Professor José Leite Lopes, a tough, 82-year-old from Pernambuco, whose birthday was on October 28, this year, is a respected personality in Brazilian science who stays close to two of the great passions of his life: “I keep up with the progress of new theories in physics and the political problems of Brazilian science”, he says. He exercises this quiet application of fidelity to his vocations, even though he is retired and far from the research into Particle Physics and into Fields Theory that made him an internationally recognized scientist, mostly at the Brazilian Physics Research Center, the CBPF, for the creation of which he struggled at the end of the 40s, which he ran from 1960 to 1964, and from which he resigned when the military coup of that year spread an unbearable dictatorship throughout the country.
Among Leite Lopes’s original contributions to physics, is the proposition of the w+w- as vectorial bosons associated with the photon, which was to unify electromagnetic forces and the weak forces that he was the first to pinpoint, and the prediction that the boson ZO existed, subsequently discovered in the 80s. He made these discoveries in physics in 1958.
Among the troubles he suffered because of the country’s political problems, he remembers his stay in France beginning in 1964, returning to Brazil in 1967, in part in response to appeals from students in Rio de Janeiro and with confidence in a return to democracy, which did not in fact happen. They also include the loss of his political rights under the AI-5 in 1969, his move to Pittsburgh, and then, in 1970, to Strasbourg, in France, where he remained until 1986.
Professor emeritus of the Federal University of Rio de Janeiro (UFRJ) – where he worked from 1946 to 1964 and from 1967 to 1969 –, and at Strasbourg and the CBPF, Leite Lopes spoke affectionately of his three children – the anthropologist José Sérgio, the IT specialist Sílvio Ricardo and the playwright Ângela – when he gave the following interview to Mariluce Moura, a real lesson about physics and life.
Let’s begin explaining your work on the unification of electromagnetic forces and weak forces.
In physics, there are four kinds of basic forces called interactions. Gravitational, which all of us, all matter, all energy, everything that exists are subject to. It was spelled out by Isaac Newton and improved by Einstein. There is electromagnetic interaction, carried by photons; weak interaction, which commands the breakdown of the neutron into proton plus electron plus neutrino; and there is nuclear interaction, which causes the neutrons and protons in the atomic nucleus to fuse, giving stability to matter. Gravity, on the other hand, from the standpoint of nuclear physics, is the weakest of all, but in the universe, it rules, because a star, for example, is made up of the gravitational attraction of matter that is beginning to contract. Everything that has mass, everything that has energy, undergoes this mutual attraction and begins to contract, but as it contracts the temperature rises until it reaches a point such that nuclear reactions are produced among these particles.
How high is this temperature?
Oooh… billions of degrees centigrade. Things heat up and then there are the nuclear reactions that emit light and waves, and that is why stars are visible. But the important interaction in the stars is the conversion of hydrogen into helium. Hydrogen reacts with itself and produces the gas helium. There is always a finite quantity and when this quantity is burnt up there is no more material for nuclear reactions. When there is any more, gravity gives a laugh and carries on in charge and contracts, consequently raising the temperature, and depending on the mass of the star, it gives off a part. These are the supernovas, and we can see them when they burn out producing great brilliance. But, there is a fundamental repulsion between the particles explained by the Pauli principle. That’s the Nobel laureate with whom I worked, Wolfgang Pauli.
Did you work with him in 1945?
Yes, at Princeton. Pauli says there cannot be more than one electron in each state. Either there is zero or one; if another electron comes along, it moves to a higher state. When matter contracts, it’s as if there were a repulsive force, the electrons cannot all occupy the same position. This force counteracts the force of gravity. And a point is reached where a black hole is formed, because gravity always dominates and ends up forming a very strong gravitational field pulling everything inside it. Light, for example, escapes normally, but it reaches a gravitational field so strong that it is trapped. That is why we have black holes, which we only know exist because they have a very large mass and no visibility at all, which disturbs the movement of other particles. These forces have always interested me; I worked with Pauli on nuclear forces, but then I went on to study weak interactions – those that govern the disintegration of the neutron and the proton, and even the boson Pi, which disintegrates into a particle called a muon and a neutrino. Pauli discovered the neutrino in 1936, because he observed that there are nucleuses that disintegrate emitting electrons and these electrons that are emitted ought to have some definite energy, the result of the son nucleus less the father nucleus. This energy must go to the electron.
But something upsets this notion.
