Klaus Hentschel
Klaus Hentschel | |
|---|---|
 | |
| Born | April 4, 1961 Bad Nauheim, Germany |
| Residence | Stuttgart, Germany |
| Nationality | German |
| Alma mater | University of Hamburg |
| Known for | Reception and criticism of relativity, solar redshift tests, history of the light quantum |
| Scientific career | |
| Fields | History of science, history of physics, spectroscopy |
Klaus Hentschel (born 4 April 1961 in Bad Nauheim, Germany) is a German historian of science who holds the chair for the History of Science and Technology (GNT) at the University of Stuttgart. He is not himself a critic of relativity theory, but his archival work is of unusual value to those who are: more than any other professional historian, Hentschel has documented in detail how contested, ambiguous and theory-laden the early "confirmations" of Einstein's theory actually were, and how Einstein's contemporaries — supporters and opponents alike — argued about them.
Biography
Education
Hentschel studied philosophy and physics at the University of Hamburg, taking a master's degree in philosophy in 1985, a diploma in physics in 1987, and a doctorate in philosophy in 1989. His dissertation, Interpretationen und Fehlinterpretationen der speziellen und der allgemeinen Relativitätstheorie durch Zeitgenossen Albert Einsteins ("Interpretations and Misinterpretations of the Special and General Theory of Relativity by Contemporaries of Albert Einstein"), ran to some 700 pages with roughly 3,200 bibliographic references. It was published by Birkhäuser in 1990 and won the Kurt-Hartwig-Siemers Prize of the Hamburg Scientific Foundation.
He was born in Bad Nauheim, the spa town where in September 1920 Einstein and Philipp Lenard confronted each other in public over relativity before the assembled German Society of Natural Scientists and Physicians — an episode that falls squarely inside Hentschel's later field of study.
Career
From 1991 to 1996 Hentschel was assistant professor at the University of Göttingen. In 1995–96 he held a fellowship at the Dibner Institute and the Massachusetts Institute of Technology, and he subsequently held visiting and research positions at Göttingen, MIT, Hamburg, the University of Bern and Stuttgart. Since 1 October 2006 he has held the chair of History of Science and Technology at the University of Stuttgart; he served as vice director of the History Department from 2007 and as its director from 2010 to 2013. He headed the German Society for the History of Science in 2013–2015 and again in 2017–2018, and has been a member of the Leopoldina, the German National Academy of Sciences, since 2003.
Work of interest to critics of relativity
Most early interpretations of relativity were misinterpretations
The central finding of Hentschel's 1990 dissertation is blunt and, for a mainstream history of science, remarkable: the great majority of the interpretations of special and general relativity offered by Einstein's contemporaries were misinterpretations. This applied not only to the declared opponents — Ernst Gehrcke, Lenard, and the wider anti-relativist camp — but equally to relativity's professional philosophical champions. Hentschel pursued that second half of the argument in Einstein und seine Exegeten: Inanspruchnahme und Deformation der Relativitätstheorie durch ihre frühen Verteidiger ("Einstein and His Exegetes: The Appropriation and Deformation of Relativity Theory by Its Early Defenders"), which shows the theory being bent to fit the prior philosophical commitments of the very people promoting it.
For researchers on this wiki who argue that relativity was accepted on sociological rather than evidential grounds, this is a professional historian's documentation of the point: the theory as understood by most of its early audience — including its defenders — was not the theory Einstein had written.
The solar redshift: the "conversion" of St. John
Hentschel's most pointed case study is The Conversion of St. John: A Case Study on the Interplay of Theory and Experiment (Science in Context 6, 1993, pp. 137–194). The gravitational redshift of spectral lines was one of the three classical tests of general relativity, and around 1920 most of the available evidence from the sun's Fraunhofer spectrum conflicted with the relativistic prediction. In 1923 the American astrophysicist Charles Edward St. John announced that his own Mount Wilson data now compelled him to abandon his earlier scepticism — an announcement conventionally reported as a clean empirical vindication of Einstein.
Hentschel reconstructs St. John's research practice step by step between 1917 and 1923 and shows that the apparent sudden "Gestalt switch" dissolves under examination. The data did not simply speak; what changed were the corrections applied, the lines selected, the treatment of pressure and Doppler effects, and the expectations brought to the reduction. His broader survey, The Interplay of Instrumentation, Experiment, and Theory: Patterns Emerging from Case Studies on Solar Redshift, 1890–1960 (Philosophy of Science), extends the same analysis across seventy years of measurement.
This is directly relevant to the many papers on this wiki that dispute the gravitational redshift and its interpretation — see for example Gravitational Redshift Revisited, The Gravitational Red-Shift, Gravitation Would Produce a Blue Shift in Place of a Red Shift According to General Relativity and The Compton Effect Interpretation of Solar Red Shift. Hentschel supplies the historical evidence that the "confirmation" those papers challenge was never the clean measurement the textbooks describe.
