A quarter of a century ago, in May 2000, I published an article entitled “Why science thrives on criticism”. The article, which ran to slightly over a page in Physics World magazine, was the first in a series of columns called Critical Point. Periodicals, I said, have art and music critics as well as sports and political commentators, and book and theatre reviewers too. So why shouldn’t Physics World have a science critic?

The implication that I had a clear idea of the “critical point” for this series was not entirely accurate. As the years go by, I have found myself improvising, inspired by politics, books, scientific discoveries, readers’ thoughts, editors’ suggestions and more. If there is one common theme, it’s that science is like a workshop – or a series of loosely related workshops – as I argued in The Workshop and the World, a book that sprang from my columns.

Workshops are controlled environments, inside which researchers can stage and study special things – elementary particles, chemical reactions, plant uptakes of nutrients – that appear rarely or in a form difficult to study in the surrounding world. Science critics do not participate in the workshops themselves or even judge their activities. What they do is evaluate how workshops and worlds interact.

This can happen in three ways

Critical triangle

First is to explain why what’s going on inside the workshops matters to outsiders. Sometimes, those activities can be relatively simple to describe, which leads to columns concerning all manner of everyday activities. I have written, for example, about the physics of coffee and breadmaking. I’ve also covered toys, tops, kaleidoscopes, glass and other things that all of us – physicists and non-physicists alike – use, value and enjoy.

Sometimes I draw out more general points about why those activities are important. Early on, I invited readers to nominate their most beautiful experiments in physics. (Spoiler alert: the clear winner was the double-slit experiment with electrons.) I later did something similar about the cultural impact of equations – inviting readers to pick their favourites and reporting on their results (second spoiler alert: Maxwell’s equations came top). I also covered readers’ most-loved literature about laboratories.

Physicists often engage in activities that might seem inconsequential to them yet are an intrinsic part of the practice of physics

When viewing science as workshops, a second role is to explain why what’s outside the workshops matters to insiders. That’s because physicists often engage in activities that might seem inconsequential to them – they’re “just what the rest the world does” – yet are an intrinsic part of the practice of physics. I’ve covered, for example, physicists taking out patents, creating logos, designing lab architecture, taking holidays, organizing dedications, going on retirement and writing memorials for the deceased.

Such activities I term “black elephants”. That’s because they’re a cross between things physicists don’t want to talk about (“elephants in the room”) and things that force them to renounce cherished notions (just as “black swans” disprove that “all swans are white”).

A third role of a science critic is to explain what matters that takes place both inside and outside the workshop. I’m thinking of things like competition, leadership, trust,  surprise, workplace training courses, cancel culture and even jokes and funny tales. Interpretations of the meaning of quantum mechanics, such as “QBism”, which I covered both in 2019 and 2022, are an ongoing interest. That’s because they’re relevant both to the structure of physics and to philosophy as they disrupt notions of realism, objectivity, temporality and the scientific method.

Being critical

The term “critic” may suggest someone with a congenitally negative outlook, but that’s wrong. My friend Fred Cohn, a respected opera critic, told me that, in a conversation after a concert, he criticized the performance of the singer Luciano Pavarotti. His remark provoked a woman to shout angrily at him: “Could you do better?” Of course not! It’s the critic’s role to evaluate performances of an activity, not to perform the activity oneself.

Having said that, sometimes a critic must be critical to be honest. In particular, I hate it when scientists try to delegitimize the experience of non-scientists by saying, for example, that “time does not exist”. Or when they pretend they don’t see rainbows but wavelengths of light or that they don’t see sunrises or the plane of a Foucault pendulum move but the Earth spinning. Comments like that turn non-scientists off science by making it seem elitist and other-worldly. It’s what I call “scientific gaslighting”.

