Praxis Archives – Page 112 of 181

Roy Glauber casts a light on particles

CCint1_09_09 — Roy Glauber talks of his work at a CERN colloquium on 6 August.

When Roy Glauber was a 12-year-old schoolboy he discovered the beauty of making optical instruments, from polarizers to telescopes. His mathematical skills stem from those early school days, when a teacher encouraged him to begin studying calculus on his own. When he progressed to Harvard in 1941 he was already a couple of years ahead and had absorbed a fair fraction of graduate-level studies by 1943, when he was recruited into the Manhattan Project at the age of 18. It was then that the erstwhile experimentalist began the transition to theoretician. Finding the experimental work rather less demanding than theory – “It seemed to depend on how to keep a good vacuum in a counter,” he recalls, “and I didn’t think I would do it any better” – he asked to join the Theory Division and was set to work on solving neutron-diffusion problems.

Following the war, Glauber gained his BSc and PhD from Harvard and after apprenticeships with Robert Oppenheimer in Princeton and Wolfgang Pauli in Zurich, he stood in for Richard Feynman for a year at Caltech and then settled back at Harvard in 1952. By this time, he says, “all of the interest was in nuclear physics studied through scattering experiments”. With increasing energies becoming available at particle accelerators, the wavelength associated with the incident particles was decreasing to nuclear dimensions and below. Viki Weisskopf and colleagues had already developed the cloudy crystal-ball model of the nucleus, which successfully described averaged neutron cross-sections, and Glauber believed that the idea could be extended. “I had this conviction that it ought to be possible to represent the nucleus as a semi-translucent ball, from 20 MeV up,” he recalls. However, what the optical models lacked, in Glauber’s view, “was a proper quantitative derivation based on the scattering parameters of individual nucleons”.

Inspired by work on electron diffraction by molecules that he had pursued at Caltech, Glauber began to think about how to apply optical Fraunhofer-diffraction theory to higher-energy nuclear collisions – in a sense, bringing about a fusion of two of his interests. At higher energies, he argued, individual collisions could be treated diffractively and allow nuclear calculations to be based on the familiar ground of optical-diffraction theory.

The result was a generalized nuclear diffraction theory, in which he introduced charges and internal co-ordinates that did not exist in the optical case, such as spin and isospin, and dealt with scattering from nuclei that contained many nucleons by treating arbitrary numbers of successive collisions. The key was to consider energy transfers that were small compared with the incident energy. This was a reasonable assumption at higher energies and it led to a useful approximation method that provided a mathematical development of the original optical model, and allowed treatment of the preponderance of inelastic transitions.

CCint2_09_09 — Roy Glauber, right, with companion Atholie Rosett, centre, and CERN’s director-general, Rolf Heuer.

The theory turned out to work quite well for proton–deuteron and proton–helium collisions in experiments at the Cosmotron at Brookhaven. “You could see single and double scattering in the deuteron and helium,” he explains, “and shadowing” – where target nucleons lie in the shadow of others. However, at the time there were no studies of heavier nuclei.

Glauber made the first of many visits to CERN in 1964 and arrived for a six-month sabbatical in February 1967. “It was a most dramatic time for me,” he recalls. The group led by Giuseppe Cocconi had begun measurements of proton scattering from nuclear targets using the first extracted-proton beam from the PS. They made a series of measurements at 19.3 GeV/c but with the resolution of the spectrometer limited to 50 MeV, they could not separate elastic from inelastic scattering. Glauber realized that, extended to inelastic scattering, the theory would cover essentially all nuclear excitations in which there was no production of new particles. Together, the calculated elastic and inelastic cross-sections agreed exactly with what Cocconi’s group was measuring. Glauber presented the results of his work with Giorgio Matthiae of Cocconi’s group at a meeting in Rehovot in the spring of 1967. “We were doing quantitative high-energy physics for a change,” he says.

The work at CERN with Cocconi’s group left a big impression on Glauber: “It was something wonderful and inspiring.” He became “hooked on CERN”, returning many times for summers and sabbaticals, working on models for elastic scattering for experiments at the ISR and for UA4 on the SPS proton–antiproton collider. However, by the 1990s – the era of the Large Electron–Positron (LEP) collider – his visits became less frequent. “I found I had nothing new to say about LEP cross-sections,” he admits.

Today there is renewed interest in Glauber’s work, in particular among physicists involved with heavy-ion collisions. His early calculations of multiple diffraction laid the foundations for ideas that are central (in more ways than one) to studies in which nuclei collide at very high energies. The basic formalism of overlapping nucleons can be used to calculate the “centrality” of a collision – in other words, how head-on it is. However, other work in the field of optical theory also finds relevance in the unusual environment of heavy-ion collisions – in this case Glauber’s work on a quantum theory of optical coherence, which led to his share of the Nobel prize in 2005.

