Praxis Archives – Page 10 of 179

The Many Voices of Modern Physics

This book provides a rich glimpse into written science communication throughout a century that introduced many new and abstract concepts in physics. It begins with Einstein’s 1905 paper “On the Electrodynamics of Moving Bodies”, in which he introduced special relativity. Atypically, the paper starts with a thought experiment that helps the reader follow a complex and novel physical mechanism. Authors Harmon and Gross analyse and explain the terminological text and bring further perspective by adding comments made by other scientists or science writers during that time. They follow this analysis style throughout the book, covering science from the smallest to the largest scales and addressing the controversies surrounding atomic weapons.

The only exception from written evaluations of scientific papers is the chapter “Astronomical value”, in which the authors revisit the times of great astronomers such as Galileo Galilei or the Herschel siblings William and Caroline. Even back then, researchers were in need of sponsors and supporters to fund their research. In Galilei’s case, he regularly presented his findings to the Medici family and fuelled fascination in his patrons so that he was able to continue his work.

While writing the book, Gross, a rhetoric and communications professor, died unexpectedly, leaving Harmon, a science writer and editor at Argonne National Laboratory in communications, to complete the work.

While somewhat repetitive in style, readers can pick a topic from the contents and see how scientists and communicators interacted with their audiences. While in-depth scientific knowledge is not required, the book is best targeted at those familiar with the basics of physics who want to gain new perspectives on some of the most important breakthroughs during the past century and beyond. Indeed, by casting well-known texts in a communication context, the book offers analogies and explanations that can be used by anyone involved in public engagement.

CERN celebrates 100 years of science and diplomacy

Since his birth in Bohemia in 1924, Herwig Schopper has been a prisoner of war, an experimentalist with pioneering contributions in nuclear, accelerator and detector physics, director general (DG) of DESY and then CERN during a golden age for particle physics, and a celebrated science diplomat. Shortly after his centenary, his colleagues, family and friends gathered on 1 March to celebrate the life of the first DG in either institution to reach 100.

“He is a restless person,” noted Albrecht Wagner (DESY), who presented a whistlestop tour of Schopper’s 35 years working in Germany, following his childhood in Bohemia. Whether in Hamburg, Erlangen, Mainz or Karlsruhe, he never missed out on an opportunity to see new places – though always maintaining the Austrian diet to which his children attribute his longevity. On one occasion, Schopper took a sabbatical to work with Lise Meitner in Stockholm’s Royal Institute of Technology. At the time, the great physicist was performing the first nuclear-physics studies in the keV range, said Wagner, and directed Schopper to measure the absorption rate of beta-decay electrons in various materials using radioactive sources and a Geiger–Müller counter. Schopper is one of the last surviving physicists to have worked with her, observed Wagner.

Schopper’s scientific contributions have included playing a major part in the world’s first polarised proton source, Europe’s first R&D programme for superconducting accelerators and the development of hadronic calorimeters as precision instruments, explained Christian Fabjan (TU Vienna/HEPHY). Schopper dubbed the latter the sampling total absorption calorimeter, or STAC, playing on the detector’s stacked design, but the name didn’t stick. In recognition of his contributions, hadronic calorimeters might now be renamed Schopper total absorption calorimeters, joked Fabjan.

As CERN DG from 1981 to 1988, Schopper oversaw the lion’s share of the construction of the LEP, before it began operations in July 1989. To accomplish this, he didn’t shy away from risks, budget cuts or unpopular opinions when the situation called for it, said Chris Llewellyn Smith, who would himself serve as DG from 1994 to 1998. Llewelyn Smith credited Schopper with making decisions that would benefit not only LEP, but also the LHC. “Watching Herwig deal with these reviews was a wonderful apprenticeship, during which I learned a lot about the management of CERN,” he recalled.

After passing CERN’s leadership to Carlo Rubbia, Schopper became a fulltime science diplomat, notably including 20 years in senior roles at UNESCO between 1997 and 2017, and significant contributions to SESAME, the Synchrotron-light for Experimental Science and Applications in the Middle East (see CERN Courier January/February 2023, p28). Khaled Toukan of Jordan’s Atomic Energy Commission, CERN Council president Eliezer Rabinovici and Maciej Nałecz (Polish Academy of Science, formerly of UNESCO) all spoke of Schopper’s skill in helping to develop SESAME as a blueprint for science for peace and development. “Herwig likes building rings,” Toukan fondly recounted.

