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What breakthrough should be awarded this year's Nobel Prize for Physics?

By Hamish Johnston

Bright and early on the morning of Tuesday 9 October, a small group of physicists will meet in Stockholm to make the final decision about who will win the 2012 Nobel Prize for Physics.

While I have no way of knowing, I’m hoping that the discovery of the Higgs boson at the Large Hadron Collider will be on the table. I know that there are many good reasons why Higgs hunters won’t bag the prize this year: the discovery came after nominations were closed; it would be too difficult to decide which individuals should share the prize; and physicists are still not 100% certain that the particle discovered at the LHC is the same boson that was first predicted in 1964.

However, my understanding is that the committee could cast aside the various historical conventions conspiring against a Higgs prize, and award the Nobel to those responsible for what surely is the most important physics breakthrough so far of the 21st century.

That’s my hope, now what about you?

In this week’s Facebook poll we ask:

What breakthrough should be awarded this year’s Nobel Prize for Physics?

Discovery of the Higgs boson
Inflationary cosmology
Discovery of exoplanets
Aharonov–Bohm effect/Berry phase
Discovery of neutrino mass
Invention of the LED laser
Invisibility/transformation optics
Slow light/electromagnetically induced transparency
First experimental test of Bell’s theorem

Have your say by visiting our Facebook page, and please feel free to explain your response – or suggest another Nobel prediction – by posting a comment below the poll.

Last week we asked “Physicists in Japan have discovered element 113. What should they call it?” Your favourite name was “nishinium”, with 37% of respondents in favour of honouring the Japanese nuclear-physics pioneer Yoshio Nishina.

Several people asked why we included “japonium” instead of “nipponium” – pointing out that Nippon is the transliteration preferred by the Japanese. Japonium is actually a name put forward by physicists at RIKEN, though I’m not sure why they have chosen the French spelling.

Shocking hearts gently

Heartbeats explained

Bodenschatz is part of an international team that is developing a technique known as “LEAP”, or low-energy anti-fibrillation pacing. Rather than shocking a patient’s heart with one large electrical pulse, the technique involves applying several weaker signals that manage to terminate erratic electrical activity in the heart. Bodenschatz has brought his background in spatio-temporal dynamics to the study of the electrical processes in the heart.

Controlling the forest fire

Bodenschatz and his team have been testing LEAP on animals. He told physicsworld.com that the technique could be ready for medical trials within the next 2–3 years.

Refining the physics

Bodenschatz believes that his background in fundamental physics is allowing him to bring a fresh approach to the study of processes in the heart. Naturally, however, there have been challenges along the way, including the need to learn the language of medicine in order to work with medical colleagues.

Language of the heart

The academic pyramid

Barnaby Rowe is a 29-year-old postdoctoral researcher at University College London. An astrophysicist by training, he came to London after a 19-month stint at NASA's Jet Propulsion Laboratory in Pasadena, California, having previously done a two-year-long postdoc at the Institut d'Astrophysique de Paris in France. By the time his contract runs out in 2014, he will have spent nearly seven years in academia, chasing job opportunities and research funding across three countries and two continents. But his current academic post, Rowe has decided, will be his last. "Some of my colleagues laugh about this, because I've been saying it for a long time," he explains. "But this time I think I'll do it."

Rowe's story is not unusual. Statistics suggest that the vast majority of people who complete science PhDs will never obtain a permanent academic post. This is vividly illustrated in a diagram published in 2010 by the Royal Society as part of a report on the future of scientific careers in the UK (figure 1). Drawing on data from various UK sources, the diagram follows a "typical academic career" through a series of post-PhD transition points, when large numbers of people leave the university environment for careers in, say, government or industrial research. These data show that less than 0.5% of science PhD students will ever become full professors, while just 3.5% will obtain lower-ranking permanent positions as research staff at universities.

For physicists, that 3.5% figure is probably a little low. Slightly older data collected by the Institute of Physics and the US National Science Foundation suggest that the fraction of physics PhD students who obtain permanent academic jobs has historically hovered between 10 and 20%. Yet even this higher number still indicates a yawning gap between the aspirations of early-career physicists and the realities of the academic job market. Indeed, according to an August 2012 survey carried out by the American Institute of Physics (AIP), nearly half (46%) of new physics PhD students at US institutions want to work in a university. The next most popular career plan among those surveyed, attracting 18% of responses, was "unsure".

Infographic showing the stages at which science PhDs leave academic research — **1 Career trajectories** Transition points in typical academic scientific careers following a PhD. Based on data from the Higher Education Funding Council for England, the Research Base Funders Forum and the Higher Education Statistics Agency’s annual “Destinations of leavers from higher education” survey. (Courtesy: Reused from *The Scientific Century: Securing our Future Prosperity*, by permission of the Royal Society)

The mass departure of PhD-level physicists from academia is not, in itself, a bad thing – either for society or for individuals. "The knowledge and skills developed [in a physics PhD] are first rate, and can be applied across many disciplines to a huge set of potential problems," notes Steve Hsu, a physicist and vice-president for research and graduate studies at Michigan State University in the US. Jobs in finance and technology, he points out, are usually better paid and more stable than the series of temporary posts that has become the norm for postdocs and other early-career researchers (ECRs). As a result, Hsu says, he often advises PhD students who have an interest in applied research to seek careers in industry, rather than academia.

But for many, the decision to leave the ivory tower is not entirely voluntary, and some postdocs have expressed concerns about their lack of preparation for alternative careers. One person interviewed for this article noted that although most postdocs do make contingency plans, "having a plan B can be seen as lacking commitment to an academic career", and might therefore harm their chances of obtaining that elusive permanent post. There are also indications that a career structure built on a series of short-term contracts is hurting science as a whole, by depriving it of talented people who leave for reasons that have nothing to do with aptitude or enthusiasm.

All of these factors – the shortage of permanent academic posts, the gap between expectations and reality, the anxieties about training and the fact that "success" depends on much more than talent and hard work – have prompted a groundswell of concern for ECRs. In July an article in the Washington Post about the lack of career opportunities for PhD-qualified scientists in the US attracted more than 3500 comments from readers, many of whom shared personal experiences of the tough academic job market. Meanwhile, in the UK, a consultation exercise carried out in mid-2011 by the pressure group Science is Vital received nearly 700 responses from scientists troubled about the structure of academic careers. Their answers to a questionnaire indicated widespread dissatisfaction about the prevalence of short-term contracts, the perceived or actual need to emigrate or relocate for jobs, and the impact of mobility on families and relationships (see "On the move" below). Some of those who responded – including senior scientists as well as ECRs – compared academic research to a pyramid scheme that produces a tiny handful of "winners" and a huge number of "losers" in the scramble for permanent posts.

