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Michel Paty

Michel Paty: A double view of science

The French philosopher and physicist examines the epistemological implications of an eventual unification of quantum and relativity theories

Eduardo CesarIt seems unlikely that any other personality could illustrate so well the intellectual dialogue that is possible between two nations as Michel Paty did, in the colloquium “Franco-Brazilian rationalities; yesterday and today,” held from September 14 to 16 at the School of Philosophy and Human Sciences of the University of São Paulo (FFLCH-USP), as part of the Year of France in Brazil. The 71-year-old French philosopher and physicist has seen his professional career, his academic work and his own personal life strongly influenced by Brazilian experiences, since he first landed here in 1965 to spend a one year in the Physics Department of the young University of Brasília (UnB). He ended up staying at the institution, which in that particular year was being hounded by the violence of the military dictatorship, for just six months, preferring to spend the rest of the time he had agreed to work in the country at the Brazilian Center for Physics Research (CBPF), in Rio de Janeiro. After this, Paty waited for democracy to return gradually to the Brazilian political scene and for his scientist friends to return to Brazil on amnesty flights, before re-starting his France-Brazil trips, which took various forms; a visiting professor at USP has been one of them.

Over the years, which were heavily underscored by the move of the researcher from the domains of particle physics to the philosophy of science, Paty’s thinking on scientific knowledge and especially on the present and future of physics has gained an obvious facility of expression, in addition to consistency. This, in fact, is very evident in a book that is accessible to non-experts, A física do século XX [twentieth century physics] published in Brazil in 2009 by the Ideias e Letras publishing house and translated by Pablo Mariconda, who is also a philosopher and professor at USP. For those who want to venture further into the realm of the critical gaze of Michel Paty, another of his books has been translated into Portuguese, A matéria roubada [Stolen matter], translated by Mary Amazonas Leite de Barros and published by Edusp in 1995. The original works in French were published in 2003 and 1988, respectively.

In this interview, given on September 18 this year (see the full version on, Michel Paty, besides talking freely about the path he has taken in life, explained at length and with passion his vision of science as a symbolic thinking system, the representations of which actually enable us to get close to a real world about which we still know very little. Taking Einstein as his master, par excellence (see Pesquisa FAPESP nº 155, January 2009 and February 2009’s special issue), he talked emphatically about science also as a work of creation and invention, which makes for large and inspired moments of synthesis that take it down unsuspected paths. Over the next few years and based on his most recent research, Michel Paty is promising three approaches that will perhaps become three different books: Science as symbolic thoughtScience as creation and The function of rationality. In the latter he is promising to lay aside a little of his caution with regard to the major themes of philosophy and risk some comparisons between western science and knowledge taken from other traditions.

I propose starting with your academic relationship with Brazil, before we get into the main theme of the interview, which is physics in the 21st century.
Well, there’s my own personal story and there’s the history of relations between France and Brazil, in particular in the field of philosophy and the philosophy of science. Therefore, I’ll start with my personal experience: I’ve known Brazil for a fairly long time now – 44 years. My initial training was as a physicist and I spent 20 years or more of my life researching physics.

In a French university?
Yes. Then I started a new career, a continuation of the other, but in the field of philosophy. While I was doing research in physics I was also studying philosophy at night, shall we say. I used to go to philosophy lectures; I did all the necessary work. I wrote a thesis in both physics and philosophy; I have a double qualification.

How do you explain your simultaneous interest in physics and philosophy, areas that normally people do not link in this way?
They’re somewhat related, but with their own profile and individual path. In fact, I got into physics – this wasn’t obvious to me – a little by chance, because I initially studied mathematics in France. I liked math a lot; I liked literature too. These were really my two inclinations.

In your book Physics of the twentieth century, there’s a phrase about how mathematics is the simplest representation of abstract thinking. Taking advantage, then, of your entry into this area…
I became fascinated with physics after I’d already started doing research. I still hadn’t got my PhD in physics, but I’d already finished all the other exams; I was already well qualified when, almost by accident, I started doing a postgraduate course in nuclear and particle physics in Bordeaux, where I was born. The course there was full of mathematics, which I was very happy about. However, there was physics, too, and that’s when I discovered that this physics was different from college physics, which I really didn’t like much, in fact.

