Until his retirement in 2017, Martin Pohl was a physics professor at the University of Geneva and worked on particle physics research projects for almost half a century. Drawing on this wealth of experience, a book has been written in which Pohl knowledgeably traces the developmental strands of this fundamental discipline. The culmination is the 'Standard Model' of particle physics - for Pohl a scientific highlight and a burden at the same time.
'Particles, Fields, Space-Time: From Thomson's Electron to Higgs' Boson' - this is the title of the 300-page book recently presented by Martin Pohl. The author brings a lifetime of passionate research and university teaching into this work: After completing his doctorate at RWTH Aachen University, Pohl worked at the German Electron Synchrotron (DESY) in Hamburg and for a long time at the European Laboratory for Particle Physics (CERN) in Geneva, but was also involved in experiments such as the alpha-magnet spectrometer (AMS) on the International Space Station (ISS) measuring cosmic radiation. The book's author can also draw on his long-time didactic expertise as a university lecturer and astroparticle physicist at the University of Geneva.
Detailed overall view
The wide-ranging knowledge of an academic career gives the book weight and defines its claim. At the same time, it limits its readership, as people who do not have a physics degree will not be able to follow Pohl's exposition over long passages. When the publisher writes in its book announcement that the publication requires little prior knowledge, this is definitely an understatement. However, anyone who wants to deal intensively with a good century of particle physics research will be offered an extremely detailed overview by Martin Pohl, which includes social references and reflections on the history of science.
The book chooses the discovery of the electron in the late 19th century as its pivotal point. This major scientific achievement marks the beginning of particle physics as a new fundamental discipline and at the same time the beginning of the momentous triumph of electronics, as Martin Pohl aptly notes. The author introduces the theory of relativity and quantum mechanics as well as their later connection to quantum field theory, and he traces the steps that led to the Standard Model of particle physics in the 1960s and early 1970s. The Standard Model provides a consistent description of the known elementary particles and the forces acting between them. And yet this edifice of thought was definitely a burden for the experimental physicist Martin Pohl, as he notes with fine irony: "I have been running after the theoretical predictions of the Standard Model for most of my professional life, trying in vain to find a breach in its fortifications." Today, he sees himself as a "victim" of the Standard Model and faces it with "some kind of fatalism".
This ambivalent feeling is probably also fed by the fact that particle physics today has large and expensive research infrastructures at its disposal, which awaken a huge appetite for knowledge among the research collaborations that conduct their experiments here, an appetite that cannot always be satisfied. In his book, Pohl not only provides a detailed account of the Standard Model, but also discusses the research approaches that are working towards physics beyond the Standard Model.
Particle beam made by human hands
After the Austrian physicist Victor Franz Hess discovered cosmic rays in 1912, they were the preferred source for research of high-energy particles for decades. Cosmic rays were later replaced by artificially generated particle beams, which were produced in particle accelerators and analysed in detectors. In 1934, the first cyclotron was built in Berkeley, California. The European countries pooled their research at CERN, which was founded in 1954.
Today, with the LHC particle accelerator, CERN is "the leading particle physics laboratory in the world", as Pohl notes. Proton-proton collisions at the Large Hadron Collider (LHC) have energies 100,000 times higher than those achieved in Berkeley in 1934. But nature can still do it better, as Martin Pohl notes: "Astrophysical phenomena can accelerate particles to energies which are many orders of magnitude higher than those man-made accelerators can ever hope to achieve." However, these natural particles are of little use for experiments: in the vicinity of the Earth, such a particle appear only once per century over an area of one square kilometre.
English replaces German as the language of science
Interestingly, Martin Pohl devotes one of the ten chapters to 'War time physics'. He describes the US-American 'Manhattan Project' to build the atomic bomb and proves in passing that Nazi Germany did have a nuclear programme, but it was modestly equipped and aimed at atomic propulsion, not at building an atomic bomb. Scientists had already had a decisive influence on the First World War with chemical weapons and submarine detection, among other things. Just after the end of the war, three German researchers - Max Planck, Johannes Stark and Fritz Haber - received the Nobel Prize. Martin Pohl, however, sees this rather as a negative caesura: German researchers were excluded from international conferences for ten years after the war, and "German, a former language of sciences, was completely replaced by English", as Pohl writes.
Martin Pohl's book is also written in English, and that is quite typical for particle physics, whose research community has left national borders behind like hardly any other. A bibliography and a keyword index form the helpful conclusion of Pohl's account.
Martin Pohl: Particles, Fields, Space-Time. From Thomson’s Electron to Higgs’ Boson. CRC Press 2021.
Author: Benedikt Vogel