jueves, 1 de julio de 2021

Entrevista con el cosmólogo James Peebles, Premio Nobel de Física 2019 (en inglés)

 Hice esta entrevista por invitación de Omar López-Cruz, que está codirigiendo la colección Biblioteca Científica del Ciudadano para la editorial Grano de Sal y con la participación del gobierno del Estado de Hidalgo. La colección incluirá próximamente el libro El siglo de la cosmología de James Peebles.

 How do you convince young students that physics is interesting?

 I wish I knew. I spent a career teaching physics. It’s a subject I love, and many of the people I see at university are already convinced of this. I have no experience teaching younger people. How does one get a young person to appreciate the nature around us? It requires great teachers. I guess in my case I simply was born curious about the world around us. That curiosity luckily was never suppressed. My parents encouraged it. I grew up in rather a small town in southern Manitoba, in Canada. Curiosity was not suppressed there. It wan’t particularly encouraged. So I am not a good example, I’m afraid, of how we persuade young people to pay attention to science. I can only say, please, don´t discourage them.


Cosmology was not all that present in the Nobel prizes for some time, say, before 2006, when it was awarded to Smoot and Mather. Why do you think that is?

There are many fields in which great advances are being made and have to be recognized by the Nobel committee. They have many more good choices than there are prizes. I think cosmology has obtained its fair share of prizes, in fact, perhaps more than most because the subject has grown rather rapidly. A half century ago cosmology was a very schematic subject, close to pure invention. The development since then has startled me time and again as pieces of evidence have come together and have made a very convincing story now, that we actually understand what happened, at least in broad terms, as the Universe evolved from a very different state from now. That’s a very striking statement, that the world around us is not forever. The Universe is evolving. It’s not something I would assert unless there were really strong evidence of it.


What motivated you to go into cosmology in the early 60s?

I arrived at Princeton University in New Jersey in the USA in 1958. My attention was soon drawn to one of the professors, professor Robert Henry Dicke, Bob to everyone, who had taken an interest in gravity physics. He was doing the sort of thing that I enjoy, namely, an individual sitting, looking at an idea, looking for evidence for or against it, working on consequences, testing, perhaps enlarging the idea. It is the sort of thing I enjoy doing. He had offered me lots of things along that line to do in gravity physics, and in particular he suggested I look into cosmology. Simple answer to your question: Bob Dicke suggested that this is what I´d do. And its amazing, I continued to do it for the rest of my entire career. How is that for perception, or just plain dumb luck?


You have mentioned in other interviews that at first you considered a career in engineering, and then you changed to physics and finally cosmology.

Yes. I mentioned I grew up in a small town. My high school there did not have a career counselor. As a student, in Saint Vital, Manitoba, I was not very attentive. I did my homework, I´d no trouble with exams, but I did not think much about academia, and so I turned to engineering simply because I knew that I liked building things. I had the impression engineers built things, so I entered engineering. It was all right. I learned a lot while in the engineering department that has stood me in good stead, but it became pretty clear to me that the courses I most enjoyed were physics. So after two years in engineering I transferred. It was one of the best things I’ve ever done.


Going forward from that time to 1964 and the Penzias and Wilson “scoop”: How did the paper by Penzias and Wilson come to be published back-to-back in the same issue of the Astrophysical Journal Letters with the one by Dicke’s Princeton Group?

Let us recall that in the late 1950s through the 1960s engineers at the Bell Telephone Laboratories were investigating means of communication by microwave radiation, radiation with wavelengths from centimeters to tens of centimeters. It gave us cell phones, for better or worse. You know, I just remark: I seriously dislike the sight of people walking the streets looking at their cell phones. Why aren’t they admiring the world around us? In any case, already in 1959 engineers at the Bell Telephone Laboratories were discovering that their microwave receivers were detecting more noise than they could account for by all the sources in their instrument. They had to match the budget of noise expected to noise discovered, so they assigned it to the antenna. Radiation will leak around an antenna from the ground. They call it side or back lobe radiation. They assigned about two degrees above absolute zero to radiation coming to the antenna from the ground. They knew perfectly well that the antennae are far better than that at rejecting ground radiation. In short, they had an anomaly, but their job wasn’t to consider anomalies, their job was to make the best possible receivers. So I would put it that in the next five years there was a dirty little secret in Bell Laboratories that all of their receivers had this excess noise. So in 1964, two young people at the Bell Telephone Laboratories, radioastronomy department, resolved to find the source of this radiation. They are to be credited for working very hard on the search for sources, clever tests of all sorts. They are to be credited for refusing to give up, and I credit Bell Laboratories management for allowing them to continue looking. And they are to be credited for complaining about their problem until someone heard.

Meanwhile, in Princeton, Bob Dicke had suggested a hot big bang, as we call it now. The Universe he imagined might be hot in the early stages of expansion, and would produce thermal radiation. The thermal radiation would not go away as the Universe expands. There’s no place for it to go. The radiation would be present, if this picture is right, and it would be characterized as having a spectrum of thermal radiation. At his suggestion, Peter Roll and David Wilkinson built a microwave radiometer, a device Bob had invented during World War Two as part of war research. And he casually said to me “Why don’t you think about the implications of the experiment?” That led me to my career, it led David Wilkinson to his career. The rest of his career almost entirely was following Bob’s suggestion. Talk about perception!