As with any good birthday party, Herwig received gifts: a first copy of his biography, a NASA hoodie emblazoned with “Failure is not an option” from Sam Ting (MIT), who is closely associated with Schopper since their time together at DESY, and the Heisenberg medal. “You’ve even been in contact with the man himself,” noted Heisenberg Society president Johannes Blümer, referring to several occasions Schopper met Heisenberg at conferences and even once discussed politics with him.

Schopper continues to counsel DGs to this day – and not only on physics. Confessing to occasionally being intimidated by his lifetime of achievements, CERN DG Fabiola Gianotti intimated that they often discuss music. “Herwig likes all composers, but not baroque ones. For him, they are too rational and intellectual.” For this, he will always have physics.

SHiP to chart hidden sector

**Full speed ahead** Layout of the SHiP experiment, with the target on the left and the experiment in the ECN3 hall. Credit: SHiP collab.

In March, CERN selected a new experiment called SHiP to search for hidden particles using high-intensity proton beams from the SPS. First proposed in 2013, SHiP is scheduled to operate in the North Area’s ECN3 hall from 2031, where it will enable searches for new physics at the “coupling frontier” complementary to those at high-energy and precision-flavour experiments.

Interest in hidden sectors has grown in recent years, given the absence of evidence for non-Standard Model particles at the LHC, yet the existence of several phenomena (such as dark matter, neutrino masses and the cosmic baryon asymmetry) that require new particles or interactions. It is possible that the reason why such particles have not been seen is not that they are too heavy but that they are light and extremely feebly interacting. With such small couplings and mixings, and thus long lifetimes, hidden particles are extremely difficult to constrain. Operating in a beam-dump configuration that will produce copious quantities of photons and charm and beauty hadrons, SHiP will generically explore hidden-sector particles in the MeV to multiple-GeV mass range.

Optimised searching

SHiP is designed to search for signatures of models with hidden-sector particles, which include heavy neutral leptons, dark photons and dark scalars, by full reconstruction and particle identification of Standard Model final states. It will also search for light–dark-matter scattering signatures via the direct detection of atomic–electron or nuclear recoils in a high-density medium, and is optimised to make measurements of tau neutrinos and of neutrino-induced charm production by all three neutrinos species.

The experiment will be built in the existing TCC8/ECN3 experimental facility in the North Area. The beam-dump setup consists of a high-density proton target located in the target bunker, followed by a hadron stopper and a muon shield. Sharing the SPS beam time with other fixed-target experiments and the LHC should allow around 6 × 10²⁰ protons on target to be produced during 15 years of nominal operation. The detector itself consists of two parts that are designed to be sensitive to as many physics models and final states as possible. The scattering and neutrino detector will search for light dark matter and perform neutrino measurements. Further downstream is the much larger hidden-sector decay spectrometer, which is designed to reconstruct the decay vertex of a hidden-sector particle, measure its mass and provide particle identification of the decay products in an extremely low-background environment.

One of the most critical and challenging components of the facility is the proton target, which has to sustain an energy of 2.6 MJ impinging on it every 7.2 s. Another is the muon shield. To control the beam-induced background from muons, the flux in the detector acceptance must be reduced by some six orders of magnitude over the shortest possible distance, for which an active muon shield entirely based on magnetic deflection has been developed.

One of the most critical and challenging components of the facility is the proton target

The focus of the SHiP collaboration now is to produce technical design reports. “Given adequate funding, we believe that the TDR phase for BDF/SHiP will take us about three years, followed by production and construction, with the aim to commission the facility towards the end of 2030 and the detector in 2031,” says SHiP spokesperson Andrey Golutvin of Imperial College London. “This will allow up to two years of data-taking during Run 4, before the start of Long Shutdown 4, which would be the obvious opportunity to improve or consolidate, if necessary, following the experience of the first years of data taking.”

The decision to proceed with SHiP concluded a process that took more than a year, involving the Physics Beyond Colliders study group and the SPS and PS experiments committee. Two other experiments, HIKE and SHADOWS, were proposed to exploit the high-intensity beam from the SPS. Continuing the successful tradition of kaon experiments in the ECN3 hall, which currently hosts the NA62 experiment, HIKE (high-intensity kaon experiment) proposed to search for new physics in rare charged and neutral kaon decays while also allowing on-axis searches for hidden particles. For SHADOWS (search for hidden and dark objects with the SPS), which would have taken data concurrently with HIKE when the beamline is operated in beam-dump mode, the focus was low-background searches for off-axis hidden-sector particles in the MeV-GeV region.

“In terms of their science, SHiP and HIKE/SHADOWS were ranked equally by the relevant scientific committees,” explains CERN director for research and computing Joachim Mnich. “But a decision had to be made, and SHiP was a strategic choice for CERN.”

