lippmann process, one of the first methods of color photography, addresses the associated training of the eye. Issues of authenticity and the much averred „mechanical objectivity” are raised with regard to retouching. The overriding theme of visual science cultures leads furthermore to unanticipated interdependencies with other scientific fields, such as geography, and draws the importance of practitioners into the foreground

During Einstein’s lifetime, the special and general theories of relativity were quite frequently interpreted by philosophers. Most of these interpretations actually were misinterpretations. Even today interpretative statements about relativity theory are often false or highly misleading. Why is this so? In my Ph.D. dissertation (Hentschel 1990a), I analyzed (mis)interpretations by 10 different philosophical schools active in the early twentieth century which widely differed in their approaches, emphasis and blind spots. Many of these interpreters – including philosophers of high standing such as Ernst Cassirer, Moritz Schlick or Joseph Petzoldt – had studied the theory intensely and many even had close contact with Einstein himself or with one of the members of his “protective belt” of close friends and allies. Rather than declaring all of these (mis)interpreters as either luminaries or idiots (which would be implausible, if not downright silly), I show structurally how these misunderstandings arose and why they were kind of unavoidable, even for highly qualified and often well-informed interpreters. More popular texts about relativity theory were often second-order interpretations of these first-order accounts, thus multiplying the first-order errors of misinterpretations. I will give a few characteristic examples but my focus will rather be on structural characteristics of these misinterpretations. I will discuss how to analyze them historically by means of interpretational frames. A link will also be made to Ludwik Fleck’s thesis that socially and cognitively stabilized “thought collectives” (“Denkkollektive”) exert strong constraints on human thinking and interpretation (“Denkzwang”). My concept of interpretational frames is one method to formalize and analyze the complex interrelations between different assumptions and inferences within such a frame of thinking (“Denkstil”). Semantic frames and word clouds are also discussed as alternative approaches but both are discarded as unsuitable for the purpose of reconstructing interpretative frames.