physicsworld.com Volume 26 No 6 June 2013
Capturing CO2 Removing the climate culprit from the air
Made in Manchester Where Niels Bohr developed his model of the atom Pretty cool things Using neutrons to probe nature’s secrets Diamond life A career in industrial product development www.acalbfi.com
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Get in touch: Email : [email protected] consult. design. integrate. physicsworld.com Contents: June 2013
Quanta 3 Frontiers 4 Pear-shaped nuclei could point towards physics beyond the Standard Model O Does antimatter fall up or down? O Evolution of foam O How nanocrystals squeeze through nanotubes O Nanowire transistor as sensitive as human skin iStockphoto/José Luis Gutiérrez Luis iStockphoto/José News & Analysis 6 UK rejoins FAIR project O US gets new fusion boss O Hawking boycott divides opinion O Los Alamos “quantum internet” revealed O China targets Chilean telescopes O Australian budget kicks up a storm O Mexican astronomers start work with gamma-ray observatory O US scientists attack “awful” peer-review bill O Leo Kouwenhoven: the man behind the particle Comment 15 In a state – R&D budgets in Europe 17–18 Location, location Forum 17 A divided union? Jose Mariano Gago Critical Point 19 The new idols Robert P Crease Feedback 20 Your views on green energy, the uses of mathematics and Maxwell’s demon, plus comments from physicsworld.com about feline thought experiments Sophia Smith Collection,Sophia Smith College Features Mopping up carbon 23 As levels of carbon dioxide in the atmosphere rise, researchers are competing to develop technologies that capture this climate culprit directly from the air, as Fragments – Dorothy Wrinch’s legacy 41-42 David Appell reports Cool things to do with neutrons 28 On the cover Peter Geltenbort explains how researchers are using ultracold neutrons to probe Removing carbon dioxide from the air 23–27 a variety of problems in fundamental physics, including looking for the effects of (iStockphoto/Frank Ramspott) Where Niels Bohr developed his model of the new particles or forces atom 34–38 Using neutrons to probe nature’s secrets Made in Manchester 34 28–32 After a hiccup at Cambridge, the young postdoc Niels Bohr truly flourished once A career in industrial product development he arrived in the positive research environment of the University of Manchester 46–47 where he developed the first quantum model of the atom, explains Brian Clegg Reviews 41 phys ic O sw Structural disputes with Dorothy Wrinch It’s that goddam particle again o r l O Web life: The Giant’s Shoulders d Careers 46 The sixth element Stephanie Liggins O Once a physicist: Janet Guthrie
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Physics World June 2013 1 physicsworld.com Quanta
For the record Seen and heard We are in danger of being left behind Lord John Browne writing in the Daily Telegraph vehicles. Due out later this year, the watch will cost “well into five figures”, according The former physicist and chief executive of oil to Hoptroff’s website. But you are likely to giant BP says that countries such as China and have to jump through a few hoops to get Brazil are doubling or tripling how much they one, as potential buyers will be subject to spend on science, leaving Western countries in security clearances “due to the nature of their wake. the device”. Those who end up with one Richard Strauss, Smithsonian of the 12 watches being produced will be Mrs Thatcher didn’t understand lucky, rich or stupid (or possibly all three). because Mrs Thatcher liked to find things to be the way she wanted Name your own exoplanet Space company Uwingu is on a mission to them to be Hear my voice rename the hundreds of exoplanets that Former CERN theorist John Ellis speaking to He may have placed the first telephone have been found by astronomers over the the South China Morning Post call, but that wasn’t the only pioneering last couple of years. Uwingu (which means Ellis was talking about the time he met and experiment Alexander Graham Bell did. “sky” in Swahili) has launched an “adopt explained his research to the former UK prime On 15 April 1885 the Edinburgh-born a planet” campaign, giving people the minister Margaret Thatcher, a former chemist, scientist also recorded his voice onto a opportunity to vote for as well as propose who died in April. wax-covered cardboard disc, which turns new names for exoplanets. Proposing a out to be the only known recording of him name will cost $4.99, while voting for one I was a swot, but I was allowed to speaking. The recording remained silent is $0.99, with the proceeds being used to for 128 years, until Carlene Stephens, fund “space exploration, research and be without any ill effects from my curator of the Smithsonian’s National education”. Uwingu has kicked things contemporaries Museum of American History, came off by seeking new names for the closest Edinburgh physicist Peter Higgs quoted on across the work of physicists Carl Haber known exoplanet – Alpha Centauri Bb – the BBC and Earl Cornell at the Lawrence Berkeley which lies some 4.3 light-years from Earth. Higgs says that being a swot was something to National Laboratory in California. The After garnering more than 750 votes, the compensate for not being able to play football, duo previously managed to play – for winning name – proposed by astronomy which he was excused from doing as he suffered the first time – a 1860 recording of an enthusiast Jay Lark – is Albertus Alauda, from asthma. unknown woman singing the French folk which beat off Rakhat and Caleo with song “Au clair de la lune” that was made 684 and 622 votes, respectively. Any using a “phonautograph”, which works name, however, will be unofficial as the This is turning out to be the most by etching sound waves onto paper that is International Astronomical Union is the desired job in history covered in soot. Using the same approach, “single arbiter of the naming process”. Bas Lansdorp, co-founder of Mars One, quoted Haber and Cornell have now made high- in Time resolution digital scans of Bell’s cardboard Chip-powered rocket More than 80 000 people have applied – at a disc and then turned the images into You might think that cost of around $50 per applicant – to become an sounds, unveiling the recording, which the American military astronaut and travel to Mars on a one-way trip to starts with the unerring words “Hear my had better things to do, establish a human colony on the red planet. voice – Alexander Graham Bell”. but Michael Courtney CC BY-SA 3.0 Spedona from the US Air Force Atomic timepiece Academy in Colorado and I’m fascinated with quantum physics. In what could be a quantum leap in luxury Elya Courtney from BTG Research have That’s the reason why I’m going back timepieces, Hoptroff, a London-based been studying how to fire potatoes out of to school this September to learn watchmaker, has teamed up with the US canons. The pair tested a range of fuels computer science firm Symmetricom to make “the world’s including ethanol, butane and propane first atomic-powered pocket watch”. and used a high-speed camera to measure Pop star Will.i.am in the Irish Examiner Called simply “No 10”, Hoptroff says the the position of the potato in the barrel The 38-year-old star of the Black Eyed Peas hints watch is the most accurate ever, losing just against time to calculate its velocity. at a possible interest in quantum computing. one and a half seconds every thousand Acetylene came out on top, producing a years. The watch is no joke – it features muzzle velocity of 138 ms–1 – much higher Nobody wants to take physics, but at a small chip that contains a caesium-gas than its nearest competitor methanol, least when he sings, it makes it fun chamber inside a temperature-controlled which shot the tuber out at around 40 ms–1. oven. A laser is shone into the chamber “Potatoes launched with acetylene were Elias Borne, a chemistry student at Haverford to excite the caesium atoms, causing also destructive to wooden boards and College quoted on philly.com electrons to oscillate – or tick – between plastic objects initially employed as Borne was commenting on the lectures of different energy levels. Symmetricom backstops before transitioning to 6 mm physicist Walter Smith who brings his ukulele originally developed the chip-sized thick steel plate,” the authors warn, before into class and sings physics-based songs to help atomic-clock system in collaboration with adding that “adult supervision and due explain difficult topics. the US Department of Defense for use care regarding safe firing directions is in cruise missiles and unmanned aerial imperative when using these devices”.
Physics World June 2013 3 physicsworld.com Frontiers In brief Nuclear physics goes pear-shaped Cold-atom random laser created Physicists in France are the first to create a transitions in radon-220 and radium-224. random laser in a cloud of cold atoms under These transitions are a sign that the nuclei
laboratory conditions. Random lasing involves L P Gaffney are lopsided and appear in the spectrum of light bouncing between particles located at gamma rays that these nuclei emit as they random positions in a gain medium, stimulating decay from an excited state. the emission of coherent light in all directions. The radon and radium nuclei were created The physicists made the laser with a cloud at the REX-ISOLDE facility at CERN by of cooled rubidium-85 atoms confined to a firing protons into a uranium-carbide tar- magneto-optical trap. They used a pump laser get. These nuclei were then accelerated and to create a population inversion between two passed through thin targets of nickel, tin and hyperfine levels of the same electronic orbital cadmium. Any radon and radium nuclei that and a second, tunable laser to stimulate emission come close to a target nucleus can be excited back to the lower level. The system could improve by its intense electric field – an experimental our understanding of astrophysics, as well as help technique called “coulomb excitation”. The better our understanding of quantum computing nuclei were then fired through CERN’s (Nat. Phys. 10.1038/nphys2614). New kind of nucleus A representation of the pear- MINIBALL detector, which can detect shaped radium-224 nucleus. gamma rays emitted from the nuclei. Glass obeys a cracking good law By looking at the energy and spatial distri- A team in France has carried out a series of An international team of physicists has butions of the gamma rays, the team could simple experiments using brittle plastic and glass found the best evidence yet that some heavy conclude that both nuclei are pear-shaped. plates to find out more about how star-shaped nuclei are not spherical or ellipsoidal – but In particular, the team found that a certain cracks grow. The physicists used an airgun to “pear-shaped”. The researchers found octupole transition was much more com- fire steel and ceramic projectiles at plates of clear signs of this lopsidedness in two par- mon than if the nuclei were not pear-shaped. either glass or poly(methyl methacrylate) – better ticular nuclei – radon-220 and radium-224. Indeed, in the case of radium, the transition known as Plexiglas or Perspex – that were no As well as providing new information about was about 30 times stronger than expected. more than 3 mm thick. The resulting cracking the forces that bind protons and neutrons The new results provide some insight into process was monitored using a high-speed together in nuclei, the discovery could the efficacy of several models that attempt camera for about half a second, which is the also help shed light on physics beyond the to describe the structure of large nuclei such time it takes the initial shock wave to reach the Standard Model of particle physics. as radon and radium. Beyond nuclear phys- edges of the plates. The team found a scaling Although some limited evidence for ics, the study of such nuclei could also shed law that describes the cracking process in terms pear-shaped nuclei was obtained in experi- light on why there is far more matter than of several fundamental parameters – a finding ments carried out on radium-226 and neo- antimatter in the universe. This is because that could have a wide range of applications from dynium-148 in the 1990s, neither study was atoms that have a pear-shaped nucleus are forensics to planetary science (Phys. Rev. Lett. conclusive. What Peter Butler of the Uni- expected to be a good place to look for vio- 110 174302). versity of Liverpool and colleagues else- lation of time (T) and charge–parity (CP) where in Europe and in the US have now symmetries beyond that allowed by the Third Bell loophole closed for photons done is to find strong evidence for octupole Standard Model (Nature 479 199). The third and final loophole in an important test of the quantum nature of the photon has been as help us to understand the precise nature closed by a group of physicists. They have shut ALPHA weighs in of dark matter and dark energy. what is called the “fair sampling” loophole, The ALPHA experiment involves captur- which says that classical – rather than quantum ing and storing antihydrogen in a magnetic – effects could be responsible for measured on antimatter trap that is then turned off, causing the cloud correlations between entangled photon pairs. of antihydrogen to expand outward. When The test involved two observers – Alice and Bob Physicists at the ALPHA experiment at an anti-atom reaches the solid interior sur- – and a source that created pairs of photons CERN have taken an important first step face of the trap it annihilates, producing a that are entangled in terms of their polarization, towards measuring the gravitational mass flash of radiation that can be detected. The wherein the polarization correlation is much of antihydrogen, which consists of a posi- team recorded the position of each annihila- stronger than is allowed by classical physics. tron surrounding an antiproton. Although tion and the time when it occurred – reveal- The photon is now the first system in which they did not see any evidence that anti- ing the trajectory followed by each atom. the violation of “Bell’s inequality” has been atoms respond to gravity differently than In its analysis of data from the 2010 –2011 unambiguously established. While few physicists atoms, the team ruled out the possibil- run, the team was able to rule out the ratio will be surprised that all three loopholes have ity that antimatter responds much more between the gravitational mass and the now been closed, doing so could be an important strongly to gravity than matter. Despite a inertial mass of antihydrogen being less step towards developing fail-safe quantum large body of theoretical and experimental than about –65 and greater than about cryptography (Nature 10.1038/nature12012). work suggesting that gravity acts in exactly +110. When experiments restart at CERN the same way on antimatter as it does on in 2015, ALPHA physicists want to rule Read these articles in full and sign up for free matter, finding even the tiniest difference out antigravity entirely by looking at ratio e-mail news alerts at physicsworld.com is crucial as it could shed light on why there values in the –1 to 1 range (Nat. Comms. is so little antimatter in the universe as well 10.1038/ncomms2787).
4 Physics World June 2013 physicsworld.com Frontiers
Innovation The human touch – via a nanowire array James Sethian and Robert Saye A team of engineers in the US has fabricated flexible, skin-like arrays of nanowire transistors that convert mechanical motion into electronic signals. The team is led by Zhong Lin Wang at the Georgia Institute of Technology, who claims they are as sensitive as a human fingertip. Reproducing a human sense of “proprioceptive” touch with electronics is far from easy. Existing tactile sensors tend to be made of materials with a resistivity that changes characteristically when touched, but the devices have low resolutions – pixels of around 1 mm. What Wang’s team has done is to slash the pixel size to just 20–50 μm, and improve on resistive sensitivities by a factor of at least 30 by Getting to the bottom of foamy physics exploiting the piezoelectric effect. Two physicists in the US have been frothing with excitement at having created a new mathematical model to When a piezoelectric semiconductor is describe the complex evolution of foamy bubbles. James Sethian and Robert Saye of the University of mechanically strained, the symmetry of its California, Berkeley have separated the various processes that determine a foam’s evolution according to the component crystals gets distorted, creating different length and time scales at which they occur – and have created a model for bulk foam dynamics. a polarization charge along the length of the They say that the model accurately describes how fluid moves within a bubble, how the individual cells form material. Wang used this principle a few years and how their junctions (or borders) are rearranged as individual bubbles within the foam burst. After testing ago to create a new electrical component – their formulae on bubble clusters of different sizes, the duo found that they could accurately predict the the piezoelectric transistor – from bundles of interactions of gases and liquids in these foamy materials. They also developed a set of equations that they zinc-oxide nanowires held vertically between used to create a movie that simulates how light would reflect off a small foam sample as its bubbles electrodes. Unlike conventional field-effect rearrange. Above is a series of stills from the movie – they picked a “beach scene” as a backdrop so that they transistors – which have a current source, a could visualize how well the model replicates what one would see in real life. The team hopes the underlying drain and a gate electrode that controls the flow equations could have a variety of applications, including helping to make better metal and plastic foams, and between them – the piezoelectric transistor also to model biological processes, such as the growth of cell clusters (Science 10.1126/science.1230623). comprises only source and drain electrodes. In the new work, the engineers fabricated deformed. Instead, the crystal deconstructs a functional array of more than 8400 touch- Squeezing nanocrystals and reforms, within the narrow passage, sensitive transistors that they dubbed tactile at the atomic scale. Electron diffraction pixels, or “taxels”. Beginning with a thin, A remarkable discovery about how an iron measurements verified that the crystals did transparent substrate, the team laid parallel nanocrystal moves through a carbon nano- not melt or experience compression. strips of indium tin oxide as the bottom electrode, tube without a uniform diameter has been Coh and colleagues use their atom-by- before the nanowires were synthesized vertically made by researchers in the US. They found atom reconstruction theory to explain using a low-temperature hydrothermal chemical- that if the crystal meets a constriction in the the crystal’s transport, saying that at the growth technique. Gold contacts and the top tube, the crystal reforms, atom by atom, to “contact region” (where the crystal is in electrode were added before the whole array fit through the constriction, without under- contact with the inner wall of the nano- was coated with a polymer to seal and protect going any melting or compression. tube), surface atoms from the far end of the it from moisture and corrosion. Each transistor Scientists have known for some time that crystal are transported along to the front. comprises a bundle of approximately 1500 metallic nanocr ystals can be made to travel Once an atom that diffused from the back nanowires, with each nanowire measuring about through a nanotube by applying a current has migrated to the front of the crystal, 500 nm in diameter. The sensors could detect to the tube. But if the tube narrows down at it quickly gets covered by more incoming pressure changes as small as 10 kPa – similar to some point, it was assumed that the crystal atoms and so becomes part of the bulk and a gentle touch such as typing on a keyboard. would cause a blockage. remains stationary. This effectively allows As well as offering robots a more adaptive Now, though, having watched the move- the entire crystal to re-assemble within the sense of touch, the technology could improve the ment of iron nanocrystals with a high-reso- confines of the constriction with its bulk functional capability of human prosthetics and lution electron microscope, Sinisa Coh and remaining essentially stationary, so long as offer new ways for us to interact with electronics, colleagues from the University of Califor- the current is applied. for example with improved electronic-signature nia, Berkeley, and the Lawrence Berke- This behaviour could have many applica- mapping. Wang identifies the team’s next ley National Laboratory have found that tions in nanomechanics and could possibly goal as building higher-density and more the metallic nanocrystals, while remain- be used to synthesize metal crystals within sensitive transistor chips (Science 10.1126/ ing solid and crystalline, manage to slip nanotubes or purify them (Phys. Rev. Lett. science.1234855). through the narrow passage without being 110 185901).
Physics World June 2013 5 physicsworld.com News & Analysis UK makes a FAIR U-turn After having largely pulled out of the FAIR nuclear-physics facility in Germany, the UK has now backtracked and taken up associate member status at the lab, as Michael Banks reports
“Bliss was it in that dawn to be alive (see box below). but to be young was very heaven.” FAIR The partial pull-out of FAIR Physicists rarely get particularly threatened to hit UK nuclear physics poetic, but it was with these words hard and late last year the Institute of from William Wordsworth’s The Physics (IOP), which publishes Phys- Prelude that William Gelletly from ics World, released a report looking the University of Surrey greeted the into the future of UK nuclear phys- UK’s decision to officially become ics. Chaired by Gelletly, one of the part of the 1.6bn Facility for Anti- recommendations in the report was proton and Ion Research (FAIR), that the UK government negotiate which is being built at the GSI heavy- for “associate member” status at the ion lab in Darmstadt, Germany. As lab so it could be involved in making a long-serving member of the UK’s at least some decisions concerning nuclear-physics community, Gel- the future of the facility. letly is delighted that the UK will Last month the STFC announced return after years on the project’s it would now become an associate sidelines – even more so because the member of FA I R , w ith around 10 U K UK also announced last month that centre in Europe after CERN. Joining the club institutions being involved, includ- it would boost nuclear physics among In 2009, however, the UK had The UK will spend ing the universities of Birmingham, students and new researchers. “I am announced that it would delay cash around £10m to Glasgow and Manchester. The UK’s very happy that my younger col- for the facility by a year following build an experiment participation at the facility will be leagues will really benefit from this a much-publicized funding black at the Facility for made through a £10m contribution step,” he says. hole of £80m in the budget of the Antiproton and Ion to the construction of NuSTAR and, FAIR, which will be one of the Science and Technology Facilities Research as well as once FAIR opens, the UK will then world’s largest accelerator centres, Council (STFC), which supports the pay some of the lab’s pay around 0.5% of its running costs. will provide scientists with a selec- UK’s presence in a number of “big- running costs. “The advances in technology that tion of very intense and energetic science” projects such as CERN will result from our scientists’ work particle beams. The facility will be and the Diamond Light Source on this hugely challenging project funded 75% by Germany and 25% in Oxfordshire. With the reduced will be a real asset to the UK in terms by nine other collaborating coun- funds, in December that same year of economic and societal benefits,” tries, including Russia and India as the STFC released the results of a says John Womersley, chief executive well as other European states such as “prioritization exercise” that saw the of the STFC, in an official statement. France and Finland. FAIR was ini- UK providing cash for the Nuclear “The UK’s associate member status tially slated to begin as early as 2015, Structure, Astrophysics and Reac- at FAIR will ensure that we play a but various factors have hampered tions (NuSTAR) experiment at leading role in the development of construction, which is now set to be FAIR but pulling funds for the facil- this groundbreaking international finished in 2020. Once complete, it ity’s Antiproton Annihilation at project, and that our researchers will be the second largest scientific Darmstadt (PANDA) experiment will have access to the latest, most FAIR factfinder The Facility for Antiproton and Ion Research FAIR covering a wide range of research. This will properties of antihydrogen, which consists of an (FAIR) at the GSI heavy-ion lab in Darmstadt, be done in the four “experiment complexes”: antiproton and a positron. Germany, will consist of two synchrotrons with Atomic, Plasma Physics and Applications (APPA); Finding the Higgs boson at CERN’s Large a circumference of 1100 m built on top of one Compressed Baryonic Matter (CBM); Nuclear Hadron Collider has helped our understanding of another in an underground tunnel. Ions from the Structure, Astrophysics and Reactions (NuSTAR); how mass is generated. However, the particle only GSI’s existing 200 m circumference synchrotron and Antiproton Annihilation at Darmstadt (PANDA). explains a small fraction of the mass of a proton or will be fed into the new double-ring facility, which Nuclear physicists will, for example, use the neutron. The PANDA experiment at FAIR will study will multiply the intensity of the ion beams by accelerated ions to generate beams of novel, the debris from matter–antimatter collisions to a factor of 100 and provide up to 1011 ions per unstable nuclei by firing them at a target made help shed light on how the remaining 97–98% of second. The new rings will also increase the of a light element such as beryllium, as well as the mass is generated. “The tremendous progress maximum energy of the beams by a factor of 20 colliding heavy ions at high energies to generate of the construction of the facility, its accelerators to about 35 GeV. a quark–gluon plasma. Atomic physicists, and experiments during the last few years is very There will be a total of 15 experiments at meanwhile, will use the facility to explore the exciting,” says FAIR project leader Boris Sharkov.
