Papers by Klaus Hentschel
Olaf Kramer & Michael Pelzer (eds.) Rhetorics of Evidence. Science--Media--Culture, Anderson: South Carolina: 287-318, 2024
this is a careful analysis of the masterful rhetorics in the widely read books and talks of the p... more this is a careful analysis of the masterful rhetorics in the widely read books and talks of the physicist, philosopher and peace researcher Carl Friedrich von Weizsäcker (1912-2017)
Deutsche Biographie online, 2024
Carl Friedrich von Weizsäckers Sprache und Rhetorik, 2014
Carl Friedrich von Weizsäcker was not only an exceptional physicist, philosopher and peace schola... more Carl Friedrich von Weizsäcker was not only an exceptional physicist, philosopher and peace scholar, but also a skilled and articulate speaker and a highly successful author. Dozens of his books were published in tens of thousands of copies despite their highly nontrivial content. This wide impact was only possible – this at least is one of the claims made in this paper – because of his sophisticated style and rhetorics. The analysis here is based on handpicked samples from all kinds of Weizsäcker texts (talks, scientic and popular papers and books, poems and Limericks). Strangely enough, this interesting stylistic and rhetorical facet of his oeuvre has hitherto not been analyzed in any detail despite its crucial importance in the broad impact on his multifarious audience. My paper starts out from a collection of striking features of his language and structural specialties in his published talks and speeches, and explore ndings from sound recordings and lm tapes which offer further insight into his manner of emphasis, usage of pauses and intonation. On the basis of these stylistic traits and their often subcutaneous, but nevertheless clever rhetorics, I close with a few remarks on the habitus of this scholar and his positioning within the ensemble of German-speaking physicists of that generation.
Isis, 1990
On the basis of FBI files, released by the "freedom of information act", I could identify an info... more On the basis of FBI files, released by the "freedom of information act", I could identify an informant of the FBI whose name had been blackened-out by the FBI-censors: Paul Weyland (1888-1972), who in 1920 had organized a series of antirelativistic and antisemitic talks against Albert Einstein and his theory of relativity in Weimar Germany, later was used as informant of the FBI during the McCarthy-era - a very unfortunate continuation of antisemitic activities under very different regimes.
Robert Crease (ed.) Between Science and Industry -- Institutions in the History of Materials Research, 2024
This chapter describes the long path from scattered research on diverse materials, – conducted fo... more This chapter describes the long path from scattered research on diverse materials, – conducted for many centuries in many different branches of knowledge – to a concerted quasi-discipline of materials science. The manipulation of materials, and to some extent also their systematic classification, form an integral part of the skills and culture of all societies. Yet it took long for proper sciences (e.g., metallurgy, glass technology, ceramics, polymer chemistry or solid-state physics) to develop out of many processing procedures, tapping the accumulated knowledge about specific material characteristics. Focusing on pertinent research and teaching institutions, relevant societies and journals particularly in Germany, Switzerland and the USA, I show that in the late twentieth century, an overarching science of workable materials emerged: materials science. This concept and term originated from major boosts in materials research during WWII and the Cold War, first financed by the U.S. Department of Defense and the Advanced Research Project Agency (ARPA). The COSMAT-Report from 1974, written by the American Presidential Science Advisory Committee’s “Committee on the Survey of Materials Science and Engineering” four years after its inception, and subsequent reports heralded in the second phase of institutionalization of materials science in the USA and with considerable delay elsewhere as well. As the field continued to expand in the late 1990s, the demand grew from within for disciplinary status. I sort these claims from the various camps (by solid state physicists vs. chemists vs. engineers) and set them in the context of unfolding institutional change. Special emphasis is given to the developments within the German-speaking realm, thus far unduly neglected in these debates. I close with a systematic discussion of eight indicators for or against a convergence of this complex field of research into a single coherent discipline. Against Bensaude-Vincent’s thesis that materials science still is an “aggregation of fragments of knowledge”, I argue that after 2000 materials science had indeed achieved disciplinary status in a historically rare and enduring process of discipline formation through “emergence by integration” rather than by differentiation.