A paradoxical situation?

When the American baseball player Yogi Berra was asked why he no longer frequented a particular restaurant, he replied, "Nobody goes there anymore. It's too crowded." In some ways, the situation for ECRs seems to echo Berra's words. In essence, the sheer number of junior researchers limits their long-term career prospects, but this does not seem to be stopping people from joining the queue. To put it bluntly, if career progression is so poor, why does the field remain so competitive?

One answer is that an academic career holds many significant attractions. "What I love about working an academia is the independence," says Sarah Kendrew, an astrophysics postdoc at the Max Planck Institute for Astronomy in Heidelberg, Germany. "Not just in terms of working hours and not having to conform to some corporate image, but independence of thought. In research, we're not just 'allowed' to have our own opinions – we're actively encouraged to develop and pursue our own ideas." In comparison with other posts she has held – including an engineering job and an internship in a scientific press office – the independence of academia is "an amazing luxury".

Others echo her views. "The best thing about being a postdoc is having the freedom to do something you are passionate about," says Aimee McNamara, a medical-physics researcher at the University of Sydney in Australia. "Even if you are employed for a particular project, you get the freedom to pursue your own research interests as well. Not many jobs in the world offer that."

But there are also some less pleasant factors contributing to the crowded postdoc pool. One is the economy. Many employers that traditionally offered well-paid research work outside a university environment have shed jobs in recent years, limiting alternative career options. For example, a report carried out in June by the scientific data firm Battelle found that the number of biotech jobs in the US shrank by 1.4% between 2007 and 2011, while employment in aerospace-related jobs fell by 2.4%. Both figures compare favourably with the 6.9% drop across the US private sector as a whole, yet there are signs that cuts in key industries have hit some early-career scientists hard. Indeed, the American Chemical Society found that only 38% of new chemistry PhDs who responded to its annual careers survey had found permanent non-academic jobs since graduating in 2011 – the lowest fraction for seven years. The fraction employed as postdocs, in contrast, went up slightly, rising from 45% in 2010 to 47% in 2011.

Another factor boosting the number of postdocs relative to the number of permanent jobs concerns the "pyramid" structure of scientific funding. At entry level, funding for PhD studentships, research assistantships and postdoctoral fellowships is often relatively plentiful. At more senior levels, however, funding tapers off and competition becomes much more intense. According to Athene Donald, a condensed-matter physicist at the University of Cambridge who often discusses career issues on her personal blog, the "pyramid" problem is particularly acute for biomedical researchers. "So much money has been thrown at 'let's cure cancer' or whatever that there are lots of entry-level positions for students and postdocs that don't go anywhere," she told Physics World. "And they will never go anywhere because there aren't enough jobs higher up."

Advice and training

Funding for physics research is not quite as pyramidal as it is in biomedicine, chiefly because there are fewer entry-level posts available. However, physicists are not immune to other factors driving the postdoc boom. One of these is a lack of advice about possible alternative careers. A recent paper by researchers in the US examined how "adviser encouragement" affects career preferences among PhD students (H Sauermann and M Roach PLoS ONE 7 e36307). They found that while academic physicists, as a group, generally encourage their students to seek university-based employment, they tend to adopt a more neutral or discouraging stance towards non-academic work (figure 2a). This was the case even though the students themselves became slightly less interested in physics research and teaching over the course of their PhDs (figure 2b). According to a 2010 report by the UK research organization Vitae, physicists may also be at a disadvantage in their knowledge of alternative careers. The report found that only 24% of physical-science students had a permanent job directly before beginning their PhDs, compared with 57% of students in the biomedical sciences and 49% of biologists.

Graphs showing the difference between careers that PhD advisers encourage and the careers their students want — **2 Career advice** (a) When giving career advice, PhD supervisors tend to encourage students to follow in their footsteps. Of the 959 US-based physics PhD students surveyed by Sauermann and Roach, 75% reported that their supervisors either “encouraged” or “strongly encouraged” them to seek careers as research faculty in a university. (b) In the same study, a sub-group of physics students nearing the end of their PhDs were asked to compare their current career preferences with their views when they started. Positive numbers indicate the share of those polled who gave each career option the highest rating at the time of the survey, but not initially (their interest in the option increased). Negative numbers show the share who rated a career highly at the start of their PhDs, but not at the end (decreased interest). (Adapted from figures in *PLOS ONE* 7 e36307)

Donald acknowledges that senior academics are partly to blame for the shortage of advice, especially when they give the impression that students who leave academia have failed or "wasted" their scientific training. "That is a terrible message [but] it's pretty pervasive," she says. "I think it happens because professors love what they do and they can't imagine how anyone wouldn't want to do it." However, she adds, the lack of advice can also stem from simple ignorance. "I think there's a real problem with principal investigators who have only ever been in academia not knowing what the job situation is like for people with particular qualifications," she says. "I'm not good at knowing what – other than academia – is out there." To fill this gap, Donald says she often refers students to Cambridge's careers service, which employs a dedicated adviser for postdocs in the physical sciences.

As well as offering better advice, Hsu believes that universities should also be offering more training to ECRs. "We could do more to prepare students specifically for careers outside physics by requiring them to take courses in, for example, computer science and management," he suggests. Exposing students to the career experiences of their predecessors who left academia would help, Hsu says.

Tending the academic dream

There is just one problem with providing better training and advice on non-academic careers: many PhD students and ECRs are not interested, or feel they do not have the time to investigate their options. "I really don't have a back-up plan," says Alan Duffy, an astrophysics postdoc at the University of Melbourne, Australia. "It's something that I often find myself briefly thinking about, but then other tasks in my day demand my attention and it's set aside." David Nataf, an astronomy PhD student at Ohio State University, agrees. "My PhD training was tightly focused on academic careers, but that's what I chose," he says. "Had I been planning to opt out, I would have asked for more teaching duties, or taken some programming and statistics courses...[but] I hope to continue in academia and specifically in research for a very long time."

Duffy and Nataf are not alone. In an informal poll carried out on Physics World's Facebook page last month, respondents were asked to pick which action would be most helpful to physics postdocs. Only 17% chose options related to training or advice on non-academic jobs. The overwhelming favourite, with 73% of the vote, was longer-term contracts – something that would help keep more physicists in academic research, rather than helping them succeed outside it.

Rowe, however, thinks that longer-term contracts would be a major improvement even for physicists who, like him, decide to leave academia. "I can't help but think that the annual-to-every-two-years round of writing applications and proposals to stave off your pre-determined unemployment is bad for productivity," he says. Fewer, longer contracts for postdocs would also benefit scientific projects that have long lifetimes compared with a typical two- or three-year contract, he adds.

