Jean-Marc Levy-Leblond

Suppose Einstein had not existed. How, in the early twentieth century, might our understanding of space–timeSpace-Time physics have developed?This paper proposes a reconstruction of history as it could have evolved, drawing on attested pre-Einsteinian works, and some little known post-Einsteinian ones, as well as introducing a few imaginary characters. The virtual rise of Minkowskian chronogeometryChronogeometry will be reviewed, focusing on: the discoveryDiscovery of the inertiaInertia of energy and the subsequent construction of velocity-dependent formulas for energy and momentumMomentum by Von Dida (1909) and Hunepierre (1909), and the application of the Erlangen program to the construction of possible space–timeSpace-Time structures and classification of chronogeometrical groups, from von Ignatowsky (1910, 1911), Franck and Rothe (1911, 1912) to Blondeville and Prostov. Some secondary sources will also be discussed Zweistein (1905). Finally, the relevance of such an approach, on educational, epistemological and cultural grounds, will be highlighted and put in perspective within the ongoing debate about the contingencyContingency vs inevitability of scienceScience history.

Les « relations d’incertitude de Heisenberg » constituent l’un des aspects de la physique quantique qui a connu depuis près d’un siècle une fortune culturelle des plus considérables. On donnera un échantillon des exégèses abusives auxquelles ce thème a donné lieu, en philosophie certes – de l’épistémologie à la métaphysique –, mais aussi en politique, en économie, en esthétique, etc. On examinera ensuite les raisons d’être des confusions qui entourent encore ce thème et l’on discutera des aléas terminologiques qu’il a connu. On verra enfin comment ces « inégalités de Heisenberg », ainsi rebaptisées plus sobrement, non seulement ne peuvent en rien être interprétées comme mettant une limite aux connaissances scientifiques, mais dûment comprises et dans le strict cadre de la physique, ouvrent au contraire des modes de compréhension spécifiques.

Cent ans après sa parution, il est possible de lire le livre de Bergson sur la relativité de façon moins polémique qu’à l’époque. La maturation et la stabilisation de la théorie d’Einstein, devenue une composante banale de l’arsenal des physiciens, permettent une évaluation précise des méprises commises par Bergson dans son exégèse, en même temps qu’elles amènent à reconnaître leur intérêt épistémologique. Nous entendons ici réfléchir sur cette lecture bergsonienne de la Rélativité einsteinienne.

The history of quantum physics has been deeply conditioned by the change in scientific practice as a social activity during the past fifty years. As a result the theory has not been allowed full maturing; both its formal and empirical advances have not resulted in a comparable conceptual progress. The recasting of quantum theory thus appears as an epistemological necessity. One of the main aspects of this process is to clear quantum theory from its persisting classical connections in order to endow it with an autonomous and intrinsic status. Problems related to the foundations, description, interpretation and approximations of quantum theory are considered in turn, and various recent works are reviewed which contribute to the proposed endeavour.

In 1587 the young Galileo was invited to give Due lezioni all’Accademia Fiorentina circa la figura, sito e grandezza dell’Inferno di Dante (hereafter Leçons sur l’Enfer) [Galilei 1587] aimed at settling an intense controversy regarding the geography of the Dantean Hell. This study in exegetics enabled Galileo to bring his mathematical talents and didactic qualities to the knowledge of the Tuscan scholars. But these lessons have a much greater importance, in that they reveal several of the major themes of Galileo’s further work from both mathematical and physical standpoints, such as the question of scale linked to the strength of materials, as well as the scientist’s unremitting interest in language and commitment to literary culture.

A little-known movie by Alfred Hitchcock, Torn Curtain — admittedly not one of his best — tells a story of spying and science. It features a strange scene, where two physicists confront one another on some theoretical question. Their “discussion”, if it may be so called, consists solely in one of them writing some equations on the blackboard, only to have the other angrily grabbing the eraser and wiping out the formulas to write new ones of his own, etc., without ever uttering a single word. This picture of theoretical physics as an aphasic knowledge entirely consisting of mathematical symbols, as common as it may be in popular representations, we know to be wrong, of course, and we have to acknowledge that, far from being mute, we are a very talkative kind; physics is made out of words. What I wish to question here, however, is the very nature of our relationship with language, particularly as concerns quantum theory. My thesis will be that we have been somewhat offhand and rather indifferent with respect to the words we use, or rather without respect for them, and that this attitude has reinforced, and sometimes perhaps even produced some of the persisting epistemological and pedagogical difficulties in our field — not to speak of the new cultural problems that we are facing

From the very beginning it was realised that quantum physics involves radically new interpretative and epistemological consequences. While hitherto there has been no satisfactory philosophical analysis of these consequences, recent years have witnessed the accomplishment of many experiments to test the foundations of quantum physics, opening up vistas to a completely novel technology: quantum technology. The contributions in the present volume review the interpretative situation, analyze recent fundamental experiments, and discuss the implications of possible future technological applications. Readership: Analytic philosophers (logical empiricists), scientists (especially physicists), historians of logic, mathematics and physics, philosophers of science, and advanced students and researchers in these fields. Can be used for seminars on theoretical and experimental physics and philosophy of science, and as supplementary reading at advanced undergraduate and graduate levels.

Dans cet entretien de conclusion, Jean-Marc Lévy-Leblond, physicien et épistémologue, professeur émérite de l'Université de Nice, directeur des collections scientifiques aux éditions du Seuil et de la revue Alliage, montre qu'il est faux de penser que les sciences exactes n'ont besoin qu'accessoirement de la langue en raison du degré de leur formalisation, contrairement aux sciences humaines. La conceptualisation en sciences ne saurait se passer de la langue, ni même des langues . Le recours à l'anglais n'est qu'un moyen, nullement une fin en soi - ce que la mondialisation rend de plus en plus évident, au fur et à mesure que la science se décline de plus en plus en hindi, en chinois, ou dans d'autres langues. En refusant d'être plurilingue comme elle l'a été par le passé, la science risque l'aphasie, non seulement linguistique, mais aussi conceptuelle, ce qui n'est pas sans gravité pour la diffusion des connaissances scientifiques à l'échelle aussi bien locale que mondiale.In this interview, conclusion, Jean-Marc Lévy-Leblond, physicist and epistemologist, professor emeritus at the University of Nice, director of scientific collections by Seuil and review alloy, shows that it is wrong to think that sciences do not need the language incidentally because of the degree of formalization, unlike the humanities. Conceptualization science can not do without the language or even language . The use of English is a means, not an end in itself - that globalization makes it increasingly obvious, as and as science comes increasingly Hindi, Chinese or in other languages. Refusing to be multilingual as it was in the past, science risk aphasia, not only linguistic, but also conceptual, which is not trivial for the dissemination of scientific knowledge to scale as both local and global