So the connection between the Princeton search and the Bell excess noise was made about January of 1965, I don’t remember exact dates. The result of the phone call from Arno Penzias to Bob Dicke was a visit to Bell Laboratories. Bob returned with the statement “I think they got something,” and so the result were these two papers, a happy mariage of an idea, looking for a phenomenon, and an experiment unrecognized presenting us with this phenomenon. I think you mentioned “scoops.” I have been asked many times, “So were you chagrined at being scooped?” The answer, I think, is very clear on my part, I think on David’s… maybe on Bob Dicke’s part, too. The search for this radiation from a hot early Universe was highly speculative. No guarantee that the detector Roll and Wilkinson were building would detect anything. It was a gamble. I recognize that completely. I thought, “Well, I´ll spend a year or so looking into the implications of this experiment, whether positive or negative, and then I´ll go on to do something more solid.” In that circumstance, you will understand, that our reaction was one of excitement, not chagrin. Here is evidence of something new. This something new could be radiation from the early Universe, or it could be something quite different. But it was new, and therefore it was something to observe for Roll and Wilkinson, and for me something to analyze. Excitement.


Shouldn’t your team have shared that Nobel Prize in 1978, or at least Robert Dicke? In your Nobel lecture you said that it was right and proper that it was that way. Were you being polite?

You know, the Nobel people, I’m pretty sure, understood my annoyance at them for not recognizing Bob Dicke. I never made a secret of it. The award was to Penzias and Wilson… and Kapitza! Kapitza, a great pioneer in condensed matter physics. Very appropriate award, but what had condensed matter physics to do with cosmology? It was an artificial joining of two fields. The obvious, the obvious, choice was Penzias, Wilson, Dicke. I could just tell you an anecdote. I received the telephone call telling me about the Nobel Prize at a convenient time in Stockholm, 5 AM in New Jersey. So I answer the phone. It begins very formally. “Are you Professor Philip James Edwin Peebles?” I said: “Yes.” “We have voted to award you the Nobel Prize in physics. Do you accept?” At that point I could have been tempted to say, “But first let us discuss the omission of Bob Dicke,” but I did not. I meekly said, “I accept,” and the conversation became a lot more friendly. But I´ve also come to see that my Nobel prize is a recognition not only of what I did –I do not apologize for that, I think I did quite a lot! I know I did—, but it’s a recognition also of Bob Dicke, and it’s a recognition also of the fact that my university, Princeton, never questioned the fact that I spent all of my time on research that I think is never going to be monetizable. It is a testament to the value we place on pure curiosity-driven research about the world around us. It is something that people across the world, I think, value. And I think that Nobel Prize was a recognition of the joy of knowledge that is not in any way useful except that we know it.


You have contributed enormously to the theory of the origin and structure of the universe, that theory being of course the “Big Bang” theory… but you dislike the “bang” part…..

Yes (chuckles). You see how inappropriate the name is. To me, a bang connotes an event in space-time. A bang occurs at a place at a time. It’s not at all characteristic of my subject. The Universe as we understand it has no special place. There are galaxies everywhere that we can observe. There’s no “place” involved, there is no “time” involved, no beginning time, anyway. Instead, this is a theory of what happened as the Universe evolved from a dense, hot early state to the present conditions. We do not know with any assurance what the Universe was doing before it was expanding. There are ideas, of course, and some are attractive. But what is well-established by the standards of evidence, experiments, observations is the evolution from a dense early state to the present.

So why do I continue to use the words “big bang”? It is pure pragmatism. The name is so embedded in our consciousness that I think there is no chance of changing it. I might say there was a time when I campaigned to change the name. One problem is that I’m not good at coining new phrases, so I never came up with anything that caught people’s attention. It’s fine. No one ever said that science is logical… oh, people say it all the time, but it’s not true. It is done by people, and people are notoriously illogical.


You just mentioned that there are ideas about what the Universe was doing before, and I know that you have at some point considered the possibility of an oscillating Universe. Do you still consider that possibility?

No. My colleague Paul Steinhardt, two doors down from me in my office at the university, is looking into such ideas and it is good that he is, because we need an alternative to standard thought about what the Universe was doing before it was expanding, so-called inflation. In my opinion, inflation is given more weight than it deserves because we have precious little evidence that something like it happened, so we should treat it with caution and we should pay attention to alternative pictures, such as Paul Steinhardt’s ekpyrotic Universe.