Intriguingly, some recent research supports the idea that longer-term contracts would be better for science. After analysing the productivity of 300 physicists, a group of complexity theorists in Italy and the US found that short-term contracts can "amplify the effects of competition and uncertainty" and thus make academic careers "more vulnerable to early termination, not necessarily due to lack of individual talent and persistence, but because of random negative production shocks" (Petersen et al. PNAS 109 5213). The theorists also found evidence of a "rich get richer" system, in which an initial bit of luck – publishing a single outstanding paper, for example – can mushroom into a career-long advantage over less fortunate (but no less talented) colleagues.

Changing the pattern

In its report on science careers in the UK, Science is Vital takes the idea of longer postdoc contracts to its logical conclusion by recommending the creation of permanent postdoc-level jobs. Kendrew agrees that this would be a good idea. "A lot of postdocs are involved in what I could describe as 'infrastructure work'," she explains, citing software development, data management and instrument building as examples. "These people often get little credit for their contribution, and as they don't publish as many papers...they fall by the wayside."

Others, however, are more sceptical. "I can see the attraction, and I know a few people for whom a permanent postdoc would be ideal," says Donald. "But if you have a mature team – a professor, a couple of senior lieutenants and a long-term postdoc – they will get into a pattern where it's terribly hard for them to do lateral thinking. Whereas if a new person comes in and asks an incredibly naive question, they can kick-start enquiry in a different way."

One alternative would be to reduce competition for permanent jobs by limiting the number of PhDs and postdocs being offered. Among those advocating this strategy is Jonathan Katz, a physicist at Washington University in St Louis, Missouri. In 1999 Katz posted an essay on his website entitled "Don't become a scientist!" In it, he outlined reasons not to pursue an academic career – including poor job prospects – and he told Physics World that his advice was still applicable today.

But there are problems with this approach too, Rowe argues. "I got a good degree, but I think there were people who had less aptitude as undergraduates who have subsequently shown more aptitude as researchers," he says. "So I would be wary about throttling back the numbers of PhD students." A better strategy, he suggests, would be to make sure that PhD students know they have other options if they choose not to stay in academia. Above all, he adds, they should not feel like their years as researchers were a waste of time.

That sentiment is echoed by Phillip Helbig, a former research assistant who now works as a systems analyst at the stock exchange in Frankfurt, Germany. When asked via e-mail whether his stint as a full-time academic researcher was "useful" to him, his reply began with the words "Define 'useful'!" and the opening lines of Charles Dickens' novel A Tale of Two Cities ("It was the best of times, it was the worst of times..."). "I don't think it was useful in terms of preparing me for other work," he continued. "This aspect is exaggerated. Doing a degree that requires a thesis and programming experience is good for many things, [but] anything beyond that is not helpful in any technical sense, and might be counterproductive among employers who prefer hiring younger people." Still, he wrote, "I am extremely glad that I spent the time I did in academia. It was worth it even if I didn't stay."

On the move

"When I started out with my PhD, the need to move around to pursue a career in science was actually appealing to me," says Aimee McNamara, a South Africa-born medical physicist who is currently doing a postdoc at the University of Sydney in Australia. "I liked the idea of experiencing different research environments as well as different cultures, and I still believe it's a very important thing to experience as a scientist."

Four head and shoulder photos of early career physicists — **On the move** Clockwise from top left: Alan Duffy, Aimee McNamara, Barnaby Rowe, Sarah Kendrew.

Moving from one location to another is relatively common for physicists. When Physics World asked – via an unscientific poll on the magazine's Facebook page – what steps physicists had taken to pursue their careers, 38% of the 111 respondents said they had moved more than 500 miles at least once, while an additional 13% had moved a shorter distance. A separate poll on the most important factor for choosing a postdoctoral position found that "location" got the lowest score of all the options offered, attracting a measly three votes out of 63.

The problem is that after a while, moving around becomes more problematic. "Being on two or three-year contracts throughout our late 20s and early 30s means it's really hard to plan a long-term future – buying a house, having children and so on," says Sarah Kendrew, an astrophysicist who moved from London to the University of Leiden in the Netherlands before obtaining her current post at the Max Planck Institute for Astronomy in Heidelberg, Germany. "I really find that I've had to be flexible and readjust my goals and expectations according to where work takes me."

Moving around can be particularly trying for early-career researchers with spouses, children or other relatives who depend on them. After obtaining his PhD from the University of Manchester in the UK, Alan Duffy – who was, at the time, single – moved to Perth, Australia, to do postdoctoral research at the International Centre for Radio Astronomy. That decision was easy, he says, but now that he has a partner, his subsequent 3000 km move to the University of Melbourne required some hard thinking. "It was too good an offer to refuse, but only because my partner was able to make it work for her career," he says. "Some postdocs just won't be this lucky."

In addition to the infamous "two-body problem", in which academic couples struggle to find two research jobs in the same location, there is also a less well-known dilemma affecting physicists who are gay. Legislation on civil partnerships and social attitudes towards homosexuality varies widely among different countries and US states, observes Elena Long, a PhD student at Kent State University in Ohio who has worked on raising awareness of gay, lesbian and transgender issues in physics. Because of this variation, she says, gay physicists may have to balance an attractive job offer with concerns about being accepted in the local community.

In some cases, the need for mobility can prompt or hasten a decision to leave academic research. "One reason why academia doesn't appeal to me so much is the lack of real freedom to choose where you want to live," says Barnaby Rowe, an astrophysics postdoc at University College London who plans to leave research to train as a secondary-school teacher. "There are a number of places where you can do astronomy, but they're quite thinly spread. If a job comes up, you may not get another job offer, so you take it...That lack of flexibility is tough on family members, and research is not something that I love enough to wish to inflict that on them anymore."

For more information on mobility in physics careers, listen to our podcast "Going where the beam is good"

Further information

www.vitae.ac.uk
http://scienceisvital.org.uk
www.nsf.gov/statistics

New theory describes ultrathin solar cells

Physicists in the US have developed a new theoretical technique for calculating the properties of ultrathin solar cells. Their method suggests that designs that boost the amount of light absorbed by such cells could sometimes have an unwanted, negative effect on other aspects of the devices' performance. The team is currently developing the technique so it can be used within numerical simulations tools that are used to design solar cells.

Ultrathin solar cells have two key advantages than their thicker counterparts: less material is needed to build them, while the electrons and holes liberated by light do not have so far to travel, so reducing losses that occur when they recombine. These benefits are, however, offset by the fact that thin devices absorb less light than thick devices, which is why researchers are keen to use nanometre-sized structures that increase the amount of light that interacts with ultrathin cells.