This work again dates back to the late 1950s and the discovery by Robert Hanbury-Brown and Richard Twiss of correlations in the intensities measured by two separated photon detectors observing the same light source. Their ultimate aim had been to extend their pioneering work on intensity interferometry at radio wavelengths to the optical region, so as to measure the angular sizes of stars – which they went on to do for Sirius and others. However, they first set up an experiment in the laboratory to reassure themselves that the technique would work at optical wavelengths. The result was surprising: light quanta have a significant tendency to arrive in pairs, with a coincidence rate that approaches twice that of the random background level. Extending the idea led to predictions that a laser source, with its narrow bandwidth, should show a large correlation effect. Glauber was sceptical, so he embarked on a proper quantum-theoretical treatment of the statistics of photon detection.

“Correlated pairs are characteristic of unco-ordinated chaotic emission from lots of sources,” he explains, “where the statistics are Gaussian. This is not a characteristic of light from a laser where all of the atoms know quite well what the other atoms are doing.” He realized correctly that this co-ordination means that there should be no Hanbury-Brown–Twiss correlation for a laser source and he went on to lay down the theoretical ground work for the field of quantum optics – the work that led to the Nobel prize.

There are similarities between the statistics in the detection of photons (bosons) and those of the detection of pions (also bosons) in heavy-ion collisions. The energetic collision should be like a thermal light source, with correlated pion emission akin to the Hanbury-Brown–Twiss correlations allowing the possibility of measuring the size of the source, as in the astronomical studies. Experiments do find such an effect but they do not see the full factor of two above the random background and the reason is yet to be properly understood. While the width of the measured peak may relate to the radius of the source, “we don’t have a theory of the radiation process that explains fully the correlation”, says Glauber, “no real quantitative explanation. Perhaps other things are upsetting the correlations.”

The LHC will explore further the realm of heavy-ion collisions and push on with measurements of the proton–proton total cross-section, a focus of the TOTEM experiment. While these links remain between his work and CERN, Glauber observes that the laboratory has changed a great deal since his first visits, but he is still “very devoted to the place as an ideal”. What then, does he hope in general for the LHC? “Pray to find a surprise,” he says. “It may be difficult to design an experiment to detect what you least expect, but we really need some surprises.”

• For Roy Glauber’s colloquium at CERN on 6 August, see http://indico.cern.ch/conferenceDisplay.py?confId=62811.

LEP – The Lord of the Collider Rings at CERN, 1980–2000: The Making, Operation and Legacy of the World’s Largest Scientific Instrument

By Herwig Schopper, Springer. Hardback ISBN 9783540893004 €39.95 (£36.99, $59.95). Online version ISBN 9783540893011.

Herwig Schopper’s energy and vitality remain undimmed, even though he turned 85 this year (CERN honours Schopper at 85). His book surveys the two decades of the Large Electron–Positron (LEP) collider, extending far beyond his own reign as CERN director-general in the years 1981–88.

From the outset, Schopper criticizes historians who have spurned his offer of first-hand but anecdotal input, preferring conventional archives and minutes. He contends that such lack of imagination can obscure the full picture. Thus the book is at its best when he relates how CERN’s history was moulded rather than recorded. Nobody was taking minutes when Schopper had working breakfasts with influential council delegates. Another example is his nomination as CERN’s director-general, where Italy was initially pushing for its own candidate. The sequel came later, when he carefully stage-managed an extension to his mandate to oversee the construction of LEP through to completion.

Fierce debate centred on the parameters of LEP: its circumference, tunnel diameter, precise footprint and the energy of its beams. Overseeing LEP called for a high level of scientific statesmanship. It was the largest civil-engineering project in Europe prior to the Channel Tunnel. As well as the technical challenge of building such a large underground ring at CERN, close to the Jura mountains, there was the diplomatic and demographic challenge of doing so beneath an international border, running close to and under suburbs and villages.

Closer to home was the thorny problem of catering for the physicists clamouring to use the new machine. How many detectors would be needed? Who would build and operate them? Who would lead the teams? With so much at stake, and so much enthusiasm, there was a lot of pushing and shoving to scramble aboard.

Schopper inherited the proton–antiproton collider in CERN’s Super Proton Synchrotron ring and while LEP was being planned and built he presided over the laboratory during the historic discovery of the W and Z particles – the carriers of the electroweak force. He recalls how this fast-moving research called for some skilful moves. In the middle of all this, the UK’s prime minister Margaret Thatcher dropped in, accompanied by her husband – “an elder (sic) gentleman whom she treated with astonishing kindness,” writes Schopper.