6 Physics World June 2013 physicsworld.com News & Analysis
advanced research facilities.” rather than sitting on the sidelines, It is the right led the project until 2009. “The UK FAIR’s scientific director Boris the UK has now become part of the time to join has now made a first step by becom- Sharkov, who is also chair of its man- club, as recommended in the IOP ing an associate member, not yet a agement board, calls the UK’s deci- report. “This is a very important FAIR – to work shareholder,” says Gutbrod. “I do sion to join FAIR a “very good thing”. facility and it is pleasing that the in developing hope that in the future the UK will “This gives an important signal to the STFC has recognized this. It has the world’s be involved in FAIR GmbH.” scientific community and promises seen beyond the feeble boundaries most important While the UK will just be an asso- further expansion of the FAIR user we erect around parts of science and ciate for now, that seems to be good base,” he says. “It is the right time realized that it will bring many new nuclear- enough for nuclear physicists in the to join FAIR – to work in developing opportunities in various aspects of physics UK who only a couple of years ago the world’s most important nuclear- basic science and its application,” research were worrying that government cuts physics research facility, which will he says. could decimate the field. As Gelletly be the case for many decades.” Gelletly, however, would like the facility succinctly puts it, membership is “one Sharkov argues, however, that U K to bec ome a f u l l member i n FA I R small step for John Womersley, one managers at FAIR “never had any in the future, which would involve giant leap for UK nuclear physics”. doubts” that the UK would join at the UK buying shares and becoming O On pages 34–38, Brian Clegg some point. “So there was no real a shareholder of FAIR GmbH – the describes how Niels Bohr harm caused by the STFC pulling company that is building the facility. developed his model of the atomic out for a certain period,” he claims. That view is shared by former FAIR nucleus at the University of Gelletly says he is “happy” that, project leader Hans Gutbrod, who Manchester 100 years ago.
Fusion scientists and weapons experts for laser shots at the “wildly successful” NIF means that Moses no longer has the time to manage user requests. Missed targets prompt NIF reshuffle That responsibility now falls to Atherton. “The appointment reflects
The Lawrence Livermore National NIF the fact that NIF has evolved into Laboratory in California has an international user facility and so appointed a new director for its there is a need to call out the position $3.5bn National Ignition Facility in a more visible manner,” he says. (NIF). Jeffrey Atherton, a chemi- A very different perspective is cal engineer who has worked at NIF offered by Robert McCrory, director for 20 years, took up the post on of the Laboratory for Laser Energet- 1 May and will take on some of the ics at the University of Rochester in responsibilities previously held by upstate New York, which is develop- the facility’s existing boss Edward ing a rival “direct-drive” technology. Moses. However, Lawrence Liv- McCrory says that there has been ermore director Parney Albright “a great deal of dissatisfaction with insists that the new appointment the way Moses has led the ignition does not amount to a demotion for campaign”, criticizing what he calls Moses and says that it has nothing the “schedule-driven rather than to do with NIF’s failure to reach an Change at the top the lasers. But when NIF missed its discovery-driven” strategy. He also important milestone on the road to Chemical engineer target, the organization overseeing accuses Moses of being “not at all fusion energy last autumn. Jeffrey Atherton the facility – the National Nuclear transparent” in setting NIF’s budget NIF is designed to use extremely replaces Ed Moses Security Administration (NNSA) – priorities and maintains that the Liv- high-energy laser beams to explode as head of the told Congress that it would change ermore scientists have a blinkered peppercorn-sized pellets of deute- $3.5bn National strategy. The NNSA outlined a attachment to indirect-drive tech- rium and tritium in order to gener- Ignition Facility. three-year plan in which it no longer nology. “They are just so sure that ate the pressures and temperatures explicitly aims to achieve ignition they are on the right path,” he adds. needed to fuse these isotopes of but instead seeks to work out what Moses, however, says he is satis- hydrogen. It has been built primar- went wrong. In financial year 2015 it fied with progress to date, arguing ily to reproduce conditions inside will assess whether NIF’s “indirect that the failure to reach ignition was nuclear warheads so that the US can drive” technology – which heats the more than made up for by improve- maintain its weapons stockpile with- fuel via the production of X-rays – is ments to the laser, diagnostics and out testing those weapons, but is also likely to produce ignition or whether target, as well as a greater know- being used to investigate the feasibil- an alternative approach is needed. ledge of the physics governing fusion ity of fusion as an energy source. Albright explains that Moses will reactions. He also says he is “very Officially in operation since 2010, continue to have overall responsibil- happy” with Atherton’s appoint- NIF was supposed to achieve “igni- ity for the operation and improve- ment, explaining that his colleague tion” by September 2012. This is ment of NIF, as principal associate has experience both as a technician the point at which fusion reactions director for NIF and the photon- and as a manager, and that “he is become self-sustaining and produce science directorate. But Albright trusted by both users and managers”. more energy than they consume from insists that increasing demand from Edwin Cartlidge
Physics World June 2013 7 News & Analysis physicsworld.com
Politics Hawking’s Israel boycott sparks heated response
The controversial decision by Ste- and does not ask academics to avoid phen Hawking to boycott a promi- working with individual Israeli aca- nent conference in Jerusalem in demics. “Academic boycott is a way protest against the policies of the of saying to Israel and to Israeli aca- Israeli government has provoked demics that there is a cost to their strong responses from academics country’s violation of international and commentators. Hawking had law and human rights,” he said. been set to talk at the Israeli Presiden- Science Lee Museum/Sarah “Had Stephen Hawking decided to tial Conference: Facing Tomorrow, attend the conference and make crit- which will take place on 18–20 June ical comments about Israeli policies and will feature a string of high- including the occupation, I believe profile speakers, including Bill Clin- that would have been an excellent ton, Tony Blair and Mikhail Gorba- outcome. But as we have seen, the chev. But following correspondence impact worldwide of his withdrawal with Palestinian academics, Hawking has been far greater than that of any decided to withdraw from the event, of science. Allowing the addition of Dividing opinion statement at the conference. Maybe writing to the conference organizers scientific academic boycotts to the Hawking is the latest actions speak louder than words.” to explain his decision. arsenal of political tools will eventu- British public figure Proponents of an academic boy- “I accepted the invitation to the ally hurt all involved,” he told Physics to boycott Israel. cott of Israel compare their actions Presidential Conference with the World. “Based on my past exchanges to the boycotts of South Africa that intention that this would not only with Hawking on such subjects I am took place during the anti-Apartheid allow me to express my opinion on saddened by the statement about era. Opponents of the Israel boycott, the prospects for a peace settlement boycotts as reported in the media in however, point out that comparisons but also because it would allow me his name.” of the present-day situation in the to lecture on the West Bank,” he Upon learning of Hawking’s Middle East with Apartheid South wrote. “However, I have received a boycott, other commentators have Africa are tenuous and unjust. Some number of e-mails from Palestinian responded with more incendiary people even believe that motives academics. They are unanimous that remarks. Nitsana Darshan-Leitner, within the pro-boycott lobby show I should respect the boycott. In view director of the Israel Law Center, a form of selective ideology that can of this, I must withdraw from the issued a strongly worded statement sometimes equate to antisemitism. conference. Had I attended, I would accusing Hawking of hypocrisy. She This was the view of Nobel laureate have stated my opinion that the pol- specifically referred to the medical Steven Weinberg when he cancelled icy of the present Israeli government condition of the British academic, a trip to the UK in 2007 after learn- is likely to lead to disaster.” who suffers from a form of motor ing of a boycott of Israeli academics The chairman of the Israeli Presi- neurone disease and can only com- by the now-dissolved UK teaching dential Conference, Israel Maimon, municate via a synthesized voice union NATFHE. Weinberg had responded with anger to Hawking’s box. “His whole computer-based been due to speak at Imperial Col- decision, accusing the British aca- communications system runs on a lege London in honour of a Paki- demic of having double standards. chip designed by Israel’s Intel team,” stani physicist, Abdus Salam, and to “The academic boycott against wrote Darshan-Leitner. “I suggest if attend a conference on particle phys- Israel is in our view outrageous and he truly wants to pull out of Israel, he ics, string theory and cosmology. improper, certainly for someone for should also pull out his Intel Core i7.” In pulling out of the Israeli Presi- whom the spirit of liberty lies at the One group to have spoken out in dential Conference, Hawking joins basis of his human and academic support of Hawking’s decision is the a list of high-profile British public mission,” Maimon said. “Israel is a British Committee for the Univer- figures to boycott Israel in the past democracy in which all individuals sities of Palestine (BRICUP). This few years, including film direc- are free to express their opinions, union of UK-based academics was set tor Mike Leigh and the musicians whatever they may be. The imposi- up in 2004 to respond to a call for an Elvis Costello and Annie Lennox. tion of a boycott is incompatible with academic boycott of Israel issued by A recent example of the charged open, democratic dialogue.” the Palestinian Academic Cultural atmosphere surrounding public dis- Various scientists have also Boycott Initiative. BRICUP sent a Had I attended, cussion of Israel in the UK was seen expressed their disappointment at letter to Hawking encouraging him I would have at the University of Oxford in Feb- Hawking’s decision, including Eliezer to reconsider his decision to attend stated my ruary. George Galloway, an MP in Rabinovici, a high-energy physicist at this year’s Presidential Conference, opinion that the Respect party, walked out of a the Hebrew University of Jerusalem. with signatures from 20 academics debate upon learning the nationality Rabinovici has been closely involved including prominent US academic the policy of of his student opponent. In a video in the SESAME project, which aims Noam Chomsky of the Massachu- the present posted on YouTube, Galloway can to build a synchrotron light source setts Institute of Technology. Israeli be heard saying “I don’t debate with in Jordan to bring together scien- Jonathan Rosenhead, the chair government is Israelis, I’ve been misled, sorry.” The tists from the Middle East, including of BRICUP, told Physics World that university’s student union later voted Israel and Palestine. “In my opinion, the academic boycott promoted by likely to lead to to reject a boycott of Israel. academic boycott is against the spirit his organization is institutional only, disaster James Dacey
8 Physics World June 2013 physicsworld.com News & Analysis
Research Los Alamos builds world’s first ‘quantum internet’
Physicists at the Los Alamos National Secret messages cialize the technology. “We have Laboratory in the US say they have Richard Hughes and LANL 27 patent applications out there developed a “quantum internet” colleagues at the now, plus two in the pipeline,” says that can transmit data securely over Los Alamos National Hughes. “Our plan – and the lab’s a network containing multiple con- Laboratory have plan – is to transfer the technology nections. The team, led by Richard been testing a out to the private sector.” Indeed, a Hughes, says that it has been running “quantum internet” search for commercial partners has its “new, scalable instantiation” of a for more than two already drawn about 20 expressions quantum cryptography network for and a half years. of interest. “We’re seeing not just a more than two and a half years. push from research; there’s also a Quantum cryptography exploits big pull in terms of new ways people the principles of quantum mechan- hub. Each photon transmitter con- want to use networks, with handheld ics to create keys for encoding and tains a so-called quantum “smart devices,” adds Hughes. “All these decoding messages with complete card” that has been invented by things have big security problems. security. These keys are made up team member Jane Nordholt. The Our approach would have something of the quantum states of subatomic hub, which knows the secret quan- of value beyond the kind of crypto- particles, which means that an eaves- tum keys generated by each client, graphic methods available today.” dropper who tries to observe the keys manages communications between The technology has uses beyond will alter them and therefore reveal them by providing individual clients conventional messaging, as Hughes’ his or her presence. Many firms have with information that allows them to team carried out a demonstration for been developing quantum cryp- turn their quantum keys into those of the US Department of Energ y where tography, but are usually limited to other clients. the system was used to secure the sending encrypted data between two “One of the big advantages of this data and commands used to control fixed points. Indeed, Swiss company is that only the hub requires elabo- the national power grid. “Research- ID Quantique sells commercial sys- rate and expensive physical security ers have shown that ordinary cryp- tems to banks and governments, but measures to prevent compromise of tography isn’t good enough for this,” each network operates only between the system,” Hughes explains. “Pre- says Hughes. “This is an area where a single sender and receiver. vious quantum communication sys- quantum cryptography has a real The Los Alamos quantum net- tems have required this expensive advantage; we’ve moved it into the work consists instead of several pho- physical security on every node.” physical world.” ton transmitters – or “clients” – that The researchers at Los Alamos Peter Gwynne are connected directly to a central are now looking at ways to commer- Boston, MA
Astronomy because of the CCJCA, although there’s still a long way for us to go compared with other developed China to set up astronomy centre in Chile countries,” he says. The CCJCA and other projects The Chinese Academy of Sciences Working together in Hawaii are just the first steps
(CAS) is to set up an astronomi- CCJCA China will for China to begin co-operating cal research unit in Chile as part collaborate with with other countries in astronomy. of a drive to extend China’s science Chile to use According to Suijian Xue, head of co-operation with Latin America. observatories in the the NAOC’s Office for International The China–Chile Joint Center for South American Cooperation who came up with the Astronomy (CCJCA) will sponsor country as well as to idea for the CCJCA, China will also collaborative research programmes build new facilities. consider collaborating with Chile allowing Chinese astronomers to and other countries to build large use telescopes in Chile. If and when ground-based telescopes in the China invests and builds telescopes southern hemisphere. “Astronomi- there in the future, around 10% of vatory of China (NAOC). Indeed, cal research advances our scientific the observing time on the new facili- Chile is expected to attract about knowledge and technical sophisti- ties would be set aside each year for 68% of the world’s newest ground- cation, so it is only natural to open astronomers from Chile. based astronomical observation our collaborations to the world,” The CAS will spend about $2.5m facilities by 2020. says Huang. this year on the CCJCA, which will Jiasheng Huang, chief scientist of The CAS is also targeting increas- have its headquarters in the Chilean the CCJCA and an astronomer at ing observation in the northern capital of Santiago. “Chile is one the NAOC and the Harvard Smith- hemisphere by planning to join the of the best places to do astronomi- sonian Center for Astrophysics, says US, Canada, Japan, and India in the cal research – especially for optical, that the CCJCA will also enhance Thirty Meter Telescope on Mauna infrared and submillimetre-wave astronomical research in China. Kea in Hawaii. observations,” says Xuelei Chen of “I believe China’s observational Jiao Li the National Astronomical Obser- research will be much improved Beijing
Physics World June 2013 9 News & Analysis physicsworld.com
Funding Australian scientists hit out at pre-election cuts
Following criticism from research across many areas ahead of the organizations at funding cuts formal budget release on 14 May announced in the Australian national – exactly four months ahead of the government’s annual budget, the Pockley Peter upcoming national election. Battling country’s chief scientist Ian Chubb opinion polls that suggest Labor will has boldly entered the debate in an be wiped out by the Conservative attempt to damp down the protests. coalition, Craig Emerson – Labor’s Chubb – a biochemist who was pre- new minister for higher education viously vice-chancellor of the Aus- and research – revealed that uni- tralian National University – advises versity funding would be slashed by R&D policy in 14 relevant portfolios, A$3.3bn per year to help the govern- but does not administer their 80 pro- ment meet commitments to school grammes. His intervention came in a education and disability insurance. public lecture when he implied that The announcements triggered there are deficiencies in the govern- a flurry of protests and petitions, ment’s overall structure for R&D the meeting will be Science & Tech- Speaking out which included adverts taken out by acknowledging that Australia – nology Australia, which represents Suzanne Cory, in the national press by Universities unlike “almost all of the countries 60 specialist organizations, including president of the Australia on behalf of all 39 of the that outperform [it]” – lacks a proper the Australian Institute of Physics. Australian Academy country’s universities. Emerson and strategy for R&D support. Suzanne Cory, president of the of Science, is critical Gillard countered with claims that As Physics World went to press, Australian Academy of Science, wel- of the country’s new universities and research would be Chubb was due to convene a meet- comed a few positive areas of the new budget. getting more support overall through ing with members of various Aus- budget, but was critical of its overall several minor programmes, although tralian learned societies to start impact. “This budget unfortunately not as much as previously planned. drafting what he calls “a whole-of- represents a missed opportunity to Meanwhile, CSIRO – the nation’s government vision for Australia’s support a strategic long-term vision largest research agency – said it national science system of education, for Australia’s future,” she says. would have to make 165 of its 5715 research, innovation and communi- Australian scientists were thrust staff redundant to cope with a budget cation”. Chubb’s plan is to take this into political turmoil in April that will be reduced in the next finan- vision to prime minister Julia Gil- when a reshuffled ministry in Gil- cial year in real terms to A$1.3bn. lard’s Science Council for implemen- lard’s minority Labor government Peter Pockley tation. Among those contributing to announced major funding cuts Sydney Mexico HAWC observatory catches first gamma rays The world’s largest and most modern do this by detecting the light, known HAWC is for the gamma rays emitted by the Crab gamma-ray observatory has carried as Cherenkov radiation, that is emitted important Nebula in a much more efficient way out its first successful observations. whenever an incoming charged particle than other similar experiments. Located inside the Pico de Orizaba hits an electron or nucleus of water. for the HAWC is also important for the national park in the Mexican state Scientists have already shown that development development of Mexican science, with of Puebla, the High-Altitude Water HAWC is working as expected by using it of Mexican astrophysicist Alberto Carramiñana Cherenkov Observatory (HAWC) is a to obtain an image of the shadow of the Alonso – the observatory’s Mexican collaboration between 26 Mexican and Moon, which blocks cosmic rays coming science spokesperson – saying it is vital to US institutions. Construction began from different parts of the universe. But have a project “in which Mexicans are in 2009 and it currently has 77 water eventually they want to use HAWC to active participants”. Cherenkov detectors, with the total discriminate between gamma rays and Lukas Nellen, a nuclear physicist from number expected to grow to 300 other kinds of particles, such as protons the National Autonomous University of when the final phase of the project is and nuclei. HAWC researchers have also Mexico who is the observatory’s co-task complete in 2014. seen a small variation in the number of leader for software and computing, Each detector consists of a cosmic rays arriving from each direction says that HAWC has forced the Mexican corrugated steel tank that is 4 m of the universe. This anisotropy was scientific community to kick-start its high and has a diameter of 7.3 m, found to match previous measurements data-handling facilities. “It has been in containing a watertight bladder and made at the former Milagro experiment general a motivator for the development four photomultiplier tubes. The tanks, in New Mexico. of academic infrastructure such as which are filled with water, are designed Continuous observations at HAWC are advance networking, which will be vital to detect particles created from the expected to start in August when about for many other scientific projects in “shower” of particles formed when high- 100 of its tanks will be fully functioning. Mexico”, he says. energy cosmic rays strike the nuclei of The observatory will then seek to make Gabriela Frias Villegas gases in the Earth’s atmosphere. They original discoveries, such as searching Mexico
10 Physics World June 2013 physicsworld.com News & Analysis
US research Sidebands
China boosts developing-world ties Scientists fight scrutiny of NSF grants The Chinese Academy of Sciences (CAS) has announced it is to boost co-operation Scientists in the US have warned Stern critic with developing countries by setting up of an attack on the process that the Incoming president research centres outside of China. The National Science Foundation (NSF) of the American CAS already runs a programme to train – the main government agency for Physical Society hundreds of new PhD students from funding basic research – uses to Michael Turner has the developing world. Now China will select its grantees. At issue is the criticized America’s extend this programme for up to 140 High Quality Research Act, a bill High Quality students per year, who will be sponsored being developed by Texas Republi- Research Act. to complete a four-year PhD in China. can Lamar Smith – the new chair- The CAS will also open several centres in man of the House of Representatives South-East Asia, Central Asia, Africa and Committee on Science, Space and South America – the precise locations Technology. The act, if passed, would of which still have to be decided. Kenya force the NSF director to certify that will be home to the first CAS overseas each grant it awards is “in the inter- as it is likely to be blocked by the centre. Jointly established with Jomo est of the United States, answers Democratic-controlled Senate. But Kenyatta University of Agriculture and questions or solves problems that many are nonetheless concerned. Technology (JKUAT), it will be constructed are of utmost importance to soci- “The worry is the name – who could on the JKUAT campus and include labs for ety at large, and is not duplicative of oppose the High Quality Research cell and molecular biology, as well as a other research projects being funded Act? And the simplistic language, conference and training centre. by the foundation or other federal which makes it sound like it is easy research agencies”. Currently, the to ensure that the NSF only funds SKA headquarters opens NSF’s guidelines only ask reviewers the most impactful research,” says The new headquarters of the Square to consider the “intellectual merits” Turner. Meanwhile, Rush Holt – the Kilometre Array (SKA) was opened last as well as “broader impacts” of pro- New Jersey Democrat who is one month by UK science minister David posed research projects. of two PhD physicists in Congress Willetts. Costing £3.34m, the SKA Smith says his bill is a way of – feels that “members of Congress Organisation headquarters will be improving NSF’s grant process were showing a fundamental misun- located on the campus of the University and excluding projects that do not derstanding of the nature of science”. of Manchester in the UK. The new deserve support. But his opponents The bill originated when Smith headquarters will eventually be home see the draft legislation as an attack and other Republicans expressed to 60 staff members, including visiting on the NSF’s traditional process of concern about five particular NSF- scientists and engineers who will manage peer review. “I think it is an awful funded projects in the social sci- the construction, design and scientific piece of legislation,” University ences, which – they felt – did not output. SKA will be a ground-based of Chicago cosmologist Michael adhere to the foundation’s “intellec- radio-astronomy telescope consisting Turner told Physics World. “It would tual-merit” guidelines. Smith zeroed of more than 3000 radio dishes that require the director to do the impos- in on the projects merely on the basis will be spread out across thousands of sible – judge which projects will ulti- of their titles – an old ploy echoing the kilometres in both Australia and southern mately have the broadest impact. “golden fleece awards” that Demo- Africa. When the facility opens in 2024, The NSF is the forward-looking cratic senator William Proxmire of astronomers will use the telescope to agency that funds work with the Wisconsin used to mockingly hand probe the early universe by looking as longest-term impact, so this is very out in the 1970s. “Congress has a far back into time as the first 100 million difficult to judge.” responsibility to review research years after the Big Bang. Turner, a former assistant director paid for by hard-working American of the NSF and incoming president taxpayers,” Smith says. MIT picks new energy boss of the American Physical Society, is According to an unnamed com- Chemical engineer Robert C Armstrong not alone in criticizing the act. Three mittee aide quoted in Science, the has been named the new director of the former NSF directors – Neal Lane, proposed legislation would involve Massachusetts Institute of Technology Rita Colwell and Arden Dement – grants being judged after the peer- Energy Initiative (MITEI). Armstrong will have already written to Smith, warn- review process as an extra step to take over as MITEI boss from Ernest ing that the draft will have “a chilling “solve the problem of so many ques- Moniz, who left earlier this year to replace and detrimental effect on the merit- tionable grants being awarded”. But fellow physicist and Nobel laureate based review process and the partici- Democrats disagreed, with Eddie Steven Chu as US energy secretary under pation of an estimated 60 000 of the Bernice Johnson – the Texas Demo- President Barack Obama. Armstrong has world’s most outstanding research- It is an awful crat who heads her party’s repre- been the MITEI’s deputy director since it ers and educators, who voluntarily piece of sentation on the science committee was founded in 2007. He was previously assist the nation by reviewing pro- – writing to Smith that “Interven- head of the MIT’s chemical-engineering posals submitted to the foundation.” legislation. It tions in grant awards by political department from 1996 to 2007. The The letter was also signed by three would require figures with agenda, biases and no MITEI carries out research, education former chairmen of the National Sci- the director expertise are the antithesis of the and outreach programmes that cover ence Board, which oversees the NSF. to do the peer-review process.” all areas of energy supply and demand, Even if the bill is introduced, its Peter Gwynne security and environmental impact. chances of passage are minimal impossible Boston, MA
