Bibliographie générale
Bibliographie générale |
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Weinberg, S. (1993). Dreams of a final theory: Search for the ultimate laws of nature. Londres: Hutchinson Radius. Added by: admin (2008-11-15 20:53:48) Last edited by: Dominique Meeùs (2011-05-03 08:46:32) |
| Resource type: Book ID no. (ISBN etc.): ISBN : 0-09-177395-4 BibTeX citation key: Weinberg1993c View all bibliographic details  |
Categories: Philosophie, Sciences Keywords: empirisme, idéalisme, matérialisme, mécanique quantique Creators: Weinberg Publisher: Hutchinson Radius (Londres) |
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p.41, Chapter 3. Two Cheers for Reductionism
For me, reductionism is […] an attitude toward nature itself. It is nothing more or less than the perception that scientific principles are the way they are because of deeper scientific principles (and, in some cases, historical accidents) and that all these principles can be traced to one simple connected set of laws.
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Keywords: réductionnisme |
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p.42, Chapter 3. Two Cheers for Reductionism
I am talking about nature itself. For instance, even though physicists cannot actually explain the properties of very complicated molecules like DNA in terms of the quantum mechanics of electrons, nuclei, and electric forces, and even though chemistry survives to deal with such problems with its own language and concepts, still there are no autonomous principles of chemistry that are simply independent truths, not resting on deeper principles of physics.
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Keywords: réductionnisme |
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p.43, Chapter 3. Two Cheers for Reductionism
The reason we give the impression that we think that elementary particle physics is more fundamental than other branches of physics is because it is.
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Keywords: physique réductionnisme science Comments: Joliment dit. On pourrait trouver que c’est le comble de la prétention, comme de dire : « Nous avons raison parce que nous avons raison. » Une autre manière de voir les choses, c’est qu’il ne fait que s’incliner modestement devant la réalité et que les prétentieux sont ceux qui ne veulent pas tenir compte de la réalité du caractère fondamental de la physique. Added by: admin (2009-10-21 21:24:44) |
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p.45, Chapter 3. Two Cheers for Reductionism
We know that the evolution of living things has been made possible by the properties of DNA and other molecules and that the properties of any molecule are what they are because of the properties of electrons and atomic nuclei and electric forces. And why are these things the way they are? This has been partly explained by the standard model of elementary particles, and now we want to take the next step and explain the standard model and the principles of relativity and other symmetries on which it is based.
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Keywords: physique réductionnisme |
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p.82, Chapter 5. Tales of theory and experiment
I have emphasized the theoretical side of this story [general relativity] as a counterweight to a naive overemphasis on experiment. Scientists ans historians of science have long ago given up the old view of Francis Bacon, that scientific hypotheses should be developed by patient and unprejudiced observation of nature.
Added by: Dominique Meeùs
Keywords: Bacon empirisme expérimentation induction théorie Comments: Bacon accordait une grande importance, non seulement aux observations, mais au travail de réflexion critique que l’on fait dessus. On a souvent simplifié sa pensée à outrance en la résumant. Il est cependant clair que, ni physicien ni mathématicien, contemporain de Galilée mais mort bien avant lui, et près d’un siècle avant Newton, il ne pouvait avoir aucune idée de ce qu’est une théorie physique et encore moins de la possibilité, lorsqu’une théorie atteint ses limites, d’en créer une nouvelle à partir de réflexions sur sa logique interne et guidé par des symétries et des invariances. Il est donc légitime pour Weinberg de résumer Bacon, ici, en une phrase, même s’il mérite, en d’autres occasions, un traitement plus fin. Added by: Dominique Meeùs (2010-08-16 06:01:20) |
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p.101, Chapter 5. Tales of Theory and Experiment
[…] a half-serious maxim attributed to Eddington : « One should never believe any experiment until it has been confirmed by theory. » […] I have been emphasizing the importance of theory here because I want to counteract a widespread point of view that seems to me overly empiricist. […] It appears that anything you say about the way that theory and experiment may interact is likely to be correct, and anything you say about the way that theory and experiment must interact is likely to be wrong. Added by: admin Keywords: fait Eddington expérimentation Lemaître empirisme expérience théorie Comments: D’après Valérie De Rath (1994, p.84), cette boutade d’Eddington était adressée à Georges Lemaître sur le ferry de Malmö à Copenhague en 1938. De Rath, V., Léonard, J.-L., & Mayence, R. (1994). Georges lemaître: Le père du big bang. Éditions Labor. Added by: admin (2009-03-19 22:55:55) |
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pp.102-103, Chapter 5. Tales of Theory and Experiment
Finally one can imagine a category of experiments that refute well-accepted theories, theories that have become part of the standard consensus of physics. Under this category I can find no examples whatever in the past one hundred years. There are of course many cases where theories have been found to have a narrower realm of application than had been thought. Newton’s theory of motion does not apply at high speeds. Parity, the symmetry between right and left, does not work in the weak forces — and so on. But in this century no theory that has been generally accepted as valid by the world of physics has turned out simply to be a mistake, the way that Ptolemy’s epicycle theory of planetary motion or the theory that heat is a fluid called caloric were mistakes. Yet in this century, as we have seen in the cases of general relativity and the electroweak theory, the consensus in favor of physical theories has often been reached on the basis of aesthetic judgments before the experimental evidence for these theories became really compelling. I see in this the remarkable power of the physicist’s sense of beauty acting in conjunction with and sometimes even in opposition to the weight of experimental evidence.