European strategy update

On 21 March the CERN Council decided to launch the process for updating the European strategy for particle physics – the cornerstone of Europe’s decision-making process for the long-term future of the field. Mandated by the CERN Council, the European strategy is formed through a broad consultation of the particle-physics community and in close coordination with similar processes in the US and Japan, to ensure coordination between regions and optimal use of resources globally.

The deadline for submitting written input for the next strategy update has been set for 31 March 2025, with a view to concluding the process in June 2026. The strategy process is managed by the strategy secretariat, which the Council will establish during its June 2024 session.

The European strategy process was initiated by the CERN Council in 2005, placing the LHC at the top of particle physics’ scientific priorities, with a significant luminosity upgrade already being mooted. A ramp-up of R&D for future accelerators also featured high on the priority list, followed by coordination with a potential International Linear Collider and participation in a global neutrino programme.

The final report of the FCC feasibility study will be a key input for the next strategy update

The first strategy update in 2013, which kept the LHC as a top priority and attached increasing importance to its high-luminosity upgrade, stated that Europe needs to be in a position to propose an ambitious post-LHC accelerator project at CERN by the time of the next strategy update. The latter charge was formulated in more detail in the second strategy update, completed in 2020, which recommended a Higgs factory as the highest priority to follow the LHC and that a technical and financial feasibility study should be pursued in parallel for a next-generation hadron collider at the highest achievable energy. A mid-term report on the resulting Future Circular Collider feasibility study was submitted for review at the end of 2023 (CERN Courier March/April 2024 pp25–38) and the final report, expected in March 2025, will be a key input for the next strategy update.

More information about the third update of the European strategy, together with the call for input, will be issued by the strategy secretariat in due course.

Strengthening science in Europe

Why theoretical cosmology?

I was first trained as a mathematician, and then as a physicist. I’ve always worked at the interface between theory and data, where one of the most interesting things is to test cosmological models inspired by some fundamental theory. For example, you can create a model based on string theory or on a non-perturbative approach to quantum gravity, and then use data to constrain the quantum gravity theory. Today we receive a wealth of data from different kinds of experiments, which allows us to test early-universe models without relying on ad hoc ideas. Although it is not something I directly work on, the current tension in the value of the Hubble constant serves as an example. This of course could be telling us something about new physics, but it seems to me it is more likely to be an issue with the way we interpret data and apply the same models across different scales. Supernovae are taken as “standard candles” when measuring the expansion rate of the universe, for example, and one may wonder how correct this assumption is. It is important to perform systematic studies of the raw data before we rush to new theories.

My current work mainly bears on gravitational waves. I am also editor-in-chief of the journal General Relativity and Gravitation. I joined the LIGO collaboration the year of the discovery, studying the implications of gravitational-wave background searches for new physics. I am working on similar studies for the proposed Einstein Telescope. Gravitational waves allow us to test high-energy models beyond the Standard Model at energy scales that are above those that can be reached by accelerators. There are also new results coming from pulsar timing arrays. We live in a time where many exciting results are coming fast.

How big is the European Physical Society, and what led you to be elected president?

The European Physical Society (EPS) is the federation of all national physics societies in Europe. It was founded in 1968 by particle physicist Gilberto Bernardini, who contributed to the foundation of CERN and later became director of the Synchrocyclotron division and directorate member for research.

Several years ago, following the LIGO/Virgo discoveries, I initiated the gravitational physics division of the EPS and, in doing so, entered the EPS council. Then I was elected a member of the executive committee and was eventually contacted to run for election. I admit that I was reluctant at first because it’s another task with a lot of responsibilities. But it turned out I was elected, and I took up the position formally on April 27th. I am proud to have been elected as president and I will do my best to serve the EPS and respect the confidence that representatives of so many European national societies have put in me.

What do you hope to achieve during your two-year mandate?

I have several goals as president. The most important one is to strengthen the position of Europe. What do I mean by that? There are important issues that we all face together, such as our economic independence (for instance, sources of energy, technological advances in electronics, biophysics and medical applications) and the preservation of the environment. The EPS can play a role by building teams of experts to address these issues, to be in a position to advise policy makers at the European level.

The proposed Future Circular Collider — **Collider talk** The EPS can support constructive dialogue about major projects such as the proposed Future Circular Collider at CERN. Credit: Pixel Rise

Scientific policy is another example. We live in an era with very large changes in the scale of experiments, the size of datasets, as well as advanced data-analysis techniques such as artificial intelligence. We should be able to have a say about how these things are dealt with and what the priorities are. The EPS can have a solid dialogue with large experimental teams and important research centres such as CERN. We can pass the message, for example via the national physics societies, and provide lists of experts able to advise politicians on such matters.