Experience had shown that LEP had to be presented from the outside as an integral part of CERN’s basic programme. However, this meant that no new money would be available. CERN’s research activities had to be pruned, a decision that did not go down well everywhere. Equally controversial were some deft moves on CERN’s balance sheets, transferring money between columns earmarked for operations and investments.

While planning and construction of the machine was hectic, it was usually predictable, but in the middle of it all, CERN was caught unawares when the UK, one of its major contributors, suddenly menaced to pull out completely. To counter the threat, CERN had to undergo painful invasive examination by an external committee. Its final recommendations were difficult to swallow but left CERN leaner and sharper. Schopper’s inside account of this period is most revealing.

Probably the biggest LEP controversy came right at the end. With its beam energy boosted to the limit in 2000, LEP was beginning to show tantalizing hints of the long-awaited Higgs particle. But the CERN juggernaut is irresistible. Before it had completed its act, LEP was kicked off the stage by the LHC proton collider for which the tunnel had been presciently designed right from the start. Schopper describes the resulting criticism and points out that it would indeed be ironic if the LHC found the Higgs inside the energy range that was still being explored by LEP.

Making decisions is not easy: long-term advantages can demand short-term sacrifices. Political popularity is another luxury, but highly visible VIP visits do seem to boost an organization’s self-esteem. Most titillating is when Schopper puts LEP aside and reveals what went on behind the scenes to get the Pope, the Dalai Lama and other VIPs to visit CERN. The initial machinations and detailed planning for the visits of French presidents and prime ministers had to be abandoned when their last-minute changes called for frantic improvisation.

The cumbersomely titled The Lord of the Collider Rings is a valuable addition to particle-physics literature but it is mainly written for insiders. The names of people, machines and physics measurements tumble onto the page with little introduction. Schopper acknowledges that some of the illustrations are not optimal. This makes the book look as though it were hastily assembled and gives the CERN reader a sense of déjà vu, which is underlined by a statutory presentation of the Standard Model.

There are a few minor errors. Schopper naturally prefers the Germanic Wilhelm von Ockham to William of Occam, of eponymous razor fame, who was English (but died in Bavaria). Physics World is published by the UK Institute of Physics, not the “British Physical Society”. Furthermore, there is little mention of the Stanford Linear Collider, which briefly trod on LEP’s toes in 1989.

Schopper’s anecdotes and insider views are certainly better entertainment – and possibly more incisive – than a dry formal history. After his LEP revelations, one now looks forward to what his successors at CERN will say about the groundwork for the LHC (historians, please take note).

The Large Hadron Collider: a Marvel of Technology

by Lyndon Evans (ed), EPFL Press. Paperback ISBN 97829400222346, €45 (SFr69).

Edited by Lyn Evans, the LHC project leader, this book outlines in a well balanced manner the history, physics and technologies behind the most gigantic scientific experiment at CERN: the LHC accelerator and its detectors. The book describes the highlights of the LHC’s construction and the technologies developed and used for both the accelerator and the experiments. The 16 chapters are all written by leaders of activities within the LHC project. The timing is perfect because the book is on the shelf just in time for the anticipated start of LHC-physics data-taking.

There are thousands of people at CERN – from universities and collaborating institutions around the globe – who have accompanied the LHC project over the past two decades or joined during the construction phase. In this book they will find a superb record and detailed account of their own activities and the many aspects and challenges that their colleagues involved in the LHC construction had to face and solve. It features excellent photos that illustrate many of the ingenious technological inventions and show the detailed LHC infrastructure, components and experimental equipment installed both in the tunnel and above ground.

The interested readers will learn about the scientific questions and theory behind the LHC. The book presents in detail the scale, complexity and challenges inherent in the realization of this wonder of technology. Readers will gain an insight into the managerial and organizational aspects of long-term planning in present-day, large-scale science projects. They will learn much about superconductivity and superconducting magnets; industrial-scale cryogenic plants and cryogenics; ultra-high vacuum techniques; beam physics, injection, acceleration and dumping; as well as environmental protection and security aspects around the LHC. They will also read about the complex political processes behind the approval, funding, purchasing and construction of these enormous scientific experiments.

Colleagues involved in new, large-scale scientific projects in Europe – e.g. ITER, XFEL, FAIR, ESS – are well advised to benefit for their respective projects by reading this book. Many unforeseen problems faced during project execution, which required unconventional flexible measures to be adopted, are openly presented and discussed, with mention of the lessons to be learnt.