That’s right, but you find electrons with all possible energies, from this maximum to zero, and nobody understood why. Until Pauli sent a letter to a meeting being held in Germany, because he had a dance, a party to go to, saying, “Dear Radioactive Ladies and Gentlemen…”, in which he observed that the fact the electron has all possible energies, even this maximum energy, derives from the fact that a nucleus, when it disintegrates into another nucleus, causes it to emit an electron and a new particle of very low mass, perhaps even zero, and the energy is distributed between the two particles: either the electron or what he called a neutron, but it is actually a neutrino – the neutron had not yet been discovered, and Enrico Fermi, to whom Pauli revealed this theory, said les particelle di Pauli sono piu tosto, they are neutrinos and not neutrons, they are small.
Who discovered the neutron?
Chadwick. There was a reaction, in which bombarding, I think it was beryllium, with alpha particles produced particles that Joliot and Irene Curie saw had the property, when absorbed by a region with a proton, of sending off protons. Joliot thought they were very high-energy photons. Hence, Chadwick said that if protons are emitted, it is because they come from a mass almost equal to that of the proton and it emits one. When there are two particles interacting, one passes all to the other, and the latter halts. A mechanical problem that I think Joliot did not understand very well. So he thought there was this particle, which ought to be a neutron, whose mass is a little bigger than that of the proton, and he was the man to discover it because, since 1919, the great Rutherford had predicted that in hydrogen you have the electron surrounding the proton. This would be disproved, and electron plus proton, negative plus positive would give a neutral particle. After Chadwick began searching and, when he saw this reaction that produced a proton, the particle he thought it was neutral, was the neutron. So, the neutron disintegrated giving a proton, plus an electron, plus the neutrino. So, Pauli discovered this neutrino. It had a particle of very small mass, perhaps even zero, and some time went before before discovering it. After this discovery, César Lattes with Occhialini and Powell discovered the pion, that disintegrated giving a muon plus a neutral particle, thought to be the same neutrino. But, inverting the reaction, bombarding the matter with this neutron emitted, it was seen that if it were the same as the neutron it would produce a neutron in this inverse reaction, which did not happen: this neutral particle emitted yielded to pions, muons and then besides Pauli’s neutrino, which appears in the disintegration of the neutron, there is a muon neutrino associated with the disintegration of the pion into a muon plus this neutrino.
So different particles have their corresponding neutrino.
Yes, there are there are three kinds of neutrino: the electron, the muon and the tauon, the latter discovered recently.
When was the neutron discovered?
In 32. The pion and the muon in 1946, 47… The tauon is quite recent, in the 70s.
Was there any connection between the discovery of the particles in 46, 47 and the research being conducted into the Manhattan project?
No. The Manhattan project was to manufacture the atomic bomb and people were only concerned to do so before Hitler could do it. At that time, I was in Princeton working with Pauli. A lot of time went by without knowing how the disintegration of the neutron into a proton plus an antineutrino. So finally, Feynman and Gell-Mann found that this weak interaction of the neutron into proton, electron, and neutrino was of the vectorial type. That means there is a geometrical shape to it. It could have been scalar, it could have been of various other types, and they thought it must have been vectorial. Then I immediately thought that there would be w+ w- bosons, which were intermediate between neutron, proton, electron, and neutrino, and ought to have been vectorial. As the light photon is also vectorial, I thought there ought to be a family connection.
Is that where the name “boson” appears.
No, before that. Bosons are particles whose spin is whole, either 0 or 1 or 2, etc. and there are fermions, like the neutron, proton, electron, neutrino, whose spin is a half, it is a fraction. I did some work in 1958, in which I proposed a relationship between bosons and photons, and hence equality between the weak interaction and the electromagnetic constant given by the electron’s charge. When I suggested this hypothesis, I had obtained the value of the mass of the w+ and w- bosons of around 60 times the mass of the electron. This was new, and C. N. Yang did not believe it. He thought that the mass of the boson would be only a little more than that of the proton. In the same work, I suggested that a neutral boson was likely to exist, which today, is called Z0 (z-zero), which should be sought in interaction of electrons with neutrons.
This boson was discovered only in the 80s, wasn’t it?
Around then, yes. But few people had read my work, although it had been published in Nuclear Physics, a very important Dutch publication. Yang then published an article in which he said that my work, although not much read, was the most connected with current research.
After your work with bosons, what did you research?
I began studying the possibility of there being leptons with excited spin. Leptons are ultra-light particles, electrons, and neutrinos. And I kept up my study of them until a few years ago.
What do you consider your most important contribution to Physics?
