Over the last decade we have discovered that 95 percent of the matter and energy of the universe is unknown to us: it is dark matter and dark energy.
The discovery of the Higgs boson, announced at CERN in the first week of July 2012, will always remain in the annals of science as a great scientific landmark.
—José Bernabéu
José Bernabéu is a Professor in the Theoretical Physics Department and the Instituto de Física Corpuscular, the University of Valencia-CSIC, Spain. After earning a doctorate in physics (with Extraordinary Prize) at the University of Valencia, he went to the European Organization for Nuclear Physics (CERN), in Geneva. Subsequently he was appointed Chair of Theoretical Physics at the University of Barcelona and then at the University of Valencia.
His research work has mostly been devoted to elementary particle physics, in the field of unified electroweak interactions within and beyond the Standard Theory. His results on the nondecoupling effects associated with the spontaneous breaking of the gauge symmetry responsible for the origin of mass and the Higgs boson have been influential. Another area in which his work has achieved international recognition is neutrino physics.
His awards and honors include the Order “Alfonso X the Wise”; Academician of the National Academy of Exact, Physical and Natural Sciences of Argentina, of the Royal Academy of Sciences of Spain, and of the Royal Academy of Medicine of the Valencia Community; the Prize King Jaime I in Basic Research (2008); and the Medal of the Spanish Physical Society-Prize BBVA (2011).
Adolfo Plasencia:
José, thanks very much for finding the time to see me.
José Bernabéu:
My pleasure.
A.P.:
Christopher Llewellyn Smith as director general of CERN once said, “Clearly, our Project has a spiritual dimension, something to do with our feelings, with the question of what our place is in the universe and what we are made of.”
Does finding the Higgs boson have anything to do with a spiritual feeling?
J.B.:
Absolutely. The human being has always been interested in the grand questions of existence. We can, with well-posed questions, understand nature. Modern science poses these types of question, just as ancient Greek culture, the basis of Western civilization, did. It’s what’s called the theory of knowledge, epistemology. Religion too tries to come up with answers to these questions. I believe curiosity has been the driving force behind the development of thought and the reason why, five hundred years ago, modern science appeared. Science seeks to combine theory with experiment so as to discover nature’s secrets and reduce them to certain laws, to certain regular behaviors. This is what the advance of knowledge is based on, and so yes, there is a religious or philosophical component to it. That component is associated with human curiosity about the grand questions, which have always been pending and which are now standardized through modern science, or what we call the scientific system.
The discovery of the Higgs boson is quite clearly one of the great landmarks in the advance of modern science. In particle physics, our aim is to reveal the behavior of the elementary constituents in the makeup of matter. Recent decades have witnessed spectacular developments, but an essential piece was missing because the advances that had been achieved to describe fundamental interactions were only understandable in a situation of massless particles, against all experimental evidence.
What I mean is that fundamental physics had a problem with this mystical question: What is the origin of mass? The Brout-Englert-Higgs mechanism, in modern theory, suggested how knowledge could be systemized, how all the results that we had could be taken into account and, at the same time, provide a mechanism for understanding how mass arises from the properties of the vacuum state. In this sense, I would go so far as to say that this has been the most important issue in recent decades that we needed to respond to in order to push forward the frontiers of knowledge rather than remain in ignorance. The frontier we are talking about, of course, is that surrounding the question, what is the origin of matter?
The discovery of the Higgs boson is being confirmed by recent results from the analyses carried out by the different groups participating in the experiments at CERN. They confirm that that particle does indeed have the properties corresponding to the Higgs boson. This particle remains as a signal, a remnant through which we may understand how matter originates in the behavior of the elementary constituents existing in nature.
A.P.:
If we know how mass originates, then we should know why the universe continues to expand. So what is missing? What is it that we still don’t see, so that the equations that confirm that expansion, that extension of the universe that is observed, make sense?
J.B.:
On the one hand, we know how it originates, but that does not say that we now have all the information on what all the constituents of the universe are. That is a fascinating question for future generations. The discovery of the Higgs boson is not the final point in understanding. On the contrary, it’s the starting point. Having a mechanism available that can provide us with information on how matter originates does not tell us what the content of matter and the energy of the universe are. I would like to make a comparison between this and the first Copernican revolution, when the human being was indeed at the center of the universe and planet Earth was the center for describing the movement of all objects in the cosmos. That revolution in modern-day cosmology meant that today we know the universe has no center. It is no longer centered on the human being, on planet Earth, the Solar System, the Milky Way. No, there is no center to the universe. Over the last decade we have discovered that 95 percent of the matter and energy of the universe is unknown to us: it is dark matter and dark energy. So it seems we are made up of a kind of constituents that only appear in 5 percent of the total contents of the universe that we know of.
