ndsbv3_H 10/2/07 5:38 PM Page 291 Herschel Hertz he and Alexander had lost the physical strength necessary HERTZ, HEINRICH RUDOLF (b. to repolish the mirror. Hamburg, Germany, 22 February 1857; d. Bonn, Ger- Much more is now known about the wealth that Mary many, 1 January 1894), physics, philosophy. For the origi- Pitt brought to their marriage in 1788. Her inheritance nal article on Hertz see DSB, vol. 6. from her late husband, and subsequent legacies from her The centenaries of Hertz’s discovery of radio waves, mother and other members of her family, rendered of his death, and of the publication of The Principles of Herschel’s annual “pension” from the crown insignificant. Mechanics served to invigorate scholarship on the life and Why then did he continue to make telescopes for sale? Part work of Heinrich Hertz. While it was true until 1994 that of the reason seems to lie in the delight he took at his inter- there was no book-length study, the next dozen years pro- national eminence in work so far removed from his profes- duced a 600-page biography, two highly focused mono- sion of music—ambassadors were reduced to writing what graphs, and a collection of essays on Hertz as classical were, in effect, begging letters, for if Herschel refused physicist and modern philosopher. These books appeared them, there was no one else to whom they might turn. But alongside numerous articles and the discovery of new it has been argued that some of his production was des- biographical sources, laboratory notes, correspondence, tined for fellow observers who might, he hoped, confirm and manuscripts. observations that hitherto he alone had been able to make. Close scrutiny of Hertz’s experimental and concep- tual procedures produced uncertainty on some biograph- ical questions, new insights on others. In particular, BIBLIOGRAPHY Hertz’s “conversion” to a Maxwellian conception of elec- Brown, Frank. William Herschel, Musician and Composer. Bath, trodynamics has come to appear as an ever more intrigu- U.K.: William Herschel Society, 1990. ing problem. The publication of his 1884 lectures on the Caroline Herschel’s Autobiographies. Edited by Michael Hoskin. constitution of matter laid bare the continuity of his Cambridge, U.K.: Science History Publications, 2003. philosophical interests. This, in turn, prompted richly Contains the two incomplete autobiographies that Caroline nuanced views of the Principles of Mechanics and yet wrote when she was in her seventies and her nineties, respectively, and much of the information concerns William. another puzzle regarding the ether. Hoskin, Michael. “Herschel’s 40ft Reflector: Funding and Functions.” Journal for the History of Astronomy 34 (2003): Between Helmholtz and Maxwell. The question of 1–32. Hertz’s “conversion” arises from his 1884 paper “On the ———. The Herschel Partnership: As Viewed by Caroline. Relations between Maxwell’s Fundamental Electromag- Cambridge, U.K.: Science History Publications, 2003. A netic Equations and the Fundamental Equations of the biography of Caroline that focuses on her relationship with Opposing Electromagnetics.” It concluded that “if the William. Mary Herschel’s finances are discussed in pp. 92, choice rests only between the usual system of electromag- 95–96. netics and Maxwell’s, the latter is certainly to be preferred” ———. “Vocations in Conflict: William Herschel in Bath, (1896, p. 289). This statement underwrites the view that 1766–1782.” History of Science 41 (2003): 315–333. in his decisive experiments of 1887 and 1888 Hertz set Discusses Herschel’s musical activities. out to prove Maxwell’s theory. However, it is odd not only ———. “Alexander Herschel: The Forgotten Partner.” Journal that Hertz never again referred to this paper but also that for the History of Astronomy 35 (2004): 387–420. he freed himself only very gradually from a Helmholtzian ———. “Unfinished Business: William Herschel’s Sweeps for idiom. The publication of his 1884 lectures and 1887 lab- Nebulae.” History of Science 43 (2005): 305–320. oratory notes did not settle the issue. On the one hand, ———. The Herschels of Hanover. Cambridge, U.K.: Science they underscore his general distrust of action-at-a-distance History Publications, 2007. theories and thus his sympathy for Maxwell’s approach. James, Kenneth. “Concert Life in 18th Century Bath.” PhD On the other hand, they indicate that he was exploring diss., University of London, 1987. the limiting case of Helmholtz’s electrodynamics which Maurer, Andreas. “A Compendium of All Known William leads to Maxwell’s equations. Herschel Telescopes.” Journal of the Antique Telescope Society, no. 14 (1998): 4–15. In his 1892 introduction to Electric Waves Hertz pro- vided several cues as to how this puzzle might be resolved. Spaight, John Tracy. “‘For the Good of Astronomy’: The Manufacture, Sale, and Distant Use of William Herschel’s On his own reconstruction of the course of experimenta- Telescopes.” Journal for the History of Astronomy 35 (2004): tion, the competing theories