The part about the ws being vectorial bosons associated with the photon. That gives unification that I was the first to pinpoint, because I suggested that the weak force had a constant g equal to the electromagnetic force e. Today g does not equal e; it is multiplied by another factor. That was my fundamental work, and Steve Weinberg, quoted it in acceptance speech when he was awarded the Nobel Prize. Yang also quoted it and many other people, but it did not meet popular taste. It wasn’t always obligatorily quoted, although Weinberg carried on quoting it, including in the book he has just published, just like Yang.
How can we, in a climate of little understanding of the role of scientific research, produce a generation of first class physicists in Brazil?
Well, this physics was founded up with the creation of the University of São Paulo (USP). The people that founded USP sent a mathematician from the Polytechnic School of Engineering, Teodoro Ramos, to look for teachers abroad. He went to Enrico Fermi, who suggested Gleb Wataghin, who came here and founded modern Physics in Brazil. He trained Mário Schenberg, Marcelo Damy de Souza Santos and I too came to São Paulo.
At that time you were in Rio.
Yes. I was doing chemistry in Recife, coming under the influence of professor Luiz Freire, who had me go to Rio, where I did the course at the National Philosophy Academy. Then when modern physics began being done in São Paulo, I came to work with Mário Schenberg in São Paulo. Everyone came to this environment created by Gleb Wataghin. Lattes came, we were colleagues, many people came, and we produced this new thing. In 1948, I went to Argentina, and I met a German physicist there, Richard Gans, who wanted to understand why this Brazilian school had been established, when in Argentina, as he told me, he had been before, and had not been able to do the same.
Well, after your time in São Paulo you tried to set up a nucleus in Rio and things turned out to be not so easy or simple. How did this happen?
When I finished my doctorate at Princeton I was appointed as a professor at the National Philosophy College. The director was San Tiago Dantas. I wanted the professors to be paid a full time salary, like in São Paulo. But there was Dasp (Public Service Administrative Department), which banned full time work. So I began to fight. We were under the Dutra government (General Eurico Gaspar Dutra) and after in the second Vargas government(Getúlio Vargas). I made speeches, I wrote articles, because I thought it was important to create an environment the same as São Paulo. I wanted Lattes to come to Rio, when he came back from England and, when he discovered the pion, I proposed they should establish a chair of nuclear physics at the UFRJ, which was done. Lattes went to Rio de Janeiro to find out what was happening, and I said to him, “it’s bad, because not even the rector supports us”. I think he didn’t even know that nuclear physics or the atomic bomb existed… Then a friend called Nélson Lins de Barros took me to meet João Alberto de Barros, his brother and an important politician, who had been part of the Prestes Column, of Tenentismo (revolutionaries movements in the 20s) … He was a Getúlio man, and Getúlio made him intervenor in São Paulo, and was then minister at the Itamaraty (Ministry of Foreign Relations). When I explained to him that we couldn’t do nuclear physics because the professors weren’t paid enough and that the university was not supporting us, he said “so we’ll do it outside the university”. And the Brazilian Physics Research Center (CBPF) was established.
Which year was this?
In 1949. As a private institution, financed by João Alberto himself, by the president of the National Federation of Industry (CNI), Euvaldo Lodi, who contributed a hundred contos a month… We went out, we asked the unions, there was a banker, Mário de Almeida, who also gave us money and we built the pavilion where the laboratory was set up, close to where we are, on the Praia Vermelha campus of the UFRJ. In 1951, the CNPq was created, and Álvaro Alberto, its president, promised us money. The center was at its apogee when Getúlio committed suicide, there was general crisis, and the project for a high-energy cyclotron was shelved. The center swung into crisis, because we had only raised half what we needed. Then came the huge rise in inflation, first with Juscelino (president Juscelino Kubitschek), then with Jango (president João Goulart). When the 1964 coup came, I resigned from the position of scientific director of the CBPF.
And then you left Brazil.
I went to France at the invitation of the physicist Maurice Levi, and I remained at the Orsay Science Faculty, in Paris, from 1964 to 1967. I came back in 1967 and took over my position again at the university and the CBPF. But in 1969 my civil rights were revoked by AI-5 (Institutional Act number 5) and I left, first for the Pittsburgh Carnegie Mellon, in the United States, but I did not want to stay, I did not like the atmosphere, after all it was the time of Nixon and Kissinger, who had supported the coup in Brazil. A year later, I received an invitation and went to Strasbourg in France, where I stayed until 1986.
Were you, like Schenberg, a member of the Communist Party?