Physics World June 2013 11 News & Analysis physicsworld.com
“But the real proof of a full discovery still lies ahead.” Glimpsing a new particle Deals on the beach Physicists had been looking for Majorana fermions since the 1950s A little over a year after by smashing together particles in accelerators or by studying the discovering Majorana-like collision of cosmic rays with the Earth’s atmosphere. But those fermions in a nanowire, Delft University attempts never proved success- Leo Kouwenhoven hopes ful and the search appeared to be they could one day be used going nowhere until various theo- rists – including Alexei Kitaev, who in a quantum computer, last year shared the inaugural $3m Fundamental Physics Prize, as well as he tells Martijn as US Fields Medal winner Michael van Calmthout Freedman – predicted that these particles could appear in specially prepared nanowires. The Majorana Room 157C in the Boston conven- fermions would not exist as single tion centre was crammed. Only those fundamental particles, but as a col- lucky enough to turn up early had lective quasiparticle existing of thou- been able to grab a seat, with anyone sands of electrons. arriving even a few minutes late hav- Kouwenhoven’s good fortune ing to stand outside in the hallways, was that he had been working with bending their ears or stretching their semiconducting nanowires for years necks to see or hear what was going before he read Freedman’s 2006 on inside. Some centre officials predictions. “To my utter surprise were even talking anxiously about I turned out to be exactly the right fire regulations. guy for the job,” he recalls. “If any- The focus of attention was not a one could build what Freedman was business leader, actor or sports star, looking for, it was us at Delft.” but Leo Kouwenhoven – a Dutch The connection with Freedman solid-state physicist from the Kavli was made in 2009 when Kouwen- Institute of Nanoscience in Delft. He hoven’s wife suggested they take was in Boston to deliver a talk, enti- their family to the US for a holiday as tled “The search for Majorana fer- part of a sabbatical from his research mions in semiconductor nanowires”, Particle pioneer in Delft. Kouwenhoven spent a week to delegates attending the March Leo Kouwenhoven. In person visiting labs around the US and it was 2012 meeting of the American Physi- then that he met Freedman, who was cal Society (APS). The reason for the Born: Rijswijk, Netherlands, carrying out research into quantum great excitement was that Kouwen- 10 December 1963 computing at Microsoft’s Station-Q hoven was there to tell the assembled Education: BSc and PhD in physics, Delft labs in Santa Barbara. “We realized physicists that his group in the Neth- University of Technology (1988–1992) we had to team up and shook hands erlands had finally found the first Career: University of Tokyo (1991); on a deal on the California beach,” evidence for the existence of “Majo- University of California at Berkeley Kouwenhoven recalls. rana fermions” in 1D nanowires. (1992–1994); Harvard University When he returned to the Neth- Physicists have been looking for (2000–2001); Delft University erlands in 2010, Kouwenhoven Majorana fermions – fundamental of Technology/Kavli Institute of convinced the physics board of particles that are their own antipar- Nanoscience (2001 – present) the Foundation for Fundamental ticles with no charge, no spin and no Hobbies: Playing football, reading arXiv Research on Matter – an agency energy – for decades. Such particles Family: Married, two children that co-ordinates funding in the had first been predicted by the Ital- country – to match a $2m contract ian physicist Ettore Majorana in Hague to talk about the discovery. proposed by Microsoft to find the 1937 – a year before he mysteriously Just two months after the APS long-sought Majorana quasiparti- disappeared aged just 31 (see August talk, the group’s work was published cle. Microsoft was interested in this 2006 pp34–36). The Majorana fer- in Science (336 1003). Some say that newly discovered particle because it mions spotted by Kouwenhoven’s Kouwenhoven’s discovery could could be used as the basis for a sta- group are not, however, fundamen- pave the way for Majorana fermions ble quantum bit (qubit) for future tal particles themselves but quasi- to be used as the basis of quantum quantum computers. particles – particle-like entities that computing. Yet speaking to Physics Kouwenhoven carried out the pio- emerge from the collective behav- World at his office in Delft, a casually neering work on nanowires, together iour of electrons in a solid. Yet the dressed and trimly bearded Kou- with his Chinese postdoc Kun Zuo, discovery still grabbed international wenhoven is modest about what he over Christmas 2011 while his fam- headlines. It even resulted in Kou- has discovered. “What we have seen ily were away on holiday. The Delft wenhoven meeting an excited Dutch is something that walks and talks like group – together with colleagues at prime minister Mark Rutte in the a Majorana quasi-particle,” he says. Eindhoven University of Technology
12 Physics World June 2013 physicsworld.com News & Analysis
– connected a nanowire of indium- After leaving school, Kouwen- antimonide to an ordinary supercon- hoven applied to study veterinary ductor electrode (niobium-titanium- science at Utrecht University, but nitride). This creates a “topological failed to get a place as candidates Delft University superconductor” in the region of the were selected by random ballot. He nanowire that is near to the ordinary only chose to study physics at Delft superconductor. The other end of as a stop-gap – his plan being to reap- the nanowire is connected to a nor- ply for the veterinary course at Utre- mal electrode made of gold. The cht a year later. But physics grabbed device is cooled to temperatures of him and what was meant to be a way tens of millikelvin and a magnetic of filling a year eventually became field is applied along the direction of his life’s métier. the nanowire. After graduating in 1988, Kouwen- The team then measured the cur- hoven stayed on at Delft to do a PhD rent flowing through the nanowire supervised by quantum-transport as a function of voltage – and, in pioneer Hans Mooij. It was during particular, how the current changed his graduate-student days that Kou- in response to changes in voltage. wenhoven discovered the quantiza- At zero applied magnetic field, two tion of electric current in tiny wires, small peaks were observed on either which not only became the subject of side of zero applied voltage. But as his thesis, but resulted in a paper that the magnetic field was turned on is still the most cited to come out of and then increased, the position of Delft University of Technology. “I these peaks remained in the same just had all the luck in the world,” he position. This also occurred when says. “Theses of former students and an electric field was applied to the postdocs [of Mooij] were everywhere nanowire. According to the team, along with large drawers full of his this lack of response by the peaks to own work.” Measuring up and creative. Your specialities can magnetic and electric fields can only Kouwenhoven completed his PhD Artist’s impression of easily become a dead-end street.” be explained by the presence of pairs in 1992 and then moved first to Japan the set-up used by Finding Majorana particles might of Majorana fermions at one end of to do a postdoc at the University of Leo Kouwenhoven to seem an esoteric pursuit, but in the nanowire. Tokyo before heading to America – detect Majorana-like December 2012 Kouwenhoven’s The effects seen in the nanowires first to the University of California particles. The group – together with theoretical suggest that Majorana particles are at Berkeley and then Harvard Uni- indium-antimonide physicists from Leiden University – formed. But the ultimate proof lies versity. He came back to the Neth- nanowire (silver) is were awarded 15m from the Euro- in demonstrating their weird topo- erlands in 2001 to work in Mooij’s connected to a gold pean Research Council’s Synergy logical behaviour, which could make quantum-transport group in the electrode (top) and programme to demonstrate the first them ideal qubits. For this, new and Faculty of Applied Science at Delft to a superconducting fully functional stable qubit based better devices with lower noise levels and soon benefited from it becoming electrode (blue). on a Majorana quasiparticle in the have to be designed and tested. “We the home, in 2004, of the first Kavli next decade. A qubit is a unit of are rebuilding our initial experiment Institute outside of the US, which quantum information – the quantum from scratch to improve the layout saw the lab gaining new facilities analogue of the classical bit. Part of and sensitivity,” says Kouwenhoven. and moving more into the nanoscale Kouwenhoven’s Delft lab will now The work is still in progress, but domain. “The Kavli support brought be refurbished for the new project, other groups around the world are us not only new resources, but also an with Kouwenhoven pondering if it starting to catch up. “We scan the image of excellence, attracting new might be possible to set up a private arXiv preprint repository every day talent and even more resources,” company on the back of his work and whenever a title with ‘Majorana’ says Kouwenhoven. in Majorana qubits. “Preferably in turns up, my heart skips a beat,” he Kouwenhoven and his group got Delft, but California would do fine adds. “But we are still leading.” to work with nanowires of indium- too,” he says. arsenide. Combining them with Whatever happens in the coming Vets and vicars superconducting elements such as decade regarding commercializa- As a result of his work on nano wires, SQUIDs, they succeeded in dem- tion, for Kouwenhoven the fun will Kouwenhoven is now one of the onstrating fractional quantum-Hall always be in the science. In the art- world’s most highly cited solid-state effects. In 2007 he was awarded the ist’s impression of Kouwenhoven’s physicists, with some in the media 2.5m Spinoza Prize – the highest Majorana device, which made it onto even tipping him as a future Nobel- scientific honour in the Netherlands the cover of the 25 May 2012 issue prize winner. But Kouwenhoven’s – which brought him financial inde- of Science, a reflection of a face can background is relatively humble. His pendence and academic freedom. be seen on the tip of the shimmering father was a farmer in the small town But the fame and fortune have not Other groups indium-antimonide nanowire (see of Rijswijk – a stone’s throw away seen Kouwenhoven resting on his around the bottom right of above picture). The from the Delft University of Tech- laurels. “At the farm you take life as face, it turns out, is that of Majorana nology – and Kouwenhoven was the it comes. So when the whole world world are himself. Kouwenhoven grins over first member of his family ever to go suddenly invites you for talks and starting to the fact that no-one at Science seems to university. In fact, he originally symposia, you just do it,” he says. catch up, but to have noticed. “It is our little salute wanted to be either a vet or a vicar, “But you tend to forget that early we are still to a man as elusive as his particle,” he as those were the only jobs he knew success pushes you into a scientific says. “In a sense we found a glimpse of as a young boy on the family farm. niche, making it hard to stay fresh leading of both.”
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Presented by View now at brightrecruits.com/webinars physicsworld.com Comment Location, location Physics World Temple Circus, Temple Way, Bristol BS1 6HG, UK Where are today’s hot spots in physics? Tel: +44 (0)117 929 7481 E-mail: [email protected] Geneva. Princeton. Göttingen. Cambridge. Grenoble. Web: physicsworld.com The roll-call of towns and cities famed for their prominence in physics might Twitter: @PhysicsWorld Facebook: facebook.com/physicsworld not always be the biggest, most glamorous or most important of destinations. But the places mentioned above have, if sometimes only briefly, been among Editor Matin Durrani Associate Editor Dens Milne those where physics has blossomed and shone. Princeton, for example, will for- News Editor Michael Banks ever be associated with the period spent there by Albert Einstein at the Institute Reviews and Careers Editor Margaret Harris Features Editor Louise Mayor for Advanced Study, while others, such as Geneva Production Editor Kate Gardner and Grenoble, are renowned for their world-leading Web Editor Hamish Johnston Multimedia Projects Editor James Dacey scientific facilities. As for Göttingen, its famed Insti- Web Reporter Tushna Commissariat tute for Theoretical Physics, which boasted the likes
Managing Editor Susan Curtis of Max Born, Werner Heisenberg and Pascual Jor- Marketing and Circulation Gemma Bailey dan, made this town in Lower Saxony a magnet in the Advertisement Sales Chris Thomas 1920s and 1930s for many rising stars – from Edward Advertisement Production Mark Trimnell iStockphoto/Ismail Akin Bostanci Akin iStockphoto/Ismail Diagram Artist Alison Tovey Teller to Robert Oppenheimer. Art Director Andrew Giaquinto But as physics has grown into a bigger, increasingly global and more con- Subscription information 2013 volume nected endeavour, are there still any true physics hot spots? Are there any The subscription rate for institutions is £340 per annum for institutes, universities or regions that really are “the place to be”? Does good the magazine, £645 per annum for the archive. Single issues are £32. US orders to: IOP Publishing, PO Box 320, Congers NY physics, in other words, depend more on who (or what) you know than where you 10920-0320, USA (tel: 800 358 4677 (toll free) or are? There have been many deliberate attempts in recent years – particularly in 845 267 3018; fax: 845 267 3478; e-mail: ioppublishing@ cambeywest.com). Rest of world orders to: Subscriptions Dept, emerging economies – to lavish money on specific projects in specific locations IOP Publishing, Temple Circus, Temple Way, Bristol, BS1 6HG, to give science a focused boost. Examples include the “Fusionopolis” research UK (tel: +44 (0)117 929 7481; fax: +44 (0)117 929 4318; e-mail: [email protected]). Physics World is available on an and development hub in Singapore (September 2010 pp12–13), the 10bn King individual basis, worldwide, through membership of the Abdullah University of Science and Technology in Saudi Arabia (November Institute of Physics 2009 pp12–13) and the Daejon “science belt” in South Korea. Copyright © 2013 by IOP Publishing Ltd and individual These initiatives have had certain success to date but perhaps just as signifi- contributors. All rights reserved. IOP Publishing Ltd permits cant as abundant cash and equipment is a steady flow – both in and out – of single photocopying of single articles for private study or research, irrespective of where the copying is done. Multiple talented scientists. The importance of having the right people in the right place copying of contents or parts thereof without permission is in is well illustrated in this month’s issue of Physics World, in which science writer breach of copyright, except in the UK under the terms of the agreement between the CVCP and the CLA. Authorization of Brian Clegg looks at the role played by Manchester in the development by Niels photocopy items for internal or personal use, or the internal or Bohr of his model of the atomic nucleus 100 years ago (pp34–38). This indus- personal use of specific clients, is granted by IOP Publishing Ltd for libraries and other users registered with the Copyright trial city was then a far cry from the quiet calm of Cambridge, where Bohr had Clearance Center (CCC) Transactional Reporting Service, originally gone to work with J J Thomson at the Cavendish Laboratory. But provided that the base fee of $2.50 per copy is paid directly to CCC, 27 Congress Street, Salem, MA 01970, USA finding working conditions at the Cavendish “very difficult” – to quote from a cache of Bohr’s letters that has been newly released by his family – the Dane Bibliographic codes ISSN: 0953-8585 CODEN: PHWOEW switched after a few months to Manchester. Printed in the UK by Warners (Midlands) plc, The Maltings, West Street, Bourne, Lincolnshire PE10 9PH What drew Bohr there was not so much the facilities at the University of Manchester’s physics department but rather its working environment and the presence of the New Zealander Ernest Rutherford, with whom Bohr struck The Institute of Physics up a great rapport. Yet Manchester’s place in physics history might have been 76 Portland Place, London W1B 1NT, UK a mere footnote were it not for sustained funding over many years, one of the Tel: +44 (0)20 7470 4800 Fax: +44 (0)20 7470 4848 fruits of which was the 2010 Nobel Prize for Physics going to two of its staff – E-mail: [email protected] Andre Geim and Kostya Novoselov – for their work on graphene. Location is Web: www.iop.org important, but long-term support is vital for true success. The contents of this magazine, including the views expressed above, are the responsibility of the Editor. They do not represent the views or policies of the Institute of Physics, Don’t miss our latest nanotechnology focus issue of Physics World, which physic except where explicitly stated. sw includes a great feature by Nobel laureate Kostya Novoselov about the o r l Physics World is an award-winning magazine and website d design of the impressive new £61m National Graphene Institute at the SIPAwards 2012: Best Use of Social Media University of Manchester. The issue has been sent to all full members of MemCom Awards 2012: Best Magazine – Professional the Institute of Physics and is also free to read in digital form at Association or Royal College http://ow.ly/l7Erc
Physics World June 2013 15 FULL PRODUCT DETECTOR WARRANTY* WARRANTY*
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16,000 Square Feet of Stocking Space Same Day Shipping Across Europe Comprehensive Inventory of Exceptional Customer Service Vacuum Products All Things Vacuum www.lesker.com 13-088 physicsworld.com Comment: Forum A divided union? Public investment in research in quite modest compared with the hopes and proposals of the European Parliament and, the EU is at a crossroads. Former above all, with the overall evolution of the Portuguese science minister national R&D budgets of member states. In view of this, we as Europeans should José Mariano Gago argues that now focus on raising national budgets for R&D: our own as well as those of all other the focus should now be on European countries. We should be helping national budgets Gutiérrez Luis iStockphoto/José each other across borders, campaigning for a stronger constituency for science, and ensuring education and research in each of In 2000 the EU approved the so-called Lis- our countries stay well funded even during bon Strategy in which it aimed to become an economic downturn. “the most competitive and dynamic knowl- As the last decade has shown, integrating edge-based economy in the world”. For the national policies at EU level – namely via first time, EU heads of state and govern- the common market, working or investing ments recognized that science and technol- across the EU and dealing with the current ogy was critical for the social and economic serious financial and economic imbalances development of the continent. As a conse- in the euro area – has been accompanied quence, much has been achieved, such as by a new political perception of the critical the information and communication tech- importance of science and technology for nologies initiative that seeks to bridge the the type of economic and social develop- social “digital divide” and to make Euro- ment Europe was aiming at. pean industry more competitive. Unfortunately, this has not been enough But much more remains to be done, espe- Split priorities There is a division between the small to automatically generate a strong politi- cially increasing investment in science and Europe-wide pot of cash and nation-level funding. cal will at national level to sustain national technology. In a decade hit by recession and R&D budget priorities. Moreover, weak economic crises, the European Commis- European Commissions were somehow sion (EC) has recently estimated that many Europe as a whole bound to fight for their own budgets only. EU countries have been unable to achieve They then proved unable – or unwilling – to R&D budget increases above GDP rises in has not met its goals play an effective political role in favour of the period 2008–2011 (see figure on p18). sustainable national R&D budgets, as they Using data from the Organisation for were also unable to campaign for ring-fenc- Economic Co-operation and Development or its promises ing R&D and education budgets from cuts. (OECD), in 2000 the combined public EU Such a move could have provided support R&D budget was very similar to that of for “anti-cyclical” national R&D measures the US when corrected by their purchas- The economic crisis seems to have even during economic turndowns. ing power parities. However, 10 years later induced – at least since 2007 – a larger the US R&D budget had grown rapidly R&D divide within the EU. Large growth The way forward while the combined EU R&D budget had in Germany and the Nordic countries has The main missing piece in the current sad stalled. This is unfortunate as sustained ris- been set against a relative global reduction state of science policy in Europe is the sci- ing national budgets for R&D would have of resources in other large countries such as entific community itself. We must plead for helped to attract talent and discouraged Spain, Italy, France and the UK. Undoubt- a greater involvement of scientists and sci- people from leaving the EU as part of a edly there has been progress in science and entific organizations, as well as universities continent-wide brain drain. It would also technology. But Europe as a whole has met and industry, in pursuing a higher priority have led to better universities and research neither its goals nor its promises in this for science and technology in all countries. facilities, helped hi-tech firms to get off the critical area of the Lisbon Strategy. Expecting that strong social and political ground and encouraged new R&D funding constituencies for scientific development in the private sector. Unfortunately, such Focusing on national budgets will arise spontaneously has proved to be budget increases failed to materialize in the Around 90% of research spending in an erroneous and naive belief. EU as a whole. Europe is via national budgets – the National constituencies in most coun- This quasi-stagnation of R&D public remaining 10% being channelled into the tries are not well organized or informed, investment in Europe during the last dec- EU Framework Programmes, which for and benefit from almost no support from ade, however, hides some major divergences the period 2014–2020 is named Horizon other partners in other countries. Euro- within Europe itself. Some countries are 2020. The priorities for these programmes pean organizations of scientists exert a spending more on R&D than 10 years ago are proposed by the EC and then decided very positive influence (and were decisive but others are spending less. In real terms, jointly by the European Parliament and the in the initiative leading to the creation of Germany, for example, now spends 50% council of research ministers. The slight the European Research Council in 2006), more on R&D than France (compared with real-terms increase in the ~ 74bn Hori- although they are usually limited by the EU 20% more in 2000), while Italy’s budget has zon 2020 programme – as compared with Framework Programmes or supporting the declined since 2007 and in real terms is now its predecessor – is, of course, good news EC campaigns for its proposed budgets. 15% lower than in 2000. for science. Unfortunately, this increase is The EU is a union of independent mem-
Physics World June 2013 17 Comment: Forum physicsworld.com
Varying fortunes: EU R&D budgets 2008–2012 budgetary priorities. I also hope that scientists and research 40 institutions have finally understood that campaigning for science must be pursued 20 both at national and at European levels, and that the effective trends of national 0 budgets for R&D are ultimately the clear- est signs of success or of defeat in their –20 political efforts. I would like to add a final suggestion: –40 the creation of a totally independent and credible international “observatory” that
difference between growth in R&D budget and growth in GDP (%) would analyse national science policies and science budgets across Europe. It would report, publicly and periodically, relevant information and give early warnings on the
Luxembourg Malta Poland Estonia Czech Republic Slovenia Denmark Austria Germany Hungary Finland Portugal Sweden Cyprus EU Netherlands Greece Ireland France UK Belgium Spain Italy Slovakia Bulgaria Lithuania Latvia Romania state of science and technology policies Difference is calculated between real growth in government budgets for R&D and real growth in GDP. and budgets both in individual European Source: DG Research and Innovation, using data from Eurostat. nations and at EU level. It would therefore help to increase the public awareness of the strategic importance of science policy deci- ber states, each of them sovereign in its future of science in Europe are now harsher sions and to strengthen the motivation of decision to reduce (or increase) its own than a decade ago. scientists to engage themselves in science R&D national budget. However, the inter- We can only hope that national govern- policy as informed and responsible citizens. national interdependence of science – and ments and parliaments have learned their its economic impact across the whole com- lesson: only sustainable, persistent, long- José Mariano Gago is at the mon market – means we should be con- term national investment in R&D can Instituto Superior Técnico, Lisbon, cerned about negative policies for science bring the conditions for private R&D and and director of the Laboratório de in other countries and should strengthen for long-term sustainable innovation. The Instrumentação e Física de social and political constituencies for sci- EU R&D budget will continue to play an Partículas (LIP), e-mail gago@ ence across Europe. Times are changing important role but the future lies almost lip.pt and social and political challenges for the entirely in the evolution of national R&D Next month in Physics World PHYSICS OF CANCER
Potential solution How electric fields could serve as a
possible way to detect and control cancer Library Photo Gschmeissner/Science Steve
Questions of origin One of the most dangerous medical conditions, cancer is usually thought to be caused by random genetic mutations, but could it in fact have ancient evolutionary roots?