Philosophers and Einstein’s Relativity. The Early Philosophical Reception of the Relativistic Revolution, 2023
During Einstein’s lifetime, the special and general theories of relativity were quite frequently ... more 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 rela-tivity theory are often false or highly misleading. Why is this so? In my Ph.D. dissertation (Hentschel 1990), 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.
Photons, 2018
Proceeding from the introductory propositions about semantic accretion and folds or ‘convolutions... more Proceeding from the introductory propositions about semantic accretion and folds or ‘convolutions’ of meaning, we now treat the conceptual history of light quanta or photons. The twelve semantic layers forming the notion are presented: (1) the particle model of light, starting with Newton into the nineteenth century; (2) light propagation having a finite high velocity; (3) the emission and absorption of light particles by matter; (4) the transfer onto matter of momentum as well as (5) of energy by light; (6) the energy-frequency proportionality E \(\sim \) v in the photoelectric effect; (7) strict energy quantization E = hv; (8) wave-particle duality, first intimated by Einstein 1909 and developed further by Louis de Broglie and others; (9) the distinction between spontaneous and induced emission, introduced by Einstein in 2 talks held 1916–17, forming the theoretical basis of the modern laser; (10) internal angular momentum (spin 1) carried by light quanta; (11) indistinguishability among light quanta, ultimately leading to Bose-Einstein statistics; (12) the photon as a virtual exchange particle of QED that thanks to its lack of mass can transport electromagnetic forces over infinitely large distances.
Photons, 2018
The mental models by early actors are presented. Sect 4.1 discusses Isaac Newton’s “globuli of li... more The mental models by early actors are presented. Sect 4.1 discusses Isaac Newton’s “globuli of light” along with amendments by some of his important adherents; the next two sections cover Einstein’s mental model of light quanta around 1909 as singularities in the radiation field, along with his doubts about it 1910–15. Sects. 4.4–4.6 review the mental models of three influential experimental physicists: Johannes Stark’s light quanta, J.J. Thomson’s model of hard x rays, and W.H. Bragg’s neutral pair model for -rays. Sect. 4.7 treats the mental model argued by Planck, Peter Debye and Arnold Sommerfeld to relegate the quantization of energy and momentum to the material resonators in a black body. Sect. 4.8 deals with Gilbert Lewis’s mental model of photons by which this American physical chemist introduced the term ‘photon’ in his reflections about the temporal symmetry between emission and absorption but still attaching to it the completely wrong notion of photon number being conserved.
Biographies in the History of Physics, 2020
How are these developments reflected in textbooks and scientific instruction? Charts and examples... more How are these developments reflected in textbooks and scientific instruction? Charts and examples show how eight significant episodes in the history of the introduction of the light quantum are barely adequately or insufficiently treated in over 100 analyzed science textbooks and almost 40 practical instruction manuals. Coming generations of scientists are repeatedly confronted with historically false myths, barring the way toward a deeper understanding of the historical processes but also to sufficient comprehension of the concepts involved, such as the light quantum a.k.a. the photon. Support is offered for the claim that professional instruction in the history of the science and technology must form a part of good scientific training.
What is today’s mental model of the photon? Naively materialistic projectile or corpuscular inter... more What is today’s mental model of the photon? Naively materialistic projectile or corpuscular interpretations of light were defended not only by Isaac Newton and his many nineteenth-century acolytes but by important experimental physicists from the following century, such as Johannes Stark or Arthur Holly Compton. Thomas Young, Augustin Fresnel and many other scientists of the nineteenth and early twentieth century countered it with an equally naively absolutist wave theory of light underpinned by Maxwell’s equations for electromagnetic radiation. Neither of these interpretations can account for the wave-particle duality established in 1909. That’s why Sects. 9.1–9.2 argue in favor of an ontologically restrained, instrumentalistic interpretation and advise against naive realism or the illegitimate assignment of locality. Sect. 9.4 goes further to warn against our tendency to individualize reality. Only thus can the Bose-Einstein statistics be duly accounted for. All of this is so coun...