Different in what way?
Different because it seemed that the reasoning was very much more assured, much stricter and fitted really well and naturally with mathematics. What I’d learned in college hadn’t allowed me to fully understand the connection between mathematics and physics. There were teachers who insisted on doing laboratory experiments and others who insisted on equation formulas and so we were left in some doubt as to what physics was all about, at the end of the day.

Isn’t this a deficiency in the teaching?
I think so. Only when you have a teacher who has a very clear view of what physics is all about can you manage to overcome this deficiency. The first real teacher I came across, and someone who delighted me subsequently, was Einstein, because his writings let people understand the reasons for physics. I understood Einstein well because, with the course I was doing, I was really getting into the field through practical reflection, through the experience of thinking.

There’s a moment in this book in which your vision of physics emerges as a set or system of ideas, in addition to also being this field of experimentation and representation of the forces of nature, and a little bit of invention and creation.
That’s precisely it. In fact, I went back to physics when I understood that it was thought that allowed you to achieve material reality, even this material reality you can’t see, which is beyond our senses, because it’s atoms – the distance between atoms and us is enormous; if you want it expressed in numbers it’s 10 to the power of 23. So, it’s a huge difference and it just so happens that the strength of thought in physics is such that you can think about these entities that you’re never going to see – directly, of course, because we’re human beings; there are a lot of atoms in everything we are and come across. I began to understand this through practicing physics and later I came across the writings of Albert Einstein and others. However, Einstein was the best and I still think so.

Fundamentally, in which works?
Initially I read the Einstein that existed in books of the “how I see the world” type, things like that. It was only later that I realized that these books were very badly translated and that a lot more lay behind his real thinking. So I looked for everything that Einstein had ever written, including his scientific texts. I discovered him as a scientist who thinks about the sense of his own world, which is physics, first, and in philosophical terms, reflection, second.

But let’s get back to your moving between physics and philosophy.
Well then, precisely: the physics I was immersed in was particle physics of the fundamental fields of matter, I mean the physics of atoms and even smaller, the physics of nuclei and of the constituent parts of the nuclei; the physics of these very small entities that are underneath the nucleus, called elementary particles and that can only be conceived of using a notion that seems very abstract, which is the quantum field notion. This discipline was later called the physics of particles and fundamental fields, because they’re not particles as we imagine them to be.

But don’t they have mass?
They have mass, but they have no defined shape; they don’t occupy a defined space, things like that. So it’s something that’s very difficult to imagine in the normal way of thinking, using images or words. The only way of imagining them is to think of them using mathematical concepts, concepts constructed with the human mind, like fields, electrical charges and others that we’ll not go into here. These concepts are, in their own right, objects with a mathematical form taken from the work that physicists have been doing since the early twentieth century.

Isn’t it easier to grasp this thinking starting with the idea of the electrical charge…
The electrical charge is a way of perceiving what’s at play. An electrical charge is something that influences other electrical charges or that affects them, in the same way that an electrical current, when it passes close to a magnetic needle, moves it in a certain direction. It was the fundamental theory of electromagnetism that explained this, that forged these notions of fields, for example. However, there they’re talking about the classic field, the electromagnetic field. In quantum physics a notion was initially constructed and developed that was inspired by the notion of a field; in other words, it’s a propagation action from one to the other between these types of entities, like the charge; actually, they are not of the same type, because they cannot be represented in space in the same way. It’s what’s called quantic, which is a mark of the difference.

But from your experience of talking to people who are not experts in physics, what’s the best way of getting them to understand a suitable notion of these particles with no shape and whose mass is so infinitesimal that it’s unimaginable?
I wrote dissemination texts, including the one you have in your hand [A física do século XX, from the French original, La physique du XXe siècle, i.e., Physics of the twentieth century]. I think of it as a dissemination text rather than a scientific text per se, even though it contains some of the things that are indispensable for allowing people to make the link between science and common sense and even though I tried to include, discreetly, some philosophical issues (I think they’re intrinsic to this presentation). My experience, in fact, is that it’s possible to communicate quite a lot of this very specialized knowledge to people who are not experts.