I never was. I supported the basic reforms and everything, but I never belonged to a party capable of carrying out a revolution I did not like. But they (the military) thought I was.
The political situation meant Brazilian physics falling behind?
Well, they removed Schenberg, me, and various others. There was a good deal of protest, letters sent by French and American physicists, Yang sent a letter to Costa e Silva (military president Arthur da Costa e Silva), but the so-called revolution was implacable. Then, minister Veloso (João Paulo dos Reis Veloso, minister of Planning) thought it was all nonsense and brought people like Sérgio Porto, and Rogério Cerqueira Leite, who returned from the United States to Unicamp, founded by Zeferino Vaz in 1970. Then, even under the dictatorship, there were many people working, the Campinas group, the Recife people, who began to develop. If there was any real delay, it was in our training.
How do you see the most recent progress in your specialty of physics, which seems to make the standard model of particles out-of-date and gives us news such as the splitting of the electron (see box)?
This information that the model is outdated is interesting. I have a lot of sympathy with supersymetry, but so far, the particles confirming it have not been discovered. Splitting the electron is an interesting innovation. In France, I studied how it can be broken down, but splitting it into a particle plus an electron is a great innovation.
Why has there never been a Brazilian Nobel prizewinner?
Carlos Chagas would have been a Nobel laureate. He was nominated, but many Brazilian doctors were against it. And there were other people too who deserved it. Henrique Rocha Lima, of the Biological Institute of São Paulo, César Lattes, who discovered the pion and didn’t win it, because Powell, who was head of the laboratory, won it, Gilberto Freyre… Argentina has Nobel prizewinners, why not us?
You yourself, for example?
I do not put myself on the list. When they saw the importance of my work, a lot of water had already gone under the bridge.
Turbulence in the world of particles
From time to time, theories as apparently solid and brilliant as diamonds are destroyed by other emerging theories, which pinpoint the faults of the earlier one and point to new ways forward. This is absolutely natural. Problems begin when an old law of science is overturned and we do not know what to put in its place. In, 1900, Max Planck published the first work on the first version of quantum theory and began to build a model of how the universe worked. A hundred years later, the result of the work of theoretical physicists, analyzing the results of the experiments coming out of the high-energy particle accelerators, are reaching a conclusion with the discovery of the particle called the Higgs boson. The problem is that the standard model, it seems, is definitively outmoded, as the magazine The Economist, of October 7, tells it.
The situation goes back to the 19th century, before Max Planck announced his ideas, when physicists had a ready-made description of the universe, a sort of catchall theory. Physicists nowadays are more cautious and they know that is imprudent to claim to have a watertight theory. They also have no notion of the next step to be taken, which may well change current paradigms.
The October 14 issue of the New Scientist published that it is the British researcher Humphrey Maris who has contributed most to the debate about the future of physics. Maris, of Brown University, claims that 30 years ago the unthinkable happened in Minnesota: researchers spit the ”indivisible” electron into fragments. And, so far no one has been able prove otherwise. “These electron fragments behave to all intents and purposes like totally separate particles”, he says. “I call them electrinos.” These claims have shaken the world of physics because in these 103 years, since it was discovered, there had been no evidence that the electron is divisible. “Humphrey managed to point out a fault in the structure of Quantum Theory”, Peter McClintock, of the University of Lancaster to the New Scientist.
Maris imagined that an electron in a ball of liquid helium could be put into a stable state in the form of dumb-bells and put under pressure in such a way as that it would be possible to separate it into two parts. Before testing the idea, the physicist searched through existing literature to see if anyone had done it before. He discovered what he was looking for in an article written at the end of the 60s, when Jan Northby and Mike Sanders, at the University of Minnesota, studied the speed of electron bubbles moving through an electric field in liquid helium. In 1971 and 1984, other researchers did similar work. It so happens that none of them described splitting the electron.
Maris himself went years without telling anyone. Only in June this year did he present his work at a conference in Minneapolis and he published it the Journal of Low Temperature Physics (vol. 120, pg. 173). At the end, more than a hundred physicists questioned every aspect of the theory. But Maris had an answer for everything and, although nobody completely ruled out the possibility of splitting the particle, the criticism was unsparing. “The idea of an electron splitting into fragments is completely incompatible with the Quantum Theory of Fields”, says Anthony Leggett, of the University of Illinois, although he admits there may be something wrong with the theory. Most physicists believe that Maris’s arguments will fall at the first hurdle, although they do not know exactly how. The fear is understandable. If the discovery it true, it means that the Quantum Theory is wrong – and there is nothing to put in its place.
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