Most of all, I hate it when scientists pontificate that philosophy is foolish or worthless, especially when it’s the likes of Steven Pinker, who ought to know better. Writing in Nature (518 300), I once criticized the great theoretical physicist Steven Weinberg, who I counted as a friend, for taking a complex and multivalent text, plucking out a single line, and misreading it as if the line were from a physics text.

The text in question was Plato’s Phaedo, where Socrates expresses his disappointment with his fellow philosopher Anaxagoras for giving descriptions of heavenly bodies “in purely physical terms, without regard to what is best”. Weinberg claimed this statement meant that Socrates “was not very interested in natural science”. Nothing could be further from the truth.

At that moment in the Phaedo, Socrates is recounting his intellectual autobiography. He has just come to the point where, as a youth, he was entranced by materialism and was eager to hear Anaxagoras’s opposing position. When Anaxagoras promised to describe the heavens both mechanically and as the product of a wise and divine mind but could do only the former, Socrates says he was disappointed.

Weinberg’s jibe ignores the context. Socrates is describing how he had once embraced Anaxagoras’s view of a universe ruled by a divine mind but later rejected that view. As an adult, Socrates learned to test hypotheses and other claims through putting them to the test, just as modern-day scientists do. Weinberg was misrepresenting Socrates by describing a position that he later abandoned.

The critical point of the critical point

Ultimately, the “critical point” of my columns over the last 25 years has been to provoke curiosity and excitement about what philosophers, historians and sociologists do for science. I’ve also wanted to raise awareness that these fields are not just fripperies but essential if we are to fully understand and protect scientific activity.

As I have explained several times – especially in the wake of the US shutting its High Flux Beam Reactor and National Tritium Labeling Facility – scientists need to understand and relate to the surrounding world with the insight of humanities scholars. Because if they don’t, they are in danger of losing their workshops altogether.

• Explore the best of Robert P Crease’s Critical Point articles in this special collection.

The post Robert P Crease lifts the lid on 25 years as a ‘science critic’ appeared first on Physics World.

I’m standing next to Yang Fugui in front of the High Energy Photon Source (HEPS) in Beijing’s Huairou District about 50 km north of the centre of the Chinese capital. The HEPS isn’t just another synchrotron light source. It will, when it opens later this year, be the world’s most advanced facility of its type. Construction of this giant device started in 2019 and for Yang – a physicist who is in charge of designing the machine’s beamlines – we’re at a critical point.

“This machine has many applications, but now is the time to make sure it does new science,” says Yang, who is a research fellow at the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS), which is building the new machine. With the ring completed, optimizing the beamlines will be vital if the facility is to open up new research areas.

From the air – Google will show you photos – the HEPS looks like a giant magnifying glass lying in a grassy field. But I’ve come by land, and from my perspective it resembles a large and gleaming low-walled silver sports stadium, surrounded by well-kept bushes, flowers and fountains.

I was previously in Beijing in 2019 at the time ground for the HEPS was broken when the site was literally a green field. Back then, I was told, the HEPS would take six-and-a-half years to build. We’re still on schedule and, if all continues to run as planned, the facility will come online in December 2025.

Lighting up the world

There are more than 50 synchrotron radiation sources around the world, producing intense, coherent beams of electromagnetic radiation used for experiments in everything from condensed-matter physics to biology. Three significant hardware breakthroughs, one after the other, have created natural divisions among synchrotron sources, leading them to be classed by their generation.

Along with Max IV in Sweden, SIRIUS in Brazil and the Extremely Brilliant Source at the European Synchrotron Radiation Facility (ESRF) in France, the HEPS is a fourth-generation source. These days such devices are vital and prestigious pieces of scientific infrastructure, but synchrotron radiation began life as an unexpected nuisance (Phys. Perspect. 10 438).

Classical electrodynamics says that charged particles undergoing acceleration – changing their momentum or velocity – radiate energy tangentially to their trajectories. Early accelerator builders assumed they could ignore the resulting energy losses. But in 1947, scientists building electron synchrotrons at the General Electric (GE) Research Laboratory in Schenectady, New York, were dismayed to find the phenomenon was real, sapping the energies of their devices.