I’m going to keep insisting on this issue because physics, in particular, seems to be an area that it is harder to translate into the language of common sense than biology or chemistry, for example.
Of course. It’s simple because the elements of knowledge in biology can even be seen under a microscope. Even the giant DNA molecule can be seen under a microscope – so it’s image, it’s visual, whereas the physics I’m talking about is not visual; it escapes this completely; it can’t be grasped through visualization, light or light rays, but by other radiation that is suitable for reaching these very small dimensions. This radiation consists of the particles themselves, or gamma rays, for example, electromagnetic waves of the same type as light, though with much greater energy; in other words, with a very small wavelength that allows these dimensions to be reached. When you consider this, you can draw a type of analogy between the sight of images through the microscope and the indirect sight you get through this type of radiation; I mean you transpose the role of light to this radiation. However, this is fairly universal, because this radiation allows you to reach not only elementary particles but also enormous objects that are very distant from us within the Universe, because they are sources of very energetic gamma rays, which reach us. We observe them and they may reveal to us what happens on these gigantic objects.

Shall we try to get to when you made your leap from physics to philosophy?
The start of my career in elementary particle physics was in a laboratory at CERN, in Geneva, where there was a particle accelerator that makes this radiation. I was able to make observations on a detector called a bubble chamber, which still existed at the time, and which enables you to see the path of a particle by means of the macroscopic expansion effect. It allows you to identify these particles, to measure and calculate their characteristics and then to find out what happens in this area of the constitution of matter. When I saw this – until then particles were an abstraction for me – when suddenly I saw the steps that allow you to know that this radiation has material effects, it was a bit like “the road to Damascus” for me, like the road of revelation for St Paul – except that my revelation was not of God, but of the innermost reality of matter. In this case, and to end this recollection, these particles resulted in the interaction of neutrinos, something that was hardly known at the time. These are particles that are much talked about nowadays and my first studies were in this, at that time, pioneering field. I hadn’t realized until then, given the way I’d been trained (and I was pretty good at equations, in calculating a field and its interaction), that all this that was expressed in the form of mathematics corresponded to something that I could even see, albeit not directly – and that’s when I realized, in a concrete way shall we say, that it’s a physical reality that has these properties that I was dealing with mathematically.

Your experience at CERN allowed you to move from high mathematical abstraction to the environment of material existence.
I can say that this was the real find in my first experience with physics. Philosophy comes immediately after, because its problems include this relation between mental representation – and mathematical form is nothing more than mental representation – and the reality of the world that is independent of myself. In other words, these representations did not invent the world, which is concrete, which exists; at least everybody rightly thinks that this makes sense. This was the fundamental problem: knowledge acquired by the mind, which is symbolic of the world and of the real world, despite its different nature, has to do with the other. I was still not talking in these terms, but later I developed my research and found that this view that scientific thinking is symbolic thinking was fundamental. Because it allows you to give everything this representation deserves and allows you to characterize the reference point with the real world. Therefore, this was the more conscious start of my journey.

It was like taking a step back to look at scientific knowledge in perspective as a symbolic field of relation, of interaction between external reality and that which the mind can understand.
Inter-relationship is the right word. Thinking, which is very abstract, which functions inside the head, you might say, is not isolated, because it is accompanied by the body and the senses. So because of this connection between abstract thought and the senses there can be a relationship between thinking and the world that exists, a world in which I can touch things, in which I can act. This is more or less the line of interaction; it’s this that allows us to explain that there’s a correspondence between the world of thought and the real world. And there’s an entire chain of interactions that makes me think of the world in one way, but I concretely question it based on my experiences, using devices that, actually, prolong bodies.

