Carlo Rovelli, an eminent theoretical physicist and a major actor of contemporary science, is one of the initiators of an innovative approach which intends to unify quantum mechanics and general relativity. But his thought also helps to re-enchant a certain relationship with the world.
Scientific and epistemological companies are a commonplace, are above all taxonomy approaches. It would be a question of classifying, ordering, separating. To sort, for example, objects and forces for the first or to erect a line of demarcation between science and non-science for the second. Intelligibility would be a case of judiciously elaborate partitions. A world for quantum mechanics, another for relativistic gravitation ; The truth for science, beauty for the arts ; Rigor for physics, depth for philosophy.
It is very exactly in relation to these very widespread schemes, that Carlo Rovelli is part of these two lectures. The first is a technical version intended for researchers in theoretical physics, the second is a very simple opuscle accessible to all. Remarkable, the latter remains extremely precise and singularly dense and rich despite the presence of many anecdotes. These parentheses and other scenes of life do not play a diversion role in punctuating reading, they deploy proposals in unexpected and often delightful directions, they weave links which, precisely, decompartmentalize the disciplinary fields.
Carlo Rovelli, an eminent theorist physicist and a major actor of contemporary science, is one of the inventors of quantum gravitation with loops. These books are therefore dives in the heart of this extraordinary theory which intends to unify the two conceptual pillars of our science that are quantum mechanics on the one hand and general relativity on the other. But they are much more than that. They also ask many questions whose scope greatly exceeds the only theoretical physical and helps to re-enchant a certain relationship to the world. Carlo Rovelli manages, in a few pages, to summon Schubert and Leibniz, to dialogue with Anaximandre and Descartes, to deconstruct scientific dogmas and to propose with the enthusiastic modesty of a child-poet a refoundation of practice and scientific thought. Not a revolution since Carlo Rovelli claims the direct heritage of a large part of tradition, but rather a new look – both more tolerant and more demanding – about what we thought we knew.
The proposal is dizzying. Almost grotesque. One of these pranks that only a disheveled physicist could invent: a world without space and without time ! A world where the physical fields, possibly quantum, would live on (or in) the gravitational field, itself holding a place of space. A world where all structures would become fundamentally dynamic. A world where time would no longer exist as such and should be reinterpreted as a measure of our unknown from the microscopic state of systems. A world that seems to have nothing in common with ours … To this ready detail that it naturally stems from a serious and simultaneous consideration of the two great physical theories that have structured the science of nature for about a century ! General relativity, which is much more than theory of the gravitational field, tells us that physics must be thought in relational terms, regardless of any “ bottom »Fixed and immutable. As a counterpoint, quantum mechanics shows that objects are always a little relocated, that must be reasoned in probabilistic terms and give physical quantities a certain “ granularity ». The conjunction of these two approaches, reputed to be incompatible, draws a new world that is both very familiar (since it only reorganizes what we had, in a sense, already discovered) and very unforeseen (since by really taking these proven models seriously, it calls into question the essential of our presuppositions on space-time).
Quantum gravitation in curls proposes to consider the universe as a kind of superposition of gigantic abstract networks (called “ spin ) Whose nodes would constitute “ space grains And the edges of the contiguity relations between these grains. It is a theory that describes the probabilistic evolution of a cloud of unscredes of space. Time plays no particular role, as it should be for a fundamental theory. It emerges as a suitable variable when you look at things “ by far ». The major inconsistencies of classical physics are absent here: the singularities, places of collapse of theories, disappear. Big-bang or the heart of black holes are reinterpreted as rebounds more than divergence points. Physics miraculously regularized. The approach is speculative and does not lack competitors – to begin, of course, by the theory of strings – but it has the merit of producing clear predictions: the space is quantified (if one could measure with great precision the surfaces and the volumes, one could not observe any values) and the traces of the era where quantum gravitation play Some vestiges of the primordial universe.