These structures take advantage of near-field optical effects such as the interaction of light with surface plasmons – oscillations in the electron density on a metallic surface. Unfortunately, these near-field effects can also affect the rate at which electrons and holes recombine within the cell, which could reduce the performance of the cell.

Thermodynamics in action

While absorption in ultrathin solar cells is relatively well understood, the effect of near-field optics on electron–hole recombination is not. Now, however, Avi Niv and colleagues at the University of California, Berkeley, have developed a new way of evaluating solar-cell efficiencies that they say can be applied to extremely thin devices. The technique takes advantage of the "fluctuation-dissipation theorem", which makes the connection between a system in thermal equilibrium and the response of the system to a tiny disturbance.

In the case of a solar cell, the system at equilibrium involves a number of processes, including the absorption and emission of photons. To calculate the efficiency of a solar cell, physicists must know both the "photocurrent" – the rate at which electron–hole pairs are created – and the "recombination current", which is the rate at which electron–hole pairs recombine to make a photon. The greater the photocurrent is relative to the recombination current, the better the solar cell.

Radiating dipoles

The team treated these recombination events as fluctuations of an ensemble of radiating dipoles. This thermodynamic approach allowed them to use the fluctuation-dissipation theorem to work out the power of the recombinations in terms of thermodynamic variables, such as the temperature and chemical potential.

Niv and colleagues then used this theoretical framework to calculate the key device parameters of voltage, current and efficiency in an ultrathin solar cell. Their idealized cell comprised an ultrathin layer of the semiconductor gallium arsenide (GaAs) on a gold substrate. Light enters the solar cell through air and light that is not absorbed is reflected back from the gold for another pass through the active region of the solar cell. The team identified four possible emission channels that had to be considered – light that is emitted back into the air and light that is emitted into the gold, each of which can occur with two different polarizations.

The team calculated the emission for cell thicknesses in the range 0–300 nm and found that the emission changed as a function of thickness. In particular, the calculations predict a large peak in the emission of parallel-polarized light into the gold substrate – something that the team identify as a clear signature of near-field effects.

Pronounced dip

To examine the effect on solar-cell performance, the team then looked at a detailed balance between the rates at which photons are absorbed and emitted by the semiconductor. A calculation of the voltage created across the cell when exposed to sunlight showed a pronounced dip at 40 nm – which is to be expected because of the large emission peak at that thickness – as well as other structure related to near-field effects. By contrast, calculation of the voltage using a technique based on conventional optics does not reveal any of these features.

According to Niv, the research shows that the use of nanostructures within cells to boost their absorption of light will also have an effect on the emission of light – and both effects must be considered when determining the overall efficiency of the design.

As well as increasing the sophistication of how they used their technique to model solar cells, Niv says that the team are also working on ways that the theory could be incorporated into a numerical simulation tool that could be used to evaluate solar-cell designs.

The research is described in Physical Review Letters.

A look at physics in Japan

By Michael Banks

If you have ever thought about studying or working in Japan, or are just curious about the high-profile international research facilities the country has, then make sure you don't miss a special online lecture next week given by Adarsh Sandhu from the Toyohashi University of Technology (right).

Sandhu has spent around 25 years working in Japan and he will give his personal take on physics in the country, including outlining key international research centres as well as what careers there are for researchers.

Indeed, there are both challenges and opportunities for physicists from abroad to go and work in Japan or to collaborate with Japanese researchers and Sandhu will address these as well as answer any questions you have.

The lecture is on Wednesday 10 October 2012 at 2.00 p.m. BST (9.00 a.m. EDT) and you can register for the free event via this link.

Also, make sure you don't miss our special report on Japan, which you can view online here. The report draws together a selection of our recent articles about physics in Japan looking at, for example, the world's first compact X-ray free-electron laser as well as a major upgrade to Japan's famous KEKB collider.

Venus as you’ve not seen it before

By Matin Durrani

You could be forgiven for thinking that we here at Physics World have a slightly obsession with that astronomical phenomenon known as the transit of Venus.

First we published a great feature by Jay Pasachoff that explained the science and history of this rare astronomical event, in which the planet Venus passes across the face of the Sun, as seen from the Earth. Pasachoff's article appeared just before this year's transit, which took place on 5 and 6 June, but the transits are so rare that the next one won't occur until December 2117.

Then Physics World columnist Robert P Crease examined the question of whether the great Russian polymath Mikhail Lomonosov did – or did not – see the atmosphere of Venus during the 1761 transit. This piece was followed a few months later by Crease's account of various attempts this summer to carry out historical recreations of Lomonosov's work. (Crease's conclusion: yes Lomonosov probably did see Venus's atmosphere.)

We also ran a photo challenge on Flickr, where we invited you to send us your images of this year's transit. You can see a selection of the best in this article here.

And if you want to watch a quick overview of why the transit of Venus occurs, then check out Physics World's own video, featuring Zoe Leinhardt from the University of Bristol.

New cloak promises to be invisible to electrons

Physicists in the US have proposed a way to make an "electron cloak" – an object that is invisible to electrons. Inspired by cloaks that hide objects from light or sound waves, the electron cloak would be made of a tiny structure that is about the same size as the wavelength of electrons it is hiding from. Although the design has not yet been tested in the lab, it could be used to make novel electronic devices and perhaps even help develop better thermoelectric materials for improved energy harvesting and conversion.

Researchers have already succeeded in making "invisibility cloaks" that hide objects from electromagnetic waves. Such cloaks are made from "metamaterials", which are artificial structures with special optical properties such as negative indices of refraction. These structures are arranged in such a way that incoming waves flow smoothly around the cloak, meeting up on the other side as if the cloak was not there. The same principle has also been applied to make cloaks that are invisible to sound waves.

Core and shell

Thanks to quantum mechanics, electrons behave like waves, and now new calculations by Gang Chen and colleagues at the Massachusetts Institute of Technology (MIT) suggest that cloaks for electrons could be made. The researchers have put forward a practical design that would be made of nanoparticles that comprise an inner core and an outer shell. The core–shell nanoparticle could then be embedded in a host semiconductor, so that it does not disturb the flow of electrons.

Electrons normally travel as waves over a certain distance before scattering destroys their wave phases. Over this so-called coherent transport length, the particles exhibit characteristic wave behaviour, such as amplitude superposition (or interference).

Reflecting electron waves

"In our electron-cloak design, the core–shell nanoparticles essentially provide multiple interfaces where electron waves are reflected," explains team member Bolin Liao. "Through careful tuning of the interfaces, the multiple reflected waves from the interfaces can destructively interfere with each other and cancel the total reflection almost perfectly. The electron waves with the 'correct energy' can thus travel through the nanoparticle structure without being reflected, as if there was nothing in their way." The nanoparticle structures are about the same size as the wavelength of electrons themselves – around 10 nm in the MIT study.