Historische Zeitschrift, 2018
Acta Historica Leopoldina, 2006
Biographical Encyclopedia of Astronomers, 2007
short biographical article about the well-known spectroscopists who worked at the Sorbonne, the É... more short biographical article about the well-known spectroscopists who worked at the Sorbonne, the École Normale, and the Collège de France, and from 1879 at the observatories of San Remo, Italy and Nice
Physics and National Socialism, 1996
Physics and National Socialism, 1996
In an attempt to avoid the continuation of the well-known attacks on German theoretical physics a... more In an attempt to avoid the continuation of the well-known attacks on German theoretical physics and in an effort to clarify the situation, the Reich leadership of the National Socialist University Lecturers League organized a debate at the ‘Physicians House’ [Arztehaus] in Munich on the 15th of November, 1940. Members of the group of assailants met with representatives of the remaining German physics community, 14 participants in all.[2] During the debate the assailants had to withdraw practically all of their factual objections, so that in the end consensus could be reached on the following five points:*[3] 1. Theoretical physics together with all its mathematical aids is a necessary part of physics as a whole. 2. The observed facts summarized in the special theory of relativity are an established part of physics. The applicability of the special theory of relativity [4] to cosmic relationships is not so certain, however, as to eliminate the necessity of further verification. [5] 3. The four-dimensional description of natural processes is a useful mathematical tool; but it does not imply the adoption of a new conception of space and time.[6] 4. Any link between the relatively theory and a general relativism is rejected.[7] 5. Quantum and wave mechanics are only known ways at present to describe atomic processes quantitatively. It is desirable to go beyond formalism and its correspondence rules [Deutungsvorschriften] to come to a deeper understanding of atoms.[8] * [Original footnote +):] “Present at the closing session: Messrs.: [Rudolf] Tomaschek, [Alfons] Buhl, [Johannes] Malsch, [Harald] Volkmann, [Ludwig] Wesch, [Herbert] Stuart, [Wolfgan] Finkelnburg, [Georg] Joos, [Otto] Scherzer, [Hans] Kopfermann, [Otto] Heckmann, [Carl Friedrich] v. Weizsacker. Not present: [Bruno] Thuring, W[ilhelm]. Muller.”
Physics and National Socialism, 1996
Physics and National Socialism, 1996
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Papers by Klaus Hentschel
quanta`. The great number of synonyms used by physicists between
1900 and now to denote this concept already signals that there are
many different mental models of what ,light quanta` supposedly are:
simply finite, ,quantized packages of energy` or ,bullets of light`?
,Atoms of light` or ,molecules of light`? ,Light corpuscles`, or
,quantized waves`? Singularities of the field or spatially extended
structures able to interfere? ,Photons` in the sense of G.N. Lewis
or in the sense of QED, i.e., virtual exchange particles
transmitting the electromagnetic force?
The term ,light quanta` made its first appearance in Albert
Einstein's 1905 paper on a ,,heuristic point of view`` to cope with
the photoelectric effect and other forms of interaction of light and
matter, but the mental model associated with it has a rich history
both before and after 1905. Some of its semantic layers lead as far
back as Newton and Kepler, others are only fully expressed several
decades later, yet others initially increased, then diminished in
importance and finally vanished. In conjunction with the various
terms, several mental models of light quanta were developed -- six
of them have been treated in closer detail in this book. Two
historiographic approaches to the problem of concept formation are
discussed and exemplified: a) my own model of conceptual development
as a series of semantic accretions and b) Mark Turner's model of
,conceptual blending`. Both of these models are shown to be useful
and should be explored further.
This book is the sgtrongly expanded 2nd edition of the first historiographically sophisticated history of the full-fledged concept of light quanta or photons as they are called since 1926. It distinguishes twelve semantic layers and systematically combines the history of science with the history of terminology and a philosophically inspired history
of ideas in conjunction with insights from cognitive science.