Where were we? Oh, yes, the oscillating Universe. The idea is of great historical interest because Bob Dicke, I remember when I was a graduate student, was occasionally asking us out of the blue what we thought of this or that. And in particular, he’d often say to us, “What do you think the Universe was doing before it was expanding?” Eventually, it was his thought, maybe the Universe collapsed and then expanded –bounced—. Bob was a consumate physicist. An experimentalist, but he understood physics so very well. And he recognized that that bounce would be, in the language of thermodynamics, seriously irreversible. It would make entropy, it would fill space with radiation. He recognized that and he said, “Well, if the Universe bounced, it would be irreversible, there would be entropy, that’s radiation. Let’s look for it.” That was before knowledge of the singularity theorems of general relativity. Those singularity theorems make it rather awkward to think about a bouncing Universe. I’m not sure that that rules out the idea, but in any case the idea of a bouncing Universe was important in the sense that it got Bob Dicke thinking on those lines, and since then the idea has more or less dropped out of sight. Paul Steinhardt’s oscillating Universe isn’t really oscillating in that sense. There’s never a bounce. But ideas can return. Maybe someday we will be thinking again about a bouncing Universe, but right at the moment I’m not.


You say that you´re not so sure about inflation. You remember in 2014 there was the announcement by the BICEP2 team of having discovered the signs of gravitational waves from the time of inflation. It turned out not to be so, but would that have convinced you, had it panned out?

Yes. Perhaps not totally convinced, but it would have made a very good case. I should add that I’m not saying inflation has no evidence. It makes two really good predictions. The rapid expansion during inflation would have truly stretched out any curvature of space and removed it, so that although our Universe in the standard theory has curved space-time, sections of constant density are very close to flat, so that the usual theorems of Euclid apply. That is a strong suggestion from inflation that is successful. Inflation also provides departures from exact homogeneity through the freezing of zero-point modes of fields during inflation that are Gaussian and near scale-invariant within the definition needed. And that’s observed. So it’s promising. On the other hand, both of these ideas were with us before we had inflation, so it’s not that persuasive. I’m not arguing against inflation, I’m only saying we have to be cautious because we don’t really have a lot of evidence. And the game in physics is evidence.


What are the best pieces of evidence that convinced you that our current model of the Universe is right?

I think it’s important to understand that there is a lot of evidence that is well-established and is well-consistent. That’s very important, the consistency. I think by far the best piece of evidence is rather complicated. Let me just try to outline the basic points. The Universe was hot to begin, dense and expanding. That’s where we start. We don’t ask what happened before that. We don’t know, but we can compute forward and see whether this postulate makes any sense. The hot Universe has thermalized matter –baryons, mostly hydrogen—. The free electrons would scatter the radiation, the ions would scatter the electrons. The result would be that the baryons, matter, and radiation would act as a fluid. I may mention that the Universe is not exactly uniform, there are small departures from homogeneity that are growing. This fluid has pressure because of the radiation. That means that any departures from uniformity will oscillate as waves. That oscillation is abruptly terminated when the temperature fell to about 3,000 K. At decoupling, matter and radiation are free to go their separate ways. No more free electrons, no scattering, no fluid. Decoupling is a sharp event. It’s a boundary condition that imposes structure on the waves that were operating earlier. It’s very similar to the pipes in an organ. Different lengths set different boundary conditions for different pitches. In a very similar way this boundary condition –the separation of matter and radiation— favors particular wavelengths, particular tones in the distribution of matter and radiation. These tones, or oscillations, were predicted already in the 1970s by me and they were detected abundantly in the years around 2000. And they agreed. These oscillations in the distribution of matter and radiation are now measured –and for radiation they are measured to exquisite accuracy, just magnificent, most recently by the European Planck satellite. They’re gorgeous measurements that fit the theory wonderfully well. The modes in the distribution of matter are less well measured because matter is in clumps and that produces noise, but the modes are detected, and to me it’s deeply marvelous that the modes in the distribution of matter and the modes in the distribution of radiation –two widely different phenomena observed in widely different ways—are consistent. That’s so dramatic. But, you know, there are lots of other measurements. Helium is quite abundant. That helium was not made in stars –they’re not capable of making nearly enough helium—. The hot big bang theory predicts a high abudance of helium and a reasonably interesting abundance of the stable isotope of hydrogen, deuterium, as well as the two isotopes of helium. The theory agrees with the observations. The observations are not very precise. It is difficult to measure the abundance of helium as it is now, but it can be done and there are reasonably secure measurements. The abundance seen around us now is consistent with the abundance of helium you predict from what happened when the Universe was very young, in fact, when it’s temperature was 109 times the present temperature. Such a great difference in situation, and yet a prediction of helium abundance that agrees with what´s observed. I might add that the abundance of helium is also inferred from what happened in these waves in the distributions of radiation and matter. It matters to these modes of oscillation because helium adds to the molecular weight of the gas, so they have a measure of helium abundance and it agrees with what’s seen now and what was inferred from the excedingly early Universe. That is to me deeply, deeply important and impressive. The convergence by very different means of observing widely different phenomena. That is what we hunger for in natural science. Here is such a gorgeous example of it.


Back in the 60s there were not that many cosmologists. There was your group at Princeton, and there was also the group led by Yakov Zeldovich in the Soviet Union. Was there tension between the two groups?

