Subject Grouping: Praxis

By P Redondi, G Sironi, P Tucci and G Vegni (eds), Springer. Hardback ISBN 9783540373537, £54 (€74.85).

Giuseppe Paulo Stanislao Occhialini, or Beppo to his many friends across the world, was a charismatic, dynamic leader of discovery in particle and astrophysics for more than 50 years from the 1930s. These essays and reminiscences, by 30 colleagues and others who knew him, review his life to celebrate the centenary of his birth in 1907.

The early years of Occhialini’s career were remarkable for two close encounters with the Nobel Prize: through his work on cosmic rays with Patrick Blackett and a decade later with Cecil Powell. His interest in cosmic rays began while studying at the Institute of Physics at Arcetri, part of the University of Florence, where he learnt to use new coincidence circuitry for Geiger–Muller counters from its developer, Bruno Rossi. After graduating in 1929 Occhialini stayed in research and in 1931 Rossi sent him to Cambridge to learn about Wilson cloud chambers from Blackett – who in turn learnt from Occhialini the advantages of using counters in coincidence to trigger the chamber. Soon, although unluckily a week or so after Carl Anderson at Caltech, they saw their first “positive electrons”, but, unlike Anderson, they observed e⁺e^– pairs and recognized that Paul Dirac’s new relativistic quantum theory predicted this. Occhialini was a keen member of the “Kapitza Club” at Cambridge’s Cavendish Laboratory, where he met Dirac.

Returning to Arcetri in 1934, Occhialini found that things had changed. Facism was taking power in Italy so he left for an appointment at the University of Sao Paulo in Brazil where he stayed throughout the Second World War. He built a strong group there using counters in cosmic-ray research before leaving at the end of 1944 for England at the invitation of Blackett, who thought that his help would be valuable in the work on an atomic bomb. Since Occhialini was Italian, this was not allowed and in autumn 1945 he went to Bristol to join Powell, who was using photographic emulsions to study low-energy nuclear reactions. Occhialini was immediately intrigued and impressed by the elegance and power of the method, but saw the need to improve the emulsions’ sensitivity. So he contacted the technical staff at Kodak and Ilford to add his influence. Ilford then produced the C2 emulsion, with eight times the silver halide concentration, which Powell and Occhialini “warmly welcomed”, according to Ilford’s man in charge, Cecil Waller.

Occhialini proposed exposing C2 plates to cosmic radiation at the top of the Pic du Midi (2800 m) in the Pyrenees, and did so in summer 1946. In January 1947 Occhialini and Powell published in Nature the first of a series of papers from the Bristol group establishing the discovery of the π-meson, its decay to the μ-meson and, after Kodak produced the first emulsions able to detect minimum ionization, the μ’s decay to an electron.

It was at Bristol that Beppo met Connie: Constance Charlotte Dilworth, who was born in 1924 in Streatham, London. She started postgraduate studies in theoretical solid-state physics at Bristol in about 1946, then switched to join Powell’s group. Together with Occhialini and others, she contributed significantly to processing thick photographic emulsions. In 1948, when Occhialini was invited to Brussels to start a new nuclear emulsion group, Connie went with him. They were married in 1950 and their daughter, Etra, who contributed to this book, was born the next year. Connie and Beppo became a very effective team, a formidable duo who would provide strong leadership in Italian and European science. Beppo’s excitable Italian temperament was complemented by the calm, organized approach of Connie, a notable scientist herself who always understood how Beppo’s aspirations could be realized.

In 1950 the Occhialinis moved to Genoa and in 1952 to Milan University where Beppo was director until he retired in 1974. He built up a strong emulsion group at Milan, making major contributions to the “G-stack” and other collaborations flying emulsions on balloons. He was always looking for new challenges in physics and advances in experimental techniques. On returning from a visit to Rossi at MIT in 1960, he showed his group a new detector made of silicon, saying “think what you can do with this”. They did, and established an expertise that later became the basis for Milan’s major contribution to the central detector for the DELPHI experiment at LEP.