A significant part of the book is devoted to the description of the four major LHC experiments by their respective spokespersons and to the LHC data analysis and the Grid. The introduction is written by T S Virdee and provides a good overview of particle-detection basics, detector developments and challenges at the LHC. This section of the book is dedicated not only to the thousands of scientists, engineers and technicians involved in preparing LHC detectors worldwide but also – an interesting idea – to the agencies that funded the LHC detectors to a large extent.

In summary, this book comes at the right time and should be on the shelf of all friends of the LHC because it represents a nicely balanced record of the historical developments, technical challenges and scientific background. It is packed with many, many photos of the LHC taken during construction and assembly.

The Quantum Frontier: The Large Hadron Collider

by Don Lincoln, foreword by Leon Lederman, Johns Hopkins University Press. Hardback ISBN 9780801891441, $25.

As I write this review, in less than one week’s time I will be starting the second year of my physics-undergraduate degree at McGill University, Montreal. During the past summer I was granted the chance to spend time at CERN, an aspiration for every young physicist. Working as a student journalist for the CERN Bulletin, I was able to get away with asking enough questions to drive everyone mad and learnt a great deal about the various experiments currently (and previously) being conducted at CERN, in particular at the LHC. However, even after two months of constant probing, the LHC still held many more secrets and fantastic intricacies that I sought to understand.

It was only during my final weeks that the answers to these questions were found, by reading The Quantum Frontier. Don Lincoln’s playful, energetic style took me from the fundamentals of contemporary physics through to the extremely complex and sophisticated guts of the LHC experiments, touching on everything from the Earth’s “inevitable” destruction by black holes to speculated future physics experiments in a post-LHC era.

Cracking it open for the first time, I was worried that a book taking under 200 pages to cover such an ambitious topic would be riddled with sterile facts listed one after the other. But the contrary is what I found. Lincoln starts by addressing the obvious misconception that is in the watching world’s mind: will the LHC destroy the planet and all of us with it? Tackling this issue first with an overview of basic material often covered in high-school science classes (the components of the atom, etc.), Lincoln goes on to peer deeper and deeper into the world of particle physics, laying out the basic building blocks of matter and what the LHC hopes to discover.

As a student of the subject, I found that some of the material was familiar, while a great deal of the new ideas and theories were elegantly explained. Lincoln kept me happily engaged with poignant and often funny analogies that facilitated the explanations and catered for a concise understanding. Like any scientifically relevant book, it uses diagrams and graphs to elaborate ideas, but their inclusion is not daunting.

Being a particle physicist himself, Lincoln gives us a chance to see the world from such a perspective and conveys the excitement and awe that is experienced working in this field.

DOE allocates Fermilab an additional $60.2 million

In the latest instalment of funding from the US Department of Energy’s (DOE) Office of Science under the American Recovery and Reinvestment Act, Fermilab is to receive an additional $60.2 million to support research towards next-generation particle accelerators and preliminary designs for a future neutrino experiment.

The new funds are part of more than $327 million announced by Energy Secretary Steven Chu on 4 August from funding allocated under the Recovery Act to DOE’s Office of Science. Of these funds, $220 million will go towards projects at DOE national laboratories. While many of the physics-related projects are associated with fusion research or light sources, Fermilab and the Brookhaven National Laboratory have both received support for activities in high-energy physics.

Taking the stimulus funds announced earlier this year into account, the Recovery Act is allocating more than $100 million to Fermilab. Out of the additional $60.2 million announced in August, the laboratory will devote $52.7 million to research on next-generation accelerators using superconducting RF technology. The remaining $7.5 million will go to fund a preliminary design for a future neutrino experiment, in collaboration with Brookhaven, which has received $6.5 million for neutrino research in addition to $3 million for improvements to its light source.

Life in physics and the crucial sense of wonder

Inspiration: Gilberto Bernardini, expressive and enthusiastic as ever.

As a grad student at Columbia around 1950, I had the rare opportunity of meeting Albert Einstein. We were instructed to sit on a bench that would intersect Einstein’s path to lunch at his Princeton home. A fellow student and I sprang up when Einstein came by, accompanied by his assistant who asked if he would like to meet some students.

“Yah,” the professor said and addressed my colleague, “Vot are you studying?”

“I’m doing a thesis on quantum theory.”

“Ach!” said Einstein, “A vaste of time!” He turned to me: “And vot are you doing?”

I was more confident: “I’m studying experimentally the properties of pions.”

“Pions, pions! Ach, vee don’t understand de electron! Vy bother mit pions? Vell, good luck boys!”

So, in less than 30 seconds, the Great Physicist had demolished two of the brightest – and best-looking – young physics students. But we were on cloud nine. We had met the greatest scientist who ever lived!