I might start by telling you that Bob Dicke started working on this subject in 1957. In the Soviet Union, Zeldovich started working on this subject in the early 1960s, essentially at the same time. And what is striking is, independently. It’s an interesting phenomenon in science that people often, apparently independently, take up a given idea. Of course, it’s not independent. The times encourage the approach. In any case, this is an example of two people quite independently starting to work in similar directions. We were not aware of Zeldovich, at least I wasn’t, until the discovery of the microwave radiation, when Zeldovich wrote a very curteous note to Bob Dicke, “I congratulate you on a great discovery.” From then on, yes, much of the research in Zeldovich´s group I was doing in parallel in the USA. On my part, and I think that on theirs, the work was independent. We were not in very close communication. You might recall that the Soviet Union had an iron curtain in those days. You might also be aware that Zeldovich had made great contributions to the Soviet nuclear weapons program. That meant that he had great authority on the bureaucracy. He was a Hero Worker Medalist. I don’t remember the exact name. He was a Hero Worker and great authority, but he could not leave the country because he knew great secrets of nuclear weapons. So we had very little communication. I think this is again a case we were working in parallel on very similar subjects with very similar results because that was the obvious way to go given the times. I certainly never felt any resentment to what the people were doing in Zeldovich’s group. I have a slight hint that maybe they were a little more resentful that perhaps I had been borrowing from their work. I had tried to convince those guys… that’s not the case, it was independent. But that aside, I think we got along very well on both sides. After all, we were doing interesting, fascinating work and great to see that both sides recognized the importance of this work.

I want to skip a few questions because I think you just answered one of my later ones, which is what do you say to people who conflate dissent among scientists with untrustworthiness of science. You were talking about convergence, how amazing it is that people working independently in different countries get the same results. I think that is what you say to them…

Right. Well, in some parts the scientists are not trustworthy: I give you inflation. It’s a good idea, but… when I remark that Bob Dicke and Yakov Zeldovich independently worked on these lines I might add that Fred Hoyle in England, also quite independently, decided to work in cosmology. He with his colleagues introduced the steady state theory. Hoyle was quite a firm advocate of the steady state theory. He was very skeptical of the hot big bang. And yet he independently recognized one of the great clues to the hot big bang, namely, the high abundance of helium in stars. He recognized that this high abundance is not to be expected if helium were made in stars. Where did it come from? He in 1964 wrote an article for the journal Nature with the very provocative title “The mystery of the cosmic helium abundance.” He recognized that this helium could have come from a hot big bang. He hated the thought. But he is a good scientist, he published it. Now, what do we make of this controversy that Fred Hoyle through his life refused to accept the evidence for the hot big bang? I did not know Hoyle well, only a few conversations, but I think it was very clear in his opinion that although empirical evidence is important for the study of the formation and the origin of stars, the scales of length and time are so vast in cosmology, that in his opinion you had to rely on philosohpy. And indeed his steady state theory is philosophically elegant. People will object to that statement, but it’s true: it was an elegant theory, but not right. He refused to accept that. What do people make of it? Well, I don’t know that it ever confused the community, but it is an example of this human tendency to refuse undesirable evidence. It happens. There are lots of examples of this confusion. For example, we suffer from confusion over whether the coronavirus causes an illness called COVID-19 and whether that illness is at all serious. You wonder why people would say such a thing, you wonder why others will accept that statement even as their friends are dying. What do we make of it? I do not know. I do have one opinion only on this subject: I think that scientists by and large tend to overestimate the power of their theories. It’s difficult to underestimate them… My favorite example is the cell phone –an object I hate, to see people walking in the streets looking at it—, but you pause to consider the knowledge of physics that went into the design of that thing. The ability to make electric and magnetic fields do their bidding to move electrons and move liquid crystals. It’s just gorgeous! How could you distrust science if it could give you such a thing?

But on the other hand, I want to say although we are right to celebrate the power of science, we should more commonly recognize that all of our theories are incomplete. Name a theory…


Lambda CDM…

Lambda CDM, incomplete. Absolutely. We should admit more clearly that although our theories are powerful, they are limited and they are incomplete. That, of course, is why we have a job, why we do physics research. To make them more complete. When we boast about how good our theories are, we should always add the qualifier –but delicately, so as not to confuse people— that our theories are good but they could be better.


Will they ever be complete?

I bet they will never be complete. That is not a popular opinion. People talk of the Theory Of Everything, and my esteemed colleague Steven Weinberg has written a book, Dreams of a Final Theory. He does not like my saying that you will never know if you have the final theory because knowledge that a theory is good depends on empirical evidence, and our national and world economies cannot afford to make arbitrarily complicated tests of arbitrarily complicate theories. In short, we will never know if we have a final theory rather than the best approximation we can get away with.


And that is good because it means that physicists will never run out of work to do…

Yes. And it should help to defuse, I think, the problem of… People ask, “If you are so smart, why can’t you answer the following question,” for example, “Why can’t you tell me what this dark matter is, if you’re so smart?” It’s a very good point! It does not take away from the evidence for the LambdaCDM theory –CDM, Cold Dark Matter—, but we have to admit that our theory is limited and we can’t answer even simple questions, much less complicated ones.


To change the subject a little bit, how does life change after the Nobel Prize?