As machines replaced cosmic rays as a source for particle physics, and while maintaining a major presence for his group at CERN, Beppo turned to other techniques to continue his interest in cosmic rays, first with balloon-borne spark chambers and then adapting these to flights on satellites. Both Beppo and Connie were influential members of advisory and scheduling bodies for the European Space Research Organisation and together, as one contributor puts it, they pushed Italy into a leading position in astronomy. Milan was a “power house” for space research, with leading roles in two satellite experiments that mapped the sky for X-ray and gamma-ray sources: COS-B launched in 1975 and Beppo-SAX in 1996. Beppo maintained his interest in the design of the latter until his death in 1993, when it was named after him. Connie died in 2004.

Research into the origins of intense gamma-ray bursts (GRBs) – by far the brightest events known – is a scientific legacy of Beppo still very much alive. Until Beppo-SAX made the first accurate locations in 1997, no GRB had been associated with a visible galaxy. His most long-lasting legacies, however, are the young scientists who entered research in his care: his irrepressible enthusiasm inspired them; his lateral, dialectical probing tested their ideas; and his quick wit, wide cultural interests in art, literature and thoughts on “the film I saw last night” entertained them. This collection of essays portrays a complex personality for whom life was never dull, who was always ready to “brain storm” with colleagues, and who experienced the excitement of discovery in his research.

One question remains: why didn’t he share one of the two Nobel prizes, Blackett’s in 1948 or Powell’s in 1950?

By Gerald E Brown and Chang-Hwan Lee (eds), World Scientific. Hardback ISBN 9789812566096 £56 ($98). Paperback ISBN 9789812566102 £22 ($38).

This book is the result of a request that Hans Bethe made at the age of 97 to his long-term collaborator Gerry Brown to explain “his physics” to the world. This is no easy feat considering that the published scientific papers, books and reports span the best part of eight decades, and include some of the most important contributions to 20th-century physics. Brown and Lee have risen to the challenge and produced a book of which Bethe himself would be proud. It even goes beyond Bethe’s initial request to explain his physics and provides a portrait of the great man in all aspects of his life, which Brown and Lee have accomplished by enlisting the help of experts, collaborators and friends.

In part one of this four-part book, we catch a personal glimpse of the man and his science through the eyes of close collaborators and friends. Brown summarizes and evaluates Bethe’s long career as a teacher and researcher, starting with a brief history of his early years in Germany and England, with a short stay in Italy. He describes how Bethe developed mathematical rigor working with Arnold Sommerfeld and gained physical intuition from Enrico Fermi.

However, Bethe found that the British had a much healthier attitude towards life than the Germans, and with the rise of Adolf Hitler and the new laws he could not hold a university position as two of his grandparents were Jewish. So in 1933 he moved to Manchester University where he was reunited with his old friend Rudi Peierls. Bethe regarded 1933–34 as his most productive time, although he had already published the famous “Bethe ansatz”. Brown ends his article by describing his own long collaborative research with Bethe in astrophysics.

Bethe’s own article, “My life in astrophysics”, highlights his strengths and the application of nuclear physics in stellar energy production, for which he won the Nobel prize in 1967. The article describes in detail the whole Nobel experience; his enjoyment is obvious. He concludes by describing his return to astrophysics after retiring from Cornell University.

“Three weeks with Hans Bethe” by Chris Adami is a transcript of conversations with Bethe and Brown over a three-week period at the Kellogg Radiation Laboratory at Caltech. Here Adami provides a unique insight into the mind of Bethe, his thoughts on science, people and politics. Adami quizzed Bethe on almost every aspect of his life, keeping a record of each day’s discussion, a real Bridget Jones’s Diary of physics. Here we learn that Bethe was an expert on shock waves and explosions, which he had ample opportunity to develop during his time at Los Alamos, and Adami was sometimes met with silence if the questioning came too close to classified work.