of electrodynamics lacked 45–69. physical meaning until Hertz’s experiments. As long as Hertz could say no more about Maxwell’s theory than that it is Maxwell’s system of equations, all theories that Michael Hoskin mathematically coincide with Maxwell’s equation were NEW DICTIONARY OF SCIENTIFIC BIOGRAPHY 291 ndsbv3_H 10/2/07 5:38 PM Page 292 Hertz Hertz equivalent, including that of Helmholtz. In respect to electromagnetic theories, one cannot sensibly ask whether Hertz was a Maxwellian or still a Helmholtzian until the time of the “philosophical … and in a certain sense most important result” of his experiments, namely that they proved the “propagation in time of a supposed action-at- a-distance” (1893, p. 19). This finding simultaneously served to distinguish Helmholtz’s and Maxwell’s concep- tions and to decide in favor of Maxwell’s. To fully realize this may have taken Hertz well into 1889. At the same time, that Hertz was a Helmholtzian by training is evident from his laboratory practice, his style of experimentation, and his manner of developing a new phenomenon by lit- erally unfolding and materially transforming a familiar laboratory device (the so-called Rieß spirals) into a sender and receiver of electric waves. Philosophical Critique. Even before he studied with Helmholtz, Hertz had been exposed in Dresden to lectures on Immanuel Kant, and in January 1878 expressed in a let- ter to his parents that he was pondering conceptual issues, “and particularly the principles of mechanics (as the very words: force, time, space, motion indicate) can occupy one severely enough” (1977, p. 77). Towards the end of his life, in a letter dated November 23, 1893 Hertz encouraged his publisher to include among the potential readers of The Heinrich Hertz. © BETTMANN/CORBIS. Principles of Mechanics “the circle of philosophical readers” (in Fölsing, 1997, p. 509). The publication of his 1884 lec- tures on the constitution of matter establishes the continu- ity of Hertz’s philosophical interest in conceptual critique. Instead, the book appears as a delicate and highly self- In the case of “force,” he rejected it as a fundamental con- conscious exercise to relate physical content and mathe- cept of mechanics since it lacked physical meaning but matical form. Suspicious that the new mathematics and served only as part of its representational apparatus. In the especially non-Euclidean geometry offer abstractions that case of “matter,” he found the concept indispensable and are detached from reality, Hertz nevertheless developed a struggled to determine its physical meaning, showing that first geometrization of mechanics. The originality of The on all available definitions it is an indissoluble mixture of Principles of Mechanics does not consist in the elimination a priori and empirical elements. In a highly suggestive pas- of force, which had been advocated already by one of sage he therefore compares it to paper money that is issued Hertz’s former teachers, Gustav Kirchhoff. Instead it arises by the understanding to regulate its relation to things. All from the way in which the new formalism suggests new this has given rise to an appreciation of Hertz as a philoso- ways of thinking about physical phenomena. Rather than pher in his own right. He rigorously applies to the concep- build up mechanics from the motion of a single mass tual tools of physics a Kantian critique of how scientific point, Hertz’s geometrization yields a forceless mechanics experience becomes possible only within clearly specified by beginning with a system of points. Accordingly, forces limits of physical knowledge. He thus offers an original are replaced by connections within and among systems of and parsimonious account of the metaphysical founda- points, phenomena that unfold in time are referred to tions of physics. time-independent material systems, causal explanation is reduced to the correspondence between dynamic models, The Geometrization of Mechanics. In the context of a and intentionality is banished along with all phenomena broadened appreciation of Hertz’s concerns, it is no longer of life from the domain of physics. The domain of physics, possible to divide The Principles of Mechanics into two however, is to be unified by a single law of mechanics, giv- parts, firstly a philosophical introduction that concerns ing rise to an unsolved biographical and scientific puzzle. the choice between empirically equivalent but concep- Hertz was clearly aware of the challenge to unify elec- tually distinct images of mechanics, and secondly the trodynamics and mechanics and emphasized the need for somewhat tedious articulation of a forceless mechanics. a theory of the ether in his 1889 lecture on “Electricity 292 NEW DICTIONARY OF SCIENTIFIC BIOGRAPHY ndsbv3_H 10/2/07 5:38 PM Page 293 Hertz Hertz and Light.” However, while the 1884 lectures express transformed to yield a novel effect; argues for Hertz’s late Hertz’s skepticism toward any material medium that can- adoption of a Maxwellian account.