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Keywords: beauté imagination création créativité réfutation simplicité théorie |
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pp.132-133, Chapter 7. Against Philosophy
The insights of philosophers have occasionally benefited physicists, but generally in a negative fashion — by protecting them from the preconceptions of other philosophers. I do not want to draw the lesson here that physics is best done without preconceptions. At any one moment there are so many things that might be done, so many accepted principles that might be challenged, that without some guidance from our preconceptions one could do nothing at all. It is just that philosophical principles have not generally provided us with the right preconceptions. In our hunt for the final theory, physicists are more like hounds than hawks ; we have become good at sniffing around on the ground for traces of the beauty we expect in the laws of nature, but we do not seem to be able to see the path to the truth from the heights of philosophy. Physicists do of course carry around with them a working philosophy. For most of us, it is a rough-and-ready realism, a belief in the objective reality of the ingredients of our scientific theories. But this has been learned through the experience of scientific research and rarely from the teachings of philosophers. This is not to deny all value to philosophy, much of which has nothing to do with science. I do not even mean to deny all value to the philosophy of science, which at its best seems to me a pleasing gloss on the history and discoveries of science. But we should not expect it to provide today’s scientists with any useful guidance about how to go about their work or about what they are likely to find. Added by: admin Keywords: matérialisme philosophie philosophie spontanée des savants physique réalisme science Comments: Il commence par minimiser l’importance de la philosophie pour la science. Il se contredit ensuite et contredit le titre du chapitre en écrivant sur le matérialisme, l’idéalisme et le positivisme plein de choses intéressantes et cruciales pour la science. Added by: admin (2009-08-23 18:34:10) |
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p.133, Chapter 7. Against Philosophy
Some of it [current work on the philosophy of science] I found to be written in a jargon so impenetrable that I can only think that it aimed at impressing those who confound obscurity with profundity.
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Keywords: philosophie des sciences obscurité profondeur jargon philosophie |
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pp.134-135, Chapter 7. Against Philosophy
Even where philosophical doctrines have in the past been useful to scientists, they have generally lingered on too long, becoming of more harm than ever they were of use. Take, for example, the venerable doctrine of « mechanism », the idea that nature operates through pushes and pulls of material particles or fluids. In the ancient world no doctrine could have been more progressive. Ever since the pre-Socratic philosophers Democritus and Leucippus began to speculate about atoms, the idea that natural phenomena have mechanical causes has stood in opposition to popular beliefs in gods and demons. The Hellenistic cult leader Epicurus brought a mechanical worldview into his creed specifically as an antidote to belief in the Olympian gods. When René Descartes set out in the 1630s on his great attempt to understand the world in rational terms, it was natural that he should describe physical forces like gravitation in a mechanical way, in terms of vortices in a material fluid filling all space. The « mechanical philosophy » of Descartes had a powerful influence on Newton, not because it was right (Descartes did not seem to have the modern idea of testing theories quantitatively) but because it provided an example of the sort of mechanical theory that could make sense out of nature. Mechanism reached its zenith in the nineteenth century, with the brilliant explanation of chemistry and heat in terms of atoms. And even today mechanism seems to many to be simply the logical opposite to superstition. In the history of human thought the mechanical worldview has played a heroic role. That is just the trouble. In science as in politics or economics we are in great danger from heroic ideas that have outlived their usefulness.The heroic past of mechanism gave it such prestige that the followers of Descartes had trouble accepting Newton’s theory of the solar system. How could a good Cartesian, believing that all natural phenomena could be reduced to the impact of material bodies or fluids on one another, accept Newton’s view that the sun exerts a force on the earth across 93 million miles of empty space ? It was not until well into the eighteenth century that Continental philosophers began to feel comfortable with the idea of action at a distance. In the end Newton’s ideas did prevail on the Continent as well as in Britain, in Holland, Italy, France, and Germany (in that order) from 1720 on. To be sure, this was partly due to the influence of philosophers like Voltaire and Kant. But here again the service of philosophy was a negative one ; it helped only to free science from the constraints of philosophy itself. Even after the triumph of Newtonianism, the mechanical tradition continued to flourish in physics. The theories of electric and magnetic fields developed in the nineteenth century by Michael Faraday and James Clerk Maxwell were couched in a mechanical framework, in terms of tensions within a pervasive physical medium, often called the ether. Nineteenth-century physicists were not behaving foolishly — all physicists need some sort of tentative worldview to make progress, and the mechanical worldview seemed as good a candidate as any. But it survived too long. Added by: admin Keywords: Descartes doctrine mécaniste Kant matérialisme matérialisme mécaniste Newton obsolescence philosophie philosophie mécaniste philosophie spontanée des savants science vision du monde Comments: La philosophie est à la remorque de la science et tarde à se mettre à jour. Added by: admin (2009-10-21 21:25:22) |
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p.136, Chapter 7. Against Philosophy
In the nineteenth century, the heroic tradition of mechanism was incorporated, unhappily, into the dialectical materialism of Marx and Engels and their followers. […] made holy writ […] and for a while dialectical materialism stood in the way of the acceptance of general relativity in the Soviet Union.