Over the past few years we have been undergoing a second Copernican revolution: not only are we not the center of anything, but also the type of material that we are made of represents only 5 percent of the total content of the universe that we know of.
A.P.:
It seems we will have to accept someday that the questions about the universe will never end and that there will be more and more facts to be discovered.
J.B.:
Yes. That’s a very interesting thought that is directly linked to the idea of epistemology or the theory of knowledge. What does advancing knowledge mean? I don’t see it as a linear advance at all, rather, as an analogy of how that advance takes place, I would say it’s something like the shoreline or the contour of an island that advances into an ocean of ignorance. In that analogy we can see that the more we know, the more frontier there is. That is, there are more and more questions.
This is case with the CERN laboratory and with the results that are being obtained in the detectors that record the results of proton-proton collisions in the Large Hadron Collider (LHC). As important as or even more so than the answers we now have to questions that we have been asking ourselves over recent decades is that the results of the LHC experiments will allow us to formulate new questions. As we will know which questions to ask, this will lead to developments for the next generation of experiments to be undertaken. What I want to say is that it’s the advance of knowledge itself that generates questions, which is something that is never going to end in science. It is the advance of knowledge that is creating the new questions we are posing for each of the stages.
A.P.:
In the end, Picasso will be proved right. He dampened the spirits of the first computer enthusiasts by saying, “Computers are useless. They can only give you answers.”1 What is important are good questions rather than the answers.
J.B.:
Exactly. The questions, as far as I am concerned, are the most important thing. When I say “new questions,” these should be put in a more important category: faced with new answers or new questions, I put the latter first. By the time we have a definite criterion on how to formulate a question to nature, we have already advanced a long way toward finding the correct answer.
A.P.:
José, you have dedicated a lot of time and effort and thought to getting thousands of physicists to agree, to convincing dozens of countries and thousands of leading politicians to build the biggest machine that humankind has ever built, and to bringing together thousands of the best physicists and engineers to work together here, in a Europe that not very long ago was at war with itself. Those nations are now reunited at CERN.
How do you feel about the fact that it is physics that has led the way from war to peace in Europe, from world wars to the twenty-first century with the Europe of CERN?
J.B.:
I think it can safely be said that science has been the pioneer in building Europe. It was scientists and science politicians in the 1950s who, after the tearing apart that took place between European nations in World War II, realized that Europe would never be able to compete as an advanced society either with the United States or with the developments of the former USSR if we didn’t take a step forward and build a united Europe.
CERN was the way of giving form to this idea. The European particle physics laboratory was created in 1954. I should remind you that 1954 was even earlier than the first European treaties on coal and steel. It’s not just that there weren’t treaties of an economic nature in Europe (let alone political ones, which in my opinion we still don’t have), there were not even commercial ones! Yet CERN came into existence in 1954, first with five countries, and then other countries joined in. CERN has consolidated the idea of Europe from the scientific point of view and is also encouraging it to take steps.
For example, CERN is now opening up its frontiers to go beyond Europe, inspired by the vision that science is a way of joining human forces with the aim of furthering universal human civilization. Besides the CERN member countries at the moment, there are also associate member countries (non-European countries) that attend advisory sessions and participate in CERN experiments, not only as external members but collaborating on building the detectors, analyzing the results with data obtained from them, and working together—American, Asian, and European physicists—as equals. CERN thus not only embodies the idea of Europe, it embraces science from all round the world, all over the whole planet, our planet.
I think that when circumstances like these arise, then automatically we should not only support science as such but also support the concept through which an advanced society can be built, in which the scientific component will play an important part. It’s for that reason that there is a consensus among all European countries that CERN is not only the most important laboratory in the world but also the most visible flagship of an advanced society, one we should all be proud of. Science is culture, understanding for understanding’s sake, the most worthy and sublime expression of humans.
Furthermore, CERN produces economic and social benefits. I’ll give you just one example, because it’s something that represents a revolution in modern times. Where was the Web invented? Tim Berners-Lee invented it back in 1989. And on April 30, 1993, CERN announced that the components of Web software would enter the public domain, so allowing them to be used, duplicated, modified, or distributed. That software, made at CERN, changed the world. It’s revealing to think that one has access to information without paying a European cent or dollar for it. It was invented at CERN, and at CERN patents are very unusual; the content is free to use, while the intellectual property right is maintained. All the development work is returned to society.
A.P.:
CERN has opened up society. I’m not sure whether you are aware of something that many people are not. Something I was told not long ago by the only Spaniard among the cofounding group of Arduino. The group wanted their Arduino Diecimila to have a universal, open source hardware license.2 The group turned to the legal department at CERN, who got their attorneys working on drawing up an open, universal license for everyone involved in the world of hardware, and within a few months they had legally created the CERN Open Hardware License (CERN OHL), which can be used by everybody.3 It’s a good example.
