Conservation and Innovation : Helmholtz's Struggle with Energy ...

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principe. L’expèrience nous montre que l’ènergie d’un champ èlectromagnètique se dècompose en deux parties, l’ènergie èlectrostatique et l’ènergie èlectrodynamique. Maxwell a reconnu (que si l’on regarde) la premiére come reprèsentant l’ènergie potentielle U, la seconde comme reprèsentant l’ènergie cinètique T." 433 Maxwell thus solves the problem, allowing in addition a Lagrangian derivation of the equations and so fulfills the possibility of a mechanical explanation of electromagnetism. The grounds of acceptance of Maxwell’s theory in Poincarè’s analysis are clearly the ones referring to energy. Maxwell’s (and not Poynting’s) approach is preferred in view of its links with the mechanical expression of both PCE and PLA. This judgment is explicit already in 1890 and was to be reasserted in 1902 434. Hertz’s experiments, instead, up to 1894 were considered doubtful and in 1902 were considered to lend only indirect support. The desubstantialisation of ether theory was to weaken the experimental difference between contiguous action and delayed action-at-a-distance theories, but was to strengthen the theoretical difference between the PCE’s of the latter theories and a local PCE expressed by the contiguous action theory. Poincarè’s choice of Maxwell from 1890 to 1902 is not referred to Poynting’s development (second step of localisation) but to Maxwell’s substantialisation (first step). This is due to the relevance he attributed to the asserted possibility of a mechanical explanation 435. Poincarè’s approach is very different from Hertz’s axiomatic assumption of Maxwell’s equations and his rejection of both a mechanical explanation and of a Lagrangian derivation. But still PCE, and specifically Helmholtz's PCE, was the principal reason for Poincarè’s choice of Maxwell. In the important process of the emergence of theoretical physics discussions on the meaning and the role of Helmholtz's approach to energy conservation were basic. Acceptance or denial of the mechanical world view, of the sharp distinction between kinetic and potential energy and of the privileged status of the central forces depending only on the distance were among the key issues, while others, non strictly mechanical interpretations of the principle of conservation, started to become mere and more important. At the end of the century in every research programme (mechanical, electromagnetic, energetic, thermodynamic) a specific version of the principle was put forward, and new 433 Poincarè La Science p. 223. 434 Poincarè La Science pp.216-25. 435 Poincarè La Science pp.216-25.
interpretations at the beginning of the new century were to be proposed in the new programmes of relativity and quantum physics. The theory-experiment interplay did not enjoy any longer a privileged position: the theory-principle one was now at the forefront of research, showing the lasting importance of Helmholtz's 1847 methodology. It is significant that the emergence of theoretical physics was joined with a deep work on the history of physics, with approaches that often were methodologically sophisticated, even for today's standard. Contemporary Historiography New trends in energy studies cannot avoid discussing what without doubt started the recalled fourth phase in the debate on the history of energy conservation: Thomas Kuhn's paper on the "simultaneous discovery" of "energy conservation" 436, published in 1959. Kuhn's paper is still unanimously defined as challenging, for the lack in contemporary historiography of a rival synthesis 437. Nevertheless analysing Helmholtz's Erhaltung , and the related primary and 436 Kuhn, Thomas. "Energy Conservation as an Example of Simultaneous Discovery." In Critical Problems in the History of Science . M.Clagett ed. Madison: Wisconsin U.P., 1959. Pp. 321-356. Rep. in Kuhn, Thomas. The Essential Tension, Chicago: Chicago U.P, 1977. Pp. 66-104. 437 Cantor, Geoffrey. "Locating the First Law of Thermodynamics." In New Perspectives in Nineteenth-Century Science. University of Kent, 1984.
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Fabio Bevilacqua Conservation and I
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different formulations 4 and priori
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and interesting results, despite th
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principle of correlation is express
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principle to the existing empirical
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the origin and meaning of the princ
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Whether physiological research, apa
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In a discussion on the origins of a
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his "Wärme" that one of the differ
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generate a determined equivalent of
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"Bericht", despite the application
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experiments in the most disparate b
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The premise reveals that the struct
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intelligible if it can be referred
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elevant consequence of the deductio
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Needless to say the plan was to be
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and from here that the direction an
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since Leonardo 113; the "ad nihilum
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But unfortunately for the whole str
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The principle of conservation of vi
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different from the one joining the
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"The equality that exists between e
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In virtue of its limitations to New
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Helmholtz, while asserting that lig
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the temperature of 1 Kg of water ca
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In his search for a mechanical equi
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had already been achieved in the Be
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approach is discussed at length and
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and unaware of Green's results190,
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potential function 201. It is worth
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and judged unreliable, despite prov
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The relevance of the first question
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principle taking this potential int
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Finally we get to the real conclusi
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conservation 234, on the theory of
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for the mechanical equivalent of he
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Page 133 and 134: Kant was a Naturphilosophe 480. The
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Page 141 and 142: force principle 522. Elkana tried t
Page 143 and 144: Blüh, Otto. "The Value of Inspirat
Page 145 and 146: Graetz, L. "Das Mechanische Wärme
Page 147 and 148: Helmholtz, Hermann. "Bericht über
Page 149 and 150: Helmholtz, Hermann. Wissenschaftlic
Page 151 and 152: Madison: Wisconsin U.P., 1959. Pp.
Page 153 and 154: Poincarè, Henry. Electricité et O
Page 155: Yagi, Eri."Clausius's Mathematical
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