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Keywords: relativité générale dialectique dogmatisme matérialisme dialectique Comments: Heureusement, les physiciens soviétiques se sont dans l’ensemble bien défendus du dogmatisme. Écrivant sur la physique, Weinberg s’abstient de mentionner Lyssenko. Le dogmatisme des années trente a dépassé les frontières de l’Union soviétique. Il est illustré dramatiquement par le combat d’arrière-garde que Labérenne (1953) croit devoir mener contre le Big Bang. Labérenne, P. (1953). L’origine des mondes. Paris: Les éditeurs français réunis. Added by: admin (2009-08-23 18:44:35) |
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pp.141-142, Chapter 7. Against Philosophy
Positivism did harm in other ways that are less well known. There is a famous experiment performed in 1897 by J. J. Thomson, which is generally regarded as the discovery of the electron. […] It turned out that the amount of bending of these rays was consistent with the hypothesis that they are made up of particles that carry a definite quantity of electric charge and a definite quantity of mass. […] For this, Thomson regarded himself, and has become universally regarded by historians, as the discoverer of a new form of matter, a particle […] : the electron. Yet the same experiment was done in Berlin at just about the same time by Walter Kaufmann. The main difference between Kaufmann’s experiment and Thomson’s was that Kaufmann’s was better. […] Thomson was working in an English tradition going back to Newton, Dalton, and Prout — a tradition of speculation about atoms and their constituents. But Kaufmann was a positivist ; he did not believe that it was the business of physicists to speculate about things that they could not observe. So Kaufmann did not report that he had discovered a new kind of particle, but only that whatever it is that is flowing in a cathode ray, it carries a certain ratio of electric charge to mass. The moral of this story is not merely that positivism was bad for Kaufmann’s career. Thomson, guided by his belief that he had discovered a fundamental particle, went on and did other experiments to explore its properties. He found evidence of particles with the same ratio of mass to charge emitted in radioactivity and from heated metals, and he carried out an early measurement of the electric charge of the electron. This measurement, together with his earlier measurement of the ratio of charge to mass, provided a value for the mass of the electron. It is the sum of all these experiments that really validates Thomson’s claim to be the discoverer of the electron, but he would probably never have done them if he had not been willing to take seriously the idea of a particle that at that time could not be directly observed. Added by: Dominique Meeùs Keywords: électron expérimentation hypothèse Kaufmann matérialisme philosophie positivisme réalisme science théorie Thomson Comments: Voir aussi (Weinberg, 1985, p.70). Weinberg, S. (1985). Le monde des particules: De l’électron au quark. Paris: Pour la Science. Added by: Dominique Meeùs (2011-05-03 08:41:17) |
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p.201, Chapter 11. What about God ?
John Wheeler is impressed by the fact that according to the standard Copenhagen interpretation of quantum mechanics, a physical system cannot be said to have any definite values for quantities like position or energy or momentum until these quantities are measured by some observer’s apparatus. For Wheeler, some sort of intelligent life is required in order to give meaning to quantum mechanics, Recently Wheeler has gone further and proposed that intelligent life not only must appear but must go on to pervade every part of the universe in order that every bit of information about the physical state of the universe should eventually be observed. Wheeler’s conclusions seem to me to provide a good example of the dangers of taking too seriously the doctrine of positivism, that science should concern itself only with things that can be observed. Other physicists including myself prefer another, realist, way of looking at quantum mechanics, in terms of a wave function that can describe laboratories and observers as well as atoms and molecules, governed by laws that do not materially depend on whether there are any observers or not.
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Keywords: observateur esprit interprétation de Copenhague mécanique quantique positivisme réalisme Comments: Nouvel exemple des dangers de l’empirisme. Du positivisme à l’idéalisme, la pente est glissante et on n’est alors plus loin de la religion. Added by: admin (2009-10-21 21:31:26) |