Higgs Force

Higgs Force: The Symmetry-Breaking Force that Makes the World an Interesting Place by Nicholas Mee

Literary Review, March 2012

Last December, with the Internet having been awash with rumours for weeks, saw the official announcement of the latest results in the search for the Higgs particle from the fellowship of the ring – the physicists working at CERN’s 27km circular Large Hadron Collider (LHC). The Higgs is the missing piece of the theory that describes the behaviour of fundamental particles and the forces that act between them. It plays a special role in giving all the other particles mass.

The teams running the two giant detectors at the LHC independently put the mass of the Higgs, which is measured in what physicists call gigaelectron volts (GeV), somewhere between 116–130 and 115–127 GeV respectively. Although the scope of the search for the Higgs has now been narrowed, particle physicists demand an extraordinary degree of precision in their measurements. As the CERN press release made clear, even a 98 per cent chance of being correct is ‘not yet strong enough to claim a discovery’.

Particle collisions at CERN

If all the data generated by the LHC were stored on CDs it would fill more than a million every second. This is one of the more astonishing facts that Nicholas Mee reports in his book Higgs Force. To overcome this problem detectors are designed to be highly selective about the data passed on for storage. When the LHC smashes beams of particles together there are a billion or so collisions per second within the ATLAS detector alone, yet only the data from a couple of hundred collision events that have the telltale signs of interesting and possibly new physics are recorded.

The system that performs the selection process and determines which information is discarded and which is stored for analysis is called the trigger. Nicholas Mee acts as the trigger as he selects the tales to tell of those whose work has helped reveal the structure of matter and the laws of nature, culminating in the present hunt for the Higgs particle. The result is an intellectual journey that ends at the LHC near Geneva but begins with the Big Bang 13.75 billion years ago.

When the universe was born there was only a single force, which Mee calls the Higgs force. Moments after its birth the temperature began to fall as the universe expanded and the original force was shattered into four disparate pieces. The strong force would hold the quarks together in the atomic nucleus, while the weak force would transmute matter and make the different elements. The electromagnetic force would bind atoms and control their chemical reactions, and then there was gravity. Mee focuses on the three forces that matter when it comes to particle physics – electromagnetism, weak and strong – and attempts the difficult task of trying to explain how physicists have discerned that although ‘the universe began in a perfectly symmetrical state, the Higgs broke this symmetry and enabled the matter that formed within the universe to evolve into complex and diverse structures’. Without the Higgs particle the universe would have remained in a state that was ‘homogeneous, lifeless and uninteresting’.

Most people have an intuitive feel for what symmetry means. They recognise symmetrical patterns when they see them. However, physicists understand symmetry in terms of transformation, such as a reflection in a mirror, a rotation around an axis or a translation through space. An object or a pattern possesses a symmetry if it does not change when it is transformed in some way. For instance, if a snowflake is rotated around its centre by sixty degrees (one sixth of a complete revolution), it will appear exactly the same after the rotation as it did before. In fact all rotations through multiples of sixty degrees are symmetries of a snowflake.

Symmetry has become fundamental to the way that physicists view the universe, and an increased understanding of the symmetries of nature has been one of the major themes in the development of physics. When a quantity remains unchanged throughout a physical encounter it helps physicists to disentangle the details of what might be an extremely complicated event. This is true of the collisions that take place at the LHC. Mee does an admirable job of explaining all this before tackling ‘spontaneous symmetry breaking’, which lies at the heart of the Higgs story.

Peter Higgs

This book is far broader and more accessible than its title may suggest. For instance, we learn that the scientific investigation of magnetism dates back to William Gilbert, the personal physician of Elizabeth I. He was one of the first to try to understand the workings of nature through experimentation rather than philosophical argument. He concluded from his many experiments that the Earth is a magnet, explaining why a compass needle points north. Among others that we meet is a physicist who compared his power to transmute the elements to the mythical alchemist Hermes Trismegistus; an astronomer who was captivated by the beauty of a falling snowflake; the British physicist whose work predicted the existence of antimatter; the theorist who transformed particle physics with his eightfold way; and Peter Higgs, whose long wait for the discovery of the particle that bears his name may soon be over.