One of the people in Stockholm told me, “Your life will be changed.” I am unnerved by the fact that many people consider me a godlike figure. I am not a godlike figure, yet somehow it is thought I know all. I receive all kinds of messages in which my knowledge could be improved by so many things, how their situation could be improved if only I would give attention to this or that new idea. I used to receive these requests from people who would love to be better well-known, to push a theory that is unconventional –maybe among all these theories there are some that are interesting, but who has the time to look? But now I receive them quite regularly. Also endless requests to do interviews. This one is a pleasure, of course, but you understand, to present lectures at this or that scholarly institute around the world. I can’t handle all that. And in fact, being of a certain age, I am very reluctant to change my ways. And I dislike Zoom because I’m not sure there is anyone there. I mean, I can’t look you really in the eye. I believe you’re there, but mostly I’m not really convinced. I have spent my life lecturing to people in person, and although I am not a social person, I find that society moves me. I can make contact and detect by movement whether or not I’m connecting appreciably with this or that person in the audience. I may look with dismay at the person whose mouth is open and eyes are closed, but I will look at another person whose eyes are wide open and they’re shaking a little bit. I’m making contact. Perhaps you’re shaking now a little bit, but, well, it’s just not the same thing. So I’m besieged by requests. “So easy, Professor, it only takes you an hour, and will interest many people.” I’m impressed that I’ve talked to groups around the world, and I’m impressed that I’m making this contact, but I can’t keep it up.


This is about something you mentioned in your speech at the Nobel ceremony banquet: what would you say is the value of pure research driven only by curiosity?

Yes. I can’t put it really in tight words. I just know from experience that many people who are not scientists are glad to know that some of us are looking into these issues and they’re saying “Isn’t that fascinating.” I guess I could mention one experience. I, until moderately recently, was a Canadian citizen, an immigrant alien in the United States. It never had any impact apart from the fact that I couldn’t vote and the annoyance of entering the country and being suspicious because of course I’m not a citizen. We became naturalized citizens, but when I was an immigrant alien I would often be greeted by the customs and immigration authorities with the question “What do you do?” And if I told them, “Oh, isn’t that interesting? I have a cousin who has a telescope, and sometimes he lets me look at the stars.” Many people just like the notion of the examination of the world around us. It’s fascinating. I think surely we are built with a curiosity about what’s around us. That sounds like a very adaptively advantageous thing to do. Maybe you´ll see a tiger lurking over there, maybe you’ll see something good to eat. And the impulse surely is real now. Many people are just charmed to learn that something is being done about the exploration of the world around us for no other reason than to discover what the world around us is doing. I can only put it that way.


Can a nation build a strong science community if it excludes non-practical research?

You understand my conditioned response (chuckles). Of course not. Short term, you certainly can. If you decide to do away with all curiosity-driven research, and you focus only on engineering, you will make great strides, but you will run behind other countries that have invested in curiosity-driven research that gave them that stupid cell phone and so many other things. We consider that when I was in Stockholm, the Nobel Prize in chemistry was given for the discovery of an engineering project, lithium ion batteries, that have revolutionized our lives, but that was driven by curiosity. What is the nature of the chemistry behind this? So chemists do wonderfully useful things, they also do curiosity-driven research that can pay off. I am struck by the example of the president of Princeton University. He had me and my wife for a little dinner with the trustees of the university. I mentioned that I was grateful to the university for supporting curiosity-driven research. After all, what I’m doing is not monetizable. And the president said, “Well, consider that Albert Einstein in the 1930s wrote an article with Rosen and Podolsky on entangled systems in quantum mechanics, and consider that this theory is now being developed for quantum computers that promise to solve problems that are impractical on normal digital computers.” Now, I do not believe that my theories of the expanding Universe are going to be similarly turned into something useful, but the general idea is, well, let many people do curiosity-driven research in so many different directions that some of them hit upon something that, quite unexpectedly, is monetizable. It’s the picture we have. I imagine the United States deciding “no more curiosity-driven research; we’ll only do engineering.” I imagine China and India saying, “Well, let’s do a little curiosity-driven research” and I think the histories of the two countries in the future will be very different.


Recently you have been trying to get the history of the development of cosmology straight. Your latest book is now being translated into Spanish, could you tell us what makes Cosmology’s Century different from other books which have attempted to report the history of cosmology?

For one reason, it is my personal experience. I can tell it as accurately as can be done because I was there the whole time. Of course, I shouldn’t admit this perhaps, but I do not consider this book a popular exposition. And I regret that, but I was wanting to get the story straight so I had to be technical. I hope sections are readable, but I have to admit that this is not going to be a big seller, or if it is, it may… you know, Stephen Hawking wrote a book, A Brief History of Time, that is said to have graced many coffee tables, but not read. Mine is even more technical and will be less well read, except, of course, for a lot of students, I hope, their teachers… but also students who want to get a feeling for what´s going on in natural science. I consider cosmology a good example of how natural science is done because it is relatively simple compared, say, to quantum physics. I could tell you –maybe I shouldn´t if I want to have sales of Cosmology’s Century— I just finished another book which is meant to be close to popular. It is closely argued, but no equations, and I hope more accesible to more people. It is on the interaction of science with sociology and philosophy.


What are your current research interests?