Signs of trouble How researchers have used atomic force microscopy to obtain a nanomechanical signature of breast cancer
In a spin Why clues to cancer could lie in the way in which cells rotate Plus News & Analysis, Forum, Critical Point, Feedback, Reviews, Careers and much more physicsworld.com
18 Physics World June 2013 physicsworld.com Comment: Robert P Crease Critical Point The new idols
What would be on Francis become so bewitching as to make them in effect Baconian idols of the theatre. Bacon’s list of idols today? Some 400 years after Bacon, however, Robert P Crease seeks your we still have not solved his second prob- lem: how to cultivate an appreciation for thoughts and ideas the value of science among government administrators. Solutions to issues involv- ing energy generation, pollution, climate The British scientist and philosopher Fran- change, food production, population con- cis Bacon (1561–1626) was an avid promoter Library Photo Source/Science Science trol and health care all require us to apply of science at a time when neither its prac- detailed knowledge of how the world works tice nor its social value was plain. Science in its full complexity. We already have much and modern life were not yet coupled and of the necessary science, but it is often bla- Bacon had two problems. One was to teach tantly ignored, misapplied or distorted. people how to study the natural world, and Denouncing the rising tide of irration- the other was to cultivate an appreciation alism and pseudoscience has not worked. in government circles of why science is use- What if we followed Bacon’s lead and ful. Moreover, Bacon had to find ways to sought to educate our peers by identifying be convincing when science was still in an and exposing what falsely subverts them embryonic state, using rhetoric that would from appreciating science? One problem is persuade his 17th-century contemporaries. Identifying problems Francis Bacon wrote a treatise that these days the word “idol” is popularly One of Bacon’s most famous rhetorical in 1620 to encourage scientific study. used to mean “star” – think of the TV series images – developed in his 1620 treatise Pop Idol or American Idol – rather than Novum Organum Scientiarum, or “New false god. Another problem is that, while Instrument of Science” – was of the “four The human mind is Bacon addressed an educated ruling elite idols of the human mind” that hinder our who spoke Latin, today we must address a study of nature. Back then, an idol was a vulnerable to its own different and more challenging audience: powerfully loaded religious term in an era the ordinary citizens who elect the officials when religious wars were common and set of idols, which who pass legislation, and who tend to think witches still persecuted. It meant a false in media-speak. Still, appealing to the con- god that distracts us from paying attention nection of “idol” with “idolatry” – bewitch- to the true god and provides us with reasons come in four species ment – may provide an important rhetorical why we need not bother. tool to influence this wider audience. The human mind, Bacon told his contem- ditions for observing nature. To be fair, poraries, is vulnerable to its own set of idols, Bacon lived in a much different world: The critical point which prevent us from seeing nature as it is when Bacon said “Knowledge is power,” it Humans keep inventing new ways to mis- and tell us that we do not have to. These idols was at a time when nature was regarded as understand nature, and we have to keep come in four species. “Idols of the tribe” fearful and threatening, and he was trying inventing new ways to expose these mis- arise from defects in the mind itself, and to encourage his contemporaries to find understandings. Our problem is not to include the human tendency to see patterns out what nature is so they could devise ways couple science and modern life but to stop where none exist. “Idols of the cave” are of protecting themselves. them decoupling. So what if we compiled different for each individual, whose back- a list of modern idols – of the false notions ground and training inevitably produce Today’s idols that bewitch us and keep us from looking biases; some people, for example, over- Today we live in the scientifically and directly at the world? rate parts over wholes, while others wholes technologically rich world that Bacon One is what I’d call “Idols of the politi- over parts. “Idols of the marketplace” stem envisioned, and have a very different cal party”. Human beings worship this idol from language and the way words are often perspective. Knowledge can have a dark when they do not consult studies to decide imprecise and misleading. Finally, “idols of side too, as we know from any number of whether, say, climate change is taking place, the theatre” are systems of thought that are examples of our power over nature being or evolution is real, or fracking is dangerous sometimes enlightening but the inner logic misused. We also live in an era when the – but instead consult the party line of their of which can also bewitch us and prevent us scientific community is established and political or interest group. This party line from seeing the world as it is. (Bacon cited thriving. Through education and train- tells them how to look in the world in the Platonism but we might think of Marxism ing, we have ways of addressing the first “right” way, and warns them that it is wrong or Freudianism.) In identifying and expos- of Bacon’s problems – namely, instructing to look at the world differently. ing these idols, Bacon sought to improve his people who want to understand nature in But what do you think are our other mod- contemporaries’ ability to practise science how best to avoid the traps and temptations ern idols? Send me your thoughts and I shall and to appreciate its value. that arise from our own intrinsic, human devote a future column to the responses. Bacon’s writings seem hopelessly naive weaknesses or from our own biases. Scien- today. Bacon had no appreciation for the tific language, too, is kept precise, and we Robert P Crease is a professor in the Department of role of mathematics in science and also have grown sceptical of systems – though, Philosophy, Stony Brook University, and historian wrote as though making discoveries were in some physicists’ minds, such complex at the Brookhaven National Laboratory, US, simply a matter of setting up the right con- theoretical packages as string theory can e-mail [email protected]
Physics World June 2013 19 NEW from Amptek physicsworld.com
Digital “mathematics” and E = mc2 is “physics”, and anything more has to be conveyed Multichannel Analyzer by abstract art. More sinisterly, is the Feedback “anything more” hidden inside computer programs, with only journalistic words Letters to the editor can be sent to Physics World, allowed outside – even for physicists? Temple Circus, Temple Way, Bristol BS1 6HG, UK, Mike Freeman or to [email protected]. Please include your address and Denbigh, North Wales, UK a telephone number. Letters should be no more than [email protected] 500 words and may be edited. Comments on articles from physicsworld.com can be posted on the The May issue of Physics World contains website; an edited selection appears here a number of comments (Feedback, pp23– 24) on the significance of mathematics in the pursuit of physics. To my regret, Tough energy choices I am poor at maths but, in my personal experience, the ideas that form the basis I read Gail Marcus’ review of Richard of innovation arise primarily from an Muller’s book Energy for Future Presidents appreciation of the physical operation The MCA8000D is a full-featured (April pp42–43) with interest. There’s a of the world, not from mathematical lot of hype associated with all the different concepts or calculations. In my work with digital multichannel analyzer for energy options out there, and when I vacuum circuit interrupters, ultrahigh- use with a wide variety of detector search the Internet for information about vacuum cryopumping of hydrogen and systems. them, it is difficult to know who to believe. a variety of electrostatic instruments Physics World has covered many of the and test methods, the ideas that have The easy to use 'Pocket MCA' can fit different technologies in recent issues, but proved fruitful have not originated I would like to see an article on how their mathematically, and only a modicum in a shirt pocket. relative “greenness” can be compared. of maths has been useful to help guide On a related note, people often talk and assess the development of ideas. FEATURES OF THE MCA8000D about reducing their carbon-dioxide This is not to decry mathematics, but to “footprint”, but what does this really recognize that in some areas, maths is not t$PNQBUJCMFXJUIUSBEJUJPOBMBOBMPH mean? How is it calculated? What are a prerequisite. QVMTFTIBQJOH the limitations and accuracy? Clearly, John Chubb we shouldn’t own a car – but if we do, is Cheltenham, UK t.$"BOE.$4NPEFT it better to own a small car for its entire [email protected] t)JHITQFFE"%$ .)[ CJU XJUI lifetime, or some other scenario? Should EJHJUBMQVMTFIFJHIUNFBTVSFNFOU I cycle to the nearby supermarket or take the car to the farm shop to buy my Demonic tendencies tLEBUBDIBOOFMT vegetables? Is there some parameter other t.JOJNVNQVMTFQFBLJOHUJNFOT than carbon dioxide that might be used? I enjoyed Phillip Ball’s article on How do I make an informed decision? Maxwell’s demon (“A demon-haunted t$POWFSTJPOUJNFOT Sheila O’Brien theory”, April pp36–39), but I am unclear t4MJEJOHTDBMFMJOFBSJ[BUJPO Ipswich, UK about the explanation/analogy provided [email protected] in the box on page 39, which discusses t%JòFSFOUJBMOPOMJOFBSJUZ recent experiments designed to probe t*OUFHSBMOPOMJOFBSJUZ certain aspects of Maxwell’s old thought t5XPQFBLEFUFDUJPONPEFTGPSOVDMFBS Two views of experiment. If the “demon” in the Chuo University group’s experiment prevents TQFDUSPTDPQZPSQBSUJDMFDPVOUFSDBMJ a ball from moving downhill by inserting CSBUJPOJODMFBOSPPNT mathematics a barrier to this motion, and then moves the barrier up one stair every time the t5XP55-DPNQBUJCMFHBUFTGPSDPJODJ How is it that, even in a publication of ball moves uphill, surely the demon is EFODFBOEBOUJDPJODJEFODF the Institute of Physics, an article about expending energy by moving the barrier? t64# 34 BOE&UIFSOFUDPNNVOJDB the wavefunction (“The life of psi”, May Please put my mind at rest with regard to pp26–31) is unable to portray the actual this issue. UJPOJOUFSGBDFT wave equation? Granted, it comes in more Frank Hawthorne t%JNFOTJPOTYYNN than one form, but these days it seems University of Manitoba, Canada there is no presentation of the equations [email protected] t8FJHIU H of physics as an art form itself. Instead, tFree%JTQMBZBOE"DRVJTJUJPOTPGUXBSF the article presents us with a fancy picture. Phillip Ball ([email protected]) replies: tFree4PGUXBSF%FWFMPQNFOU,JU 4%, This might be acceptable on the front You are correct to state that the “demon” cover of the magazine, but does it really expends energy in moving the barrier, $PNQMFUFQSPUPDPMBOEFYBNQMFDPEF have to take up nearly a full page inside but the point is that when one does a full GPSDVTUPNTPGUXBSFBQQMJDBUJPOT as well? Even an “exploded diagram” of energy accounting, it turns out that the the equation with its components labelled energy expended in moving the barrier ® would carry something of the real world of is slightly less than the energy gained by AMPTEK Inc. theoretical physics. the system, as measured experimentally. [email protected] I fear we are pandering to the The small excess is the result of the energy www.amptek.com layperson’s view that 2 + 2 = 4 is content of the information used by the
20 Physics World June 2013 physicsworld.com Feedback &U\RVWDWVIRU/RZ 7HPSHUDWXUH3K\VLFV Comments from physicsworld.com “How fat is Schrödinger’s cat?” The and a supercooled quantum cat is going to be headline of our story about quantifying the dead already – unless we can revive supercooled “macroscopicity” of objects in quantum animals, in which case we may already have had superposition states (25 April) proved as a simultaneously alive and dead classical cat. irresistible as catnip to physicsworld.com Seriously though, visual observing is neither readers. A few commenters wondered whether here nor there – it’s more the case that any Stefan Nimmrichter and Klaus Hornberger’s observation removes (or adds?) some energy newly defined macroscopicity parameter – from the system, thus destroying the quantum called μ, naturally – might have other uses; state. Superpositions are demonstrably possible ra_mckenna, for example, suggested that μ for inanimate solitary objects, but I imagine that could become a “figure of merit” for evaluating putting a living organism into a superposition the relative viability of different quantum would not last long no matter how small the animal computing systems. Other readers, however, is. In a way, it would always be observing itself. weighed in with their own feline-themed feizex ideas for exploring the boundary between the quantum and classical worlds, and it all got a This is fascinating. As a medical researcher &ORVHG&\FOH&U\RVWDW 2SWLFDO6SHFWURVFRS\ bit silly. working on tuberculosis (TB), I have always .². wondered about the “macroscopability” of this This is very interesting, and may even turn out disease. The bacteria that cause TB lie in a state to be quite an important achievement. I like the of dormancy when they cannot be grown, but idea of being able to quantify astonishment. are not dead either. I call this “Schrödinger's On the other hand, [Tony Leggett’s] remark tuberculous cat”. This may sound like heresy for that “macroscopicity should instead reflect our pure physicists but I just wonder. common-sense intuition” leaves me dangling in vdrnathan, India empty space. Any intuition I thought I had about such matters was left in the ditch in 1999, when The bacteria may lie in a dormant state, but you buckyballs were made to interfere with each know that they are not dead – implying that there 7RS/RDGLQJ other. Frankly I will believe that story when I see is no quantum-mechanically superposed state )DVW6DPSOH it with my own eyes. As for interfering cats, try like that of the cat, because this knowing kills the &KDQJH hurling a moderate-sized tomcat at a pair of gaps desired wavefunction. cut in a sheet of plywood. I won’t be there, but let M Asghar me know what happens. Just kidding! No animals were harmed in The problem with all of these cat thought the making of this thought experiment. When experiments is that they are not taking into I ran it in my head, the cat effortlessly split account the fact that the thought cat would into nine lives, passed through the slits, and observe the experiment and collapse the wave. rematerialized in perfect condition on the other Plus have you ever tried to herd thought cats in side. I heard the miaow. Granted, I haven’t an experiment? It's almost impossible! And my actually seen him since, but I’m pretty sure he thought cats never want to go in the box. I can't is out there somewhere, waiting patiently for a blame them, actually... chance to get even. alreaud, US dratman, US 0LFUR5DPDQ0LFUR3/ 8OWUD/RZ9LEUDWLRQ @dratman – hilarious – best laugh I’ve had QP in a while! Just one thought: a supercooled quantum-mechanical cat is most likely going to Read these comments in full and add your own at put a hole in your plywood slit apparatus. That, physicsworld.com
&U\RJHQLF automatic feedback system to “make the to reality at as many points as possible. 3UREH6WDWLRQ decision” to move the barrier. But what are the SI units of pounds +HOLXP)UHH )DVW&RRO'RZQ sterling? Much of economics is a fairy story, and unhelpful predictions leading to More defined physics unhelpful behaviour are to be expected. John Thornley In his letter (May p23) on the definition of University of Guelph, Canada physics, David Fisk remarks that “thinking [email protected] like physicists when constructing models of financial transactions was no small part My old professor, under whom I carried of why we are in our current economic out my research, had his own definition mess”. He is wrong. It is because of physics. He always said, “Physics is physicists and mathematicians did not organized common sense.” What do you Advanced Research Systems think like physicists that things went think of that one? 7HO awry. A physicist would define units for Tony Scott )D[ the model’s symbols and make sure that University College Dublin, Ireland ZZZDUVFU\RFRP DUV#DUVFU\RFRP quantities were both measurable and tied [email protected]
Physics World June 2013 21 Where better to train to teach than in a school? School Direct. The new way into teaching. School Direct is an exciting new training route for top graduates who want to be part of a school team from day one. Places are still available this year at some of the country’s best schools. For details of vacancies in your area call 0800 389 2500 or search ‘School Direct’. Rewarding Challenging Teaching physicsworld.com Feature: Carbon capture Carbon Engineering Carbon
Mopping up carbon Technologies that capture carbon dioxide directly from the air would help us to manage climate change and make profitable by-products in the process. But the financial feasibility of such schemes is controversial, as David Appell reports
The problem of climate change essentially boils Existing efforts to remove CO2 are based at power David Appell is a science writer living down to this: can we find a way of keeping the num- stations – which give off 40% of global CO2 emis- in Salem, Oregon, ber of carbon dioxide (CO2) molecules in the atmos- sions – and involve capturing the gas as it leaves the phere to four out of every 10 000 molecules of air – or plant. But these techniques do nothing to counteract US, www. will the figure rise to five or more? If only that extra the 60% of global emissions that come from cars, davidappell.com molecule could be plucked from the air, the climate buildings, ships, planes and other “point sources”. problem could be mostly solved without a drastic The search is therefore on for new techniques that restructuring of the world’s energy infrastructure. It directly capture CO2 from the air. Facilities perform- may sound madly ambitious but that is just what a ing this “air capture” could be located anywhere, uti- few scientists and engineers are planning to do, and lizing the atmosphere as a pipeline from billions of hoping to make some money from it to boot. sources of CO2, however minute or mobile. Removing CO2 from the air is not an especially Despite doubts arising from theoretical studies of new idea. In fact, it is relatively simple and done on the cost of carbon capture, those getting their hands spacecraft and submarines all the time. But achieving dirty think that CO2 could be removed directly from “negative emissions” economically, at large scales, is the air in massive quantities for perhaps as low as a much harder and more urgent problem. Unless the $100 per tonne. Once collected, the CO2 could then energy used for the removal is carbon free, or suf- be pumped underground into geologic storage areas ficiently small, the benefits will simply not cover the – a technique known as sequestration – where it costs. And therein lies the challenge. would be trapped for potentially millions of years,
Physics World June 2013 23 Feature: Carbon capture physicsworld.com
1 Chemical capture process
CO2 compression water and clean-up hydroxide solution kiln solids heat air in air out
oxygen carbonate solids plant carbonate contactor solution natural gas
Air capture of CO2 by a chemical process known as “scrubbing” occurs in two steps that complete an entire cycle. In the case of the firm Carbon Engineering, it first uses a fan to pull air over an aqueous hydroxide solution in the “contactor”. The hydroxide is typically sodium
hydroxide (NaOH, also known as lye) or potassium hydroxide (KOH) and any CO2 in the air reacts with it to form water and a carbonate. A crystallizing device causes the carbonate to precipitate out of solution, leaving a solid carbonate. The solid carbonate is then sent to a hot
kiln, powered by natural gas or a carbon-free energy source, where it is mixed with iron oxide and heated. The CO2 that is given off is combined with the CO2 produced by the natural gas, compressed, cleaned and sent to a high-pressure pipeline. The remaining solids are sent to a mixing tank, where they react with water to produce iron oxide as well as fresh, usable hydroxide, which is fed back into the contactor to be used in the initial step. The heating step generates all the electricity the plant requires (yellow).