Such electron cloaks may find use in applications where high electron mobility is required, such as in semiconductor electronics, says Chen. "We might also be able to design novel electronic switches that go from the visible ('open' structure) and invisible ('closed') states," he says. "What is more, the electron scattering versus energy profile of the structures, which varies greatly, could benefit applications that call for strong energy-dependent scattering mechanisms, like those at work in thermoelectric devices."

The team is now busy putting its theories into practice, by trying to make real core–shell nanoparticle electron cloaks. "We are also looking at extending our idea to lower-dimensional structures," adds team member Mona Zebarjadi.

The current work is detailed in Physical Review Letters.

My life on Mars

With the lights from the Habitat Module glowing faintly behind me, I turned off my head torch, comms device and air-circulation system. Holding my breath, I stopped for a moment on the edge of a vast darkness. As my eyes adjusted, I could begin to see hills in the distance, their edges smudged into unfocused murkiness like a Monet landscape. But there were no artificial lights over this alien horizon, and I knew that I could walk for days without seeing any traces of human life. "Welcome to Mars," I thought.

Of course, I had not really travelled millions of miles through space to reach this empty, other-worldly landscape. The Habitat Module behind me was actually part of the Mars Desert Research Station (MDRS), a facility dedicated to developing and testing field tactics and protocols for a human expedition to Mars. Located in a remote area of the Utah desert, the station's paprika-coloured surroundings mimic the landscape of the red planet, lending an air of realism to research on such topics as design features of habitat modules, psychological studies of crew members, assessment of crew-selection procedures and even tests to determine the best kinds of food for Mars explorers.

My journey to this earthly version of Mars began in August 2011, when I applied for an engineering position at MDRS and was selected as part of a crew of six people. My fellow crew members came from several different disciplines and countries. They included a Spanish-born artist and journalist, Alicia Framis; Michael LeClair, a Canadian geologist, programmer and psychologist; Usha Lingappa, an American astrobiologist; another American, Mike Lotto, who like me is an aerospace engineer by training; and our commander Charlotte Poupon, an industrial designer for extreme environments and naval officer from France. Each year, around 10 of these six-person crews stay at the MDRS, typically for two weeks at a time, while a similar number carry out studies at a sister station in the Arctic for several months at a time. Three additional stations are currently under construction in Hawaii, Iceland and Australia, and all five are run by the Mars Society – a group that mainly consists of professional scientists, engineers and academics with an interest in Mars exploration. The stations also receive significant collaboration and funding from NASA's Ames Research Center and the entrepreneur and former physicist Elon Musk.

The main purpose of our expedition was to conduct the sorts of fieldwork that might take place during a Mars mission. Within this, my role was to maintain the Habitat Module systems and the quad bike all-terrain vehicles, while also serving as an extra set of hands for scientific projects and fieldwork. In addition, all of us would be partaking in long-term food, protocol and psychological studies.

Welcome to "Mars"

After several months of feverish preparation and eager e-mail exchanges, I finally met the other members of my team at the airport in Grand Junction, Colorado – a 15-hour trip from my home in the UK, where I was then studying for a PhD in aerospace engineering at the University of Liverpool. As we drove from the airport, we received a briefing from Jean Hunter, an expert on space life-support at Cornell University who would be carrying out food studies on all six of us in collaboration with NASA. After several hours of driving through the desert, we swung onto a rib-shattering dirt track, bumping through an increasingly Martian-looking landscape towards our destination. By the time we reached our stark outpost, we had left the rest of humanity far behind. We began what promised to be two weeks of the ultimate Mars experience on Earth.

On arrival, we met John Barainca, the station's engineering co-ordinator and a walking knowledge bank of physics, chemistry and biology as well as engineering. Barainca has the far-off gaze of someone whose thoughts are always on a distant planet, but from now on he would be one of our main links to "Earth", advising us on maintenance tasks via Mission Support channels. The rest of Mission Support would observe us via cameras and monitor our daily reports to ensure protocols were followed and unnecessary dangers avoided.

First, however, Barainca gave us a thorough tour of our new home: the Habitat Module, or HAB. Its structure and features are based on the designs and mission architecture for the "Mars Direct" plan for a relatively low-cost manned mission to Mars. This plan was conceived by a group led by Robert Zubrin at the aerospace firm Martin Marietta (now Lockheed Martin) and later developed in collaboration with NASA's Johnson Space Center. The building is split over two floors and is silo-shaped, with a diameter of 10 m – small enough to fit atop the main rocket booster of a heavy-lift launch vehicle. The engineering and electronics work station on the ground floor had more tools than even the A-Team would know what to do with, while the scientists in our group were in geeky fits of excitement over the array of microscopes, scales, rock saws, incubators and other equipment in the biology and geology labs. The HAB's lavatory and shower were both quite modest, but the extra-vehicular activity (EVA) room – which contained six spacesuit analogues and their chargers – got Lotto's and my engineering juices flowing. The upstairs contained our living quarters, which included six compact bedrooms (each a little over 1 m by 3 m), a communal area with plenty of reading and entertainment material, computer workstations and a kitchen. The finishing touches were the airlocks at the front and back of the HAB.

Photo of the Habitat Module of the Mars Desert Research Station

Home comforts

Barainca briefed us on all the procedures we needed to follow and the systems we would have to maintain inside, outside and beneath the HAB. These included an observatory with an 11-inch telescope; communication systems linking team members to each other and to Mission Support; a diesel-powered generator; and the heat tapes under the HAB's flooring that regulated its temperature. The quad bike all-terrain vehicles (ATVs) we would use to travel around the Martian landscape also needed regular checks, and we had to monitor water levels in the tanks (two external, one internal) if we wanted to avoid unnecessarily harsh water rationing. Finally, the algae septic filter in the greenhouse required regular maintenance, since it recycled dirty water into "grey" water for use in the toilets.

Jet-lagged and hallucinating with fatigue, I shadowed Barainca for several hours, noting down his instructions and suggestions in indecipherable scribbles. Later that evening, when he felt we were sufficiently prepared, he stepped out of the HAB into the desert night. The temperature was –12 °C and the Moon behind him was sending pale, cold fingers of silver across the landscape. "You know, guys," he said, reflectively, "we all have one thing in common: we're all nuts." And with that, he sealed the exterior airlock door behind him. Our two-week simulation had begun.