I quote another segment about the future of physics from Physics of the twentieth century: “A representation cannot be identified with what it represents, which is given as something external to thought. Nature and matter are independent of us and their representations that we make are obviously imperfect and subject to transformations.” So I ask you: how are they independent from us? Aren’t we also nature and matter?
Yes, but in this case we’re obliged not to be so self-centered because from what I’ve just said there really is our thinking and there’s the world we can touch, for example, or that we can’t touch, but that we know exists: planets and stars exist regardless of whether we touch them. Therefore, what you’re asking is: could it be that when we talk about the world we are talking in the world? By expressing the thought, doesn’t this world become part of us?

And at the same time, we’re also nature.
Well, that’s the point: the world is inside our thinking in a way, but it’s a world transformed by the conditions of thought. We could be solipsists and say “I know nothing outside my thoughts, so nothing outside exists,” but let me tell you, you’d not get far with this line of reasoning. So you have to formulate a hypothesis: in reality, it’s not only what I touch, not only what I can represent that exists. Let me put it like this: the world exists and the world is that which exists regardless of me. However, over and above this I can say nothing of this world without making use of thought. With the type of thinking that science is, I can represent or try to represent this world, I can achieve it up to a point, I can assimilate this world within my thinking. What I can know of it can only be achieved through my representation.

At this time, when you regarded scientific thinking as symbolic thinking, how was your professional life affected by this, in practical terms?
Well, I left CERN, I mean I finished the thesis I’d done in physics at the University of Paris and then I had to do my military service. It just so happens that in Geneva, which is a very international place, I made the acquaintance of a Brazilian physicist, Roberto Salmeron, and we became friends. At the time, he had decided to return to Brazil to found a new and pioneering university in Brasília. Since I had told him when we were in Geneva of my interest in the Third World and said that I knew about things…

You were politically engaged.
Concerned, rather than engaged, because I didn’t belong to any political party. However, I was really very interested. In my student days, at the time of the war with Algeria, I’d been involved with opposing the war and colonialism, things like that. However, later, when I was in Geneva, the war had already ended and I became interested in the general situation of the Third World, in the problems of hunger and development in the world. I’d also read about Brazil via various authors, in economics and literature. That’s why, from my conversations with Salmeron, the following invitation materialized: “Look, I’m going to Brazil to set up this university; don’t you want to come with me?” As at the time in France anyone who had a good university background, instead of doing military service, could cooperate through the university in various developing countries, I said: “I accept, of course.” So these were the circumstances under which I went.

To set up the University of Brasília?
It had already been set up, but it was just beginning. Salmeron went back a little before the military dictatorship was installed. At the time, it was a question of keeping things going. However, the six months I spent there were a struggle to try and survive in honorable conditions when the military dictatorship really wanted to crush us, to impose demands that were totally anti-scientific and that led to the arbitrary dismissal of professors. That’s when almost all the professors resigned, saying “We refuse to work under these circumstances.” I had a lot of admiration for them. It was a great human experience for me; a political experience in the broadest sense of the word; I think it was something of a lesson in philosophy and politics.

How old were you at the time?
I was 27. I was very open to everything and very enthusiastic.

Were you attached to the Physics Department at UnB?
Yes. I stayed until the end of the year, because the university closed down and after that there was no possibility of reconciliation, so…

So this happened in the second half of 1965?
That’s right. I had been hired through a cooperation agreement between UnB and the French embassy, but later it was modified and I was lent to CBPF [Brazilian Physics Research Center] in Rio de Janeiro to complete my period. I didn’t want to stay at the University of Brasília, because my colleagues had been obliged to leave. So I acted in solidarity with them but in such a way as to not create problems for the French embassy, which was responsible for me. As a foreigner, I couldn’t do a lot. It just so happens that I had been put in prison for one day during this period. Salmeron mentions this in his book about the university [A universidade interrompida (The interrupted university)]. Overall, this was a great experience for me and I can say it helped me as I moved on to becoming a philosopher. The University of Brasília was small, it had excellent professors, a type of selection of the best and so it was easy when you were in one discipline to meet people from others. In my case, as I sometimes had free time because there were strikes and courses had been shut down, etc., I used to attend the sociology or cinema courses… I attended lectures about the New Cinema taught by its protagonists.

