Experiments to verify dark matter are producing contradictory results (Image: Peter Mock/Untitled)

Physicist Katherine Freese drinks deep of her life’s adventures and cosmic mysteries alike in her captivatingly frank book The Cosmic Cocktail

WHY do tales of major scientific endeavours, told from the viewpoint of a single participant, rarely make captivating reading? Frankly, because few scientists are that interesting to the general public, and fewer still possess the trick of passionate engagement. Luckily, The Cosmic Cocktail is an exception.

We follow the search for dark matter – that mysterious stuff which outweighs the visible stars and galaxies by a factor of about six. Our guide is Katherine Freese, a mountaineering, tennis playing, extreme skiing “fan of fast cars”. Oh, and she also swims, as we find out when she recounts how she attended an important dark matter seminar despite having concussion caused by a head-on collision with another swimmer.

Freese is now George Eugene Uhlenbeck Collegiate Professor of Physics at the University of Michigan. She got into astroparticle physics by working with a pioneer of the field, David Schramm at the University of Chicago.

Like Freese, Schramm lived life to the full. Sadly he overstepped the mark with his risk-taking, and died when the plane he was piloting crashed in a Colorado field in 1997. Freese clearly misses him a lot, one of many honest insights into her personal and scientific life. In another, she talks of working with “my housemate Emil Mottola, my former fiancé Josh Frieman and my then-fiancé Fred Adams. It was quite a collaboration.” There’s an understatement.

In Sweden, Freese is asked by Queen Silvia how to define space. She answers, but is immediately embarrassed by what she feels is an unsatisfactory response. “An awkward silence followed, and I felt a mounting sense of panic,” she writes. I cannot imagine a man making such an admission.

Freese has made her way for four decades in a profession with few other women. She writes of working, in her early 20s, as a hostess in a Tokyo bar, where she learned “to deflect men’s advances and demand to be treated professionally – skills that later proved invaluable in the male-dominated physics world”.

A picture in the book, which she calls “Dark matter women”, shows her with Laura Baudis and Elena Aprile of the XENON experiment and theorist Lisa Randall of Harvard University. Such a gathering must be rare: physics can be a lonely world for women.

Nevertheless, many women have made pivotal contributions to our understanding of the universe. Freese mentions Vera Rubin, among others, who with Kent Ford showed that dark matter dominates spiral galaxies. Oddly, though, she omits Cecilia Payne, the astrophysicist who discovered that most of the ordinary matter in the universe is hydrogen.

Elsewhere, Freese tells of using the “nuclear shell model” to calculate how certain dark matter particles might be scattered by an atomic nucleus, and how this led her to regret skipping lectures on the shell model as “uninteresting” while a graduate student at Columbia University. The founder of the shell model, Maria Goeppert Mayer, is the only woman theoretical physicist to win the Nobel prize for physics.

But the meat of this book is the search for dark matter, and the people and experiments involved. Who knew that a dark matter particle may be passing through you every minute? Or that some physicists are suggesting using DNA to detect dark matter? Or that mini black holes made in the big bang are still in the running as dark matter candidates? At the moment, though, experiments to verify dark matter are producing contradictory results.

Freese gives short shrift to the alternative candidate to explain the missing matter, modified Newtonian dynamics. MOND is the idea that the faster-than-expected motion of stars and galaxies, and galaxies in clusters, is caused not by the gravitational tug of invisible dark matter but by a modification of gravity or inertia not predicted by Newton.

But MOND has a very simple formula, which perfectly describes the orbital path of most stars in a spiral galaxy. Surely, at the very least, dark matter advocates will need to explain how dark matter clusters in such a way as to lead to that formula?

One of the most exciting ideas proposed by Freese is that the universe’s first stars were powered not by nuclear fusion, but by the annihilation of dark matter particles. Such “dark matter stars” could have been huge and, when their power source was exhausted, might have collapsed to form giant black holes. This may explain one outstanding cosmic mystery: the origin of the “supermassive” black holes found at the heart of most galaxies.