Some years before this memorable event, I had recently been discharged from the US army, having been drafted three years earlier to help General Eisenhower with a problem he had in Europe. It was called World War II. Our troop ship docked at the Battery and, having had a successful poker-driven ocean crossing, I taxied to Columbia University and registered as a physics grad student for the fall semester.

I was filled with enthusiasm to resume my study of physics but also exhausted by three years of mostly mindless military service. Things quickly degenerated towards disaster. I had indeed forgotten simple equations, how to study and, most crucially, forgotten the joy that I had found in my college physics classes. Full-time, intense study did not seem to help. I failed the crucial qualifying exam, twice. I was ready to quit.

I had been assigned a lab on the 10th floor of the Pupin Physics Building where I had been given the job of making a cloud chamber work. This was a 12-inch cylinder of glass and plastic filled with N₂ alcohol vapour. This device can render the path of a nuclear particle visible since the “wake” of the intruder particle produces a trail of disturbed atoms. This encourages alcohol vapour to coalesce from vapour to drops of liquid. A flash photograph then captures a record of the nuclear particle – much like the vapour trail of a jet airliner. But as much as I tried, my cloud chamber produced no tracks, only a cloud of white smoke. This failure, added to the failed tests and joyless lectures, brought me misery and to the point of quitting. I decided to take the PhD qualifying test once more and took two weeks to study.

After the test (I felt only slightly better), I returned to the lab to find a janitor mopping the wire-strewn floor and singing an Italian operatic tune. As I entered, the guy shouted something in Italian and offered a handshake.

I said, “Okay, but be careful. The wires are carrying a high current and your wet mop may produce a short circuit.” He stared cluelessly and, in total disgust, I walked out in the hall to wait for the guy to leave.

In the hall, there was the department chairman. “We have a new, dumb janitor, huh?” I said.

“New? No, wait! You mean the guy in your lab?”

“Yeah.”

“That’s no janitor, dummy, that’s Professor Gilberto Bernardini, a world-famous Italian cosmic-ray expert whom I invited to spend a year here to help you in your research.”

“Oh, my God!” I gasped and rushed in to repair my damage.

Over time, Bernardini and I learnt how to communicate and I began to watch Gilberto. There was his habit of entering a dark room, pushing the light switch: light. Pushing it again: off. On, off five or six times. Each time there would be a loud “fantastico!” Why? He seemed to have this remarkable sense of wonder about simple things.

Then the cloud chamber.

Gilberto: “Wat’s dat wire in de middle?”

Leon: “That’s carrying the radioactive source.”

Gilberto: “Tayk id oud.”

Leon: “It makes tracks.”

Gilberto: “Tayk id oud.”

After a few minutes, tracks appeared. My source had been far too radioactive for the chamber! Now we had a success.

But this was only the beginning of my learning from Bernardini. Next, we constructed a kind of Geiger counter. We machined, soldered, polished, flushed with clean argon gas and watched the oscilloscope. Soon we had tracks.

Bernardini went nuts. “Izza counting!” he screamed. Half of my height and weight, he lifted me and danced me round the lab to the music of Bernardini’s sense of wonder. He explained: “Dese particles, cosmic ray, come from billions of miles away to say buonjourno to us on de tenth floor of Pupin Physics Building. Izza beautiful! So little particle, so long da trip.”

So, through Bernardini, I began to recover my love of physics, of searching for simplicity and elegance of how the world works. I recovered academically and eventually graduated to a professorship.

Fantastico! Lederman received the 1988 Nobel prize in physics, together with Jack Steinberger and Melvin Schwartz, for the experiment at Brookhaven that demonstrated the existence of two different neutrinos, associated with the electron and the muon. The long track here reveals a muon created by an incident neutrino.
Image credit: BNL.

Gilberto warned me about what happened next. Some years into my Columbia career, I was on the night shift of an experiment. It was 3 a.m.; I had checked that all the apparatus was working when one computer began to beep out of tune. I tuned it to scan the data and – there it was, the most spectacularly beautiful track I had ever seen. What I was seeing was a muon entering from a thin metal plate and passing through 10 more plates. A muon! The only explanation was that a neutrino had generated this track – a muon neutrino! Its implications dawned on me – two neutrinos – this would change how we taught physics; this would make headlines from Scotland to Argentina… My palms were wet, my breathing became difficult. I tested everything, but only confirmed the discovery. At 4 a.m. I telephoned Gilberto, who was then visiting in Illinois. His wonderful “fantastico!” had been Americanized and when I told him what we had found, out came “Holy shit!”

Gilberto knew everybody. Fermi, Amaldi, Bohr, Schrödinger, … Einstein. At a meeting (after receiving my PhD), we heard Einstein describe relativity: “scarcely anyone who truly understands this theory can escape its magic.”