Last but not least is education. We need to adapt the programmes offered to the students because there is huge demand for soft skills, and I am not sure they are adequately provided. We also need to offer opportunities to welcome students and early-career researchers from regions around the world that need support. We should collaborate with them and provide scholarships to enable them to spend time at a facility such as CERN or DESY and develop key skills.

To achieve all that, we should strengthen the links between the EPS and the national societies (be they small or large). We represent the interest of all physicists in Europe equally. We also need to have a more active dialogue with our colleagues in North America and Asia because we share common challenges. Of course, to do that requires hard work and commitment.

How can the EPS support fundamental research such as particle physics?

We have a high-energy physics division, of course. From my point of view, we need to accentuate the motivation for exploring the laws of the universe. CERN obviously plays a key role in this because colliders are one of the basic experimental devices to do so. Gravitational-wave observatories are another example. These experiments have to go hand-in-hand because they have a common ambition. The EPS can give an extra voice to the scientific aspects of this enterprise. Of course, the question of financing next-generation experiments remains to be solved, as well as the balance between fundamental science and applied research. For me there is no doubt that such experiments should continue. Unfortunately, today one often has to state the implications for industry and the applications for society. This can sometimes be difficult to square with curiosity-driven science.

If approved, would a new collider at CERN take away funding from other fields?

This is a very simplistic view. Science funding is not a zero-sum game. As CERN did for the LHC, it’s good to find external sources. Money can’t go to everyone in equal amounts, so we need a way to set scientific priorities in Europe. First and foremost, this should take into account the scientific case. Then we should look at the number of countries that are interested and the level of investments that have been made – for example, also involving industry.

Money can’t go to everyone in equal amounts, so we need a way to set scientific priorities in Europe

Is the scientific case for the Future Circular Collider sufficiently clear in this respect?

If the argument is to find super-symmetry, or particles predicted by some other framework of physics beyond the Standard Model, then I’m afraid it will fail. Of course, in scientific working groups you need to go into specifics such as which hypotheses will be tested, and which signatures are possible. But such detail is a trap when engaging with broader audiences because we can’t be sure that such things exist at the energies we can explore. Instead, the argument should be that we try to understand better the elementary particles and laws. We need to pass the message to politicians, to the person on the street and to scientists that there are some important questions that can only be addressed with future colliders. While CERN and particle physicists should not be defensive, they should be clearer about what the role and ultimate hope of a collider is. Then there is no argument that can go against it. This is something that could be elaborated by the high-energy physics division of the EPS, for example by providing a document stating the views of particle physicists. We should also be prepared for a critical dialogue, to identify the strengths and weaknesses of the arguments. One should in any case ensure that anyone invited to give their views should have an established scientific reputation within their field, a prerequisite that is not met in some high-level discussions and media outlets.

Does the existence of several future-collider options pose a problem from a communications perspective?

I think it’s problematic if, scientifically, a consensus cannot be reached. There is something similar going on in the gravitational-wave community, where divisions exist about where to build the Einstein Telescope and which configuration it should have. This may lead to a healthy process of course, but discussions should be kept between experts. Indeed, it can weaken the case for a new experiment if scientists are seen to be disagreeing strongly.

What effects are current political shifts in Europe having on physics?

I’m afraid that there could be very negative effects. To this we have to add the risks created by the conflicts we see expanding. One effect could also be the changes in priorities for funding. As one of the largest scientific societies, we need to keep supporting collaborations among scientists no matter their country of origin, ethnicity, gender, or any other discriminating factor. We also need to provide financial support where possible, for example as we have done recently for Ukrainian colleagues to participate in our activities, and to make statements in response to events going way beyond the world of physics.

Sabbatical in space

Sławosz Uznański had to bide his time. Since its foundation in 1975, the European Space Agency (ESA) had only opened four selection rounds for new astronauts. When a fresh opportunity arose in 2021, Uznański’s colleagues in CERN’s electric power converters group were supportive of his ambitions to take an extended sabbatical in space. Now confirmed as one of 17 astronauts selected from among more than 22,000 applicants, Uznański is in training for future missions to the International Space Station (ISS).