Settling into a routine

During the mission, our days started at 5 a.m., with breakfast – and an accompanying pot of strong coffee – an hour later. After a plan-of-action meeting, Lotto and I would do a round of engineering tasks, and though we were snowed in for a chilly couple of days, we usually managed to get outside for two three-hour EVAs each day, before and after lunch, to conduct various projects. For safety reasons, nobody was left alone in the HAB or on EVAs, and constant communication was maintained between EVA groups and the HAB crew. While the engineers carried out maintenance on the HAB, ATVs and spacesuits, the scientists typically spent time in the lab or wrote reports. Every evening, each team member completed a set of surveys about the food and our psychological states. Among other things, the latter surveys were aimed at determining whether "cabin fever" was setting in. After this we would watch a film (usually a sci-fi horror of some sort), then end the day at 11 p.m. after another round of engineering tasks.

We each had our own projects to accomplish during the mission, but we also participated in each other's studies. For example, Poupon, our mission commander, specializes in designing equipment that can operate in extreme environments. One of the projects Lotto and I worked on with her was a small, custom-built, remote-controlled rover that carried wireless video cameras and a monitor. She was trying to assess its functionality as a "scout" in hard-to-reach places, but her research revealed that the need to keep a line-of-sight between the rover and its controller was a significant issue. I intend to carry out a comparable study, but using a low-flying remote-controlled quad-rotor/airship hybrid specially built to deal with the Martian atmosphere. It would avoid rough terrain and ground obstacles entirely by taking to the air.

Left: rock varnish on a rock near the Mars Desert Research Station. Right: Scanning electron microscope image of rock varnish

1 Rock varnish

The astrobiologist on our team, Lingappa, has a background in Mars-analogue geomicrobiology. She is particularly interested in studying a bacterium that is thought to produce a substance called "rock varnish", which appears in many places on Earth (figure 1). There is photographic evidence that rock varnish exists on Mars, and if its presence there is confirmed – and if rock varnish turns out to be indisputably biological, not geochemical, in origin – then that would be a massive discovery. Finding microbial life on Mars would answer questions about the prevalence of life in the universe. It might also indicate whether the life-forms produced on Earth follow the pattern for all life (for example, using RNA and DNA to pass on genetic information) or whether we are merely one thread in a vast tapestry of what could be considered "alive".

During the mission, however, Lingappa's main task was to study how spacesuits impose limitations on a person's ability to collect samples and isolate organisms – something that is clearly very relevant when planning an actual Mars mission. Similarly, the crew's geologist, LeClair, carried out geology missions both with and without the spacesuit in order to analyse what delays and problems it caused. He also mapped and developed our understanding of the local terrain as a basis for future geological fieldwork at the station.

Complications and mishaps

As with any human space mission, before we so much as touched a tool, we needed to put forward a proposal to Mission Support detailing exactly what we intended to do, how we would do it and which instrument we would use. To simulate the effects of signals travelling between Earth and Mars, a delay of around 40 minutes was added on to each communication between us and Mission Support. Typically, there would be an extensive discussion between the support engineers on the "Earth" side before they gave us the "go" signal – or, more likely, asked a question.

Another interesting aspect of life during the mission was the fact that Mission Support was observing all of our activities via six streaming cameras in the HAB. These cameras captured a frame every 30 seconds and fed it to the world at large through the MDRS website, so naturally we tried to avoid doing anything ridiculous. However, this did not stop LeClair, who held love letters up to the camera each morning for his girlfriend to read back home in Canada.

One day while the scientists were writing reports and preparing food, Lotto and I (appropriately suited and booted) were outside on an engineering round. Looking across the desert, I recall thinking that I would not be surprised if pre-historic creatures materialized from the mountains that surrounded us, such was the bizarreness of the landscape. Suddenly, our respective comms devices began to resonate with screams in French and Spanish from Poupon and Framis. Through our helmet visors, Lotto and I exchanged a knowing glance indicating near-certainty that our crewmates back in the HAB were going to die in the next few seconds. We dropped what we were doing and sprinted inside for re-pressurization.

Still hearing screams through our comms, we were convinced that one of our crewmates had lost it and was now in the process of murdering the others, possibly with one of the many scalpels in the biology lab. Still suited up, we were making our way up the stairs of the HAB as stealthily as we could when Framis suddenly appeared and tearfully shoved down a bucket containing a desert mouse, which was itself squeaking with terror. We had encountered our first "Martian"!

Later, I was reliably informed that as LeClair set about capturing the mouse, the rest of the crew had heroically continued their food-preparation task even while standing on chairs and screaming. In an effort worthy of the UN, "Marty" the Martian mouse was taken out on the next EVA and released into a more suitable environment. It took several minutes for him to say his goodbyes to each of us before scampering off.

Another mishap – this one potentially more serious – came during the 10-mile return leg of a fossil-hunting field expedition. I was motoring down a hill on an ATV between LeClair and Lotto when the setting Sun momentarily blinded me. When I could see again, I realized I was heading into a bend far too quickly. I overshot the bend, the ATV flung me into the air over a dune and sent me barrelling towards a ditch. I managed a series of graceful pirouettes before landing theatrically on both feet – quite an achievement while wearing a spacesuit!

Photo of a crew member doing geological field work in a simulated space suit

Getting around

Through the scratchy comms, a rather agitated Lotto announced that the nearest hospital was some three hours away. Fortunately, I was unhurt, but the incident did highlight the risks of driving instead of walking over rough terrain. The advantages ATVs bring in mobility and expedition range are great, but they also introduce an element of human error that should be taken seriously. Even a minor puncture to a spacesuit would kill an astronaut in minutes as their blood boiled in the low-pressure Martian atmosphere. Isolated on Mars, with the Earth just a "pale blue dot" in the night sky, there would be no room for error.

Some of the problems we faced were more subtle. Although all of us wore watches, and thus had a sense of the immediate time of day, one by one we lost track of how many days we had been in the simulation. Without looking at the logs, our minds' dependency on our (clearly fallible) internal clocks was exposed. Gradually, events merged and became confused in our memories. On several occasions, members of our team mixed up events that had taken place that day with those from the day before; sometimes as a group we completely forgot what we had shared for lunch several hours earlier. LeClair, the team's geologist and psychologist, put it best when he commented that "our experience of time is just an illusion".

Around the dinner table

Food at MDRS consisted of strictly rationed, non-perishable, vacuum-sealed and dehydrated meals – and yes, that's about as exciting as it sounds. Chewing on food is something I did not realize I would miss, but for astronauts, any time taken away from their duties in order to prepare meals is significant. During an actual Mars mission, the crew would have to spend around 30 months on this dietary regime. Hence, one of the major studies being carried out at MDRS aims to minimize meal preparation and consumption time without harming the psychological well-being of the crew.