Bethe’s commitment to nuclear energy is highlighted in the short article by Jeremy Bernstein, who had written a piece about Bethe for the New Yorker, highlighting his enthusiasm for nuclear energy. At the time, Bethe debated the nuclear option with Barry Commoner, a committed environmentalist and the magazine’s energy guru. Such debates are again increasingly relevant, but without a Bethe, explaining the nuclear option is more difficult. Part one concludes with a well crafted piece by Ed Salpeter who interacted with Bethe over a 60 year period.

Kurt Gottfried introduces part two, followed by Silvan Schweber who gives an account of Bethe’s education, swift rise to international prominence and immense impact on American physics. The other four papers in this section deal with distinct aspects of his research. Salpeter and the late John Bahcall expand on Bethe’s work on energy production in stars, nuclear astrophysics and neutrino physics. Bethe wrote an important and influential paper in 1986 on the missing solar neutrinos, explaining the Mikheyev–Smirnov–Wolfenstein effect. This is the best explanation of matter effects on neutrino oscillations that I have come across. Freeman Dyson traces Bethe’s influence on the development of quantum electrodynamics and the story of how he solved the Lamb shift problem, claiming that “Hans Bethe was the supreme problem solver of the past century”. John Negele describes Bethe’s work on the theory of nuclear matter and the post-war contribution he made to the nuclear many-body problem. Brown concludes this section by providing an intimate look at his remarkable collaboration with Bethe on supernovae and mergers between neutron stars and black holes as possible sources of gravitational waves.

Part three contains papers by Chen Ning Yang and Mo-Lin Ge on the impact of what Yang had termed the “Bethe ansatz”, which extended to many systems beyond the 1D problem in quantum mechanics that Bethe originally considered. David Mermin and Neil Ashcroft describe how influential Bethe was in solid-state physics. However, although he played a major role in developing the quantum theory of solids, he realized by 1933 that his real interest was in nuclear physics. Jeremy Holt and Brown provide a historical summary of nuclear physics where they put Bethe’s major contributions into context. Sometimes in physics the exact details of discovery are not well documented, but not in this case I am pleased to say. This section ends with the paper “And don’t forget the black holes”, which Bethe co-authored with Brown and Chang-Hwan Lee shortly before his death.

The last part of the book concludes with a set of papers discussing Bethe’s contribution to science policy at all levels. Sydney Dell recounts the various ways in which Bethe’s integrity, together with his incredible scientific knowledge, made him an admirable adviser to policy makers. Bethe’s panel helped shape the Limited Test Ban Treaty of 1963. He was deeply concerned with new threats posed by nuclear weapons and was deeply involved in all aspects of the global-energy problem. The article by Boris Ioffe on “Hans Bethe and the global energy problem” outlines Bethe’s commitment to the peaceful use of nuclear energy. He also advocated strategies to police and limit the amount of weapons-grade material, a very real threat in today’s global political scene. The book concludes with obituaries by Richard Garwin, Frank von Hippel and Gottfried.

This book does an admirable task in drawing a portrait of a great scientist and a great man. Bethe’s power, in my experience, was that he could always easily get to the heart of a problem in any field and solve it in the most economical way, and this comes through clearly. The book is a “must read” for every researcher and teacher of science.

par René Bimbot, Vuibert. Broché ISBN 9782711771943, €35.

Dans son Histoire de la radioactivité, René Bimbot s’adresse à un très large public dans un style limpide et son livre se lit aisément, cela d’autant plus que de nombreux graphiques et illustrations facilitent la compréhension. Au fil du texte, le lecteur peut aussi s’attarder sur des encadrés expliquant certaines notions simples de physique, accessibles dès la fin du secondaire, qui, au prix d’un effort minime, permettent d’approfondir la compréhension du sujet traité.