The Einstein Tower and Freundlich's failed tests
Der Einstein-Turm (1992; English translation The Einstein Tower: An Intertexture of Dynamic Construction, Relativity Theory and Astronomy, 1997) treats the Potsdam solar observatory built by Erich Mendelsohn as a single fabric of architecture, institutional politics, astrophysics and experiment. Its subject is Erwin Finlay-Freundlich, the first German astronomer to take Einstein's theory seriously and to attempt to test it — and, in Hentschel's account, a man whose enthusiasm for the theory made him so unpopular among his colleagues that Einstein's personal intervention was required for him to continue working at all.
Hentschel developed the point in Erwin Finlay Freundlich and Testing Einstein's Theory of Relativity (Archive for History of Exact Sciences 47, 1994, pp. 143–201). Freundlich's stellar statistics of 1915–16, his gravitational-redshift work and his eclipse expeditions produced inconclusive results throughout; the observational programme that was supposed to settle general relativity did not settle it. Freundlich later turned to speculations about photon–photon interaction — an idea with clear affinities to the tired-light and non-Doppler redshift mechanisms argued for by dissident cosmologists.
Physics under National Socialism
With Ann M. Hentschel he edited Physics and National Socialism: An Anthology of Primary Sources (1996; expanded edition 2011), a volume of translated documents covering the Nazi period in German physics, including the "Deutsche Physik" campaign of Lenard and Johannes Stark against "Jewish" theoretical physics. The anthology is a primary-source record of what happens when the assessment of a physical theory is driven by non-physical considerations — a warning that cuts in more than one direction, and one reason the volume is cited across the whole spectrum of writing about the relativity controversy.
Spectroscopy, instruments and the photon
Outside the relativity debate, Hentschel's work concerns the material and visual practice of physics. Mapping the Spectrum: Techniques of Visual Representation in Research and Teaching (2002) analyses how spectra were actually recorded, drawn, printed and taught. Visual Cultures in Science and Technology: A Comparative History (2014) generalises the argument to scientific images at large, and Photons: The History and Mental Models of Light Quanta (2018; expanded German second edition 2023) traces the shifting and often incompatible mental models physicists have attached to the light quantum — a concept whose ambiguity is itself a recurring theme in dissident critiques of modern optics. He also directs the Database of Scientific Illustrators (DSI, 1450–1950), a prosopographical database of more than 13,000 largely uncredited scientific illustrators.
Position on this wiki
Hentschel is included in Jean de Climont's Worldwide List of Dissident Scientists, though he writes as a historian rather than as a proponent of any alternative physical theory. His value here is evidentiary. Where dissident authors argue that the classical tests of relativity were oversold, Hentschel has gone into the archives, the observatory logbooks and the correspondence and shown in detail how the results were produced, corrected and presented — and how much interpretive work stood between the plates and the published confirmation.
Honors and awards
- Kurt-Hartwig-Siemers Prize, Hamburg Scientific Foundation (1990)
- Heinz Maier-Leibnitz Prize (1992)
- Paul Bunge Prize (1993)
- Marc-Auguste Pictet International Prize for the History of Science (1998)
- Georg Uschmann Prize, Leopoldina (1999)
- Donald E. Osterbrock Book Prize (2017)
- Neu-Whitrow Prize (2017)
Books
- Interpretationen und Fehlinterpretationen der speziellen und der allgemeinen Relativitätstheorie durch Zeitgenossen Albert Einsteins (1990)
- Der Einstein-Turm (1992); English translation The Einstein Tower: An Intertexture of Dynamic Construction, Relativity Theory and Astronomy (1997)
- Einstein und seine Exegeten: Inanspruchnahme und Deformation der Relativitätstheorie durch ihre frühen Verteidiger
- Physics and National Socialism: An Anthology of Primary Sources (with Ann M. Hentschel, 1996; expanded edition 2011)
- Mapping the Spectrum: Techniques of Visual Representation in Research and Teaching (2002)
- The Mental Aftermath: The Mentality of German Physicists 1945–1949 (2007)
- Visual Cultures in Science and Technology: A Comparative History (2014)
- Photons: The History and Mental Models of Light Quanta (2018; expanded German 2nd edition 2023)
Selected articles
- "The Conversion of St. John: A Case Study on the Interplay of Theory and Experiment", Science in Context 6 (1993), pp. 137–194
- "Erwin Finlay Freundlich and Testing Einstein's Theory of Relativity", Archive for History of Exact Sciences 47 (1994), pp. 143–201
- "The Interplay of Instrumentation, Experiment, and Theory: Patterns Emerging from Case Studies on Solar Redshift, 1890–1960", Philosophy of Science
External links
- Klaus Hentschel at the University of Stuttgart
- Klaus Hentschel on Wikipedia