The flagship that CERN represents, as you say, is the flagship of grand science. Can we understand grand science as a catalyst for civilization?
Does more science mean more civilization?
J.B.:
It’s clear that in modern societies, science plays a fundamental role in development, but also in coexistence. What I mean is that science consolidates the advances that are taking place in society. Science, of course, may be used for ends that may not be the most appropriate ones, but one cannot attack science for that. That’s the fault of certain individuals using scientific results.
A.P.:
We often talk about grand science, but CERN is not just words. It is a huge mechanism, an enormous machine, and a fact that really functions. I think that the CERN mechanism may be seen as a real instrument for “catalyzing civilization,” don’t you?
J.B.:
Yes. I’m 100 percent in agreement with that idea because CERN is a meeting point not only for scientists but also for people interested in culture and the development of society, who wish to take CERN as an example of how to effectively achieve communication and collaboration. I’d just like to add one thing that contributes to this idea. Now, using the results of the Higgs boson, there are two different experiments going on at two different intersection points of the proton beams at the LHC. Clearly, if there are two experiments, it is because in science, it is essential to compete. Competition arises from the fact that the results of one group have to be compared with another. It has to be like that, but at the same time the two groups collaborate. In the commercial world, competition normally means the opposite of collaboration. They are usually two opposing terms. It’s not like that in science. In science you can compete at the same time as you collaborate. They are complementary terms.
A.P.:
Your life seems to be closely linked to CERN even during your holidays.
J.B.:
Not only my scientific life but also my personal life. When I return to CERN, I feel at home. I don’t consider it a foreign laboratory. Recently I was at SLAC, the laboratory of the University of Stanford concerned with the results of broken time-reversal symmetry. Although scientific atmosphere is universal and friendship without frontiers is a much-appreciated value among scientists, I did feel that I was abroad. However, when I go to CERN, because I have a strong link with the laboratory and its surroundings, for me it’s like being at home.
A.P.:
What are the great challenges of CERN?
J.B.:
The first great discovery at CERN took place in 1973. I have always said that it was the first experimental result leading to the Standard Model of particle physics. The paper with the observation of a new weak force was “Discovery of Weak Neutral Currents at CERN.”4 This was a great catalyst for later theoretical and experimental developments, which took place quickly and in great depth. When the ideas are there, there’s immediately a hurry, and everything accelerates. That’s what I was saying before. When we know how to formulate the questions, the answers come quickly and everything advances at great speed. That is something that Carlo Rubbia, the Nobel Prize winner in 1984 and later director general of CERN, said at the beginning of the 1980s. Only ten years after the discovery of the weak neutral currents there are data to confirm what I was telling you earlier about competition versus collaboration. Since then there have been more American physicists working at CERN than European physicists working in the United States. What I mean is that the advance that a laboratory like CERN represents for Europe is considerable. Nobody today disagrees that it is the number one world laboratory, and that should make Europe proud because it’s true it is the catalyst for great developments that are taking place in scientific advances.
A.P.:
What for you would be the second greatest landmark? The Higgs boson?
J.B.:
The discovery of the Higgs boson, announced at CERN in the first week of July 2012, will always remain a landmark in the annals of science.
But that is not the end of the story in the advance of fundamental knowledge. On the contrary, both from the consistency of the theoretical scheme of the Standard Model and from unequivocal experimental signals, we are convinced that a new type of physics will have to arise that is capable of explaining pending problems, such as the mass of neutrinos, dark matter, and dark energy, or why at present the universe contains hardly any antimatter in natural form. Moreover, the present experimental results will provoke new questions that we still do not know of as yet.
A.P.:
In Shakespeare’s Hamlet, act 2, scene 2, the prince says:
“I could be bounded in a nutshell
and count myself a king of infinite space.”
This verse was the inspiration for the title of Stephen Hawking’s recent book, The Universe in a Nutshell.
Did you feel like the king of infinite space at the LHC once the tunnel and machine had been built in that gigantic subterranean space at CERN?
What kind of emotions do you feel there?
J.B.:
Well, you feel satisfaction and, obviously, excitement, because the fact that humans are capable of building a machine that can provide answers to the secrets of nature in this way, a fantastic way, is very positive and exciting. But that’s true not only with the experiments being done at CERN but also with the experiments that are being undertaken from satellites for observing the fossil trace that remains from the beginning of the universe. The advance on the two frontiers of physics from the smallest to the biggest is fantastic. Moreover, there is a sense of unity and—talking about emotions—a great human feeling that we are all involved in trying to reduce phenomena that appear very distinct to a single great law.
Today, the study of the conditions of particle physics and of what the physics associated with the primordial universe consists of is all coming together. It’s a wonderful manifestation of the unity of physics and well expressed in that quotation from Hamlet. From the observation of the most intimate detail we are answering the question of how the universe behaves overall and why the universe has evolved as it has up till now in accordance with several conditions that now are being recreated in the laboratories of particle physics.