His new colleagues are a diverse bunch, including geologists, medical doctors, astrophysicists, biologists, biotechnologists, jet fighter pilots and helicopter pilots. His own background is as a physicist and systems engineer. Following academic work studying the effect of radiation on semiconductors, Uznański spent 12 years at CERN working on powering existing infrastructure and future projects such as the Future Circular Collider. He’s most proud of being a project leader in reliability engineering and helping to design and deploy a new radiation-tolerant power-converter control system to the entire LHC accelerator complex.

Preparing for orbit

For now, Uznański’s astronaut training is mostly theoretical, preparing him for the ISS’s orbit-trajectory control, thermal control, communications, data handling, guidance, navigation and power generation, where he has deep expertise. But lift-off may not be far away, and one of his reserve-astronaut colleagues, Marcus Wandt, is already sitting up in the ISS capsule.

“I had the chance, in January, to see him launch from Cape Canaveral. And then, thanks to my operational experience at CERN, being in the control room, I came back directly to Columbus Control Center in Munich. Throughout the whole mission, I was in the control room, to support the mission and learn what I might live through one day.”

Rather than expertise or physical fitness, Uznański sees curiosity as the golden thread for astronauts – not least because they have to be able to perform any type of experiment that is assigned to them. As a Polish astronaut, he will have responsibility for the scientific experiments that are intended to accompany his country’s first mission to the ISS, most likely in late 2024 or early 2025. Among 66 proposals from Polish institutes, a dozen or more are currently being considered to fly.

CERN is extremely open in terms of technologies and I very much identify myself with that

The experiments are as diverse as the astronauts’ professional backgrounds. One will non-invasively monitor astronauts’ brain activity to help develop human–machine interfaces for artificial limbs. Another – a radiation monitor developed at CERN – plays on the fact that shielded high-energy physics environments have a similar radiation environment to the ISS in low-earth orbit. Uznański hopes that this technology can be commercialised and become another example of the opportunities out there for budding space entrepreneurs.

“I think we are in a fascinating moment for space exploration,” he explains, pointing to the boom in the commercial sector since 2014. “Space technology has gotten really democratised and commercialised. And I think it opens up possibilities for all types of engineers who build systems with great ideas and great science.”

Open science is a hot topic here. It’s increasingly possible to access venture capital to develop related technologies, notes Uznański, and the challenge is to ensure that the science is used in an open manner. “There is a big overlap between CERN culture and ESA culture in this respect. CERN is extremely open in terms of technologies and I very much identify myself with that.”

However societies choose to shape the future of open science in space, the two organisations are already partnering on several projects devoted to the pure curiosity that is dear to Uznański’s heart. These range from Euclid’s study of dark energy (CERN Courier May/June 2023 p7) to the ongoing study of cosmic rays by the Alpha Magnetic Spectrometer (AMS). With AMS due for an upgrade in 2026 (CERN Courier March/April 2024 p7), he cannot help but hope to be on that flight.

“If the opportunity arises, it’s a clear yes from me.”

Peter Higgs 1929–2024

Peter Higgs, an iconic figure in modern science who in 1964 postulated the existence of the eponymous Higgs boson, passed away on 8 April 2024 at the age of 94.

Peter Higgs was born in Newcastle upon Tyne in the UK on 29 May 1929. His family moved around when he was young and he suffered from childhood asthma, so he was often taught at home. However, from 1941 to 1946 he attended Cotham Grammar School in Bristol, one of whose alumni was Paul Dirac. He went on to study physics at King’s College London, where he got his bachelor’s degree in 1950 and his PhD for research in molecular physics in 1954. After periods at the University of Edinburgh, Imperial College and University College London, in 1960 he settled at the University of Edinburgh where he remained for the rest of his career.

Seeds of success

Following his PhD, Higgs’s research interests shifted to field theory, with a first paper on vacuum expectation values of fields in 1956, followed by a couple of papers on general relativity. Then, in 1964, came his two famous papers introducing spontaneous gauge symmetry breaking into relativistic quantum field theory and showing how a vector boson could acquire a mass in a consistent manner – as long as it was accompanied by a massive scalar boson.

Related ideas had been discussed previously by Phillip Anderson and Yoichiro Nambu in the context of non-relativistic condensed-matter physics, namely in models of superconductivity, where a condensate of electron pairs enables a photon to acquire an effective mass. Anderson conjectured that a similar mechanism should be possible in a relativistic theory, but he did not develop the idea. On the other hand, Nambu used spontaneous symmetry breaking to describe the properties of the pion, but also did not discuss the extension to a relativistic vector boson.

