In 1895, the German physicist Wilhelm Röntgen noticed that a phosphor-coated screen gave off a green light when exposed to a cathode ray tube. He quickly realised that he’d found a new invisible ray. Asked what he thought when he saw this green light, he replied: “I didn’t think. I investigated.” In fact he spent seven weeks investigating, locked away in his laboratory and only coming out when his wife, Anna, insisted he eat something. He rewarded her concern for his wellbeing by using the unknown rays to make an image of her hand on a photographic plate. It proved that they could travel through skin and flesh: the plate revealed her bones and wedding ring. When she saw the image, she was appalled, saying: “I have seen my death!”
In his notebook, Röntgen used a letter to denote the unknown rays: “X-rays”. As Sheehy says, this is “possibly the best unintentional branding in the history of physics”. Within a year of his discovery, X-rays were being used to find shrapnel in soldiers’ bodies on the battlefield.
The question of how cathode ray tubes emitted X-rays led to the seminal discovery in 1897 of the electron – the first subatomic particle. Atoms were no longer regarded as the smallest indivisible entity in nature. Indeed, the next century would reveal a whole catalogue of particles, utterly transforming our understanding of matter.
The key question for Australian physicist Suzie Sheehy is this: “What is matter, and how does it interact to create everything around us – including ourselves?” She describes her work, in which she tries to answer this question by studying the tiniest constituents in nature and the forces that govern them, as “one of the most awe-inspiring, intricate and creative adventures that humans have ever embarked on”.
Her specialism is accelerator physics, a field that deploys some of the largest machines ever invented to manipulate matter on a tiny scale. An esoteric field, you might think, one that has little relevance to our everyday lives. But as she shows, particle physics has changed how we live dramatically over the last century. Your nearest hospital almost certainly has a particle accelerator, your smartphone relies on quantum mechanics, and Tim Berners-Lee invented the world wide web to help scientists share the vast amounts of data produced by particle experiments.
Sheehy is not a theoretician, a modern-day Einstein creating speculative hypothesis about the nature of reality. Rather she is an experimental physicist who designs equipment that pushes the limits of current technology and generates new data and questions. It’s demanding work that requires curiosity, passion and tenacity.
In her book – which is often complex yet never less than fascinating – she uses 12 experiments to show how particle physics has shaped our understanding of the world we live in. She begins with Röntgen’s discovery, before moving on to early experiments showing that the atom was composed mostly of empty space, with a dense nucleus surrounded by electrons, and on to the creation of the first particle accelerators in the 1930s.
After the success of the top-secret Manhattan Project to build an atomic bomb during the second world war, physicists embraced a large-scale, collaborative approach. This was the beginning of Big Science. Gone were the days of lone researchers, like Röntgen, toiling away in their laboratories – physics was now about gigantic, expensive machines, designed by groups of experimental scientists, maintained by specialist engineers, and operated by a dedicated staff. Results were interpreted by teams of scholars around the world. These methods yielded a deluge of new particles, from pions to positrons.
The quest culminates – for now at least – with the Large Hadron Collider at CERN, a 27-km circular proton collider, 100 metres below ground near Geneva. It took two and a half decades to build, overseen by the Welsh physicist Lyndon Evans, affectionately known as “Evans the Atom”.
Sheehy, who has worked at CERN, guides the reader round this triumph of engineering and scientific cooperation, “one of the greatest experiments ever built”. Described as the biggest machine on Earth, it is so sensitive that it has to be corrected for unbelievably small effects, such as the movement of the Earth’s crust due to the sun and the moon, or the passing of high speed trains – anything that will disturb the proton orbit.
A proton is a million million times smaller than a grain of sand. The LHC “delivers two beams of hundreds of billions of protons to 99.999999 percent of the speed of light, focuses them down to less than the width of a hair, and then collides them”. Its task was to detect a single and very elusive particle – the Higgs boson, predicted in 1964. This goal was achieved in 2012, thanks to the collaboration of half of the world’s 13,000 particle physicists, and drawing on the resources of 110 countries.
In the end, as Sheehy tells us, physics is not just about the search for how the Universe works: “Physics is all about people.” Her journey through the history of particle physics reveals the extraordinary ingenuity of experimental scientists and their selfless dedication to answering big questions about matter and the universe. It is a field that has brought huge benefits to humankind, from new medical imaging technologies to cancer treatments. But in the end, it may well be the physicists’ example of working together to solve problems that will prove the most valuable to us all, at a time when the world faces unparalleled challenges. As Sheehy says: “There is nothing more powerful than humans who come together in collaborative endeavour.”
• The Matter of Everything: Twelve Experiments that Changed Our World is published by Bloomsbury (£20). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply.