As Keats said: “Truth is Beauty and Beauty Truth. That is all ye know of Earth.” And Plato: “The soul is awestruck and shudders at the sight of the beautiful.”

Some years later, Gilberto and my wife, Ellen, were in Sweden to help me receive the Nobel prize. Gilberto’s “fantastico!” was ubiquitous. And I said to Ellen, “Did you ever in your wildest dreams imagine that we would be in Sweden dining with the king and queen?” Ellen, as ever sceptical, said, “You were never in my wildest dreams!”

Science has always been and will continue to be a mixture of 96% frustration and (if lucky) 4% elation. But having a Bernardini to restore that crucial sense of wonder sure helps.

the queen of all sciences and Intelligent Design

In the mid-1930s, physics was heavily attacked by the most famous Italian philosopher of the time, who called physicists “vile mechanicians”. It was on this occasion that Enrico Fermi told his young fellows: “Don’t worry. Physics is the queen of all sciences.”

We physicists cannot remain silent and keep ignoring the cultural debate on “Intelligent Design”. Other scientists discuss what their observations allow them to say about Intelligent Design: practically all fields of science are present in the debate. Physics, however, is absent. But it is the only science that studies the fundamental logic of nature. Therefore we are the most involved in the hypothesis of Intelligent Design. The purpose of this note is to review, briefly, the scientific basis for this hypothesis, which I describe more fully elsewhere (Zichichi 2008).

Mankind has always been concerned with this extremely important problem but it is only in the past four centuries that, following Galileo Galilei, an impressive series of experimental discoveries has allowed us to reach the conclusion that a fundamental logic of nature exists. The point I would like to make clear is that all other fields of scientific research are not in a position to study this logic for the very simple reason that, no matter what the field may be, the root of our existence has to be investigated in order to overcome the basic difficulty in dealing with the foundations of this logic.

For example, whether we study the evolution of inert matter or the evolution of matter endowed with the property of life, at the very end we discover that all forms of matter – with or without life – have to obey the same fundamental logic. No matter what form of evolution we attempt to study, the key issue is that if a fundamental logic exists, then nature – including its evolution – has to obey this logic.

For the universe to be as it is now, three basic transitions are needed and each must obey the logic of nature.

The field of research where this logic is studied is physics. For the universe to be as it is now, endowed with the properties of life and reason, three basic transitions are needed and each must obey the logic of nature.

The first of these transitions is the Big Bang, which describes how the universe – consisting of inert matter – came into being from a vacuum and subsequently evolved. I call this Big Bang 1. There are many problems to be studied for Big Bang 1 to be rigorously described on the basis of first-level “Galilean Science”; that is, through experimentally reproducible results that can be described with the rigour of mathematical formalism. Although Big Bang 1 and the subsequent cosmic evolution are a one-off event, every step must obey the fundamental logic discovered with first-level Galilean science; this logic is based on three fundamental forces (electroweak, strong and gravitational) and three families of elementary particles.

The second transition in the universe, Big Bang 2, deals with the problem of how to describe the transition from inert matter to living matter. So far no one has been able to solve this problem but once it is solved, the evolution of all different forms of living matter must be studied and referred to the fundamental logic of nature before the evolution of the living matter can be classified as Galilean science.

Then, Big Bang 3 – the transition from living matter without reason to living matter endowed with reason – must be described. It is thanks to Big Bang 3 that we are able to discuss Big Bang 2 and Big Bang 1. The fact that out of the innumerable number of different forms of living matter, there is only one endowed with the property called reason, needs to be examined in detail.

Once all of these problems have been solved we will be able to say that we have a scientific description of the theory of evolution. The present status of our culture takes for granted that the Darwinistic approach to the theory of evolution is scientifically founded. As I have outlined above, this is not the case.

The basic message coming from science is that a fundamental logic exists that governs all forms of inert and living matter. If a fundamental logic exists then the author of this logic must exist too. The atheistic culture claims that the author is not there, but no one is able to prove, using either theoretical logic (mathematics) or experimental logic (science), that this is the case. Those who claim that this logic does not exist are in conflict with science and its most advanced achievements.

Four centuries ago Galilei discovered why it is not enough to be “smart” in order to understand the logic of nature. He pointed out that experiments need to be implemented if we want to know the correct answers to our questions. To express a question in a rigorous way – as is the case, for example, for a supersymmetric world, using a relativistic quantum string-like theory – is not enough; experimental proof of its existence is needed. The reason is that the fellow who created the world is smarter than all of us, no one excluded.

This is at present all that physics can say on the author of Intelligent Design. The hypothesis of which, to the extent that it is based on the argument that this fundamental logic exists, proposes nothing other than that there is an intelligence that designed such logic. And this is in perfect agreement with the most advanced frontier of our field of activity which was defined by Fermi as “the queen of all sciences”.