Freese is as straight talking about science as she is about her personal life. She admits that cosmologists’ greatest fear is of a major ingredient lacking in their current understanding: Is it possible dark matter and dark energy don’t exist? “Perhaps an entirely different way of looking at the world will replace the need for these invisible pieces of the Universe.” Respect to Freese for having the courage to say that.

“Cosmologists’ greatest fear is of a major ingredient lacking in their current understanding”

Overall, The Cosmic Cocktail is a refreshingly honest account of a frontier field where the author’s enthusiasm and sense of fun shine through every page.

This article appeared in print under the headline “The dark matter woman”

Artists’ impressions of Pluto are all we have until a probe reaches it in 2015 (Image: ESO/L. Calçada)

Three new books bring us up to speed on extraterrestrial life, its prospects and possible forms – but it remains “queerer than we can suppose”

THERE are some 100 billion galaxies in the observable universe, with about 100 billion stars in each of those galaxies. And in recent years, we have discovered that there are probably more planets than there are stars. In fact, there are more planets in the universe than there are sand grains on all the beaches of all the coastlines of all the continents. Yet, in all this immensity, there is only one place where we know there is life – the tiny, fragile “blue dot” we call Earth.

“There are more planets in the universe than there are sand grains on all the beaches on Earth”

This rather handicaps our speculations about life elsewhere. Not that you would know it, to judge by the hundreds of books published every year about extraterrestrial life, its prospects and possible forms. Some are exuberant and ambitious in scope, other pure entertainment, and still others modest and fact-based.

Luckily for me, three new books combine most of the elements above – to varying degrees. First up is From Dust to Life: The origin and evolution of our solar system, by planetary scientist John Chambers and writer Jacqueline Mitton. I recently built an app about the solar system, and my research would have been made a lot easier if I had possessed a copy of this excellent book. It provides a truly comprehensive overview of our solar system’s origins and is written in plain, jargon-free language.

As the title suggests, Chambers and Mitton begin with dust particles coagulating in a protoplanetary disc around the newborn sun – pointing out that an unsolved mystery is just how dust grains grew into mountain-sized “planetesimals”. They go on to explain the origin of the disparate bodies in the solar system, from rocky planets like Earth to gas giants like Jupiter, from asteroids to Kuiper belt objects.

We are at the dawn of a golden age of planetary exploration. Although we have stunning images of most of the planets and large moons, we have barely begun to document what is out there.

Chambers and Mitton describe how the NASA probe New Horizons is due to fly by Pluto at a distance of 10,000 kilometres in July 2015, and perhaps most excitingly, that the Rosetta probe, sent by the European Space Agency (ESA), is due to go into orbit around Comet 67-P/Churyumov-Gerasimenko in November 2014 and deploy a lander with a drill to sample its interior.

The hope is that Rosetta will prove as useful at unravelling the mysteries of the past as the Rosetta Stone in Egypt. But these mysteries go back to the dawn of time: by sampling what may prove to be pristine material from which the solar system formed 4.6 billion years ago, Rosetta may help us decode the message recorded in the comet’s nucleus, thereby shedding light on the origin of the Earth and the other planets.

If space means extraterrestrial life to you, however, then that’s well covered in Life Beyond Earth: The search for habitable worlds in the universe by French astrophysicists Athena Coustenis and Thérèse Encrenaz. The authors consider the best places to find life in our solar system to be Mars, Jupiter’s moons Europa and Ganymede, and Saturn’s giant moon, Titan.

The big surprise has been tiny Enceladus, Saturn’s sixth largest moon, which has ice fountains spewing into space and an internal ocean. The message seems to be that we should be looking even more widely for life-bearing bodies.

Coustenis and Encrenaz make a good case for Europa being second only to Mars in its potential for hosting life. The 100-kilometre-deep ocean beneath the surface of Europa is believed to rest on rock, rather than ice as on the other giant moons, Ganymede and Titan.