with little leakage, doing no harm to planet or people. work as a business.” The gas could also be sold to oil companies, which According to climate expert James Hansen, there routinely inject carbon dioxide into oil reservoirs to is certainly a need for such enterprises. As he wrote reduce the oil’s viscosity, enabling easier extraction. in 2007, the global surface warming that has already Other customers could include large-scale flower been (or is bound to be) created – coupled with the growers, who fill their greenhouses with CO2 to keep unceasing increase in carbon emissions, and the plants warm. currently inadequate mitigation efforts (see box on The technology to do all of these things already p26) – implies that “a feasible strategy for planetary exists, but in bits and pieces; the challenge is to put rescue almost surely requires a means of extract- the various components together on a large scale, ing greenhouse gases from the air”. If CO2 could be and to do so cheaply. One interesting initiative is captured from ambient air more quickly than nature the Virgin Earth Challenge, which was launched in does it, the world might even be able to overshoot 2007. Sponsored by Richard Branson, it offers $25m whatever warming threshold is deemed “dangerous” to whoever can demonstrate a sustainable and scal- and later stabilize the climate gradually via net nega- able design to permanently remove a billion tonnes tive carbon emissions. of carbon from the air every year for 10 years. Some 2600 groups applied to the challenge and last Novem- Chemical capture ber the finalists were picked – six from the US and One of the most straightforward ways to remove CO2 one each from Denmark, Sweden, the Netherlands, from air is with a solid or liquid chemical compound Switzerland and Canada – who now have five years that soaks up the gas. Known as “carbon dioxide in which to win the prize. scrubbing”, it is a tried and tested technique that has One finalist is Carbon Engineering – a firm based been used at power plants, and Carbon Engineer- in Calgary, Canada, that is financially backed by Bill ing and other similar companies have made it their Gates, the Canadian government and others. “We’ve method of choice because the process is simple, made a huge amount of technical progress,” says the proven and continuous. Ambient air is first drawn company’s chief executive David Keith, who is also through a scrubber or “contactor” where an alkali a prominent climate scientist at Harvard University, solution (such as aqueous lye) absorbs CO2 molecules “and we’re understanding how we might make it and converts them into a carbonate salt. After the salt is heated in a kiln, the CO2 is then released and captured, before the residue is reacted with water and One of the most straightforward other compounds to produce the same liquid alkali, which is then fed back into the contactor to be reused. ways to remove CO2 from air is with The net yield is concentrated CO2 gas (figure 1). Carbon Engineering has successfully built air- a solid or liquid chemical compound capture prototypes powered by natural gas, the CO2 from which is directly captured and combined with that soaks up the gas that extracted from air. Because atmospheric CO2 is well mixed, such plants could be sited where energy costs are lowest, environmental conditions such as
24 Physics World June 2013 physicsworld.com Feature: Carbon capture Statoil; Brian Bell/Science Photo Library; iStockphoto/alrisha Photo Bell/Science Brian Statoil;
temperature or humidity are most favourable, or tonnes of carbon would be trapped per year. (If this Working on it (Left) At the Sleipner where CO2 disposal is cheapest and most convenient. carbon was instead allowed to decompose it would gas field in Norway, (In contrast, power plants are not necessarily located release 10.3 gigatonnes of CO2 into the atmosphere.) CO2 is captured from where CO2 sequestration is possible or most practi- Likewise, in a world stressed for agriculturally pro- cal, often requiring that the gas be piped elsewhere.) ductive land, planting (or recovering) enough forest its flues and sequestered Scrubbing CO from the waste flues of power land looks out of the question, which is why some 2 beneath the ocean plants today costs $50–100 per tonne of CO2, a scientists are looking at making artificial leaves and floor. (Centre) value that air-capture proponents dream of someday artificial trees. These structures not only take CO2 Scientists are reaching. Once the CO2 is captured it is ready for out of the air as does conventional photosynthesis, working on extracting sequestration or reuse, ideally at the same location. but some also produce carbon-neutral liquid fuels in oils and other forms
Pipelines and injection wells would have their own the process. of fuel from CO2. regulatory challenges, issues of public acceptance In photosynthesis, plants convert the energy of (Right) Planting new regarding impacts and leakage, and expense (see sunlight into stored energy in the form of carbohy- trees is useful for September 2006, pp24–29). The few sequestration drates, removing CO2 and producing oxygen and CO2 absorption but projects that exist today, such as that at the Sleipner water in the process. Scientists are trying to do much the gas is later gas field in Norway, which has been running since the same thing, but with “leaves” made of silicon released when the trees decompose. 1996, all involve capturing CO2 from flue gases, but or polymers. Some implementations are sources of bury only about a million tonnes of CO2 per year. carbon-free energy, collecting sunlight that gener- ates oxygen and hydrogen gas for fuel cells. But for Artificial leaves Klaus Lackner, a physicist at Columbia University, Ambitious carbon-capture schemes are all very the focus is to absorb CO2. His carousels of plastic well and good, but there already exist amazing filters are laced with a CO2-absorbing material; as machines capable of removing CO2 from the air: they become saturated with CO2, they are rinsed plants and trees. Every year, land vegetation sucks with water in a vacuum chamber and the dissolved 9 up about 220 gigatonnes (220 × 10 tonnes) of CO2 in CO2 separates for collection. photosynthesis, although it is, of course, returned to Lackner’s leaves are about 1000 times more effi- the atmosphere when the plants and algae die and cient at absorbing CO2 than real leaves, per unit decompose. Vegetation is therefore not a net sink of surface area, and need not be exposed to sunlight, CO2 – but there are clever ways to turn it into one. so they can be closely spaced. However, they do not Since carbon makes up about half the dry weight of come cheap: a single tree, which can remove one a tree (depending on species), Ning Zeng, a climate tonne of CO2 a day, currently costs about $20 000. scientist at the University of Maryland, suggested in Kilimanjaro Energy, Lackner’s company, plans to 2008 how to temporarily solve part of mankind’s car- develop and commercialize this and other carbon- bon problem by using forests as “carbon scrubbers”. capture technologies, and is one of the Virgin Earth This would involve actively managing them by col- Challenge finalists. lecting trees and woody debris, before anaerobically burying them deeper than five metres. Cost controversy Zeng published another paper last year, which Accompanying these emerging air-capture technolo- found that if wood was harvested from half the world’s gies is the ultimate hope that they might be useful to forested land and then buried underground, 2.8 giga- help stop climate change, and perhaps even reverse
Physics World June 2013 25 Feature: Carbon capture physicsworld.com
The carbon problem support for arguments in favour of procrastination in dealing with climate change that are based on Despite all warnings, emissions of greenhouse gases are increasing exponentially the imminent availability of direct air capture as a – a predicament the seriousness of which many still do not appreciate. The compensating strategy”. But Workman feels “the CO2 emitted by the average Briton over just 80 minutes – about 1.3 kg – will mitigation narrative isn’t working” and sees negative- ultimately trap a Hiroshima bomb’s worth of heat: 63 terajoules. That heat will emissions technologies as an essential bridge. “We alter the Earth’s climate and oceans for millennia – the CO2 content of the Earth’s need to develop this line of research in order to buy atmosphere will be about 10% higher 100 000 years from now than it would be time to introduce the low-carbon economy at rates without today’s emissions. at which energy-system technologies take to diffuse, But solving the problem by replacing our energy system is daunting indeed. With which is up to 100 years, rather than being com- colleagues, Ken Caldeira of the Carnegie Institution for Science has calculated pressed into the next 30–40 years,” he says. that the world needs to install roughly one large (900 MW) carbon-emissions-free Carbon Engineering research scientist Geoffrey power plant every day for the next 50 years to stabilize overall global surface Holmes, on the other hand, thinks that air-capture warming at 2 °C. And if, as seems likely, the target is relaxed to something like plants in reality will be more efficient than the model 4 °C, the required number is still about one power plant every two days. used as the basis for the report’s predictions. “One To date, mankind has emitted about 1400 gigatonnes of CO2 from burning crucial point,” says Holmes, “and one opportunity fossil fuels, and another 600 gigatonnes from land-use changes such as that the APS authors missed in their system, is that deforestation. But there are still enormous amounts of economically viable fossil our heat and power generation are integrated on-site, fuels left to extract and burn, of which 70% is in the form of coal; if we used it so when we use energy to capture CO2 from the air, all it would unleash a further 3200 gigatonnes of CO2. In fact, burning all the we also generate all the electricity demand for our fossil fuels on the planet would create at least 37 000 gigatonnes of CO2, and for own plant, and we capture the CO2 created by the every 1000 gigatonnes emitted, the climate response is about 0.4 °C of surface gas combustion to produce that energy.” This avoids warming, plus or minus a third. Humans could easily create an inverse ice age if emitting new CO2 that would partially counteract the we wanted to – a mean global surface warming of 6–7 °C, or more. CO2 just captured. Another way Carbon Engineering has lowered its costs is by designing its contactor structures around its effects by returning the atmosphere and oceans cooling tower technology – which is optimized to to something like their pre-industrial state. A 2011 cheaply and efficiently ingest bulk quantities of air report by the American Physical Society (APS) enti- – rather than traditional gas scrubber technology. tled Direct Air Capture of CO2 with Chemicals, how- While the details are proprietary, their structure ever, cast doubt on such ambitions. The APS report costs less than half of a similarly sized contactor con- set out to explain the basic principles, technology sidered in the APS report. and economics of air capture with chemicals to non- The company has now started work on a pilot plant experts, and to encourage discussions among a broad near Alberta that aims to capture 500 tonnes of CO2 audience of scientists and policy-makers. per year and test equipment and designs ready for One key figure in the report is that a typical sorb- a commercial-scale plant that is planned to capture ent would capture, per square metre over which air 100 000 tonnes of CO2 annually. While Carbon Engi- flows, only about 20 tonnes of CO2 per year. Since a neering’s carbon-capture rate is slightly higher than 1000 MW coal-fired power plant emits about 6 mega- the APS report’s prediction, to achieve it they will tonnes of CO2 annually, a 10 m high capture mate- need to use many stacked vents and contactors. rial would need to be 30 km long to adsorb the plant’s Carbon Engineering chief Keith sees the removal entire emissions. The report also estimated that a of CO2 as just one prong in the attack on climate direct air-capture system, built today, would cost at change and, along with other entrepreneurs, is far least $600 per tonne of CO2. Direct air capture, it more interested in the business opportunities. Keith concluded, “is not currently an economically viable sees the big prize as being direct fuel synthesis. Cap- approach to mitigating climate change”. tured CO2 could be fed to algae to produce biofuels, Critics hit back, suggesting that these pessimistic or reacted with hydrogen molecules (obtained by predictions were premature at best, and even poten- splitting water using renewable energy) to produce tially misleading. Indeed, the report and its backlash high-energy-density carbon-neutral hydrocarbon from some respected scientists garnered a good deal fuels that could power cars, trains and planes that of media attention, including a lengthy write-up in emit no net carbon pollution. Keith believes the price the New York Times. Mark Workman, a researcher of such carbon-neutral liquid fuels might someday at the Grantham Institute for Climate Change at slash prices at the pump. Imperial College London, who recently co-authored There are certainly many other ideas for how an assessment of negative-emissions technologies, CO2 might be removed from air faster than natural calls the report “controversial” and says “estimates processes. For example, iron fertilization of ocean of the cost of negative-emissions sequestration are regions would create algal blooms that, when they often used to either negate or endorse the role of die, take the carbon with them to the ocean floor. negative-emissions technologies in addressing cli- Another options is “accelerated weathering”, which mate change, and therefore often subject to political could fix a concentrated stream of CO2 as carbonate bias”. The high cost estimates are motivated, he says, by reacting it with natural silicates, speeding up a by “a desire to keep the focus solely on preventing process that in nature takes millennia. Reforested climate change via mitigation”. land, meanwhile, would remove about 50 kg of CO2 The report does indeed state that it provides “no per square metre.
26 Physics World June 2013 physicsworld.com Volker Steger/Science Photo Library Photo Steger/Science Volker
Green ideas Researchers are investigating how best to take advantage of the
CO2-absorbing ability of certain types of algae.
Race against nature Should a climate emergency appear – perhaps a sharp acceleration in the melting of the Greenland or Antarctic ice sheets, or a steep rise in radiative forcings as rapidly thawing permafrost releases methane – the world may be willing to pay whatever it takes to remove CO2 from the air. Our best guess is that the CO2 from the roughly 40% of emissions coming from power plants could be captured for about $50 per tonne. If air-capture technology drew down the remaining 60% from smaller sources for, say, $100 a tonne, the total cost would be more than $2 trillion to negate one year’s emissions at current rates of about 30 gigatonnes of CO2 per year. This is equivalent to a hefty 4% of the world’s total GDP. While that figure is about twice as expensive as the (revised) estimate of the Stern Review – a report compiled for the British government in 2006 to assess the costs associated with mitigating climate Article Packs ARTICLE PACKS change – air capture would have several advantages over currently envisioned mitigation schemes. Pri- marily, it would not require unilateral action across With IOPcorporate Article Packs, the entire planet or rebuilding an infrastructure the you can download exactly what world has spent the last 150 years perfecting. Like you need, when you need it, carbon offsets, carbon could be captured by whom- to maintain your competitive edge. ever can do it easiest and wherever they can do it cheapest. And it would eliminate the morality play • Choose from a range of download that now accompanies the climate debate, where limits, and use them at your own pace ends and means are often reversed as different fac- • The easy way to pay-per-view tions use climate change as a cudgel in the fight for • Exclusive to industry their individual causes. For more information, e-mail As Keith wrote in Science in 2009, “Unless we can [email protected] remove CO2 from the air faster than nature does, we will consign Earth to a warmer future for millennia, or commit ourselves to a sustained programme of Current subscriptions must be maintained. climate engineering.” iopcorporate.com And those are options nobody wants. Q
Physics World June 2013 27 Feature: Ultracold neutrons physicsworld.com physicsworld.com Feature: Ultracold neutrons
Top view of the ILL reactor pool at the The effects of new particles or forces ILL, showing the reactor at the centre may show up in the static and decay Cool things to do and the neutron guide (leading to the properties of the neutron turbine) at right.