Though the food was far from inspiring, our conversations around the dinner table were always a rich and colourful distraction. Everyone in the crew had real enthusiasm and a wealth of knowledge about Mars inside and outside their own fields of expertise, and talking with them was one of my favourite parts of the mission. Naturally, many of these discussions focused on the red planet itself.

Lingappa, our astrobiologist, had strong convictions about its potential habitability. As she pointed out, a day on Mars lasts a very Earth-like 24 hours and 37 minutes, and it was once a warm and wet planet. If we could somehow melt its frozen oceans of water, a "second genesis" of life might be introduced if one is not awoken in the process. I suggested that, with the use of super greenhouse gases, raising the planet's atmospheric temperature in the southern polar region by a few degrees would begin a self-sustained gasification process of the carbon dioxide in the soil. This would catalyse a runaway process of Martian global warming that would, eventually, return it to its former, more habitable state.

With today's technology, I reasoned, a relatively small push could help Mars go through a transformation. After 100 years or so, this transformation might produce a planet with an average surface temperature of about 7 °C, oceans of water covering approximately a third of its surface, and an atmospheric pressure and density equivalent to that found in Nepal. Making the Martian air breathable by humans would be more difficult, since it would take thousands of years for plant life to extract sufficient oxygen from the planet's carbon-dioxide rich atmosphere. However, as Poupon observed, it is always possible that our capabilities – both in altering a planet's atmosphere and in developing adaptations for humans – will in the next few decades develop beyond our current limited comprehension of what is possible.

LeClair – ever the geologist – added that Mars contains an abundance of many elements needed to sustain a technological civilization, including oxygen, carbon and hydrogen as well as useful metals such as iron, aluminium, copper, chromium and magnesium. He compared it to North America in the previous age of human exploration – "the next logical step towards the furthering of humanity".

Two crew members sitting on a rock outcropping overlooking the desert

Alone in the wilderness

Other discussions took a more political turn. Lotto and I, for example, often discussed the future of manned space exploration. His outlook on the US space programme was fairly gloomy, and he was particularly concerned about the possible knock-on effects on science education. During the Apollo era, he pointed out, the number of students getting scientific qualifications at every level – from high school through to PhD – doubled. What do we have to inspire the next generation?

My own impression is that, after several decades without a clear direction, the US space agency is now entering a period of stagnation or even retreat. A few months after our mission ended, NASA announced its decision to pull out of its collaboration with the European Space Agency (ESA) on the ExoMars project, which was designed to search for Martian bio-signatures. Though I am optimistic that human space exploration will continue, we cannot assume that the first astronauts on Mars will be carried there by NASA or ESA rockets. If western countries continue to be held back by political inertia – if we cannot conjure the courage of a new Columbus or Livingstone – then humanity's next step will simply be taken by someone else.

As the mission wore on, it became customary for the crew to go out late in the evening and look up at the Milky Way, the backbone of the night sky. The 4500 ft altitude of the Utah desert just about guarantees cold, clear skies at night and we were lucky enough to witness a meteor shower, the Geminids, during our mission. We also saw the International Space Station (ISS) pass over, which sparked another discussion on space funding. One of the main scientific purposes of the ISS was to study the long-term effects of zero-gravity on human biology, but as Lotto commented, "I don't remember Columbus spending years off the coast of Spain observing the health effects of life at sea before making his voyage over to America". Simply spinning the spacecraft on a tether in transit to and from Mars would generate an artificial gravity through inertia. When you compare the $196bn spent on the Space Shuttle programme to the $55bn cost of setting up the architecture around and getting the first crew of humans to Mars via NASA's Design Reference Mission (the equivalent of two weeks' worth of US defence spending in 2011), you really do have to wonder whether it has been worth it.

Saying goodbye

My "Monet landscape" experience came during our last night together, while the crew was taking in another "Mars" light show. I moved away, turned off all the devices I was wearing and looked up at the sky. As a child growing up in Namibia and South Africa, I would often gaze up at the stars above the Kalahari Desert, wondering who had stuck diamonds into the black sky. For me, that was where my interest in space began, and since then it has taken me from the San Bushman country to the ivory tower of academia. And for two weeks last December, it had even – sort of – taken me to Mars. As our mission came to a close, I realized that I would be bringing a little bit of each of my crewmates back to England with me. The two-week simulation had been a unique experience, and each of us learned valuable lessons not only about our chosen subjects, but about ourselves.

Walking back to my team, I turned on my air-circulation system, head torch and comms device. Soon Lingappa's voice crackled over the radio. "We were getting a little worried about you!" I could hear the smile in her voice, and for almost the last time, I stepped back to join my colleagues in the artificial world of the HAB.

Dark-matter alternative tackles elliptical galaxies

An alternative theory to dark matter has successfully predicted the rotational properties of two elliptical galaxies. The work was done in Israel by Mordehai Milgrom using the modified Newtonian dynamics (MOND) theory that he first developed nearly 30 years ago. By showing that MOND can be used to explain the properties of complicated elliptical galaxies – as well the much simpler spiral galaxies – Milgrom argues that MOND offers a viable alternative to dark matter when it comes to explaining the bizarre properties of galaxies.

Dark matter was proposed in 1933 to explain why galaxies in certain clusters move faster than would be possible if they contained only the "baryonic" matter that we can see. A few decades later, similar behaviour was detected in individual galaxies, whereby the rotational velocity of the outermost stars was found not to "drop off" as a function of distance but instead remain flat. These observations directly contradicted Newtonian gravity, which should hold true in extragalactic regions just as it does on Earth and in the solar system. But by assuming there are "haloes" of invisible matter in and around galactic structures, Newton's familiar inverse square law is restored.

Since it was first invoked to explain these galactic irregularities, physicists have tried to make direct measurements on dark matter to try to work out exactly what it is – with very little success. As a result, there are some researchers who do not believe that dark matter exists and have proposed alternative explanations for the strange behaviour of galaxies.

Spectacular success

Now a new analysis suggests that one alternative theory called MOND describes the properties of two elliptical galaxies just as well as dark matter. MOND was originally formulated to describe spiral galaxies and has had spectacular success in predicting certain properties of these structures. Its extension to cover elliptical galaxies could strengthen the arguments in favour of this alternative theory. This is because elliptical galaxies are predicted to have formed by a different process from spiral galaxies and their properties are much more difficult to calculate.

MOND was first proposed in 1983 by the astrophysicist Mordehai Milgrom of the Weizman institute in Israel. The basic premise of the theory is that at extremely small accelerations of less than 10^–10 m s^–2 Newton's second law does not hold. Instead, Milgorm modified Newton's formula so that under certain circumstances the gravitational force between two bodies decays more gently than the inverse square of the distance between them.