Did you go to the lessons taught by Nelson Pereira dos Santos?
Yes, and by Jean-Claude Bernardet as well. I knew Nelson Pereira dos Santos’ movies; I’d seen Vidas Secas [Dry Lives] before coming to Brazil. It was fantastic. I’d also had a lot of discussions with philosophers and sociologists and in particular with Professor Paul Arbousse-Bastide, a French visiting professor at UnB at the time, who had been one of the founders of USP. I struck up a friendship with him and for six months of my life in Brasília we spent practically the whole time together. I had a jeep, so I used to take him into the countryside on weekends and as he knew Brazil incredibly well I made the most of this fact. Thanks to him I really started getting to know and liking Brazil a lot.

For how long did you work at CBPF?
I stayed there for the remaining six months of my year-long contract. It was good there, because I gave lessons undisturbed. At the time, CBPF was not being persecuted and I got to know other physicists better, besides those whom I’d met in Brasília: Jaime Tiomno, Fernando de Souza Barros, etc. I had met José Leite Lopes before, because he’d been in Paris for several years teaching physics at the University of Orsay. Later, when I returned from Brazil, he was still in Paris. That’s when we became firm friends. When he returned to Brazil, the dictatorship stripped him of his rights. I talked to my colleagues in Strasbourg. I’d been hired by the Louis Pasteur University in Strasbourg when my period in Brazil ended. They had both nuclear and particle physics there and I was able to work well. At a particular point in time, Salmeron told me by letter about Leite Lopes losing his rights. So I talked to my colleagues and the physics professors were all interested and called him to take up the position. He was a full professor there until he retired. For me, Leite Lopes was a great friend and also a teacher.

How long did you stay at the Louis Pasteur University?
I stayed there 16 years and graduated in philosophy from there. I was working with physics, but I used to go to philosophy lessons. In so far as possible, I attended the lectures and took the exams. I used to read and study the history of philosophy course texts; I used to do the homework that had to be done and so on. I liked philosophy. The professors were very happy with my essays and suggested that I study the philosophy of science rather than other fields. In fact, I was also pretty interested in the philosophy of existence, in metaphysics and in ethics. I liked philosophers such as Paul Ricoeur and his professor, Jean Nabert, a lot; people like that.

What was your philosophy thesis on?
Well, there was a metaphysics professor called André Canivez, an expert on the late nineteenth century French philosopher of education, Jules Lagneau. He used to teach this author, but also recent philosophers. I still didn’t know which direction to choose and he liked my profile and my essays and said to me: “You’re going to do a Master’s degree now and then a thesis, so my advice is that you work on the philosophy of science because you’ve got a good background in science, you know this, you practice it. It would be a pity to lose it all and go into a very different field.” He observed that unfortunately there were few philosophers of science there, but there was a major expert in the history of ideas and, in particular, the beginning of modern science, I mean the 18th century, the Century of Light, of Enlightenment, in short. This professor was Georges Gusdorf. He’d written volumes about the thinking of human sciences and three or four of his books were dedicated to the 18th century; in one of them, he talked more about the exact sciences. He emphasized, in particular, the role of a great philosopher and mathematician of the time, Jean d’Alembert, who, along with Diderot, was the director of the Encyclopedia. I went to see him when I was choosing a subject for my PhD thesis and he said to me: “There’s an author that’s perfect for you: D’Alembert.” So I plunged into the works of D’Alembert and did my thesis. It took time because I was working at the same time, but I finally defended my thesis.

In other words, your tasks included giving physics lessons, doing research in physics and preparing your philosophy thesis, all at the same time.
Precisely. My official work was really research in physics. I was the head of an important team and I was a thesis advisor. There was a time when I was the sub-director of the Research Center in Physics at Strasbourg. At the same time, on my own, I was studying philosophy. It took me seven years to write my thesis. From time to time Professor Gusdorf used to say to me “This thesis is never going to be finished!” But he understood.