The quest for unification revealed its effective. In particular, it has played a central role in the development of the standard model of particle physics. The principle of gauge, by placing symmetry at the heart of the understanding of the forces, made it possible to unify electromagnetic interactions and low nuclear interactions. Invarins dictate the form of laws. For nevertheless to restore to the world its diversity – it is fortunately not unified to the energies which are familiar to us – we must invoke a principle of compensation: the spontaneous breakdown of symmetry. The solutions are less constrained than the equations that govern them. Invention of contingency. Principle of gauge and symmetry broken are the Apollinian and Dionysiac slopes-or rather perhaps the parmenid and Heracleian dimensions-of the same physics. However, unification is not a conceptual necessity. It is heuristically founded and strongly resonates with the Platonic foundations and the Judeo-Christian origins of our culture. But it is not engraved in the marble of science (especially since, by definition, science is not serious in marble). Quantum gravitation with curls does not seek to unify all of the forces and to constitute a “ Theory at all ». It simply tries to reconcile principles which, they cannot remain partitioned in autonomous spheres for essential reasons for internal coherence. The space is then reinterpreted as an immense tangle of loops which are not located in it but constitute it structurally. Space “ by body »From Anaximandre and Descartes is rehabilitated against space« in itself »De Démocritus and Newton. The extrinsic, Augustinian time, supplants the intrinsic clock having value and meaning by itself. For strange that this new cosmo-logy may seem (it’s here logos which is first), it is part of a long philosophical filiation and only confuses us as formatted in Newtonian thought.
Quantum gravitation with curls is not only a disconcerting and innovative theory, it is also the framework of another way of thinking about physics. New image of a real relational. Carlo Rovelli draws the deepest consequences of general and revisited relativity, inspired by Leibniz, quantum mechanics. According to, in a way, the Wittgensteinian prescription aimed at supplanting a dynamic of the facts to an ontology of things, he draws the lineaments of a world where the relationship becomes the fundamental element. Objects are not “ in themselves “, they are “ compared with ». A large part of the interest of the approach is due to the constant and confusing tension which unfolds between the strict and simple use of ultimately banal and known concepts and the apparently revolutionary consequences which come from their serious and simultaneous consideration. Make new with old, in short. As Nelson Goodman showed, we never make a world from nothing but by composition and decomposition, weighting, layout, supplementation and deformation from another already built world. Quantum mechanics and general relativity are the “ unfinished revolutions »From which the author offers us to build the new world.
Not content with revising our most fundamental concepts in depth, Carlo Rovelli invites us to think about what physics is and even more about what we expect from it. Without explicitly choosing your camp between the different epistemologies offered at XXe Century, he built a coherent proposal by implicitly borrowing from Bachelard, Carnap, Popper, Khun, Bourdieu, Latour and perhaps even Feyerabend. Taking very wisely its distances from the idea of a science which would have a privileged link with the truth, its vision of physics is fundamentally dynamic: it is defined by doubt and permanent deconstruction. Incredulity is erected in method.
It should be banal, almost uninteresting, to read that the teaching of science has something subversive, that it is above all a learning of critical thinking and the capacity to question, that science does not have the exclusive of intelligence and that the development of rationality only has meaning if it is thought of in counterpoint to that of the arts and letters. It should be boring to hear a new pleading in favor of teaching physics distant of any form of dogma, open to contradiction, sensitive to troubled periods, imbued with magic and, let us dare the word, of beauty. These positions, openly defended by a university professor, member of the Institute, are however – in fact – quite exceptional and, in more than one way, comforting. Although obviously going by themselves for anyone who has a little thoughtful of the question, it is clear that they come very much to make a litter of the dominant and almost institutionalized practice of primary, secondary and higher education. Thinking, retrospectively, the genesis of a science in a sociological, political and philosophical context, to weave links between scientific concepts and aesthetic ruptures-if only to consider the last as condition of the first-are of these apparently elementary ideas which, however, remain in practice superbly ignored … What is time ? What is space ? So also invite to rethink the challenges of science and its teaching in a being-in-the-world freed from disciplinary partitions and societal corporatisms.
In a sense, Carlo Rovelli’s works are obviously physics treaties (intended for the specialist for one, in the profane for the other). They are also obviously metaphysical and poetic walks. But they are also, and even above all, images of freedom. Creative and introspective freedom, demiurgic and contemplative freedom, ethical and scientific freedom. Carlo Rovelli writes on the world, about nature and thought with the enigmatic evidence of those who have definitely turned the page of disenchantment and have chosen to remain permeable to strangeness. A precious invitation to astonishment.