vice versa). On the Soviet side, Yakov Borisovich with neutrons Zel’dovich made an important theoretical advance in 1959, when he published a paper proposing a method of storing neutrons at low temperatures and Testing basic principles of particle physics does not also made the first predictions of the properties of necessarily require a high-energy accelerator. As ultracold neutrons and what they could be used for. Despite this, it was not until nearly 10 years later that Peter Geltenbort explains, a growing community of his countryman, Fedor L’vovich Shapiro, succeeded neutron scientists is probing similarly fundamental in extracting them from a reactor at the Joint Insti- tute for Nuclear Research (JINR) in Dubna, Russia. problems at the opposite end of the energy scale For their neutron source, Shapiro and his team used the JINR’s pulsed reactor. After slowing down, Last summer, the neutron celebrated its 80th birth- or “moderating”, the fission neutrons with paraffin, day. This was not, of course, the 80th anniversary the resulting population of slower – but still warm, of its birth, for the neutron is only about one second or “thermal” – neutrons was then sent through a younger than the universe itself. Rather, the celebra- curved guide system that was designed with several tions marked eight decades since James Chadwick sharp turns in the horizontal plane. These neutrons published a paper announcing the discovery of an could not travel the whole length of the guide with- electrically neutral particle to sit alongside the pre- out striking the guide wall. Only neutrons in the viously discovered proton within the atomic nucleus. very-low-energy “tail” of the Maxwellian distribu- Quite soon after Chadwick’s landmark discovery, tion of thermal neutrons were reflected, rather than scientists realized that this neutral particle held enor- absorbed, when they collided with the guide walls, mous potential as a tool for studying nature’s funda- and were thus able to reach the detector at the other mental laws. Neutrons offer a complete laboratory end. The flux of ultracold neut rons in the extracted for experimental physicists. They experience all four beam at Dubna was only about two or three neutrons known fundamental forces – gravity, the electromag- per 1000 seconds, but despite this obstacle Shapiro netic force, the weak force responsible for radioactiv- pressed ahead, convinced that slow-moving neutrons ity and the strong force that keeps the particles in could help answer some of the fundamental ques- atomic nuclei bound together – but crucially, they are tions in physics. In the summer of 1968, he and his electrically neutral and thus insensitive to the effects colleagues successfully defied cynicism from their of electric fields. Neutrons are therefore excellent peers by observing these tiny cold particles and prov- candidates for investigating how gravity operates at ing they could be stored for several seconds. the microscopic scale and how it fits in with the weird At around the same time, on the other side of the and wonderful world of quantum mechanics. Iron Curtain, ultracold neutrons were also being However, the neutron’s greatest asset can also be extracted from the research reactor at the Technische a drawback in practical terms. Since they have no Universität München in Germany. Albert Steyerl electric charge, neutrons can easily pass through sub- was working on research of a more applied nature, stances or penetrate deeply into them. Indeed, this investigating the scattering of low-energy neutrons property is exploited in condensed-matter research in different materials as a function of their veloc- and certain types of imaging. But it also means that neut rons for a relatively long time, and thus to make often high enough to reproduce temperatures, densi- ity. He selected neutrons from a secondary graphite – unlike beams of protons, such as those in the Large very high-precision measurements of their properties. ties and conditions not seen since shortly after the moderator and used the Earth’s gravitational field Hadron Collider (LHC) at CERN – neutrons can- Today, a growing community of scientists at my Big Bang. In contrast, ultracold-neutron research to slow them down, sending the neutron beam verti- not be guided or focused using electric fields, and institution, the Institut Laue-Langevin (ILL) in takes place at much lower energies, so we do not cally through an 11 m long curved tube. Some of the in general they are difficult to isolate and “hold” for Grenoble, France, and other facilities around the actually produce new particles that can be directly neutrons that emerged at the top end of the tube had further study. world are using ultracold neutrons to test aspects observed in a specialized particle detector. However, lost so much energy that they had become ultracold, The solution – which was already being hinted at of the Standard Model of particle physics. Like our theory predicts that the effects of new particles or and Steyerl was able to confirm this by measuring in the 1950s, though it would be more than a decade high-energy counterparts at the LHC, our goal is to forces may show up in the static and decay proper- their velocities. before it was put into practice – is to cool the neut- find evidence of “new physics” beyond the Standard ties of the neutron. Careful study of these proper- Regardless of which group came first, what is cer- rons down to very low temperatures. Neutrons are Model – which, despite its tremendous success, can- ties therefore enables us to test predictions from the tain is that following these initial breakthroughs, Peter Geltenbort officially “ultracold” at 2 mK above absolute zero. At not explain or predict some of the most basic, yet Standard Model and look for new physics beyond it. the 1970s and 1980s saw a number of institutes in is a physicist at such temperatures, their mean velocity is less than unanswered, questions in physics, such as why the ele- both East and West set up their own ultracold-neut- the Institut Laue- 6 m/s, so they can only travel about 2 m upward against mentary particles have the masses that they do, and Early experiments ron “factories”. However, the highest achievable Langevin in the pull of the Earth’s gravity. They are also totally why the universe evolved to have more matter than The identity of the first person to observe ultracold densities of stored neutrons were still relatively low, 3 Grenoble, France, reflected from certain materials, such as copper or antimatter. However, ultracold-neutron research- neutrons is a minor Cold War mystery, one of sev- typically 0.1 per 1 cm , which limited the measure- e-mail geltenbort stainless steel, at any angle of incidence. This is useful ers go about this task in a very different way. In an eral that arose as a result of frequent obstructions to ments that could be performed. As a result, scientists @ill.fr as it makes it possible to store and observe ultracold accelerator, the energies of the colliding particles are the free flow of information from East to West (and started to investigate other techniques for produc-
28 Physics World June 2013 Physics World June 2013 29 Feature: Ultracold neutrons physicsworld.com
1 Bouncing neutrons separated by a distance 6z that could be varied by a few tens of microns (figure 1). The upper plate had collimator a rough surface that absorbed any neutrons that col- variable height lided with it, while a lower plate made of standard Δz neutron absorber optical polished glass reflected neutrons like a mir- neutron detector gravity ror. The combination of the mirror and the Earth’s neutron path gravitational field formed a potential well: a neutron falling towards the mirror would interfere with its surface own reflected wave, and this self-interference cre- mirror repulsion ated a standing wave in the neutron density along the vertical direction. One would normally expect the neutron transmis- To test the behaviour of ultracold neutrons under the influence of gravity, the researchers 1.5 sent the neutron beam through a narrow slit formed by a mirror and a neutron absorber. sion rate T to be proportional to 6z (the additional When the slit height Δz was less than the 15 μm spatial extent of the neutron wavefunction, power of 0.5 is down to the fact that increasing 6z almost no neutrons reached the detector on the other side. allows neutrons with a greater spread of vertical velocities to enter the system, as well as improv- ing their chances of being transmitted through it). ing cold neut rons, such as cooling down the neutron Instead, the researchers saw T rise sharply from a spectrum within the reactor itself. This strategy negligible background level as soon as they increased increased the proportion of neutrons with velocities 6z above 15 μm – the height at which the spatial low enough for them to be stored for further study. wavefunction of neutrons in the ground state began The technique adopted at the ILL in 1985 begins to “fit” between the two plates. This study marked with energetic fission neutrons produced in the insti- the first time that quantum states of matter had been tute’s high-flux reactor. These neutrons are mod- observed in a gravitational field, and it opened the erated by heavy-water molecules in the tank that door to more complex experiments. For example, in contains the reactor core. Inside this tank is a second 2011 a research team from the Vienna University moderator full of liquid deuterium at 25 K. As the of Technology and the ILL modified the parallel- thermal neutrons pass through this second modera- plate arrangement so that the mirrored plate could tor, they lose energy by colliding with the cold deu- be vibrated at particular frequencies, boosting the terium nuclei and emerge with average velocities of neutrons into higher quantum energy states (T Jenke around 700 m/s. As in Steyerl’s early experiments, et al. Nature Phys. 7 468). the neutrons are then sent upwards through a guide, The next step will be to measure very precisely slowing down further under the influence of gravity. the energy differences between the various quantum The neutrons emerge at the top of the pipe with aver- states of a neutron in the Earth’s gravitational field. age speeds of about 50 m/s and are then sent into a Such measurements are important because they large vacuum vessel. This vessel contains a turbine provide a means of testing Newton’s theory of grav- with metal blades that rotate backwards when the ity at length scales of a few microns or millimetres. neutrons hit them (a design first proposed and imple- Any deviations from predicted values could reveal mented by Steyerl in 1976). This back-rotation “cush- the existence of a new, short-range “fifth force” that ions” the neutrons and causes them to lose some of couples to the neutron via some as-yet-undiscovered their kinetic energy. The basic principle is similar to force-mediating boson. Conversely, if such devia- pulling back your tennis racket just as the ball hits it; tions are not observed, that would place limits on the in technical terms, the neutron gets Doppler shifted strength of the hypothetical fifth force and constrain from a velocity of about 50 m/s down to about 5 m/s. theories of physics, such as string theory or extra As well as being highly effective, the turbine’s dimensions, that incorporate such a force. mechanical mechanism provides researchers with a very reliable, constant-intensity source of ultracold Here today, gone…when? neutrons. This has proven to be a major benefit to Although neutrons remain stable for billions of years scientists working on high-precision measurements, within the atomic nucleus, free neutrons decay into as the flux of ultracold neutrons and the storage den- protons, electrons and electron antineutrinos after a Finding a sities achievable with this system are about 50 times little less than 15 minutes. But the neutron lifetime more precise higher than was previously possible. As a result, the is not known with great accuracy, and the accepted value for the ultracold neutrons produced at the ILL have been value for it has changed several times as experi- neutron’s the foundation of some of the longest-running and ments became more precise. Even after 60 years of lifetime would most important experiments in this field. experiments, there remains about a second’s worth of uncertainty in the current figure. Finding a more be tremendous The fall of a neutron precise value for the neutron’s lifetime would be tre- as it could One of the experiments performed using the ILL’s mendous as it could help to answer a number of fun- help to answer turbine system involved “bouncing” ultracold neut- damental questions in physics. a number of rons along a mirror to see how they behave under the The first of these questions concerns the synthe- fundamental influence of gravity. In this experiment (V Nesviz- sis of nuclei in the aftermath of the Big Bang and hevsky et al. 2002 Nature 415 297), neutrons leaving the make-up of the matter that formed in the first questions in the turbine were directed through a slit composed few minutes of the universe. We know that during physics of two parallel plates, each about 10 cm long and this period, protons and neutrons came together to
30 Physics World June 2013 physicsworld.com Feature: Ultracold neutrons form the first light elements, which in turn became 2 Flipping asymmetries the raw material for the first stars. We also know that the most common element formed was hydrogen, Charge or C symmetry exists for physical processes that remain unaltered if followed by a much smaller amount of helium and charged particles in a system are replaced by their antiparticles, which have traces of lithium. However, the exact ratios of these opposite charge elements actually depend to a large extent on the Systems that obey parity or P symmetry behave the same if the spatial lifetime of the neutron. Had that lifetime been much coordinates of all the particles in the system are reversed smaller than it is, the universe would consist almost The combined charge–parity or CP symmetry is preserved if a system exhibits entirely of hydrogen; much larger, and it would con- both C and P symmetry – but also if it violates both of them, because two tain only helium. The neutron’s true lifetime must be violations cancel each other out somewhere between these two extremes, and being Time or T symmetry is preserved for physical processes that look the same able to pin down its value more precisely would allow whether time runs forwards or backwards us to test theories of the early universe. As well as helping us to understand the make-up of “normal” matter in the early universe, knowing + + the precise lifetime of the neutron would also help scientists make more accurate predictions of the T reversal total amount of matter created. This, in turn, might – dn S – dn S reveal how much dark matter must exist to make our theories of the universe’s evolution consistent. Finally, a better knowledge of the neutron’s life- time could provide insight into the operation of the weak force, since the decay of free neutrons is based purely on weak interactions. Precise measurements of the neutron’s lifetime can tell us much about the + – strength and structure of this force, which also gov- P transform erns nuclear fusion reactions, such as those that take dn S place within stars. – + dn S Experiments that aim to improve the accuracy of the lifetime measurement can be grouped into two categories, known as “counting the dead” and “count- Top: A spinning particle with an electric dipole moment dn does not obey T symmetry ing the survivors” (F E Wietfeldt and G L Greene because the direction of its spin angular momentum S changes if time is reversed. 2001 Rev. Mod. Phys. 83 1173). The first type of exper- Bottom: A P transform flips the positions of the centres of positive and negative charge, iment uses a beam of neutrons that are counted as altering the direction of the electric dipole moment, so the system also violates P symmetry. they pass through a detector. After the beam has trav- elled some distance, a second detector measures how many protons or other decay products (“dead neut- experiments. However, they are sensitive to leakages rons”) are left behind. With experiments of this type, caused by the scattering or absorption of neutrons in such as the one at the National Institute of Stand- the storage container. Such leakages are one reason ards and Technology (NIST) in Maryland, US, the why magnetic bottles are being developed to replace principal challenges are correctly counting the “live” forms of storage that allow the neutrons to bounce neutrons entering the beam and then ensuring that all off the container walls like ping-pong balls. of the neutron decay products in the beam path are detected and accounted for. Several techniques, such Broken symmetries as beam guides and new types of detectors, have been Although the neutron appears electrically neutral developed to improve this counting accuracy. overall, it is composed of up and down quarks, which The second type of experiment uses neutrons that carry opposing fractional electric charges. If the are stored in a container coated with a neutron- average positions of these charges within the neutron reflecting material, or in a magnetic “bottle” that did not coincide, the neutron would have an electric traps neutrons using their sensitivity to magnetic dipole moment (EDM) and would be affected by fields. After neutrons are loaded into the container an electric field. The existence of a neutron EDM and a certain number of seconds have passed, the would directly violate symmetries of nature (fig- “surviving” neutrons are counted and the neutron ure 2) related to parity (P) and time (T). To get a bottle is emptied. This measurement is then repeated physically intuitive picture of why this is so, imagine for several different storage times in order to trace the neutron (which has a nuclear spin) as a spinning out an exponential decay curve from which the neut- top. If you take a symmetrical top, flip it upside down ron’s lifetime can be calculated. and watch a time-reversed film of it precessing as it In stored-neutron experiments, the absolute num- spins on its axis, it will look the same as it did before ber of neutrons remaining after a particular time these transformations took place. But if the top is not is not important. Instead, what matters is how this symmetrical – if, in this analogy, the neutron has an number changes as storage times are increased. EDM – you will be able to tell the two systems apart, Hence, stored-neutron experiments, such as the one so P and T symmetries must be violated. currently operating at the ILL, are less sensitive to The violation of T symmetry implies that a neutron detector inefficiencies than is the case for beam-type EDM would also violate the combined charge–par-
Physics World June 2013 31 Feature: Ultracold neutrons physicsworld.com
ing a spin-polarized sample of ultracold neutrons into a storage bottle. A very stable, homogeneous and well-controlled magnetic field is then applied to the system, and as the neutron spins precess around
Bernhard Lauss, PSI the field’s axis (similar to the principle upon which magnetic resonance imaging, or MRI, is based) their Larmor precession frequency is measured. Next, a very strong electric field is applied in a direction that is either parallel or anti-parallel to the magnetic field. If the neutron has an electric dipole moment, it will “detect” whether the electric and magnetic fields are parallel or anti-parallel, and its spin precession frequencies will be different in the two cases.
More neutrons, more science The sensitivity of this frequency-difference meas- urement depends on three factors: the strength of the applied electric field; the storage time; and the number of neutrons in the apparatus. It is difficult to increase the field because of the need to avoid Shine on ity (CP) symmetry. The reason for linking the two is charge breakdown. As for the storage time, it cannot Highly polished that there is no physical process that simultaneously be higher than the 880 s lifetime of a free neutron – stainless steel disobeys charge, parity and time (CPT) symmetry; though in practice, leakages reduce the storage life- ultracold-neutron as far as we know, all physical laws would remain the time to around 250 s. Physicists are therefore looking guide during the same if the electric charges and spatial coordinates for new materials that offer a higher charge-break- production process of all the particles in the universe were inverted and down threshold and longer storage times. However, at the Paul Scherrer Institute in time went into reverse. Hence, either both CP and perhaps the most promising strategy for improving Switzerland. T symmetries must be violated, or neither of them. the sensitivity of the neutron EDM measurement is Examples of CP violation are of great interest to instead to increase the number of neutrons we can physicists because most explanations for why our store. This approach is also true for other types of universe is full of matter, and not antimatter, rely measurements on ultracold neutrons (and, generally, on a significant degree of CP violation taking place all particle-physics experiments): the more particles just after the Big Bang. And while there are several you have, the more precise the results you can obtain. experimentally verified examples of CP violation in Consequently, groups around the world are devel- processes associated with the weak force, these do oping a new generation of sources that should deliver not contribute enough to explain the matter–anti- higher densities of stored neutrons and open up matter imbalance we now observe. This is one of the new avenues for research. At present, new sources significant shortcomings of the Standard Model – it are either planned, under construction or have does not include a sufficient degree of CP violation. recently gone into service at facilities in Canada The idea that the neutron might have a non-zero (TRIUMF), Germany (Technische Universität EDM was first proposed by Norman Ramsey and München, Johannes Gutenberg University Mainz), Edward Purcell in 1950 and the first experiments Japan (J-PARC, Research Center for Nuclear Phys- (using thermal neutrons) to put an upper limit on ics), Russia (Petersburg Nuclear Physics Institute), the EDM’s magnitude were conducted at the Oak Switzerland (Paul Scherrer Institute) and the US Ridge National Laboratory in Tennessee, US, a (Los Alamos National Laboratory, North Carolina year later. Subsequent experiments using ultracold State University). We hope these new sources will neutrons have lowered this limit, but searching for a make it possible to improve our measurements of neutron EDM is by no means an easy task. To give the properties described in this article – as well as you an idea of the challenge the neutron-science others not discussed, such as the neutron’s degree community faces in trying to measure it, imagine of neutrality and the spatial asymmetries in the way blowing a neutron up to the size of the Earth. On it decays (D Dubbers and M G Schmidt 2011 Rev. this scale, the current limit on the maximum size of Mod. Phys. 83 1111). the neutron EDM would correspond to a separation As storage densities increase and losses are between positive and negative charge centres of less reduced, new applications of ultracold neutrons may than 3 μm – about the width of a hair – within the become feasible. For example, the wavelength of centre of the Earth (C A Baker et al. 2006 Phys. Rev. ultracold neutrons is comparable to the diameter of Lett. 97 131801). a nanoparticle, and since they tend to bounce along However, some theories that go beyond the Stand- a surface many times before being absorbed, it might ard Model (and that might resolve the issue of why be possible to use them as probes to study surface and the universe is composed of more matter than anti- interface physics at scales of a few angstroms. Long matter) predict a neutron EDM somewhat smaller hailed as a means of probing fundamental theories than this, so neutron researchers are developing about the nature of matter and the early universe, it is even more sensitive experiments to measure it. The possible that these extremely cold particles could find experiments taking place at the ILL begin by load- a use in more down-to-earth applications, too. Q
32 Physics World June 2013 The society book publisher in physics
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For more information about purchase options for 2014 please contact [email protected] or visit ioppublishing.org/books. Feature: History of physics physicsworld.com Made in Manchester Brian Clegg describes how the young postdoc Niels Bohr developed his famous model of the atom, published 100 years ago, after he had a productive stay with Ernest Rutherford in Manchester
Brian Clegg is a One hundred years ago next month, Danish physicist tion was that all the mass of the atom came from the science writer based Niels Bohr published a paper on his atomic model electrons, though in later versions of his theory he in Wiltshire, UK, that would lay the foundation of our understand- allowed for some mass in the positive charge. e-mail brian@ ing of the atom and form a major part of the early By the time Bohr arrived in Cambridge, Thom- brianclegg.net development of quantum theory. The paper was pub- son’s model was under threat as a result of Ernest lished when Bohr held a lectureship in physics at the Rutherford’s analysis earlier that year of the famous University of Copenhagen, but its genesis was in the gold foil experiment by Ernest Marsden and Hans north of England, inspired by the new contacts Bohr Geiger, which he had directed at the University of made there. Manchester two years previously. It seemed to show The chances are that Manchester meant no more that most of an atom’s mass was concentrated in a to Bohr when he first planned to come to England nucleus, leaving a central positive charge, in Ruther- than Denmark’s third city, Odense, would to most in ford’s words, “surrounded by a compensating charge the UK. His initial focus was the University of Cam- of N electrons”. Rutherford’s main interest in this bridge and its already famous Cavendish Laboratory, experiment had been the mechanism of scattering, where he would come under the wing of J J Thom- rather than a structure of the atom, which he did son. Bohr had received a grant from the Carlsberg not give much consideration to beyond the impact Foundation to spend a year studying abroad, and few of the nucleus. But these results – important though locations offered more possibilities in physics than they were – did not prevent Bohr from feeling that the Cavendish. Cambridge, with Thomson at the helm, was the place to be. Unfortunately, any collaboration might have Anglo ambitions gone better had Bohr’s first meeting with Thomson The young Bohr had very little English when he set not consisted primarily of Bohr bluntly telling the out at the age of 25 in September 1911 for Cam- older scientist that a calculation in one of his books bridge to meet Thomson – something he tried to was wrong. remedy by working through Charles Dickens’ Pick- After this uncomfortable start, as he described in wick Papers with a dictionary alongside. But what a letter to the Swedish physicist Carl Wilhelm Oseen, Bohr did have was clear academic promise. Before Bohr found Thomson difficult to talk to – and Thom- he had even gained his doctorate at Copenhagen on son was disinclined to even read Bohr’s doctoral the- the behaviour of free electrons in metals, Bohr had sis. Rather than sharing ideas with the great man, already won the Danish Academy of Sciences’ gold as he might have envisaged, Bohr found himself pri- medal and published two papers in the Philosophical marily occupied attending lectures on electromagne- Transactions of the Royal Society. Thomson, the dis- tism and undertaking experimental work on cathode coverer of the electron, would inevitably have made rays (electron beams in vacuum tubes). As Bohr Cambridge hugely attractive to Bohr, who had in his wrote, in one of a set of recently released letters, to thesis referred to Thomson as a major figure in the his then-fiancée Margrethe Norlund, “The reason development of atomic theory. that it has not gone so well, besides my own fault, is In 1904 Thomson had proposed a “plum pudding that Thomson is so busy with his own things that he model” whereby the atom is formed by electrons cares about nothing else at the moment, and...that (the plums), arranged within a spherical, positively the work conditions at the Cavendish Laboratory are charged matrix (the pudding). His initial assump- very difficult, at least in the beginning for a stranger.” (Excerpts of the letters, released by the Bohr family, will be published next month by Oxford University Bohr’s move to Manchester seems Press in the book Love, Literature and the Quantum Atom by Finn Aaserud and John Heilbron.) to have been cemented when In November 1911, just two months after arriving at Cambridge, Bohr visited a friend of his late father’s he encountered Rutherford at a who lived in Manchester. Rutherford was also invited and Bohr mentioned that he would be interested in 10-course dinner at Cambridge coming back to Manchester to discover more about radioactivity, the main focus of work in Ruther- ford’s lab. This move seems to have been cemented a month later when Bohr encountered Rutherford at a 10-course dinner at Cambridge for physics depart- ment members past and present (Rutherford having
34 Physics World June 2013 physicsworld.com Feature: History of physics Mehau Kulyk/Science Photo Library
done his PhD there in 1895–1898 following his move in England seems to have switched his focus from from New Zealand). By March the next year, Bohr primarily classical physics to quantum theory – an was on his way north. interest that first developed while at Cambridge but that flowered in Manchester. Indeed, Bohr was to Radiation revelation base his own management style, when later running When Bohr arrived in Manchester, the personality his own teams, on Rutherford’s successful blend of differences between the Dane and the New Zea- personal research and the development of a strong lander (see box on p36) did not present a problem. coterie of younger physicists. In fact, the situation was quite the reverse – Bohr The Victoria University of Manchester – as it was was hugely influenced by Rutherford. Bohr’s time formally known in Bohr’s day – had been established
Physics World June 2013 35 Feature: History of physics physicsworld.com
Bohr the introvert The young postdoc Niels Bohr and his supervisor Ernest Rutherford proved an interesting pairing. Bohr was poles apart from Rutherford’s bluff and open persona. Quiet and reserved, the young Dane had to organize his thoughts before speaking, where Rutherford would leap in to comment. When he was thinking, Bohr would withdraw from reality in a way that seemed to leave little more than a shell. A colleague, James Franck, once commented “His face became empty, his limbs were hanging down, and you would not know this man could even see. You would think that he must be an idiot. There was absolutely no degree of life. Then suddenly one would see that a glow went up in him and Lost in contemplation Bohr and Einstein in 1930. Ehrenfest/AIPPaul Segrè Emilio Visual Archives a spark came, and then he said: ‘Now I know.’ ” This same intensity of concentration comes through in Bohr tended to pace around and repeat a word over and Bohr’s most entertaining encounter with Albert Einstein. In over until he had assembled a complete sentence in his 1948 Bohr was staying at the Institute for Advanced Study mind. In the instance at the IAS, Pais recounts, the word (IAS) at Princeton, using Einstein’s office, which was vacant was “Einstein” and Bohr came up with it again and again as as Einstein preferred to use the smaller assistant’s office. he walked around the office. After a while he was standing Bohr had asked fellow physicist Abraham Pais to make some looking out of the window, continuing to occasionally say notes for him. “Einstein”. At this point Einstein quietly entered the room. This reflected a practice that Bohr followed through most He had been forbidden to buy tobacco by his doctor, so of his working life – he preferred to assemble ideas in his had decided to purloin some of Bohr’s. Einstein tiptoed head and then dictate, rather than write things himself. It has across to the desk to help himself as Bohr continued to been suggested that apart from his tendency to construct mutter “Einstein”, while he peered out of the window. As elaborate text in his mind before pouring it out, this was Einstein reached the desk, Bohr came out with a final, firm also because his handwriting was appalling. So bad was its “Einstein!” and turned to find the subject of his monologue reputation that when Bohr was operating under the assumed standing mysteriously before him. “There they were,” Pais name Nicholas Baker during the Second World War, known commented, “face to face, as if Bohr had summoned him as “Uncle Nick”, there was dispute over whether a letter from forth. It is an understatement to say that for a moment Bohr him to Los Alamos was signed Niels Bohr or Uncle Nick. was speechless.”