I’m going to take advantage of this interview to ask you a question about your philosophical view of physics. In a section of your book about physical thinking and critical thinking you wrote the following: “In a more general way, beyond the detail of descriptions, explanations and even reflexive and critical returns in the various fields of relevance, the learning we get from physics about nature and about thinking about nature compete to form in us a representation of the world. This is a broader concept of the universe, of thinking and of the situation in which each one sees himself.” So, my question is, how is physics, which today seems to be not just one discipline, but many, which moves between quantum physics, particle physics, astrophysics, cosmology – in short, how does this highly complex physics influence the way in which we, in the 21st century, view the world?
First of all, I’d like to emphasize that I’m talking about physics here, but this has to be extended to lessons in the other areas of science, and to biology, in particular. Today, we can’t think about the world without thinking about what we know of biology, for example. In fact, in the book I warn physicists about the need to be a little modest sometimes, although now it’s not so much the physicists who pretentiously want to reduce everything to physics: rather, it’s certain biologists who want to reduce everything to biology. Thought, for example, would be reduced to biology; and mathematics would only be an effect of the biological organization of our bodies and our brains, which I don’t believe, because mathematics is something else. In the nineteenth century, many physicists thought that only physics was a science, while the other disciplines were not as scientific, because physics was the first to be clearly developed with a well-formulated, well-established scientific method. However, science developed in very diverse areas, each one with its own peculiarities, but all scientific, without detracting from the others. All sciences should play a part in our representation of the world. If I’m a physicist, or was, I’m going to favor physics a bit more, because it’s going to teach me more than the others (talking for myself, because I know it better). However, I’m obliged not to ignore that others exist and I’m going to include biology, or sociology, psychology… Economics too, which pretends to be a science, but which at times, when you see how it’s applied in the world, is not very scientific at all, but has scientific pretensions and authoritative arguments, which is very bad. I don’t mean that economics isn’t a science, but it should really be sure of being a science when it is being formulated. Many economists don’t take this step back and would have us accept as science what in fact is ideology.

In your book there’s a reference to Amartya Sen.
Yes, to show that economics should be considered in a much broader and more open light than it predominantly was for a very long time. It has to be considered in a much more socially-based way too, of course, because to some extent economics belongs to the science of society, as Amartya Sen, has done, it seems to me.

In dealing with the developments of science in the future, there’s a phrase of yours that has great impact: “What we know forms part of the whole of what is, the greater part of which we are ignorant of.”
That’s the difference: the world that’s out there doesn’t need us. However, we try to reach up to it with our small mind – despite being small it’s strong and powerful, but it’s small compared with the world (even taking into its their social, collective and historical dimension, which expands it), it does not include the world. As scientist, mathematician and philosopher Henri Poincaré used to say: “The world is much bigger than the mind that is in it and cannot be fully included in the mind.”

There’s this observation: “It’s for this reason that these apprehensions allow us to advance, progressing toward greater clarity, since there is this great lack of knowledge of what it’s for. However, at times this clarity is only achieved at the cost of profound changes in the very way of thinking.” In your view, where must our way of thinking change so that scientific knowledge and particularly physics advance in a highly creative direction in the 21st century?
Well, I state the problem, but I don’t have the solution. What I consider the advances of science, using the lessons we’ve learned from the past until now, is that in fact every time we think we have a practically finished, fully coherent, satisfactory representation, there’s a necessary modification; everything is weakened and has to be rethought in another way. That’s what happened in the twentieth century in physics, with the theory of relativity and with quantum physics. I think that physics today continues along the same line, roughly speaking; we haven’t seen any major revolution since these theories. The only substantially different thing that is being looked for is for the joining up of these two great theories, in other words, the theories of continuous and discontinuous matter. This is a great objective of physics, but we don’t know whether it will be achieved. It might be, but until then we can think philosophically, up to a point. Scientists have to transform themselves a little into philosophers in order to imagine how one can achieve such a perspective. However, I’m not talking about everything; I’m talking about the field of physics. The search for this unification makes sense; perhaps one theory is better than two when dealing with common objects.