Oh, I’m glad you asked! Perhaps I should just remind you of what has been called “the science wars.” In the late 20th century some sociologists, by no means all, took the position that physical science is a social construction, it’s made up by authority figures who impose their will on students and require students to suspend disbelief and to accept their dogma. Physicists, naturally, were incensed at this proposal. The result, I’m sorry to say, is a very serious disconnect between sociology and physical science. There is a real role for sociology of science, there’s a big role for philosophy in its connection to science, so the book is an attempt to see the commonality around science, sociology, and philosophy. The science, you will not be surprised to learn, is that of cosmology. So I attempt to interweave thinking by sociologists of what I would consider a more sensible group about the way we do science, thinking from philosophers as to what they consider to be science, and how science is really done. It has fascinated me, maybe it will interest some readers.


I can tell you that many people I know, some of whom are philosophers of science, will be interested to hear what you have to say.

We will only hope they will no be offended. Oh, very important. I have been in contact with quite a few sociologists and philosophers. They’re polite, so I’m not too nervous.



martes, 16 de marzo de 2021

Libros al acecho

  Escribí este texto para la revista de libros y cultura Leer y leer en 2008. Si hablo de lo que leía yo, no es pura impudicia: fue el encargo. Lo basé en algo que escribí para leerlo en la presentación de las Bibliotecas de Aula en 2004 en la FIL.

Desplegar las velas

Los barcos de antes para moverse desplegaban velas más amplias cuanta más fuerza necesitaran recoger del viento para desplazarse. Una partícula a la que se acribilla de energía en un experimento físico tiene más o menos probabilidades de captar esa energía según sean sus propiedades –su masa, su carga, su tamaño. Los físicos llamamos sección de dispersión a esa capacidad de captar. Ahora bien, captar –pero no energía, sino información y significados— es lo que tiene que hacer una persona para desempeñarse mejor en la vida y disfrutarla más. El propósito de la educación debería ser aumentarles la sección de dispersión a los alumnos, dotarlos del más amplio velamen para que puedan captar el mundo en toda su asombrosa riqueza y complejidad.

            Se ha dicho, aunque con otras palabras, que ésa es la función de los libros. Hoy en día ya no basta la información que puede extraer el individuo de su propia experiencia. Por suerte existen los libros, que nos liberan de ser sólo nosotros mismos porque nos dejan aprovechar la experiencia de otros. El efecto de los libros es aumentarnos la sección de dispersión: un buen lector puede viajar, aprender y conocer a mucha gente —captar más cosas a su paso por el mundo— sin levantarse de la silla. El libro es experiencia concentrada.

            Ésa es una forma de ver los libros. Otra es considerarlos azadones que van abriendo surcos y echando semillas, preparando el terreno de la mente del lector para fructificaciones y abundancias futuras. También se les puede ver como aparatos de ortodoncia cerebral que van abriendo espacio en la mente.


El entendedor (casi) independiente

¿Qué lee un científico en ciernes? No conozco la historia lectora de ninguna persona importante en la ciencia, pero la mía es más o menos típica (por lo menos entre mis amigos científicos y divulgadores), por lo que me permitiré la impudicia de contarles una parte. Le debo a un libro mi primera experiencia del placer de entender (y mi primer dolor de cabeza por esfuerzo mental). Era un libro que saqué de la biblioteca de mi escuela. No recuerdo ni el título ni el nombre el autor (tenía nueve años), pero sí que era un libro pequeño, de unos 10 por 15 centímetros, y que explicaba cómo funciona el motor de un coche. Nunca se me había ocurrido preguntárselo a mi papá, y quizá él no hubiera podido explicármelo muy bien. Ni siquiera se me había ocurrido que aquello podía estar a mi alcance. Me llevé el libro a mi casa, me senté en mi sillón preferido y me enfrasqué en la lectura reveladora.

            Para las ocho de la noche, hora en que había que estar en la cama sin remedio, ya había entendido yo que la potencia del motor se gestaba en cuatro tiempos, durante los cuales le ocurrían cosas complicadas a la gasolina: primero entraba en los cilindros como nebulizaciones mediadas por el carburador, luego se comprimía, luego el distribuidor hacía soltar una descarga eléctrica a la bujía correspondiente. Con esto, la mezcla de gasolina y aire explotaba, obligando al pistón a bajar, lo que transmitía la fuerza de la explosión al cigüeñal, que a su vez  la transmitía a las ruedas. Pasado el momento culminante de la explosión —que era como el do de pecho de un motor de combustión interna— el pistón subía (mientras otro de sus compañeros  explotaba: ése era el secreto de la continuidad del movimiento), con lo cual expulsaba los gases sobrantes de la combustión y quedaba listo para empezar otra vez, todo en cuestión de fracciones de segundo. ¡Ajá!

            Esa noche me fui a la cama muy satisfecho de saber que nada podía ser tan complicado que me rebasara, y que para entenderlo no me hacía falta que mis adultos lo supieran: bastaba con que hubiera un libro.