In early 1964 Walter Gilbert (later a winner of the Nobel Prize in Chemistry) wrote a paper arguing that Anderson and Nambu’s ideas for generating mass for a vector boson could not work in a relativistic theory. This was Higgs’s cue: a few weeks later he wrote a first paper pointing out a potential loophole in Gilbert’s argument (though not a specific model). He sent his paper to the journal Physics Letters, which quickly accepted it for publication. A few days later, he wrote a second paper, which contained an explicit model for mass generation, but was taken aback when the same journal rejected this paper as not being of practical interest. Undeterred, Higgs tweaked his paper to make his message more explicit, and submitted it to Physical Review Letters, where it was accepted.

Unknown to Higgs, François Englert and Robert Brout had already sent a paper describing a similar model to the same journal, where it was published ahead of Higgs’s paper. Both papers postulated a scalar field with a non-zero vacuum expectation value that gave mass to a vector boson. However, there was a key difference: Higgs pointed out explicitly that his model predicted the existence of a massive scalar boson, whereas this was not mentioned in the Englert–Brout paper. For this reason, the particle he predicted became known as the Higgs boson. Shortly after the publication of the Higgs and Englert–Brout papers, Gerry Guralnik, Carl Hagen and Tom Kibble published an article referring to their papers and filling in some aspects of the theory, but also not mentioning the existence of the massive scalar boson.

In 1965 Higgs went for a sabbatical to the University of North Carolina, where he continued working on his theory. Remarkably prescient, he wrote a third paper discussing how his boson could decay into a pair of massive gauge bosons as well as calculating associated scattering processes. However, he encountered scepticism about the validity of his theory, and neither his nor the other pioneering mass-generation papers garnered significant attention for several years.

This started to change in 1967 and 1968 when Steven Weinberg and Abdus Salam incorporated the mass-generation mechanism into their formulation of the electroweak sector of the Standard Model. But interest only really took off a few years later, after Gerard ’t Hooft and Martinus Veltman showed that spontaneously broken gauge theories are renormalisable and hence could be used to make accurate and reliable predictions for comparison with experiment, and when neutral weak interactions were discovered in the Gargamelle bubble chamber at CERN in 1973.

The search begins

During the 1970s interest in the experimental community moved towards searches for the massive intermediate vector bosons, the W and Z. However, it seemed to Mary Gaillard, Dimitri Nanopoulos and myself that the key long-term target should be the Higgs boson, the capstone of the structure of the Standard Model, and in 1975 we wrote a paper describing its phenomenology. At the time the existence of the Higgs boson was still regarded with some scepticism, and we ended our paper by writing that “We do not want to encourage big experimental searches for the Higgs boson, but we do feel that people performing experiments vulnerable to the Higgs boson should know how it may turn up.” I met Peter Higgs for the first time around 1980, and he was clearly flattered by our interest in his boson, but unprepared for the subsequent interest in the big experimental searches that followed.

Higgs pointed out explicitly that his model predicted the existence of a massive scalar boson

Searching for the Higgs boson moved to the top of the agenda following the discovery of the W and Z at CERN in 1983, when the Superconducting Super Collider project was launched in the US, followed by the first LHC workshop in 1984. Being a profoundly modest man, Higgs followed these developments from a distance as a somewhat bemused spectator. In the 1990s, precision experiments at LEP and elsewhere confirmed predictions of the Standard Model with high accuracy – if and only if the Higgs boson (or something very like it) was included in the theoretical calculations. Higgs became quietly confident in the reality of his boson. By the time the LHC started accumulating collisions at an energy of 7 and 8 TeV, anticipation of its possible discovery was growing.

Following early hints at the end of 2011, the word went around that on 4 July 2012 the ATLAS and CMS experiments would give a joint seminar presenting their latest results. I was tasked with locating Higgs and persuading him that he might find the results interesting. Somewhat reluctantly, he decided to come to CERN for the seminar, and he had no cause to regret it. He wiped tears from his eyes when the discovery of a new particle resembling his boson was announced, and confessed that he had never expected to see it in his lifetime.

Famously, in October 2013 as the Nobel Prize was being announced, Higgs went missing, in order to avoid being thronged by the media. Some months previously, in a pub in Edinburgh, he had told me that the existence of the Higgs boson was not a “big deal”, but I assured him that it was. Without his theory, electrons would fly away from nuclei at the speed of light and atoms would not exist, and radioactivity would be a force as strong as electricity and magnetism. His prediction of the existence of the particle that bears his name was a deep insight, and its discovery was the crowning moment that confirmed his understanding of the way the universe works.

Peter Higgs is survived by his two sons, a daughter-in-law and two grandchildren.