But do they have common objects?
Yes. Modern cosmology, for example, as we see it today, is an offshoot of the two theories. I mean, cosmology, the science of the Universe – since space is huge and formed – is within the scope of the theory of relativity. However, primordial cosmology, the early periods of cosmology, which we have to think existed because traces of them are there, belong to quantum physics, of necessity, because they refer to states of matter that are the same as those that particle and quantum field physicists study. They’re states ordered by weak and strong interactions and by quarks, those things. So in cosmology, to see the entire development of the history of the Universe according to time and space, there has to be a link between the theory of relativity and quantum theory. The problem has been posed and there are good arguments for it. If we carefully think how we’re going to manage a more coherent vision, it might be that the most natural path is either to unify these two theories we know, or not. It could be that ahead of us another more fundamental principle awaits us, one which might not correspond to a spatial representation or to the things of quantum representation – but it’s difficult to think in a vacuum.

In the field of astrophysics, the question of the Universe’s dark energy is considered a great challenge in upcoming years. Might facing up to this problem end in a shortcut to a unified theory?
These things are being proposed by the cosmologists who talk about dark energy and dark matter. I also think that black holes are good objects for this articulation, because they are revealed by the general theory of relativity; we know from observation that they exist because they produce effects that correspond precisely to what was described by the general theory of relativity and if they exist they have a lot to do with quantum physics because their matter is quantum-related. As for dark mass, dark energy, etc., the former appears to be necessary if we want to understand the movement of the galaxies relative to one another, which the theory of gravitation normally takes care of. Visible mass is not enough. There’s probably an invisible, black, “dark” mass, even though we don’t know what it is, that’s much more responsible for this movement. For the time being, that’s all we can say. The second, dark energy, is because when we consider the Universe’s expansion pace, which is measured indirectly, the presence of invisible energy is also required, but it is energy causing the expansion of the Universe to accelerate that can explain certain cosmological phenomena. It’s not known what it might be, but we know it’s necessary. I don’t know up to what point an explanation underlying these phenomena might not be found in different terms. Perhaps this “dark energy” has to do with the quantum properties of matter in the primordial Universe, particularly with the passage from the quantum regime of the Universe to its relative gravity regime. However, now I’m taking the philosophical point of view and I’m not going to compete with physicists’ hypotheses; I leave the hypotheses up to them. I only suggest that from time to time we reflect on the bases of our physical, classic, quantum-related and cosmological knowledge and its interfaces. My last epistemological research is about what knowledge in quantum physics means.

I was left in doubt when I finished reading the last chapter of your book. Within the scientific field, what place seems to you to be effectively reserved for physics over the next few years and decades, compared with other sciences?
I don’t claim a privileged place for physics, because all sciences have the right to be developed. The problem is the choices that society makes; in fact, the states and international organizations that think about this. These choices are not always the best. I think that physics deserves to continue; I’m not going to say that it deserves to take all the money. However, I think it’s going a little in the other direction now: anything to do with biology is going to get more money than the other disciplines. This is not well balanced and the reasons for it can be studied. However, one of the many, often wrong, reasons is the possibility of applying the knowledge. If one science leads to many applications that are going to be profitable in one way or another, then it’s favored. It’s just that the applications generally do not come from the known sciences; they come from knowledge that is yet to be acquired. This is what always happened in physics: without fundamental physics research, engineering would not get very far. So the minimum has to be guaranteed, and a little more than the minimum, to go on inventing, because, if it invents, physics has to go beyond what is known now. To maintain this pace, which is necessary for knowledge, I think that it really has to be decided to continue with fundamental research in this field – which goes for all the others as well. Look at information technology today; do you know how it developed to this point? Thanks to physics, and in particular to particle physics, because the internet network, the issues with e-mail and everything, the biggest progress in this came from physicist engineers, from research, people who developed information technology and this language of the Internet so that laboratories all over the world could communicate with each other. All this is the product of physics: indirect, but a product, nonetheless.