Des vignettes présentent en quelques paragraphes les chercheurs qui ont écrit les pages les plus remarquables de cette histoire ou y sont étroitement associés, c’est le cas successivement de Röntgen, Becquerel, Marie Curie, Pierre Curie, J J Thomson, Planck, Einstein, Rutherford, Bohr, de Broglie, Chadwick, Fermi, Yukawa, Frédéric et Irène Joliot, Lawrence, Gentner, Seaborg et Charpak.

Trop souvent, sous différents prétextes, les physiciens présentent de façon caricaturale le développement historique de leur sujet de prédilection; ici au contraire René Bimbot s’attache à suivre en grand détail le cheminement des idées en faisant ressortir les influences réciproques des acteurs ayant joué les premiers rôles dans les découvertes sur la radioactivité.

Curieusement ce livre semble combler un vide; en effet, une recherche rapide montre qu’il n’existait pas d’ouvrage dans la langue de Becquerel traitant complètement du sujet. En anglais on note le récent ouvrage de G I Brown (2003) intitulé Invisible Rays: A History of Radioactivity qui traite des mêmes sujets. L’auteur a joué un rôle très actif dans certaines des célébrations des divers centenaires remarquables de la physique que nous avons connu au cours de la dernière décennie, une bonne préparation pour l’élaboration de son Histoire.

Le livre comporte trois parties intitulées «De la radioactivité naturelle au noyau de l’atome», «De la radioactivité artificielle à l’énergie de fission» et «Rayonnements et radioactivité aujourd’hui».

Les sept chapitres de la première partie s’attachent aux premiers travaux de Becquerel, puis de Marie et Pierre Curie, et guident ensuite le lecteur à travers les bouleversements de la physique qui ont caractérisé le début du 20 e siècle jusqu’à l’élucidation par Gamow de la radioactivité alpha en 1928 (expliquée par l’effet tunnel permis par la mécanique quantique) et la théorie de Fermi de la radioactivité bêta en 1933. En résolvant les énigmes posées par la radioactivité, les physiciens nucléaires ont enrichi la physique de deux nouvelles forces, la force forte et la force faible. Ils ont ainsi légué à leurs successeurs de la physique des particules deux sujets essentiels dont l’élucidation théorique a pris plusieurs décennies pour arriver à l’unification électrofaible et à la chromodynamique quantique.

La deuxième partie traite en sept chapitres du sujet associé du positon et de l’antimatière, puis de la radioactivité dite artificielle et des diverses applications de la radioactivité. Parmi celles-ci, René Bimbot souligne bien sûr le rôle toujours croissant en médecine nucléaire des multiples radionucléides à usage médical et de l’imagerie avant de passer au domaine de la datation, en particulier par la méthode du carbone-14. Il consacre trois chapitres à la fission, aux armements nucléaires, aux diverses filières électronucléaires (sans éluder l’accident de Tchernobyl) et à la question des déchets.

Plus courte, la troisième partie du livre discute des détecteurs puis des deux faces contrastées des rayonnements: leurs dangers mais aussi leurs bienfaits en radiothérapie. Le chapitre final aborde des manifestations plus rares de la radioactivité, comme la capture électronique, l’émission de un ou de deux protons et aussi d’un neutron post-bêta. René Bimbot insiste par ailleurs sur le fait qu’il reste des radioactivités à découvrir après celle des ions lourds (comme le carbone-14) et que la sensibilité croissante des méthodes de détection promet la découverte de radioactivités ultrafaibles par des nucléides considérés comme stables. Ce chapitre considère aussi la désintégration bêta au niveau des quarks, après les niveaux moins élémentaires du noyau et du proton présentés auparavant.

On peut regretter l’omission de la double désintégration bêta qui aurait particulièrement intéressé les lecteurs du CERN Courier. De plus, un index analytique des sujets traités aurait utilement complété celui des scientifiques cités dans le livre.

Le livre de René Bimbot remplit donc de façon convaincante l’objectif annoncé par le titre et il intéressera en particulier le lecteur recherchant une perspective historique sur un sujet qu’il connaît déjà.

by Mark Fox, Oxford University Press. Hardback ISBN 9780198566724, 9.95 ($89.50). Paperback ISBN 9780198566731, £24.95 ($44.50).