This raises the tantalising possibility of volcanic vents spewing chemicals into the water. On Earth, such vents support complex ecosystems of sulphur-eating bacteria and arm-length tube worms. Might they do the same on Europa? Unfortunately, we will have to wait for the Jupiter Icy Moons Explore (JUICE) probe, which ESA hopes to get to the Jovian system in January 2030.

In their thorough and entertaining book, Coustenis and Encrenaz also discuss the prospects for life on the 800 or so planetary systems so far discovered around other stars. In 2011, the planet Kepler-22b was discovered 600 light years from Earth and in the habitable zone of its star. But the reality is that finding life in such remote locations is going to be hugely more difficult than in the cosmic backyard of our solar system.

Let’s face it, though, the big question for most of us is not whether there is a second biology out there in the shape of microorganisms, plants or animals, but whether there are aliens we can actually talk to. This is a subject of particle physicist Don Lincoln’s Alien Universe: Extraterrestrial life in our minds and in the cosmos.

By necessity, his book is high on speculation and fun, and low on fact. He surveys our ideas about aliens from television, film and novels – all depressingly humanoid – before discussing some of the features aliens are bound to share with humans. These include a similar (though not identical) biochemistry, and appendages with which to manipulate the environment. As Lincoln remarks, drily, how else would aliens build spaceships?

But here the fact that we only know about terrestrial biology – and have no idea what is special or general about it – is an enormous handicap. Our speculations inevitably come up against the truth highlighted by the British biologist J. B. S. Haldane: “The universe is not queerer than we suppose,” he said, “it is queerer than we can suppose.” And that is one problem no Star Trek or Star Wars movie can ever seem to escape, even at warp speed.

“We only know terrestrial biology, and not what’s special or general about it. It’s an enormous handicap”

This article appeared in print under the headline “Is there anybody out there?”

The Higgs generates mass, but only a minuscule part of it (Image: Naresh Singh/Millennium images)

After all the excitement surrounding the discovery of the Higgs, a new book called Beyond the God Particle asks where we go next

IN 2012 American Independence Day was a high-water mark for European science: it saw the announcement of the discovery of the Higgs boson at the Large Hadron Collider, near Geneva, Switzerland.

For , though, it was a low-water mark for American science. The Nobel prizewinning physicist is a former director of Fermilab, the Fermi National Accelerator Laboratory near Chicago. He is also the person who, tongue in cheek, gave the Higgs boson its “God particle” moniker.

In Beyond the God Particle, co-written with fellow particle physicist , Lederman bemoans the short-sightedness of American politicians who pulled the plug on the Superconducting Supercollider (SSC) in 1993 and signalled the retreat of the US from the high-energy frontier of fundamental physics.

But while the US Congress may well have lacked what Lederman and Hill call “leadership cojones”, it is perhaps unfair to blame Congress entirely. The plan for the SSC was to excavate a vast circular tunnel in Waxahachie, Texas, while the LHC plan proposed reusing an existing subterranean ring. Confining a superfast beam to such a small particle racetrack could be achieved only with superconducting magnets of such power that they were pure science fiction at the time the LHC was proposed.

In short, European scientists displayed the kind of daring, can-do spirit formerly seen in American scientists of the Apollo moon-shot era. As a consequence, and ironically, they presented their collective funding governments with a far lower total bill for the enterprise.

Although Lederman and Hill mourn the SSC, they seem to have accepted that European-style international collaborations with their pooled financial resources are the sensible way forward for particle physics.

Even so, they want to see the US punching its weight in particle physics again. In 2015, the LHC will start operating at even higher energies. Lederman and Hill suggest an American “Project X” to coincide with this, to look for ultra-rare, low-energy processes that may reveal a new fundamental physics.