Mykola Shulga 1947–2024

Mykola Shulga, an outstanding Ukrainian theoretical high-energy physicist, passed away on 23 January 2024. Born on 15 September 1947 in Kharkiv, Ukraine, he graduated with honours from Kharkiv State University in 1971. In 1973 he joined the Kharkiv Institute of Physics and Technology (KIPT) where he worked for the rest of his life. He held many leadership positions at KIPT and became its director general in 2016.

A significant role in Shulga’s formation as a scientist was played by his PhD advisor and prominent KIPT theorist Oleksandr Akhiezer. Together they developed the quasi classical theory of coherent radiation of channelled and over-barrier electrons and positrons in crystals. This theory provided an understanding of the basic emission mechanisms in oriented crystals, which is crucial for creating an intense gamma-ray source as well as a crystal-based positron source for future electron–positron colliders.

Mykola Shulga always worked to ensure that his theoretical predictions were tested experimentally. Many of them were confirmed recently at CERN. In 2005–2010 the NA63 collaboration confirmed the Ternovsky–Shulga–Fomin effect – a suppression of bremsstrahlung radiation from ultrarelativistic electrons in thin layers of matter. In 2009–2017 the UA9 collaboration confirmed his prediction of a stochastic Grinenko–Shulga mechanism of high-energy particle-beam deflection by a bent crystal. This mechanism allows the deflection of both positively and negatively charged particles, and is planned to be implemented at the PETRA IV synchrotron at DESY and future electron–positron colliders.

Shulga was a laureate of the State Prize of Ukraine in the field of science and technology (2002), won prizes of the National Academy of Sciences of Ukraine (NASU) named after O S Davydov (2000) and O I Akhiezer (2018), and received many other awards. In 2009 he was elected an academician of NASU and in 2015 became head of its department of nuclear physics and power engineering. From 2004 to 2013 he was vice-president of the Ukrainian Physical Society.

Shulga paid great attention to working with young physicists, whom he taught for many years at V N Karazin Kharkiv National University. He trained eight PhD students and eight doctors of science, and among his students are eight laureates of the State Prize of Ukraine in the field of science and technology.

Thanks to his high human qualities, exceptional diligence and amazing capacity for work, Mykola Shulga gained great authority and respect in the scientific community. He led National Science Center KIPT (NSC KIPT) through two years of the full-scale invasion of Ukraine by the Russian Federation, working to eliminate the consequences of more than 100 missile strikes on the NSC KIPT territory, which left not a single building undamaged. Undeterred by the war, until his last days he continued to promote the creation of a new international centre for nuclear physics and medicine on the NSC KIPT site (CERN Courier January/February 2024 p30).

His bright memory will forever remain in the hearts of his colleagues, friends, relatives and loved ones.

The coolest job in physics

Surviving long polar nights — **Light in the dark** (clockwise from top left) The Aurora Australis, a music room and a greenhouse help IceCube winterovers such as Marc Jacquart survive long polar nights. Credit: M Jacquart

IceCube’s 5160 optical sensors positioned deep within the Antarctic ice detect around 100,000 neutrinos per year, some of which are the most energetic events ever recorded. To make sure that the detector is operational throughout the year, people are required to spend extended periods at the South Pole, where temperatures are on average around –60°C during the winter.

Marc Jacquart was one of two “winterovers” for IceCube during the season November 2022 to November 2023. Having completed his master’s degree, during which he analysed IceCube data, he saw an internal email about the position and applied: “It was a long-time dream-come-true. I had wanted to go to the South Pole since I heard about IceCube six years earlier.” First he had to pass medical tests, a routine requirement for winterovers because it is difficult to evacuate people during the winter. His next stop was the University of Wisconsin–Madison, the lead institution for the IceCube collaboration, where he and his colleague Hrvoje Dujmović received three months’ training on how to operate, troubleshoot, calibrate and repair IceCube’s hardware and software components using a small replica of the data centre. “Our job is to ensure the highest detector uptime, so we need to know how to fix a problem immediately if something breaks.”

The pair made their way to McMurdo Station on the shores of Antarctica closest to New Zealand in early November 2022. From there, a plane took them 1350 km to the Amundsen–Scott station, located 2835 m above sea level and only 150 m from the geographic South Pole. During the summer, up to 150 people stay at the station to make major repairs and upgrades to the research facilities, which also include the South Pole Telescope, BICEP and an atmospheric research observatory. By mid-February, most people leave. “We were only 43 winterovers left, and that’s when you can help each other and busy yourself with all kinds of things,” says Marc.