Nuisances of physics, however, have a way of turning into treasured tools. By the early 1950s, scientists were using synchrotron light to study absorption spectra and other phenomena. By the mid-1960s, they were using it to examine the surface structures of materials. But a lot of this work was eclipsed by seemingly much sexier physics.

High-energy particle accelerators, such as CERN’s Proton Synchrotron and Brookhaven’s Alternating Gradient Synchrotron, were regarded as the most exciting, well-funded and biggest instruments in physics. They were the symbols of physics for politicians, press and the public – the machines that studied the fundamental structure of the world.

Researchers who had just discovered the uses of synchrotron light were forced to scrape parts for their instruments. These “first-generation” synchrotrons, such as “Tantalus” in Wisconsin, the Stanford Synchrotron Radiation Project in California, and the Cambridge Electron Accelerator in Massachusetts, were cobbled together from discarded pieces of high energy accelerators or grafted onto them. They were known as “parasites”.

In the 1970s, accelerator physicists realized that synchrotron sources could become more useful by shrinking the angular divergence of the electron beam, thereby improving the “brightness”. Renate Chasman and Kenneth Green devised a magnet array to maximize this property. Dubbed the “Chasman–Green lattice”, it begat a second-generation of dedicated light sources, built not borrowed.

Hard on the heels of  Synchrotron Radiation Light Source, which opened in the UK in 1981, the National Synchrotron Light Source (NSLS I) at Brookhaven was the first second-generation source to use such a lattice. China’s oldest light source, the Beijing Synchrotron Radiation Facility, which opened to users in Beijing early in 1991, had a Chasman–Green lattice but also had to skim photons off an accelerator; it was a first-generation machine with a second-generation lattice. China’s first fully second-generation machine was the Hefei Light Source, which opened later that year.

By then instruments called “undulators” were already starting to be incorporated into light sources. They increased brightness hundreds-fold, doing so by wiggling the electron beam up and down, causing a coherent addition of electron field through each wiggle. While undulators had been inserted into second-generation sources, the third generation built them in from the start.

The first of these light sources was the ESRF, which opened to users in 1988. It was followed by the Advanced Photon Source (APS) at Argonne National Laboratory in 1995 and SPring-8 in Japan in 1999. The first third-generation source on the Chinese mainland was the Shanghai Synchrotron Radiation Facility, which opened in 2009.

In the 2010s, “multi-bend achromat” magnets drastically shrank the size of beam elements, further increasing brilliance. Several third generation machines, including the APS, have been upgraded with achromats, turning third-generation machines into fourth. SIRIUS, which has an energy of 3 GeV, was the first fourth-generation machine to be built from scratch.

Set to operate at 6 GeV, the HEPS will be the first high-energy fourth-generation machine built from scratch. It is a step nearer to the “diffraction limit” that’s ultimately imposed by the way the uncertainty principle limits the simultaneous specification of certain properties. It makes further shrinking of the beam possible – but only at the expense of lost brilliance. That limit is still on the horizon, but the HEPS draws it closer.

The HEPS is being built next to a mountain range north of Beijing, where the bedrock provides a stable platform for the extraordinarily sensitive beams. Next door to the HEPS is a smaller stadium-like building for experimental labs and offices, and a yet smaller building for housing behind that.

Staff at the HEPS successfully stored the machine’s first electron beam in August 2024 and are now enhancing and optimizing parameters such as electron beam current strength and lifetime. When it opens at the end of the year, the HEPS will have 14 beamlines but is designed eventually to have around 90 experimental stations. “Our task right now is to build more beamlines” Yang told me.

Looking around

After studying physics at the University of Science and Technology in Hefei, Yang’s first job was as a beamline designer at the HEPS. On my visit, the machine was still more than a year from being operational and the experimental hall surrounding the ring was open. It is spacious unlike of many US light sources I’ve been to, which tend to be crammed due to numerous upgrades of the machine and beamlines.