in 1880 as Owens College, the UK’s first civic univer- Bohr’s initial ideas were on the newly developing sity. The building where Bohr worked, now called the (though yet to be named) concept of isotopes. He Rutherford Building, was a shiny new facility when believed that the defining factor for an element was he arrived, having opened in 1900 with a state-of- not its atomic mass, but its atomic number – the posi- the-art ventilation system that drew outside air over tive charge on the nucleus – and Bohr worked out oil baths to remove the soot particles of the smoky how alpha particles or beta particles emitted from industrial city. It was here, and in his rented rooms, the nucleus would change the element. Rutherford, that Bohr would undertake his crucial work. at least at the time, played down the significance of After attending a course on radioactivity, Bohr a nuclear atom, perhaps because his focus was on was directed by Rutherford to carry out an experi- scattering effects rather than atomic structure, and ment – never truly his forte – in this case studying the seems to have discouraged Bohr from taking his absorption of alpha particles by aluminium. For a few thinking any further. Instead, Bohr built on the work weeks he spent all day in the lab, most appreciating of Charles Darwin’s grandson Charles Galton Dar- the time when Rutherford – always more approach- win, who around that time was attempting to explain able than Thomson had ever been – would come the way that alpha particles lost energy when passing around and the pair could discuss Bohr’s observa- through matter. tions. “Professor Rutherford was precisely such a Darwin had correctly suggested that this energy man as I thought,” wrote Bohr in another recently loss was the result of alpha particles interacting with released letter to Hanna Adler, his aunt, “and takes atomic electrons, but had problems bringing his such great interest in each and every one who works theory into line with experimental data because he with him.” But Bohr was enthusiastic to focus more assumed those electrons were floating freely. Bohr on theory and after a few weeks had put aluminium looked instead at the possibility that they were bound aside for pencil and paper. via some kind of elastic connection to the nucleus, meaning they should vibrate with specific frequen- cies. Max Planck’s 1900 theory of radiation from Bohr’s insight into the atom while in an atom had been based on the idea of a minimum amount of energy that could be radiated by an atomic Manchester was simple but stark vibration and in June 1912 Bohr made the connec- tion that the radiation of energy from these electrons could be limited by Planck’s constant, thereby bring-
36 Physics World June 2013 physicsworld.com Feature: History of physics Niels Bohr Archive Bohr Niels The UniversityThe Manchester of
Life-long friends Niels Bohr and Ernest Rutherford in Brussels in 1933, while Site of inspiration The Rutherford Building at the University of Manchester, where attending a Solvay Conference. Bohr devised his atomic structure. ing the early quantum theory into the structure of no “mechanical foundation” – in effect one that the atom for the first time. behaved differently from the expected behaviour of This work seems to have inspired Bohr to apply the macro world. When mechanics had proved una- his undoubted thinking skills to a bigger prize. As he ble to explain the workings of the atom, it was time wrote from Manchester to his brother Harald, “Per- to abandon the conventional approach. haps I have found out a little about the structure of Specifically, Bohr called on the thinking that had atoms. Don’t talk about it to anybody…It has grown been introduced with the first, tentative steps into out of a little information I got from the absorption quantum theory. His hypothesis, he commented, was of alpha rays.” the only one that seemed to offer an explanation of the experimental results confirming the radiation Birth of the quantum atom mechanism proposed by Planck and Einstein, the Bohr wrote up his first thoughts in Manchester in a idea that atoms could only radiate energy in fixed draft he prepared for Rutherford called “On the con- “packets” of energy called quanta. He envisaged an stitution of atoms and molecules” – the same title as atom in which there was a relationship between the his final paper. It was here that for the first time any- energy of an electron and the frequency of its orbit. one dared take on the implications of Rutherford’s Bohr’s insight while in Manchester was simple but nucleus for the structure of atoms. stark. There was no hope, he reasoned, of under- Rutherford’s theory placed the positive charge in standing atomic structure using classical physics. It the atom in a tiny nucleus. The negative charge was can only be stabilized by taking a quantum approach. known to reside in electrons. But what would provide The final piece in the picture had to wait until a stable structure for those electrons and the nucleus after Bohr left Manchester in July 1912, when his to coexist? It seemed initially as if there was no way year’s grant ran out, to return to Copenhagen where forward. It is possible to imagine that there would he went on to take up a lectureship in physics the be some stable configuration where fixed electrons following year. Although the atomic model Bohr repelling each other could sit fixed in place around devised in Manchester had a quantized orbit, it was a positive nucleus, but it had been shown a little ear- still unstable because it was still capable of radiat- lier that mechanically there was no such stable con- ing its way into the nucleus. In early 1913, however, figuration. If, however, the electrons did move, that Bohr became aware of work by the Swiss physicist induced its own problems too. Johann Jakob Balmer that fitted a simple formula to It had been known since Maxwell’s time that when the spectral lines of hydrogen. It was known that all an electrical charge is accelerated, it gives off elec- elements emit and absorb such specific frequencies tromagnetic radiation. Moving in any kind of classi- of light – Balmer had quantified this. cal orbit, which implies acceleration as it involves a The existence of these specific, limited emissions change in direction and hence a change in velocity, filled in the last piece of the Manchester jigsaw for electrons would radiate away their energy and crash Bohr. It became clear to him that these fixed frequen- into the nucleus, rather as a satellite losing energy in cies could correspond to limited orbits – that unlike a decaying orbit would spiral into the Earth. Further, a classical planetary orbit, the electrons in the atom simply putting electrons equally spaced around a could only exist in specific, discrete orbits, which he rotating ring was mechanically unstable for anything called stationary states. He arbitrarily decided that other than a single electron. the electron would not be allowed to move to any Rather than give up at this point, Bohr took the orbit between the states, including the entire region mental leap of developing a hypothesis that had between the ground state and the nucleus, forcing
Physics World June 2013 37 physicsworld.com
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4(.5,;:@:;,4: ; Library Photo Murray/Science Louise T*-4: :\P[HISLMVYUL_[NLULYH[PVUNYHWOLULZHTWSLZ
Fitting tribute Niels Bohr on a 500 kroner Danish banknote, which is fluorescing under ultraviolet light. Fittingly, the science behind this phenomenon relies on Bohr’s atomic model.
stability on the atom. Bohr published his theory in three parts in the summer of 1913 once he was firmly established back in Denmark, but it is clear that the formulation of his atomic model began in Manchester, lacking only the insight that would emerge from his discovery of Balmer’s theory. It was working at Manchester with the individuals he met there that proved the trigger for one of the most remarkable developments in all of physics.
An open approach As Bohr commented, it was in this environment that he experienced “the enthusiasm with which the new 9V[H[PUN/L prospects for the whole of physics and chemical sci- YLMYPNLYH[VY ence, opened by the discovery of the atomic nucleus, WYVILMVY\ZL PU*Y`VNLU were discussed in the spring of 1912 among the pupils -YLL=;0 of Rutherford”. In contrast with the seemingly cold, detached reception that Thomson provided, Bohr *VTWSL[LS`KY`Z`Z[LTYLX\PYPUNUV found the approach taken in Manchester much more SPX\PKOLSP\T conducive to developing his ideas. Every afternoon there was an opportunity to discuss new ideas over 4HNUL[PJÄLSK [LZSHPUHTPUP tea and cake, as well as during informal get-togethers KLZR[VWJY`VZ[H[ often presided over by Rutherford, and his more for- :HTWSLZWHJLVM TTVYTTPU[OL=;0 mal Friday afternoon colloquia. The big difference for Bohr seems to have been this more collaborative, =HYPHISL[LTWLYH[\YLYHUNLMYVT [V2 information-sharing approach. Bohr’s quantum model of the atom was at the /PNOS`Z[HISLTHNUL[PJÄLSK heart of the first generation of quantum theory, and /L0UZLY[^P[O[LTWLYH[\YLZKV^U[V in 1922 Bohr deservedly received the Nobel Prize for T2HUKOV\YZOVSK[PTLVW[PVUHS Physics for this work. His model was successful in providing a stable model for the atom and the exist- /PNOWV^LY7\SZL;\ILJY`VJVVSLY^P[O ence of atomic spectra. However, it did not explain SV^]PIYH[PVU the intensity of the different spectral lines and it was 5VTHPU[LUHUJLMVY`LHYZJVU[PU\V\Z\ZL riddled with ambiguous behaviour and inconsisten- cies of interpretation. In the mid-1920s it would be 0UKLWLUKLU[HUKLHZPS`[YHUZWVY[HISLHZP[ transformed by quantum mechanics, where Heisen- Y\UZMYVTZ[HUKHYKLSLJ[YPJHSZ\WWS` berg’s matrix mechanics and Schrödinger’s quan- tum wave equation came together to provide a solid structure that would replace the hazy foundations of Bohr’s pioneering model. But it was in Manchester, in the heady atmosphere of Rutherford’s lab, that the ^^^JY`VNLUPJJV\R quantum atom was conceived. Q
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Athene Donald was part of this tribe of scientists. At the time, of course, the comput- ers we today take for granted did not exist; indeed, the term “com- puters”, in the early days, referred Structural disputes to people who worked out compli- cated calculations to produce, for instance, tables of functions. These calculations were long and difficult. Hence, even had the theories of the time been robust, moving from the observed diffraction pattern (which necessarily lacks information on the phase of the contributing waves) to the underlying structure seemed like an intractable problem; progress on both theoretical and experimental fronts was slow. Undoubtedly, Wrinch made sig- nificant contributions to the field, particularly in her fairly late work Fourier Transforms and Structure Factors (1946), in which she laid down in detail much of the field’s mathematical basis. But it was her model for protein structure itself that led to many personal attacks and damage. Wrinch was convinced that proteins were not long chains of Dorothy Wrinch Papers, Sophia Smith Collection, Smith College, Northampton, Mass. molecules (described at the time as resembling Christmas tree lights). Instead, she believed they were an indefinite fabric of rings, which she Gender bias? In March this year, the author of to symmetry and beauty in nature. termed “cyclols” (see figure on p42). Dorothy Wrinch a well-regarded science website Ultimately, she became interested This idea was initially compatible (shown here with was revealed to be – wait for it – a in protein structures. At this point, with the limited evidence, but she students at Smith woman. The identification of Elise she ran up against Linus Pauling, to clung to it long after new data made College in the Andrew as the founder of the pro- her great detriment, and she died in it scientifically untenable, and pos- 1960s) has been vocatively titled x page “I Fucking relative obscurity. sibly right up to her death. largely forgotten Love Science” was greeted with Does Wrinch’s losing encoun- To begin with, she had many influ- despite her many astonishment, tinged in some cases ter with Pauling explain why she is ential supporters, including the contributions to the with outrage. This anecdote says largely forgotten today? I had cer- chemical physicist Irving Langmuir. science of crystal much about the general reaction to tainly never heard of her before I However, her inflexible attitude as structures. women in science: even in 2013, it is was sent this new biography, I Died the counter-evidence built up did still not taken as a given that women For Beauty (the title comes from nothing for her reputation, and it I Died For Beauty: may be good at science and enjoy it. an Emily Dickinson poem). Or is it seems that she was always something Dorothy Wrinch and Imagine how hard it must have been because she was a woman – and, as of a divisive character. The book’s the Cultures of 80 years ago, when Dorothy Wrinch far as I can judge from the book, a author, Marjorie Senechal, knows Science was struggling to make a name for cussed and difficult woman at that this firsthand: she describes herself Marjorie Senechal herself as a mathematician working – at a time when they weren’t fully as a mathematical crystallographer, 2012 Oxford at the interface with biology. accepted into the scientific fold? and towards the end of Wrinch’s life, University Press Wrinch (1894–1976) was educated The book left me uncertain as to the when both women were at Smith Col- £22.50/$34.95hb at Girton College, Cambridge at a answer to those questions, although lege in Massachusetts, they worked 312pp time when women still had to ask it does describe some rather interest- together informally. Senechal draws permission to attend lectures that ing episodes in the history of science. on this personal experience in the were given by men for the univer- During Wrinch’s heyday of the book, but she also had access to sity’s “real” students, i.e. the men. 1930s to 1950s, there was huge inter- extensive diaries kept by senior Over the years, she variously worked est in crystals and lattices as many members of the Rockefeller Trust, in Cambridge, London and Oxford scientists across a variety of disci- whose role it apparently was to travel (always in short-term posts with plines tried to work out how these around asking senior scientists to insecure funding), tackling philo- complex crystal structures, in par- comment on colleagues whose work sophical problems with Bertrand ticular proteins such as insulin and the trust might fund. Quotations Russell and other giants of the day haemoglobin, could be inferred from taken from these diaries include the and considering questions related X-ray diffraction patterns. Wrinch statement that “[Wrinch] is in bad
Physics World June 2013 41 Reviews physicsworld.com
favour in many quarters in England” into being. But was she a flawed and “P said flatly that he has always genius whose central thesis about said she is a fool but that B insists she cyclols was wrong, so the rest of her is only mad”. And these quotes actu- work, important though it was, has ally precede the fracas over Wrinch’s been allowed to sink into obscurity? cyclol model, where she clashed so Maybe – but then, Pauling himself painfully with Pauling. made a glaring mistake late in his Senechal chooses to make the life, yet his reputation has survived chapter on Wrinch’s exchanges pretty well intact. One might rea-
with Pauling into the skeleton of an Smith Collection,Sophia Smith College sonably conclude that Wrinch’s gen- opera, outlining the acts though not der was a factor in the way she was fleshing out the libretto in full. As treated. But does this make her a she puts it, “Dorothy Wrinch’s epic brilliant woman in science, ahead of battle with Pauling is the stuff of her time, whose strong personality opera. There is no other way to tell it. led her to dare to challenge a patri- Two brilliant, arrogant, competitive archal society and come off worst? antagonists with a flair for publicity Contentious Wrinch’s lantern slide showing Or was she just a run-of-the-mill and a touch of the devious! And what cyclol fragments as denatured proteins. scientist with an awkward character a plot!” These few sentences demon- and a colourful personal life, whose strate the flavour of the book. Sene- D’Arcy Thompson to mineralogists vanishing from the list of the period’s chal’s style is personal and staccato, and members of the Smith College “great and good” is justified? I sus- and throughout the book, her own faculty. But at the end of the book I pect Senechal herself is ambivalent interactions, interests and driving felt I had not grasped the essence of on these questions, but it is a pity that forces creep in, leading to multiple Wrinch herself. she doesn’t give readers enough solid digressions in chronology and topic. Clearly, she was a multi-faceted information to allow us to form our This can be confusing, although and hugely original scientist. She was own firm judgement. the anecdotes are also illuminating also struggling to cross the divide and often intriguing. I learnt, for between many disciplines, some of Athene Donald is a soft-condensed-matter example, about diverse background which, such as molecular biology, physicist at the University of Cambridge, UK, issues and individuals ranging from were at the time only just coming e-mail [email protected]
Web life: The Giant’s Shoulders different areas of science, sometimes grouped hosts and contributors, while keeping its content into discipline-independent categories such as fresh and interesting. But there is one gigantic “pseudoscience” or “heroes”. In the carnival’s downside to this crowdsourced carnival: many early days, entries had to be about classic of the blogs that hosted or contributed to it in scientific papers. For example, the sixth edition of have subsequently moved to new addresses or The Giant’s Shoulders includes a post about Isaac gone to that great web portal in the sky, leaving Newton’s first contribution to the Philosophical a trail of broken links in their wake. As a result, Transactions of the Royal Society. In later editions, browsing the archive of The Giant’s Shoulders can the focus was broadened to include general be an exercise in frustration as page after page science-history topics, not just individual papers. comes up as “Not Found”. A mid-2010 dust-up at A few editions have also pushed the definition of National Geographic’s ScienceBlogs portal, which URL: http://ontheshouldersofgiants. “history” by featuring posts on, for example, the saw numerous contributing bloggers decamp wordpress.com meteor that broke up over Russia in February. to other sites, seems to have been a particular culprit in this 404-fest, but other blogs may have So what is the site about? Who is behind it? simply disappeared after their authors became The Giant’s Shoulders describes itself as “a Dozens of science bloggers have carried this bored or busy. In short, The Giant’s Shoulders monthly science blogging event in which authors giant on their shoulders, but the main organizers is both a tribute to what a loose network of are invited to submit posts on topics in the these days are Thony Christie and Greg Gbur. enthusiasts can achieve and a reminder of the history of science”. Each month, a participating Christie, a research jack-of-all-trades, describes ephemeral nature of the Web. science blogger agrees to host an “edition” of the himself as “an aging freak who fell in love with the event – a process that involves sorting through history of science”; Gbur is an optical physicist Why should I visit? all of the submitted posts and then, on an agreed at the University of North Carolina at Charlotte Every month, the science blogosphere generates date, posting an entry on his or her blog with links who also writes his own blog, Skulls in the Stars, hundreds of wonderful, fascinating and well- to the best submissions. Because of its mobile about physics and horror fiction. written blog entries. Trouble is, these gems tend and celebratory nature, this arrangement is to be scattered across dozens of different sites, known as a “blog carnival”. How long has it been going on? and only the most dedicated blog-watchers will The Giant’s Shoulders started in June 2008, come across more than a few of them. By dishing What are some of the topics covered? which makes it – hmm, let’s see, we reckon that’s up a giant-sized portion of bloggy goodness each The subject matter in each edition depends on about 60 in “blog years”. The carnival format has month, The Giant’s Shoulders provides a useful the host. As you might expect, physicist hosts undoubtedly contributed to its longevity, since service to time-poor science enthusiasts in every tend to pick more physics-related entries, medical it spreads the burden of hosting and curating discipline. Agreeing to host one of the monthly bloggers are more attuned to good writing in successive editions among many different editions can also help new bloggers get noticed the life-sciences blogosphere, and so on. Most people. Appearing on a different blog each month and drive more traffic to their site – provided they editions, however, include blog posts from several also helps the project attract a steady supply of keep their links maintained, of course.