So now it’s not just a question of advancing knowledge. It’s the unity of science, the knowledge that we are capable of working together to understand what is happening from observations of the smallest things to observations of the biggest things. When we talk about the smallest and the biggest, we have to bear in mind that, from our metric scale to the constitution of the atom, there are ten orders of magnitude in length, to use our jargon. This means we have to multiply the length of an atom by one followed by ten zeros to reach one meter. And there are eight other orders of magnitude down, to reach from the atom to what is now being explored at the smallest distances. On the other hand, we have also to go to the greatest distances. But then we are asked, “Why go to the greatest distances if what you want to know is the primordial universe?” This is another wonderful aspect of that analogy of the nutshell—that we are capable from there of arriving at the limits of the universe, and not only that but to find out from there what the universe was like in the past, because signals are transmitted at a finite speed and, therefore, when I am observing what is happening out there. …
A.P.:
In the universe, the further out you look, the earlier in time you are looking.
J.B.:
You see an earlier time, exactly. That is what is taking place with the Hubble Space Telescope and other telescopes.
A.P.:
That is: the further, the earlier.
J.B.:
Earlier, yes. An alternative is the observation of the background radiation we have in the present universe, because it has remained like a fossil from that primitive period. These are the two ways through which we have access to all that. That quotation from Hamlet is wonderfully appropriate because if there is something today that is a manifestation of the unity of science, it is that convergence between the physics of the smallest thing and the physics of the largest thing, the connection between particle physics and the physics of the primordial universe.
A.P.:
Physics seeks to unify natural laws that describe different phenomena in a common dynamics. That dynamics provides us with evolution over time and it is linked to symmetries of matter. But that doesn’t happen with time itself. So I have the following questions:
Why is time asymmetric?
What does the “time reversal” that you speak about in your research and publications mean?
J.B.:
The great scientific advances that have been made, and with them the knowledge attained, have gobbled up a considerable part of the ocean of ignorance by unifying what were two apparently distinct phenomena. The names of Newton, Maxwell, Einstein, and Bohr, or the recent unification of forces, electromagnetism, responsible for the formation of the atom, and the “weak” interaction, responsible for the generation of energy by our Sun, are associated with that unifying dynamical laws as a consequence of symmetries.
Time is a concept that runs in a single direction. For that reason we speak of the “arrow of time.” We see that complex systems have to follow the dictates of the second law of thermodynamics, always evolving (if they are isolated) toward an increase of so-called “entropy,” an increase of disorder! If a glass falls and breaks into a thousand pieces it is impossible that, spontaneously, the pieces will get together again and the glass reconstruct itself. The falling of the glass is irreversible! That is how Eddington almost a hundred years ago explained, with the increase of entropy, the meaning of the “arrow of time” concept.
A.P.:
That’s clear, but what about that expression you use, “time reversal,” for a possible symmetry of the physical laws?
J.B.:
That arrow of time does not eliminate the question of whether the dynamics of the fundamental laws for elementary particles, for those that we observe to have reversible processes in time, are able to describe both the direct process and the reverse process in time. Perhaps the expression “time reversal” is not the best one because people think it means reversal of time, time running backward. That makes no sense. What is reversed is the movement. So, in the same year, 2012, a few months after the discovery of the Higgs boson, it was experimentally established that several processes governed by weak force are asymmetrical under time reversal. Although reversible, the two processes occurring in one sense of time evolution and in the reverse sense do not show up with the same frequency. This discovery was made in the BaBar experiment installed in the SLAC laboratory, in which IFIC scientists participate and play an essential role, both in the theoretical proposal and in the analysis of the results.
A.P.:
But how did you arrive at that idea?
J.B.:
It was known that, in certain processes resulting from weak interactions, there is an asymmetry between the behavior of matter and antimatter. It was natural to ask whether, in these processes, there is a breaking of time-reversal symmetry too. However, these are processes in which the particles decay. If the particle disappears, the process is irreversible; you cannot study the reverse process; it is like the arrow of time discussed before for a falling glass. We proposed a bypass to this no-go argument using some spectacular properties of quantum mechanics, able to transfer the information from the decaying particle to a partner that is still alive! And you do the experiment with the partner. Thus the difficulty of this experiment was in knowing what one had to measure. The concept and the method are explained in my article, “Time-Reversal Violation with Quantum-Entangled B Mesons.”5
Today we do know that, in certain processes in which there is a breaking of the symmetry between matter and antimatter, there is an asymmetry under time reversal, too.
A.P.:
José, thanks for speaking to us and for providing such fascinating conversation.
J.B.:
You’re welcome. Thanks for coming. It’s a pleasure.