The Infinity Puzzle

                                                                 
The Infinity Puzzle: How the quest to understand quantum field theory led to extraordinary science, high politics, and the world's most expensive experiment by Frank Close

Literary Review, December 2011


‘A desk or table, a chair, paper and pencils,’ was what Einstein asked for in 1933 when he arrived at the Institute for Advanced Study in Princeton. Then he remembered one last item: ‘Oh yes, and a large wastebasket, so I can throw away all my mistakes.’ In the next two decades before his death in 1955 there were plenty of them, but Einstein had earned the right to make those mistakes in search of his holy grail – a unified field theory.

In 1864 the Scottish physicist James Clerk Maxwell showed that electricity and

magnetism were different manifestations of the same underlying phenomenon – electromagnetism. His great achievement was to encapsulate the disparate behaviour of electricity and magnetism into a set of four elegant mathematical equations that were to be the crowning glory of nineteenth-century physics.

Einstein sought a single, all-encompassing theoretical structure that would unify electromagnetism with his theory of gravity, the general theory of relativity. Such a unification was the logical next step for Einstein, but few were convinced, for in the twentieth century two new forces were discovered and given names that alluded to their strengths relative to the electromagnetic: the so-called strong and weak forces.

The strong force is the binding force that holds atomic nuclei together; conversely the weak force destabilises nuclei, causing a form of radioactivity that plays an essential role in the way that the sun produces its energy. As the years passed the belief grew that these four forces – electromagnetism, gravity, and the strong and weak forces – would be reunited in a Theory of Everything.

With the exception of general relativity, physicists have been able to ‘quantize’ the other three forces, since quantum mechanics deals with the atomic and sub-atomic domain. In effect they managed to get three trains running on the same size track. The quantum gravity train is still stuck at the station. In The Infinity Puzzle Oxford particle physicist Frank Close tells the tale of quantum field theory – the attempts to understand and then unite electromagnetism and the strong and weak forces.

In the 1930s the union of Maxwell’s theory of electromagnetism, Einstein’s theory of special relativity, and quantum mechanics gave birth to a theory of the electromagnetic force known as quantum electrodynamics, or QED. However, in the bowels of the theory lurked a monster – infinity. The equations of QED kept predicting that the chance of some things occurring was ‘infinite’. When infinity pops up in physics it spells disaster since, as Close explains, it is ‘proof that you are trying to apply a theory beyond its realm of applicability’. In the case of QED, if you can’t calculate something as basic as a photon – a particle of light – interacting with an electron without getting infinity, you haven’t got a theory.

It was the late 1940s before a way was found to solve the infinity puzzle in QED by a process called renormalisation. The calculations of many properties of atoms and their constituent particles, including those for the mass and charge of an electron, gave infinity as the answer. However, these two quantities of the electron had already been measured to a high degree of precision using other methods and the results were sufficient to provide benchmarks for anything else physicists wished to compute in QED. Instead of infinity, many of the answers now turned out to be finite and correct. Some physical quantities that have been calculated using renormalisation agree with earlier experiments to an accuracy of one part in a trillion, which is an order of magnitude akin to the diameter of a hair when compared to the width of the Atlantic.

Renormalisation may have been inelegant but its ‘recipe for extracting sensible answers for QED worked’. Those who cooked it up independently of each other – Richard Feynman, Julian Schwinger and Sin-Itiro Tomonaga – won a share of the 1965 Nobel Prize in Physics.

Gerard 't Hooft

When it came to the weak force, infinity was not so easy to banish, even with the efforts of the world’s leading physicists over a quarter of a century. It was the brilliant Dutch postgraduate student Gerard ’t Hooft who finally found a solution. The nature of the problem, how it was solved, and the inevitable jostling for Nobel Prizes are major themes of Close’s gripping and extensively researched narrative history of particle physics over the last sixty years.

It may be a collective enterprise but, as Close’s book reveals, science is full of wrong turns, partial answers, missed opportunities and misunderstandings. How could it be otherwise, since the dispassionate, logic-driven stereotype of the scientist is a fiction? The physicists in The Infinity Puzzle ‘experience the same emotions, pressures and temptations as any other group of people, and respond in as many ways’.

A timeline of who did what when, together with a glossary, could be added to the paperback, to help readers as they grapple with gauge invariance, parity violation, spontaneous symmetry breaking, gluons, colour, the Higgs boson and SU(2)xU(1). Yet Close has succeeded in humanising a dramatic era of physics in what is my science book of the year. Some sections of his narrative are difficult because of the inherent nature of the ideas he’s trying to explain. But then, it took exceedingly clever people to devise them.

‘Hold Infinity in the palm of your hand,’ William Blake wrote in the ‘Auguries of Innocence’. Frank Close does a fabulous job of reconstructing how physicists like Feynman and ’t Hooft managed to do exactly that.