It’s a bold plan, and well argued, but the real meat of Beyond the God Particle is the Higgs boson itself and its raison d’être. And this is a truly fascinating story, well told.

Mass, in a nutshell, is not what you think it is. Not by a long chalk.According to Lederman and Hill, a subatomic particle such as a muon, which feels the weak nuclear force, flickers back and forth between a right and a left corkscrewing form (the flicker is known as Zitterbewegung).

If, however, the muon could be boosted to the speed of light, its time would slow to a standstill, as predicted by Einstein’s special theory of relativity. A particle that experiences no passage of time is a photon, so the muon would appear like a photon. Since a photon has no rest mass, running with the photon analogy, neither would the superfast muon. Its mass would have been “switched off”. But all that has happened to it is that the flickering between left and right forms has stopped. The inference is that this oscillation is what gives a muon its mass.

So where does the Higgs come in? In switching from the left to the right form, a muon must destroy its “weak charge”, which is as impossible as destroying the ordinary electric charge. Hence the left-right switch must be mediated by another particle that takes away the weak charge.

The particle is not obvious so it must be short-lived, which in quantum theory is synonymous with being massive. It cannot add electric charge, so it must have zero electric charge. And it cannot add quantum “spin”, so it must have zero spin, making it a boson. Hey presto, the recipe for the Higgs.

According to Lederman and Hill, the defining characteristic of bosons is their gregariousness. Just like the photons that make up an electromagnetic field, the bosons of the Higgs field like to be with their mates, crowding the vacuum that fills the universe. And it is the drag exerted on a muon as it continually has to interact with Higgs bosons in the vacuum that endows it with mass.

But while photons are easy to pluck from the electromagnetic field, Higgs bosons are immensely hard to pull from their field. In fact, that takes a whopping 125 gigaelectronvolts to be precise – which is why nothing less than the $9 billion LHC could do it.

All of this is about as far from the standard cocktail party description of how the Higgs generates mass as it is possible to get. And it is worth the price of the book alone. Mind you, three-quarters of the way through, Lederman and Hill do belatedly admit, with a sheepish apology, that the Higgs explains only a minuscule part of mass. The lion’s share – 99 per cent – comes from the strong nuclear force and has nothing whatsoever to do with the weakly interacting Higgs. But then, this fact has been omitted by almost all particle physicists in their eagerness to big up the Higgs to the media.

Lederman and Hill’s book is a great read and a mine of stuff you may not know about the standard model of particle physics and about the Higgs. In places, however, I found the explanations a little baffling: for instance, the description of the unobservable “gauge fields” that underpin our reality left me puzzled – and I have a background in physics. Also, we sometimes have to wait a little too long for an explanation of terms: “wave function”, for instance, is defined nearly five pages after it is introduced.

As for what is beyond the God particle – the title of the book, after all – that turns out to be anyone’s guess. Frustratingly, the Higgs has as yet provided no clues about the deep physics we did not already know. The outstanding question remains: if the Higgs gives other particles mass, what gives the Higgs its mass?

“The outstanding question remains: if the Higgs gives other particles mass, what gives the Higgs its mass?”

It is to answer this kind of question that Lederman advocates building a higher-energy machine in the shape of the International Linear Collider – probably in Japan – plus that American Project X, to look for oddball events at lower energies that do not fit the standard model.

But it’s hard not to think that, as particle physicists make these grandiose plans, the universe looks on and mocks their efforts. After all, we now know that the stuff particle physicists are trying to understand accounts for a mere 4.9 per cent of the mass-energy of the universe. No one has the slightest idea about the true identity of the major components, dark matter and dark energy.

If anything, the discovery of the God particle has shown just how much further we have to go to penetrate the heart of nature. It all makes me think of the words of American poet Stephen Crane in A Man Said to the Universe:

A man said to the universe,

“Sir, I exist!”

“However,” replied the universe,

“The fact has not created in me A sense of obligation.”

This article appeared in print under the headline “Is the universe mocking us”