• A Zichichi 2008 Rigorous Logic in the Theory of Evolution, presented at the Plenary Session on “Scientific Insights into the Evolution of the Universe and of Life”. Proceedings of the Pontifical Academy of Sciences (Vatican, 31 October – 4 November 2008), pp101-178.

Introduction to Elementary Particle Physics

By Alessandro Bettini, Cambridge University Press. Hardback ISBN 9780521880213, £35 ($70). Also available in e-book format.

CCboo1_04_09 — Introduction to Elementary Particle Physics, Bettini.

I was a graduate student when the first version of Introduction to High Energy Physics by Donald H Perkins appeared; the slim one with the plain grey cover, written before the discovery of charm. This book was a welcome sight to many of us “youngsters” because it contained a wealth of concentrated information so valuable to the budding experimentalist. The book began with a nice discussion of the passage of radiation through matter in a form that was not as dated or cumbersome as the two must-read classics by Bruno Rossi and Emilio Segrè. It was also sufficiently detailed to call upon as a ready reference for an upcoming oral exam. Since then, perhaps in part because I have lived through all subsequent discoveries in particle physics, I have not been impressed with any of the rather few particle-physics texts that have appeared; not, at least, until the publication of Alessandro Bettini’s Introduction to Elementary Particle Physics. Like Perkins before him, Bettini’s expertise as a careful, methodical and experienced experimentalist shines brightly throughout the text. The reader is never left in any doubt that physics is an experimental science.

The choice of topics and the level of detail are excellent and the explanations are clear. The book is rich in physics content, especially its emphasis of important concepts, including relativistic kinematics, the wave nature of particles and quantization of fields. Some of my favourite examples are determination of the spin and parity of the pion and why this is important, the Lamb shift in quantum electrodynamics and the discussion of α_s and the proton mass. The author is an expert in neutrino physics and this comes through in the material clearly. He does a good job of emphasizing the physics at an appropriate level without getting absorbed in the mathematics of Feynman diagrams, which belongs in a course on field theory. The text is sprinkled with a few historic gems, such as the story of Marty Block asking Dick Feynman who asked C-N Yang at the 1956 Rochester conference: “Is it possible to think that parity is not conserved?” The book is extremely well written, topically informative and easy to read – but best of all it is full of physics.

Bettini’s text is suited for a one-semester introductory course in particle physics; the one I have taught at Boston University is attended by a mixture of beginning graduate students and advanced undergraduates. The text (431 pages) is organized into 10 chapters, which can be easily covered in 16 weeks. Each chapter contains a number of accessible and readable references, as well as a generous number of end-of-chapter problems. A complete instructors’ solution manual is also available in electronic form.

After this well deserved praise, do I have any complaints? Sure, but they are relatively minor: the use of dashed lines instead of wavy lines for W and Z propagators; time not going “up” in Feynman diagrams; and &Lamda;_QCD written unconventionally as &lamda;_QCD. I would personally have introduced several aspects of the weak interaction much earlier, such as parity violation in beta decay, helicity in pion decay, and the discovery of the τ. I would also have covered deep-inelastic scattering before QCD and included more details on hadron jets, but these are largely personal choices. I was somewhat disappointed that a large number of complete solutions to end-of-chapter problems are available in the text, limiting what I could assign from the book as homework. The bottom line, however, is that as a particle physicist I enjoyed Bettini’s book three times – not unlike a fine wine: the first time when admiring its contents; the second when reading it; and a third time when teaching from it. Bravo, Sandro!

Cosmology

By Steven Weinberg, Oxford University Press. Hardback ISBN 9780198526827, £45 ($90).

Those who think that a book on cosmology and gravitation overlaps with science fiction should probably not even try to flick through the latest treatise by Nobel laureate Steven Weinberg. Conversely, those who believe that gravitation, astrophysics and cosmology could offer fertile playgrounds for the analytical methods of theoretical physics will find in Cosmology a stimulating source of intellectual excitement. Finally, those who think that the physics of the early universe is a mere mathematical game with no observational relevance will also be disappointed, because observations play a central role in the book’s nearly 600 pages.

On the 30th anniversary of the discovery of neutral currents by Gargamelle, a round-table discussion took place in the main auditorium of CERN. Various Nobel laureates, including Weinberg, were present. Some of the questions from the audience addressed the worries of the particle-physics community, always anxious about novelty and excitement; some of Weinberg’s replies in that discussion reverberate in the preface of this book: “Today cosmology offers the excitement that particle physicists had experienced in the 1960s and 1970s”.