As with any light source, the main feature of the HEP is its storage ring, which consists of alternating straight sections and bends. At the bends, the electrons shed X-rays like rain off a spinning umbrella. Intense, energetic and finely tunable, the X-rays are carried off down beamlines, where are they made useful for almost everything from materials science to biomedicine.

We pass other stations optimized for 2D, 3D and nanoscale structures. Occasionally, a motorized vehicle loaded with equipment whizzes by, or workers pass us on bicycles. Every so often, I see an overhead red banner in Chinese with white lettering. Translating, Yang says the banners promote safety, care and the need for precision in doing high-quality work, signs of the renowned Chinese work ethic.

We then come to what is labelled a “pink” beam. Unlike a “white” beam, which has a broad spread of wavelengths, or a monochromatic beam of a very specific colour such as red, a pink beam has a spread of wavelengths that are neither broad nor narrow. This allows a much broader flux – typically two orders of magnitude more than a monochromatic beam – allowing a researcher fast diffraction patterns.

Another beamline, meanwhile, is labelled “tender” because its energy falls between 2 keV (“soft” X-rays) and 10 keV (“hard” X-rays). It’s for materials “somewhere between grilled steak and Jell-O” one HEPS researcher quips to me, referring to the wobbly American desert. A tender beam is for purposes that don’t require atomic-scale resolution, such as the magnetic behaviour of atoms.

Three beam pipes pass over the experimental hall to end stations that lie outside the building. They will be used, among other things, for applications in nanoscience, with a monochromator throwing out much of the X-ray beam to make it extremely coherent. We also pass a boxy, glass structure that is a clean room for making parts, as well as a straight pipe about 100 m long that will be used to test tiny vibrations in the Earth that might affect the precision of the beam.

Challenging times

I once spoke to one director of the NSLS, who would begin each day by walking around that facility, seeing what the experimentalists were up to and asking if they needed help. His trip usually took about 5–10 minutes; my tour with Yang took an hour.

But fourth-generation sources, such as the HEPS, face two daunting challenges. One is to cultivate a community of global users. Nearby the HEPS is CAS’s new Yanqi Lake campus, which lies on the other side of the mountains from Beijing, from where I can see the Great Wall meandering through the nearby hills. Faculty and students at CAS will form part of academic users of the HEPS, but how will the lab bring in researchers from abroad?

The HEPS will also need to get in users from business, convincing companies of the value of their machine. SPring-8 in Japan has industrial beamlines, including one sponsored by car giant Toyota, while China’s Shanghai machine has beamlines built by the China Petroleum and Chemical Corporation (Sinopec).

Yang is certainly open to collaboration with business partners. “We welcome industries, and can make full use of the machine, that would be enough,” he says. “If they contribute to building the beamlines, even better.”

The other big challenge for fourth-generation sources is to discover what new things are made possible by the vastly increased flux and brightness. A new generation of improved machines doesn’t necessarily produce breakthrough science; it’s not like one can turn on a machine with greater brightness and a field of new capabilities unfolds before you.

Instead, what can happen is that techniques that are demonstrations or proof-of-concept research in one generation of synchrotron become applied in niche areas in the next, but become routine in the generation after that. A good example is speckle spectrometry – an interference-based technique that needs a sufficiently coherent light source – that should become widely used at fourth-generation sources like HEPS.

For the HEPS, the challenge will be to discover what new research in materials, chemistry, engineering and biomedicine these techniques will make possible. Whenever I ask experimentalists at light sources what kinds of new science the fourth-generation machines will allow, the inevitable answer is something like, “Ask me in 10 years!”

Yang can’t wait that long. “I started my career here,” he says, gesturing excitedly to the machine. “Now is the time – at the beginning – to try to make this machine do new science. If it can, I’ll end my career here!”

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