This is a modern text on quantum optics for advanced undergraduate students. It provides explanations based primarily on intuitive physical understanding, rather than mathematical derivations. There is a strong emphasis on experimental demonstrations of quantum optical phenomena, in both atomic and condensed-matter physics. Other topics include squeezed light, Hanbury–Brown–Twiss experiments, laser cooling, Bose–Einstein condensation, quantum computing, entangled states and quantum teleportation. The book also includes worked examples and exercises.

By Gordon Fraser (ed.), Cambridge University Press. Hardback ISBN 9780521816007, £30 ($60).

Seventeen years ago a book called The New Physics illuminated – vividly for the layperson and sensibly for the student – a series of scientific advances and philosophical obsessions, and it trailed them as signposts for the future. As so often happens, the future went off in a somewhat different direction. While Paul Davies was editing the first volume, physicists wondered loudly and publicly about dark matter and cosmic strings; black holes and the end of time; grand unification theory and cosmic inflation; the new window on the universe by the yet to be launched Hubble Space Telescope; and the claim by the Nobel prize-winner Luis Alvarez that an asteroid had crashed into the planet 65 million years ago and ended both the Cretaceous era and the dinosaurs. In fact, Alvarez and his planet-bruising bolide never got a mention in the Davies volume, but at the time there seemed quite a lot else to be getting on with.

What a difference the decades make. In the past 17 years, experimental physicists have delivered a fifth state of matter in the Bose–Einstein condensate; slowed light down first to walking speed and then to a complete standstill; dropped the idea that time might run backwards and instead proposed interminable heat death in an ever expanding cosmos; demonstrated quantum entanglement and teleportation; mapped the fluctuations in the cosmic background radiation; introduced branes and apparently dropped cosmic strings; and discovered dark energy in a big way – so big that it accounts for three-quarters of everything. Nanotechnology emerged as both engineering obsession and practical investment, amid royal alarm in the UK about global death by grey goo. The Hubble telescope went up with a faulty mirror, and NASA launched its International Space Station but seemed to run out of steam. Global warming – physics at a practical level for most people – announced its arrival with a procession of record temperatures globally, and the debate about the Cretaceous catastrophe flowered into a much larger argument about asteroid impact-warning and deflection.

Physics never seemed so glamorous, but student numbers continued to fall and university departments continued to close. The old New Physics didn’t look so new and now CERN’s own Gordon Fraser has produced a companion volume of 19 essays, just as substantial, just as wide-ranging, and in some cases just as much fun.

Physics is not easy (it is after all done by PhDs, not dilettantes) but each essay begins comprehensibly and even enticingly, before diving quite briskly into mathematics, hard argument and occasionally hostile language. (Did Michael Green, writing about superstring theory, really have to head a section “beyond the naive perturbative approximation”?) Chris Quigg looks at particle physics and puts the Large Hadron Collider handsomely in its scientific context. But Fraser plays no special favourites. Nanoscience is there, and the Grid, and there are welcome surveys of biophysics and medical physics; the last essay is a reminder that without the physics of imaging, some neuroscience would be little more than voodoo.

All the classical preoccupations – cosmology, astronomy, gravity and the quantum world – get a fresh look. Robert Cahn’s survey of the physics of materials is a big help for the benighted. Ugo Amaldi ends the volume with a handsome canter through the connections between physics and society, and echoes many of the themes tackled in the book’s previous 18 chapters. The bad news is that physics still has an image problem. The good news is that this time Alvarez gets a mention, although not for bolide impacts, dinosaurs or the present concerted international effort to identify and track near-Earth objects. No, he gets a mention for not solving the world’s energy crisis: to be fair, for admitting that, for a few exhilarating moments, he thought that he had solved the world’s fuel problems for all time by fusing a proton with a deuteron to form helium-3. This anecdote appears, a little unkindly, under the heading “usable knowledge”.