            El proceso se repitió con el libro Nuestro amigo el átomo, de Heinz Haber, ilustrado por Walt Disney (o sus animadores). Recuerdo especialmente la ingeniosa metáfora que me ayudó a entender lo que era una reacción en cadena, fenómeno sin el cual no se podría extraer energía del átomo ni para bien ni para mal. En una página del libro se veía un lugar sembrado de ratoneras. Cada ratonera tenía encima una pelota de ping pong que salía volando al dispararse el aparato. Había que imaginarse qué pasaría si uno lanzara otra pelota entre las ratoneras cargadas. La pelota caía en una ratonera y la disparaba, con lo que salían volando dos pelotas, las cuales iban a dar a sendas ratoneras. Éstas saltaban. Ya había cuatro pelotas en el aire. Las cuatro pelotas se convertían en ocho y éstas en 16, y así sucesivamente. Al rato el recinto era una pesadilla de ratoneras desbocadas y pelotas enloquecidas. Eso es, más o menos, lo que sucede en un pedazo de uranio al que se bombardea con neutrones. Los neutrones son la primera pelota de ping pong, las ratoneras son los átomos de uranio y su carga de pelotas son los neutrones y protones de sus núcleos. El disparo de la ratonera es la desintegración radiactiva de un átomo de uranio. La cosa estaba clarísima. “Reacción en cadena” pasó de inmediato a formar parte de mi léxico y de mi universo imaginario. ¡Cuántas veces habría de evocar la imagen de las ratoneras de pesadilla cuando me explicaron con más detalle en qué consistía una reacción nuclear años más tarde, en clase de física en preparatoria y luego en la universidad! Todavía me parece una metáfora luminosa.


Verano y asombro

Un día, cuando yo tenía 12 años, mi mamá llegó del súper con libros, como hacía de vez en cuando. Uno de esos libros era El reto de las estrellas, de Patrick Moore y David A. Hardy, un libro grande de pastas duras negras con el título en letras futuristas y cautivadoras ilustraciones de astronautas del futuro dando saltos de gigante en el terreno accidentado de un asteroide. El libro todavía tiene pegada en la contraportada una etiqueta verde que dice “Oferta 29.90”. Por menos de 30 pesos me enteré de que se estaba construyendo una nave reutilizable llamada “transbordador espacial” (cuando leí el libro el transbordador ya estaba casi listo), que había planes para estaciones espaciales, bases en la luna, naves que aterrizarían en Marte y sondas para explorar Titán, la luna más grande del sistema solar. En la página 16 había una ilustración de la superficie de Marte con un promontorio de roca en medio de un paraje desértico, todo iluminado por un lejanísimo sol verde en un cielo entintado. El sol de esa ilustración resaltaba tanto que no se podía leer esa página sin tenerlo presente continuamente, como si brillara con luz propia como el sol de verdad.

            Ese mismo verano las naves Viking aterrizaron en el planeta rojo y tomaron fotografías del entorno. El suelo marciano resultó ser más rojizo y el cielo más luminoso que en las ilustraciones hipotéticas de El reto de las estrellas. Comparar las ilustraciones del libro con las fotografías reales fue muy formativo para mí: los científicos podían equivocarse y no por ello quedaban en ridículo. Mucho después aprendí que equivocarse es parte fundamental de la vida de un científico.

            Algunas de las maravillas que prometía el libro se realizaron durante mi adolescencia y temprana juventud, y sigo esperando las que no. El reto de las estrellas me proporcionó mi primera visión panorámica de nuestro lugar en el universo y la voluntad de exploración de la especie humana. Por si fuera poco, los autores generosamente añadían al final unos capítulos más especulativos —menos científicos, quizá, pero más evocadores— sobre las exploraciones del futuro más remoto. Tal vez llegará el día en que, no contentos con explorar nuestro rinconcito de espacio, nos lancemos a otras estrellas (aunque para eso, no lo omitía el libro, faltaba muchísimo tiempo por las distancias inenarrables a las que se encuentran las estrellas). El reto de las estrellas me llenó el verano de asombro.


Las estrellas se mueven

No era mi primer libro sobre el espacio y la astronomía. En 1972, en la feria del libro de mi escuela, me compré el libro Fun With Astronomy, de Mae e Ira Freeman. Me costó mucho trabajo leerlo porque estaba en inglés y a mis ocho años no se podía esperar que fuera yo muy ducho en lenguas extranjeras. Con todo, algo colegí de mi lectura de Fun With Astronomy. Recuerdo de manera especialmente vívida la frase “Mantén fija la vista para ver moverse las estrellas”, que estaba impresa junto a la fotografía de un niño en una silla plegable de madera que mira un cielo salpicado de estrellas desde el pórtico de su casa en el campo. ¿Las estrellas se mueven? Ésa sí que era una novedad. Decidí comprobarlo. A falta de pórtico en el campo, puse mi silla frente al ventanal de la sala-comedor de nuestro departamento en la Colonia Cuauhtémoc, que daba a nuestro estacionamiento y los traspatios de todos los edificios vecinos. Encima de este paisaje urbano se veía una buena parcela de cielo. ¿Con que las estrellas se mueven? Eso lo vamos a ver. Me senté. Mantuve fija la cabeza. Esperé como si quisiera ver moverse la manecilla horaria de mi reloj (adquisición reciente, como el libro).