Predictably, a theory that advocates changing Newton's laws is destined to meet with widespread scepticism, and MOND is no exception. Nevertheless, it also has undeniable attractions, such as the ease with which it makes testable predictions and the fact that it does not rely on an as-yet unseen dark matter. And, since a version of MOND consistent with Einstein's general theory of relativity was derived in 2004 by Jacob Bekenstein of the Hebrew University of Jerusalem, the wider physics community has begun to take notice.

No coincidence

In the new research, Milgrom analyses the hydrostatics of a spherical envelope of hot, X-ray emitting gas in two elliptical galaxies and shows the predictions of MOND are equally valid in these. This is important, Milgrom argues, because elliptical galaxies are thought to have evolved in a completely different way from spiral galaxies and other disc galaxies – they are thought to be formed by the collision and merging of two other galaxies. MOND's success, he argues, means that its predictive accuracy cannot simply be a coincidence and that it must hint at a deeper underlying truth.

He also suggests that the fact that the same mathematical law can be used to predict the rotation speeds of two different types of galaxies formed in two different ways significantly undermines the dark-matter hypothesis. "In the dark-matter picture" he says, "The galaxies we see today are the end result of very complicated and very haphazard formation processes. You start with small galaxies – they merge, they collide – there are explosions in the galaxies and so on and so forth. During this stormy evolution the dark matter and the normal matter are subject to these processes in very different ways and so you really do not expect to see any real correlations between the dark matter and the normal matter. This is a very weak point of the dark-matter picture."

Particle astrophysicist and dark-matter expert Dan Hooper of Fermilab in the US, argues that MOND will not win over sceptics by showing its applicability to galaxies, even if those galaxies are of types that have not been previously tested. "I have found it to be the case for quite some time now that MOND does a very good job of explaining the dynamics of galaxies," he says. "And this paper is yet another example of where MOND succeeds at the galactic scale. Where MOND fails is on larger scales such as in clusters of galaxies and on even larger cosmological scales." He cites the anisotropy of the cosmic-microwave background as one example of this.

The research is published in Physical Review Letters.

Between the lines

A piezoelectric silicon chip — Crystal qualities: *Sand and Silicon* begins with a look at piezoelectricity. (Science Photo Library)

Playing in the sandbox

Silicon is the oxygen of human technology. Without it, much of modern civilization as we know it could not exist, since silicon and its compounds – particularly sand and quartz – are found in all manner of electric components and household goods. In Sand and Silicon, the physical chemist Denis McWhan makes an impressive case for the scientific interest of these two related substances, as well as their importance. The book begins with a chapter on piezoelectricity, or the ability of certain types of crystals (including quartz) to become electrically polarized in response to applied pressure. Discovered by Pierre Curie and his older brother Jacques in 1880, piezoelectricity went on to play a major role in the younger Curie's famous studies of radioactivity. As McWhan describes, piezoelectric crystals lay at the heart of Pierre and Marie Curie's radiation-detecting apparatus. In the same chapter, the author also delves into the crystal structure of quartz, and shows how piezoelectricity arises from particular types of crystal symmetry. This mixture of theory, applications and history is repeated in later chapters on the crystal architecture of sand, the role of impurities in materials such as semiconductors and the design of photovoltaic solar cells. Written without much mathematics, but with a high level of technical detail, the book would make an excellent introduction for advanced secondary-school students, undergraduates or physicists seeking to fill a gap in their knowledge of materials science.

2012 Oxford University Press £29.95/$55.00hb 160pp

Think carefully

Physics is full of apparent paradoxes that, when examined with due care and attention, turn out to make sense after all. This, in a nutshell, is the premise of Paradox: the Nine Greatest Enigmas in Science, the latest book by the British physicist, broadcaster and science communicator Jim Al-Khalili. The book begins with some of the earliest known paradoxes: those of the Greek philosopher Zeno, who in the 5th century BC articulated puzzles concerning arrows in flight and a race between a tortoise and the mythical hero Achilles. After showing how each of Zeno's paradoxes can be resolved with a little knowledge of kinematics and infinite series – and offering a tantalizing glimpse of a quantum version of Zeno's Arrow Paradox – Al-Khalili moves on to more recent enigmas. One of these is Olbers' Paradox, which asks why the night sky appears dark even though there are stars in every direction you look. Fascinatingly, the first person to resolve this paradox seems to have been the American writer Edgar Allen Poe, who intuited in 1848 that the sky is dark because most stars are too far away for their light to have reached us yet. Poe, however, had no proof – a proper resolution to the paradox would not come until 1901, when Lord Kelvin published full calculations – and, as the book's subsequent chapters illustrate, intuition is seldom a reliable guide in modern physics. (What would Poe have thought about Schrödinger's cat?) Professional physicists will find few surprises in Al-Khalili's book, which is aimed more at readers who have never encountered such bread-and-butter physics topics as the Big Bang, special relativity and the second law of thermodynamics. However, Al-Khalili's explanations of these topics are clear and well written, and the "paradox" concept is an attractive means of grouping them together.

2012 Bantam Press £16.99hb 256pp

Into the white abyss

A little over a century ago, a patent clerk with a penchant for physics was preparing to embark on the project that would define his life. His name was Salomon August Andrée (who did you think we were talking about?) and in July 1897, he and two companions set off from the Svalbard archipelago in an attempt to reach the North Pole in a giant silk balloon. They expected the journey to take less than a week and, in retrospect, their optimism seems inexplicable. As Alec Wilkinson notes in his book The Ice Balloon, Andrée's knowledge of polar wind currents was practically non-existent; his balloon leaked hydrogen from some eight million tiny needle-holes in the fabric; and although the group carried extra provisions in case they had to return by foot or boat, none of them had prepared, mentally or physically, for the sheer effort involved in hauling 300-pound sledges across pack ice. But as Wilkinson explains, the Arctic in the late 19th century was a magnet for scientific dreamers. Moreover, some of these dreamers – including the American Adolphus Greely and the Norwegian Fridtjof Nansen, whose expeditions are described briefly in the book – managed not only to survive, but even to achieve a degree of success. Andrée must have believed himself capable of a similar triumph over adversity. One certainly gets a sense from the book that he was not lacking in confidence. In Wilkinson's words, Andrée acted as if "moving among disciplines [was] not a matter of broadening oneself...so much as applying one's customary judgement to new circumstances". There would be no happy ending for Andrée and his fellow adventurers, but this book about their failure is a moving epitaph for what Wilkinson calls "the heroic age of Arctic exploration".

2012 Knopf $25.95hb 256pp