The treatise consists of 10 chapters organized around the three observational pillars of the standard cosmological paradigm, i.e. the physics of the cosmic microwave background (CMB), the analysis of supernova light-curves and the observations of large-scale structures. The first four chapters, following a didactical trail, cover the basic aspects of the standard paradigm, often dubbed the &Lamda;_CDM scenario, where &Lamda; stands for the dark-energy component and CDM refers to the cold dark-matter component. The remaining six chapters cover, with more theoretical emphasis, the description (chapter 5), the evolution (chapter 6), the effects (chapters 7, 8 and 9) and the normalization (chapter 10) of inhomogeneities in Friedmann–Robertson–Walker universes.

Readers will not find the usual pretty pictures and maps that often decorate cosmology books. Instead the author adapts the style of theoretical particle physics to cosmology and gravitation: solid, analytical calculations and semi-analytical estimates are preferred over fully numerical results. Analytical methods are implicitly viewed as a mandatory step for an effective comprehension of natural phenomena. The latter aspect is evident in the discussion of the anisotropies in the CMB, where the author exploits some of his own results that have appeared over the past five years in Physical Review. The book contains eight assorted appendices, which are useful for both newcomers and experienced readers. The notations used by the author are unusual at times but may quickly become a standard.

While the relevant technical aspects of the presentation can only be fully appreciated after a careful reading, a clear message emerges with vigour after the first reading: atomic physics, nuclear physics, field theory, high-energy physics and general relativity all come together in the description of our universe. In other words, Cosmology provides a vivid example of the basic unity of physics, which is something to bear in mind during the decades to come.

The Strangest Man: The Hidden Life of Paul Dirac, Quantum Genius

by Graham Farmelo, Faber. Hardback ISBN 9780571222780, £22.50.

On 13 November 1995 the president of the Royal Society, Sir Michael Atiyah, unveiled a plaque in the nave of Westminster Abbey in London commemorating the life of Paul Dirac. Speaking at the ceremony, Stephen Hawking summed up Dirac’s life: “Dirac has done more than anyone this century, with the exception of Einstein, to advance physics and change our picture of the universe.” The plaque depicted Dirac’s equation in a compact relativistic form and the man himself would no doubt have appreciated its terse style. At the time of his passing in 1984 Dirac ranked among the greatest physicists of all time. With the publication of Graham Farmelo’s book The Strangest Man, we have an account of Dirac’s life that is a tour de force.

Dirac’s Swiss father, Charles, taught French at the Merchant Venturers’ Technical College in Bristol and married Florence Holten in 1899. They had three children, Beatrice, Reginald (who committed suicide in 1924) and Paul, who was born on 8 August 1902 – the same year that Einstein started work at the patent office in Bern and Planck initiated the quantum theory of matter and light. This was the start of the modern era in which classical physics was revolutionized by two great advances – special relativity and quantum mechanics.

Dirac’s early years were overshadowed by his domineering father and a browbeaten, needy mother. “I never knew love nor affection when I was a child,” Dirac once remarked. Certainly, his difficult childhood seems to have deeply influenced the development of his “strange” character. Farmelo also explores another explanation for Dirac’s introversion, literality, rigid behaviour patterns and egocentricity: perhaps Dirac, like his father, was autistic. Nonetheless, in his thirties, Dirac met and married Manci Balázs, an extroverted and passionate woman – his “antiparticle”. Farmelo’s candid and sympathetic account of the couple’s improbable life together makes compelling reading. Yet, according to Farmelo, Dirac only cried once in his life, and that was when Einstein died.

Dirac’s seminal contribution to physics was the unification of Heisenberg and Schrödinger’s quantum mechanics with Einstein’s special relativity, which allowed him to write down a relativistic equation for the electron – the famous Dirac equation. With it he revealed the concept of spin and predicted the existence of antiparticles, subsequently discovered in studies of cosmic rays. In 1933, aged 31, he shared the Nobel prize with Schrödinger.

Dirac was also the creator of quantum electrodynamics and one of the chief architects of quantum-field theory. For him, the beauty of mathematical reasoning and physical argument were instruments for discovery that, if used fearlessly, would lead to unexpected but valid conclusions. Perhaps the single contribution that best illustrates Dirac’s courage is his work on the magnetic monopole, the existence of which would explain the quantization of electric charge. The monopole’s story is still far from complete and more revelations could be forthcoming.

Farmelo succeeds brilliantly in unifying all of the shadowy and contradictory perspectives of Dirac’s character with his life as a scientific genius, and creates a complete picture of the man who played a leading role in the growth of modern physics. The book reveals how Dirac, although aloof and unworldly, was deeply affected by the turbulent and troubled history of the 20th century.

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