            ¡Se movían! Y aquello no era más que el reflejo de la famosa rotación de la Tierra, fenómeno tan cacareado por las maestras de la escuela pese a ser difícil de creer. Pues bien, ahí estaba la prueba ante mis ojos, gracias —no a la escuela, sino a un libro.

            El brevísimo capítulo sobre los cometas (no más de un párrafo) tenía a pie de página una foto que decía: “El cometa Halley, que nos visitará otra vez en 1986”. Faltaba muchísimo tiempo, pero yo me puse a esperar. Un libro también puede enseñar a tener paciencia.



Los libros de divulgación científica eran sólo una parte de mi vida de lector. El primer libro que leí fue Príncipe y mendigo, de Mark Twain. Tenía siete años e iba en primero de primaria cuando mi mamá decidió que ya estaba grandecito para poder leer en la cama solo. Me puso el libro en las manos (el ejemplar había sido suyo cuando era niña) y me dijo: “lees un ratito y cuando te canses, marcas dónde te quedaste y metes el libro debajo del colchón para seguir mañana”. Esa costumbre me ha durado hasta hoy.

            Príncipe y mendigo fue el primer Everest literario que coroné. Al terminarlo me sentí orgulloso como el alpinista que llega a la cima, pero al mismo tiempo melancólico. Esa noche descubrí la tristeza de tener que abandonar a unos personajes con los que me había encariñado. Era como separarse de un amigo de carne y hueso. Todo buen lector conoce esa tristeza. Más tarde, con otros libros, el dolor de la separación fue tan insoportable, que en ese momento volví a empezar el libro. Así me pasó con El señor de las moscas, de William Golding, pocos días antes de cumplir 13 años. De hecho, la historia de los niños ingleses que fundan en una isla una sociedad tan defectuosa y destinada al fracaso como la de sus padres me embelesó tanto, que leí el libro cuatro veces entre el martes y el jueves de esa semana: leía en la cama, en el coche de camino a la escuela y de regreso, en clase, en recreo y por la tarde después de comer. Fue una experiencia muy intensa, aunque quizá no tan vívida como la de leer Mila 18, de León Uris, por la misma época.

            Con ese libro sobre la vida de la resistencia judía en el gueto de Varsovia durante la ocupación alemana en la Segunda Guerra Mundial sentí como nunca lo que es entrar en una historia. Durante la lectura se me olvidaba que estaba leyendo y me creía niño judío en el gueto de Varsovia. Un día, estaba yo oculto en un sótano a punto de morir de hambre y de frío, enfermo y sin saber dónde estaban mis padres, muerto de miedo porque arriba los alemanes estaban haciendo una inspección, cuando se me ocurrió cerrar el libro. El sótano desapareció, los alemanes se esfumaron. No me encontraba en Varsovia en invierno, sino en Cuernavaca en primavera, y todo era luz y alegría de vivir. Bueno, no todo. Tan absorto había estado yo en mi lectura, metido en una llanta de flotación en medio de una alberca, que el sol me achicharró y al poco rato no podía yo ni enderezar las rodillas del ardor. No había pomada que  me lo calmara. Llegada la noche por fin me consiguieron una crema maravillosa que me alivió el dolor y me curó a toda velocidad la piel semifrita. Al día siguiente me desprendía de las piernas sábanas de piel muerta y transparente con descuido… mientras seguía leyendo Mila 18. Ese libro estuvo a punto de matarme.

La emboscada de los libros

“Somos lo que leemos”, iba yo a decir, pero para ser franco, no sé si es verdad. O más bien, no sé si esa afirmación es verdad en el sentido de que nuestras lecturas nos determinen, pero creo que sí es verdad que lo que elegimos para leer dice mucho acerca de nosotros. Quizá haya una influencia mutua entre lo que por accidente nos cae entre las manos y nuestros gustos como lectores, y en ese caso tal vez valga la pena no desoír las recomendaciones del escritor francés Daniel Pennac.

            En su libro Como una novela, Pennac aboga por una lectura ajena a todo fin utilitario, especialmente entre los aprendices de lector. Que la lectura no sea una obligación. La lectura como castigo —o como manda— resulta contraproducente. Usted como buen lector, ¿no deja libros a medias? ¿No se cansa de leer por temporadas? Daniel Pennac enumera los diez derechos del lector, que se han de observar para que la literatura no se convierta en instrumento de tortura. He aquí algunos de los derechos del lector según Pennac: el derecho de no leer, el derecho de saltarse páginas, el derecho de dejar un libro a medias. Los buenos lectores que conozco ejercen estos derechos por lo menos ocasionalmente. ¿Por qué no concedérselos a los estudiantes?

            Eso sí: hay que tener libros por todas partes, libros al acecho del niño o el adolescente desprevenido que pueda un día abrirlos por descuido y quedar enganchado para siempre. ¿Qué tipo de libros? De todo: novelas, cuentos, divulgación científica (¡no olvidar la divulgación científica!). Se trata de dotar a nuestros estudiantes del más amplio velamen, de ofrecerles un menú variado. Si es necesario, como dice Pennac, incluso se les puede leer en voz alta. Todo con tal de aumentar su sección de dispersión, que no es más que la posibilidad de cosechar de la vida más experiencias y más sensaciones.