Part of station life is volunteering for teams, which in Marc’s case included the fire fighters, amongst others. To bide their time during a nearly six-month-long night, the inhabitants can go to the library, music room or grow vegetables in a repurposed biology experiment to freshen up the preserved foods. While winter in the Antarctic Circle is harsh outside, says Marc, it has one major highlight: the southern lights. “I remember one time, they were just dancing, moving and very bright. We stayed outside for a full hour packed in layers and layers of clothes!”

The only real downtime for the detector is when operators perform a full restart every 32 hours

As a winterover, Marc ensured that the IceCube detector worked 24/7 and recorded every incoming neutrino. “Usually, we have 99.9% uptime. If there is something wrong, we have a pager that pings us, even in the middle of the night.” To ensure that the rarest high-energy neutrinos are recorded, the only real downtime for the detector, he says, is when operators perform a full restart every 32 hours. For such events, which could point to high-energy phenomena in the universe, IceCube sends a real-time alert to other experiments. About 200 machines are located in the data centre and collect 1 TB of data per day, only 10% of which are sent north to a data centre in the US due to satellite-bandwidth limitations. The remaining data gets stored on hard drives, which must be swapped manually by the winterovers every two weeks. During the summer, when aircraft can reach the South Pole on a regular basis, boxes stashed with hard drives are taken back for thorough data analysis and archiving.

Since returning home to Switzerland, Marc is considering his next steps. “I have the opportunity to work on a radio observatory in the US next year. After a year operating the IceCube detector, I’m interested to work with hardware more. And I am definitely considering a PhD with IceCube afterwards, as there is a lot coming up.” Currently, the IceCube collaboration is working towards IceCube-Gen2, with the first step being to add seven strings with improved optical modules to the existing underground complex. In a second step, 120 further cables with refined light sensors will optimise the detector, and two radio detectors as well as an extended array will be placed on the surface. The upgrades will enlarge IceCube’s coverage from one to eight cubic kilometres, offering more than enough tasks for future winterovers during the decade . “Maybe in a few years I would be keen to return to the South Pole. It’s a very special place.”

Advances in cosmology

On the 30th anniversary of the discovery of weak neutral currents, the architects of the Standard Model of strong and electroweak interactions met in the CERN main auditorium on 16 September 2003 to debate the future of high-energy physics. During the panel discussion, Steven Weinberg repeatedly propounded the idea that cosmology is part of the future of high-energy physics, since cosmology “is now a science” as opposed to a mere theoretical framework characterised by diverging schools of thought. Twenty years later, this viewpoint may serve as a summary of the collection of articles in Advances in Cosmology.

The papers assembled in this volume encompass the themes that are today associated with the broad domain of cosmology. After a swift theoretical section, the contributions range from dark-matter searches (both at the LHC and in space) to gravitational waves and optical astronomy. The last two sections even explore the boundaries between cosmology, philosophy and artistic intuition. Indeed, as former CERN Director-General Rolf Heuer correctly puts it in his thoughtful foreword, the birth of quantum mechanics was also a philosophical enterprise: both Wolfgang Pauli and Werner Heisenberg never denied their Platonic inspiration and reading Timaeus (the famous Plato dialogue dealing with the origin and purpose of the universe) was essential for physicists of that generation to develop their notion of symmetry (see, for instance, Heisenberg’s 1969 book Physics and Beyond).

In around 370 pages, the editors of Advances in Cosmology manage to squeeze in more than two millennia of developments ranging from Pythagoras to the LHC, and for this reason the various contributions clearly follow different registers. Interested readers will not only find specific technical accounts but also the wisdom of science communicators and even artists. This is why the complementary parts of the monograph share the same common goals, even if they are not part of the same logical line of thinking.

Advances in Cosmology appeals to those who cherish an inclusive and eclectic approach to cosmology and, more generally, to modern science. While in the mid 1930s Edwin Hubble qualified the frontier of astronomy as the “realm of the nebulae”, modern cosmology combines the microscopic phenomena of quantum mechanics with the macroscopic effects of general relativity. As this monograph concretely demonstrates, the boundaries between particle phenomenology and the universe’s sciences are progressively fading away. Will the next 20 years witness only major theoretical and experimental breakthroughs, or more radical changes of paradigm? From the diverse contributions collected in this book, we could say, a posteriori, that scientific revolutions are never isolated as they need environmental selection rules that come from cultural, technological and even religious boundary conditions that cannot be artificially manufactured. This is why paradigm shifts are often difficult to predict and only recognised well after their appearance.

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