The Reason Why

The Reason Why: The Miracle of Life on Earth by John Gribbin

Literary Review, November 2011

In the summer of 1950 the New Yorker magazine published a cartoon suggesting that aliens were behind the mysterious disappearance of rubbish bins from the streets of New York. Not long after the cartoon appeared, a group of scientists at the Los Alamos Laboratory in New Mexico were joking about it with their distinguished visitor, the Italian physicist Enrico Fermi. During lunch Fermi suddenly asked, ‘Where is everybody?’ It took a moment for his colleagues to realise that he was referring to extraterrestrials.

With hundreds of billions of galaxies, the universe could easily be teeming with extraterrestrial life. However, the enormous intergalactic distances involved rules out the possibility of a visit. Yet Fermi was not thinking about the entire universe, only our tiny part of it – the Milky Way. After a quick calculation, then and there, he concluded that space-faring aliens, should they exist, would have colonised our galaxy long ago and therefore have visited Earth. As Fermi was regarded as one of the great physicists of the twentieth century, his back-of-the-envelope reasoning was taken seriously and led to what was called the Fermi Paradox: ‘If they are there, why aren’t they here?’ The reason why, argues science writer John Gribbin, is simple: ‘We are alone, and we had better get used to the idea.’

Gribbin begins his entertaining polemic by referring to an equation devised in 1961 by the American astronomer Frank Drake that attempted to quantify the chances of detecting intelligent life elsewhere in our galaxy. Starting with the total number of stars, Drake calculated how many of them were Sun-like, and then asked what fraction of these had planets, how many of them were capable of supporting life, and so forth. With one guesstimate piled upon another it’s a futile approach that, at best, succeeds only in demonstrating our ignorance, for the answers generated range from zero to the hundreds of billions.

Gribbin, though, is prepared to play the numbers game while treating Drake’s equation for what it is, ‘a kind of mnemonic to remind us of the sort of things we have to take into account when considering the possibility of finding intelligent life elsewhere’. For Gribbin, the reasonable thing to do is to look at the history and geography of our galaxy and try to understand why, and how, intelligent life emerged on Earth. For he seeks to understand not whether we are alone but why we are alone. It’s Fermi’s paradox repackaged as: ‘If they are not there, why are we here?’

Gribbin sets out the arguments that the Earth occupies a special location in both space and time that has allowed the development of the only technological civilisation in the Milky Way. The Sun, for example, is fortuitously situated in what is called the Galactic Habitable Zone, a kind of Goldilocks region that’s just right for life. Critically, five billion years ago when the solar system was being formed, the zone had an abundance of metallic elements that allowed the formation of a planet like Earth. Any closer to the galactic centre would have been hazardous for life because of radiation from supernovae explosions, while the outer regions were poor in metals.

Gribbin only entertains the possibility of ‘life as we know it’ and therefore the presence of water is essential. Fortunately for us, Jupiter is of the right size and in the right place to have sent water-rich asteroids and icy comets crashing to Earth early in its history. In yet another piece of luck, the Earth acquired a relatively large moon. Others have covered before much of what Gribbin describes about the Moon’s essential role in the development of life on Earth, but he does so in an easily accessible style befitting the author of more than 100 books. He explains how the fledgling Earth was formed close to Theia, another proto-planet the size of Mars, and that when the two collided the surface of the Earth turned into magma as it swallowed up Theia’s core.

The vast quantities of debris ejected into space as the result of these worlds colliding eventually formed the Moon. The collision tilted the Earth on its axis and set it spinning much faster than it does today. The Moon has acted as a stabilising influence ever since and continues to shield the Earth from the full effect of Jupiter’s gravity. And our neighbour has certainly prevented cosmic debris from striking the planet, says Gribbin. He argues convincingly that the Moon is the single most important factor in making life on Earth possible.

The collision that led to the creation of the Moon resulted in the Earth having a thin crust and, through plate tectonics, the dynamic surface required to sustain the temperature range required for liquid water – and therefore, eventually, us. Otherwise it would probably have become a hot desert like Venus or a frozen world as cold as the Moon.

Life on Earth, argues Gribbin, is the product of such an improbable sequence of chance events that the possibility of finding any other technological civilisation in the galaxy is effectively nil. Yet the fact remains that we are here to ponder the reason for our existence because things are the way they are, because they were the way they were. Elsewhere they could have been different, leading to life, but not as we know it.