42 Physics World June 2013 physicsworld.com Reviews
Patrick Fox It’s that particle again in 2015 after a period of scheduled ery of a “new boson” back in July maintenance, it is expected to col- 2012, subsequent data releases later lect even more data at almost twice in 2012 and early 2013 mean that the energy. even if the new particle may not Complementing this successful yet be said to quack exactly like an experimental programme has been SM Higgs, it certainly looks like an an equally successful theoretical aquatic bird. Carroll’s book – which effort. One of the great achieve- came out in late 2012, before some ments of modern science has been of the new results – proceeds under the uncovering of the rules that the hypothesis that this new particle govern subnuclear processes. These is a Higgs boson, and that 4 July 2012 rules, which are unimaginatively was the day we learned that Nature called the Standard Model (SM), chose the Higgs mechanism over the predict the existence of various par- alternatives as the way to break the ticles and interactions. The principle symmetries of the SM. of symmetry played a central role in Books about particle physics their development. The laws govern- often follow a standard format. ing the physics at these very short After describing the history of the Xavier Cortada (with the participation of physicist Pete Markowitz)/CERN distances display a huge amount of field and the developments that led symmetry – so much so that, naively, to where we are now, they devote a one might think that the SM should couple of chapters to open questions be a theory of only massless parti- in the field and then conclude with cles, since the electroweak symme- an outline of some of the more exotic try forbids the equations governing possibilities that could be found the SM from having masses in them. at future experiments. Carroll’s However, even if the interactions book, in contrast, provides a more are symmetric, it is possible for the dynamic perspective on how science lowest-energy state of the system proceeds. It presents the field as it to break this symmetry in so-called currently is: slightly giddy and in a spontaneous symmetry-breaking. state of great flux. His writing style is How this symmetry is broken light, lively and often humorous, and and how the fundamental particles he does a good job of capturing the acquire a mass has been, for many excitement in the field. Carroll is a years, the outstanding question cosmologist, and as a working scien- within the SM. There are various tist he has seen the developments in competing proposals for how this the field that have led us to this point occurs, but in the SM, the symmetry- and knows the personal investments breaking is carried out by some- that people have made to make the thing called the Higgs mechanism. discovery possible. His position Associated with this mechanism is also affords him closer access to the a new particle – a fundamental sca- main players than a science journal- lar boson – called the Higgs boson. ist might be able to get. As a result, This mechanism, the particle, the the book is littered with anecdotes developments in science that led to and inside stories that don’t often Hunted down The quest by particle physicists to its prediction and the decades-long see the light of day. His discussion Sean Carroll’s book understand nature at its most fun- experimental effort to find it are the of bets that physicists make among recounts the search damental level has necessitated the focus of Sean Carroll’s book The Par- themselves is particularly amusing, for the Higgs boson. construction of ever larger “atom ticle at the End of the Universe. but perhaps makes it into the book smashers” to probe ever shorter dis- There are many popular-science because both of his own bets – made The Particle at the tances. The Large Hadron Collider books about particle physics and with the unlucky Brian Schmidt on End of the Universe: (LHC) at CERN is the latest in a the search for the fundamental laws the subject of measuring the density How the Hunt for long line of these machines. From of nature. Two things set Carroll’s of matter and energy in the universe, the Higgs Boson late 2010 until early 2013, the LHC apart: its rather singular focus on and whether the Higgs would be Leads us to the was colliding protons together at the the Higgs, and the timeliness of its discovered at the LHC – were ulti- Edge of a New World unprecedented energy of 7–8 TeV, release. As Physics World readers mately decided in his favour. Sean Carroll collecting enormous amounts of data are no doubt aware, the last year or This attention to the human side 2012 Dutton/ in the process – data that led, among so has seen the LHC’s search for the of the field does not come at the Oneworld $27.95/ other things, to the announcement Higgs take centre stage and receive expense of the science, which is pre- £16.99hb 352pp on 4 July 2012 that a new particle much media attention. While CERN sented with a deft touch. Nor does with a mass of 125 GeV/c2 had been officials were understandably cagey Carroll’s focus on the Higgs sector observed. When the collider restarts when they announced their discov- of the SM mean that he ignores what
Physics World June 2013 43 Reviews physicsworld.com
else might be in store for the LHC. In – had appeared in the main text. one of the later chapters, he describes It presents the This book is an enjoyable and some of the more exotic suggestions informative read and does an excel- for what lies beyond the SM, and field as it is: lent job of explaining “how science there are also frequent discussions is done” and in particular how the of dark matter and other cosmologi- Higgs boson was found. It accurately cal discoveries. Throughout, Carroll slightly giddy and reflects the scientific and emotional seems well aware that he is writing state of the field at this momentous for dual audiences of lay readers and in a state of flux time while also putting it in a his- professionals, and he does a good job torical context. Towards the end of of keeping both on board as the book the book, Carroll finds time to dis- progresses. He is, for example, care- The fact that they are included at all cuss what new discoveries may lie ful with the science and clear about should insulate him to some degree ahead, and one can only hope that where his analogies break down, and from colleagues’ complaints; how- when these discoveries are made – the book is littered with comments to ever, this colleague would still have whether at the LHC or elsewhere – the cognoscenti. On the other hand, preferred it if Carroll’s detailed but he is around to chronicle them. he serves his less-expert readers by accessible description of the Stand- relegating certain technical details ard Model and its interactions – Patrick Fox is a theoretical physicist at the to appendices, allowing the story to especially those of the Higgs, which Fermi National Accelerator Laboratory in flow and maintain the excitement. are central parts of much of the story Illinois, US, e-mail [email protected] Between the lines
Statistically speaking Wheelan writes, “has nothing to something cold and sophisticated. Particle physicists use statistics do with the example, but it kind of Its subject, broadly speaking, is the to distinguish new particles spices things up”.) He keeps the history of particle physics, and it is from meaningless blips. Climate tone light even as the book moves organized into three sections. The physicists need it to turn incomplete on to more complex topics, such first of these deals with the electron, data into robust models. And pretty as the “garbage in, garbage out” proton, neutron and neutrino, which much everyone in science wheels it problem of doing statistics with bad Bernstein describes as the “primary iStockphoto/Viorika Prikhodko out to calculate error bars. Despite data and the various biases that colours” on nature’s palette. Next its usefulness, however, the field of can lead people to form erroneous up are more exotic particles such as statistics has a reputation for being conclusions. At the heart of the the pion and muon, antiparticles, Sexed-up stats dull and confusing; as a former book is the central limit theorem, strange particles and quarks; these Charles Wheelan’s classmate of your reviewer’s put it, a pillar of statistics that, crudely are the “secondary colours”. The new book aims to “If I had one day left to live, then I speaking, states that a random final section is devoted to nature’s enliven a subject would live it in stats class, because sample of a given population will “pastels”, beginning with the often considered that way, it would last longer.” In resemble the population as a whole. relatively vibrant Higgs boson and deadly dull. his book Naked Statistics: Stripping That might not sound terribly earth- shading away to shadowy objects the Dread From the Data, author shattering, but Wheelan shows that such as tachyons and gravitons. Charles Wheelan concedes that if properly applied, the central limit Bernstein is both a physicist himself his subject could do with a bit of theorem can do some amazingly and a veteran observer of other a boost. The statistical sexing-up useful things – such as detecting physicists; in many cases, he met begins with the book’s front when someone’s been fiddling or was personally acquainted with cover (which depicts a cartoon experimental data. The theorem the people he describes, including character holding a suggestive and also allows us to infer that while Wolfgang Pauli, Emilio Segrè and strategically placed bar graph) and most physicists won’t learn much Sheldon Glashow. Perhaps as a continues with the kind of writing from the first few chapters of Naked result of this familiarity, the book that made Wheelan’s previous book, Statistics, nearly everyone will get sometimes reads as though it was Naked Economics, into a bestseller something out of it by the end – a written not for its stated audience despite its “dismal science” subject. pretty good result, whichever way (“a general reader with an interest In addition to clarity, Wheelan’s you slice it. in science”), but for insiders who, favourite tactics for keeping the O 2013 W W Norton/Wiley like the author, are already familiar reader hooked include a nice line in £18.99/$26.95hb 320pp with the main characters and their silly examples and a ready spoonful histories. It is, if you like, a bedtime of wit to make the statistical A classy bunch of particles story for quantum connoisseurs medicine go down. In the second Following the success of Brian rather than a bracing wake-up chapter, for example, he tells a Greene’s The Elegant Universe, the call for newcomers – and like story about a bar patronized by word “elegant” has been somewhat the best bedtime stories, it offers Bill Gates, a talking parrot and 10 over-used in popular-science plenty for readers to think about. low-paid workers. The point of this writing. However, there is no other In Bernstein’s view, “nature [is] anecdote is that mean values can be word to describe Jeremy Bernstein’s something like those Russian dolls, distorted by outliers; when Gates A Palette of Particles: this is an except in this case I think there may walks into the bar with the parrot elegant book, elegant in its writing be no limit. The deeper we probe, on his shoulder, the average annual and in its packaging, the sort of the more will be left to probe.” income of the patrons leaps from book that ought to be read with O 2013 Harvard University Press $35 000 to about $91m. (The parrot, freshly washed hands and a glass of £14.95/$18.95hb 224pp
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The sixth Six Element element Stephanie Liggins describes how her PhD research on defects within the structure of diamonds led her to a career in industrial product development
I’ve always been interested in how things work, and this natural affinity (com- bined with ability) led me to study physics throughout my school and undergraduate years. When it came time for me to decide what to study for my PhD, condensed- matter physics seemed like a natural pro- gression. This was partly because I was Diamond days Stephanie Liggins works on R&D for a variety of synthetic-diamond products. swayed by the enthusiasm of Mark New- ton, who became my PhD supervisor at the that diamond is a form of carbon – the sixth definitely exciting to work on this unusual University of Warwick. But I also became element in the periodic table.) I was drawn application of diamond-synthesis tech- fascinated by the idea of adapting and con- to the company because I knew I would be nology, and to see it achieve the Queen’s trolling the properties of different materi- able to get involved right from the start and Award was a real validation of all the hard als in order to achieve specific outcomes, have my work taken seriously. Thanks to the work we put in. such as sensing in extreme environments or experience I had gained during my PhD, I single-spin magnetometry, and to develop was thrown in at the deep end, immediately Cutting edge technological solutions for the many chal- becoming involved in the company’s R&D Element Six is a growing mid-size company lenges that scientists face today. team after I started in November 2010. with around 2500 employees worldwide Newton’s research is on the extreme Many of the synthetic-diamond products and I have always found it a very personal properties of diamond, including its very that Element Six develops, such as drill bits and friendly place to work. Things “felt large electronic energy gap, its optical for road picks and windows for high-power right” from the outset, and I very much transparency from the ultraviolet into optical lasers, have very practical uses. enjoy being part of a team full of people the infrared and the defects that give it However, the first project I worked on was I can learn from and who are always keen its character. My PhD project was about different: a synthetic diamond “tweeter to learn more themselves. On a day-to-day identifying and characterizing some of dome” for a loudspeaker system. The basis, the work I do is pretty varied. I spend these defects, and I was fortunate enough tweeter, as its name implies, is a specific roughly half of my time in the laboratory, to be sponsored by the Diamond Trading speaker designed to reproduce the high- running chemical vapour deposition reac- Company, part of the De Beers Group. est-frequency sounds; the dome is the part tors, analysing material and designing Through this sponsorship, I became aware that vibrates to generate sound waves. The further experiments. The rest of my time of another firm, Element Six, in which light weight and extreme rigidity of dia- is divided between answering technical the De Beers Group is a majority share- mond makes it a great material for tweeter queries from customers, supporting my holder, and which applies the properties domes, and a high-end hi-fi company, Bow- colleagues in R&D and production, and of synthetic diamond to solve customers’ ers & Wilkins, asked Element Six to help reporting to stakeholders. There’s defi- materials-science problems. I soon realized develop this key component for their new nitely a balance between the academic that I was attracted by the idea of working 800 Diamond Series range of loudspeakers. aspects of the role and the more commer- with a material that has so much scope for My role in this project was to re-engineer cial ones, so while my technical and data- innovation, and it seemed like a natural fit some elements of the synthesis process that analysis skills are important, I also need to join Element Six’s research team after I had been initially developed for the origi- to be able to work with customers, under- completed my PhD. nal 800 series tweeter dome so that they stand their concerns and present solutions were suitable for an associated application, to them. An award-winning product extending the product range. Both the ini- I would say that because of this variety, Element Six’s business is the design, tial and continued stages of the dome devel- the working environment at Element Six development and production of synthetic opment process led to Element Six winning is fast-paced and intellectually challeng- diamond supermaterials for commercial a major industry prize, the Queen’s Award ing, and you need to be prepared for your applications. (Its name comes from the fact for Enterprise in Innovation, in 2012. It was colleagues to critically assess your ideas
46 Physics World June 2013 physicsworld.com Careers
and thought processes. That said, there There will be a number of job opportuni- is a real sense of achievement that comes It’s great that I am ties as the new centre gets up and running, from seeing your ideas in an actual product, so current postgraduates who are consid- one that provides a tangible solution for able to use what I ering a career in the industrial synthetic- customers. It’s great that I am able to use diamond industry should think about what I learned in my PhD in a commercial applying now. Applicants will need to setting, and overall I feel that the company learned in my PhD understand the industry and have a strong has given me a wealth of opportunities to background in materials science, but it do this. synthetic-diamond research and develop- could be a great fit for people who, like me, When I started working at Element Six, I ment facility. I’m looking forward to work- want to work in R&D and innovation at a was part of a team based at Ascot in Berk- ing more closely with colleagues from a commercial organization. shire, but we will soon be moving to the range of scientific disciplines, and I also company’s new Global Innovation Centre hope to use the company’s international Stephanie Liggins is a senior research scientist in in Oxford. This centre has been designed R&D footprint and global customer base the R&D team at Element Six. For more information to bring all of the company’s R&D teams to follow some of my ideas into the field – about careers at the company, go to www.e6.com/ together, and it is now the world’s largest wherever they are being used. careers Careers and people
Spotlight on: Andrew background outside Germany. award, the Canadian Association of Fraknoi and Metin Tolan Fraknoi, 64, has given public lectures Physicists’ Medal for Outstanding This month’s spotlight on such topics as “What were the atoms Achievement in Industrial and Applied falls on two researchers, in your body doing 8 billion years ago Physics, went to Xiaoyi Bao, a photonics Andrew Fraknoi (left) and and why should you care?” and has been scientist at the University of Ottawa. Metin Tolan, who have a frequent guest on local and national The Physical Measurement Laboratory recently been honoured radio and television since the 1980s, at the US National Institute of Standards for their work as science including appearances on National and Technology has a new director. communicators. Fraknoi, who has won Public Radio’s Science Friday programme Joseph Dehmer took over from the the Faraday Science Communicator and NBC’s Today show. He has also previous director, Katharine Gebbie, who Award from the US National Science worked to debunk astrology and related had led the laboratory and its predecessor Teachers Association, is the only full- pseudoscience, and is the founder of since 1991. time astronomer at Foothill College, a Project ASTRO, a programme that pairs Vladimir Fortov has become one of two small community college nestled in the volunteer astronomers with primary and researchers to win the 2013 Global Energy mountains above California’s Silicon secondary-school teachers across the US. Prize, which is supported by Russia’s Valley. Tolan is a soft-matter physicist at three leading energy companies. Fortov, the Technische Universität Dortmund in Movers and shakers a plasma physicist and former deputy Germany whose “diverse and innovative” Eshel Ben-Jacob and Shimon prime minister of Russia, will share the approach to communicating physics with Yankielowicz of Tel Aviv University $1.2m award with the Japanese industrial journalists and members of the public in Israel have been awarded the 2013 chemist Akira Yoshino. has won him the German Research Weizmann Prize in Exact Sciences. Spintronics researcher Atsufumi Foundation’s Communicator Award. Dominik Berg’s PhD research on a Hirohata of the University of York, Both Fraknoi and Tolan were novel annealing approach for thin films materials scientist Hywel Jones and recognized for outreach efforts that in solar cells has garnered the top prize applied physicist Shankar N E Madathil, span many different formats. Tolan, 48, in a Europe-wide competition sponsored both of Sheffield Hallam University, presents a series of Saturday-morning by the materials firm Umicore. Berg, who are among eight UK-based researchers lectures at Dortmund entitled Between is now a postdoctoral researcher at the to win one of the Royal Society’s new Buns and Borussia – Modern Physics University of Delaware, US, received the Industry Fellowships, which are aimed for All and has written books about the 10 000 Umicore Scientific Award for his at strengthening links between academia physics of James Bond and the sinking of work at the University of Luxembourg. and industry. the Titanic. The son of a German mother Medical physicist David Chettle of Metamaterials pioneer John Pendry and a Turkish father, he regularly teaches McMaster University has won the Peter of Imperial College London has won the physics classes at a school in Dortmund Kirkby Memorial Medal for Outstanding American Physical Society’s James C where most of the children have a family Service to Canadian Physics. A separate McGroddy Prize for New Materials.
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Physics World June 2013 47 Careers physicsworld.com
Once a physicist: Janet Guthrie the possible exception of where it says ‘PhD or equivalent experience’”. I thought, “Oh wow – the Read the most exciting adventure of the 20th century!” So I applied, and I got through the first round before I was eliminated in the second – presumably new-look because I didn’t have a doctorate, but one doesn’t know.
digital How did you get to the Indianapolis 500? I spent 13 years building my own engines, supporting my racing with my salary as an magazine engineer and sleeping in the back of my tow car. I won my class a couple of times at the 12 Hours online of Sebring manufacturers’ championship race, but by 1975 I had reached the end of my rope. I was out of money and my career in physics was basically down the tubes; at one point I Janet Guthrie is a retired American race car had started a Master’s degree in physics, but driver. In 1977 she became the first woman then it got to be spring and I needed to build an to compete in the Indianapolis 500 and the engine, which conflicted with final exams, so I Daytona 500 took an “incomplete” in 1964 and that was the end of that. Then, at that 1975 nadir, somebody How did you get into physics? I’d never heard of called me up and asked if I’d I started flying at a very early age. I was putting like to take a shot at the Indianapolis 500. Well flying time in my logbook when I was 13, and – yes! Back then, any racing driver would have made a parachute jump when I was 16, but given their eyeteeth for that. I was eventually back then a woman couldn’t fly for the military successful in qualifying, and that led to a ride in or the airlines, so instead I decided to study NASCAR’s top series as well, so in 1977 I became aeronautical engineering. But then I spent my the first woman to earn a starting spot in the freshman year at the University of Michigan Indianapolis 500 and also the Daytona 500. read drawing pictures of the threads on screws and mixing up batches of concrete, which really What was the biggest challenge you faced? wasn’t what I had in mind, so I switched to Finding the money to get it done with, no question search physics. That was a much better fit. The beauty – nothing else even comes close. In 1976, of of it just entranced me – I’ll never forget deriving course, there was this great uproar about how Maxwell’s equations, and the elegance and having a woman on the track was going to result inevitability of them. in the deaths of the other drivers and all that kind translate of thing. But once the drivers realized that I knew How did you get interested in racing? what I was doing and could give them some good After I graduated in 1960 I went to work in the competition – and that I was a clean driver – then aerospace industry, and I almost bought a half- all that calmed down. It was just a matter of their share share of an aeroplane. But there was no place gaining the experience in running against me. But in the area (this was on Long Island, near New finding the money to get good equipment was York City) where I could go and have fun with it, impossible or close to it. and I needed a car, so I bought a 1953 Jaguar listen XK120 M coupé instead. That was the watershed. What are you working on now? I started doing solo competitions – called Not much! I wrote a memoir that was published gymkhanas at the time – in the car I drove to work in 2005 and I was inducted into the International every day. Oh, the Jaguar! So beautiful, so prone Motorsports Hall of Fame in 2006, which was save to breakdowns! My heart still goes pit-a-pat quite a thrill. And I still hike in the mountains here whenever I see one of them, that first XK120 M. in Colorado, where I live. I’ve quit skiing, though Then in 1963 I bought an XK140 that had been – I’m not willing to go out on the mountain and set up for racing and took it to the Sports Car subject myself to getting hit by a snowboarder. print Club of America’s Driver’s School. Being 75 sort of gets your attention. One doesn’t bounce quite so well at this age. You also applied to be an astronaut. Yes. By that time I’d been working in the Skiing, flying, racing – what gave you this love archive aerospace industry for four or five years, and I of adventure? was sort of a junior-grade all-purpose physicist; Oh, I was born that way. I think it’s just in some if we got something that nobody knew anything people’s nature to want to find out what it’s like about, I would go down to the library and become out there at the edge of human capabilities, Sign in to MyIOP at the instant expert in it. One day a co-worker and fortunately I was born in the machine age members.iop.org showed me a magazine article about NASA’s when broad shoulders and big muscles didn’t scientist-astronaut programme and said, “Look make that much difference – didn’t make any at this – you fit all these requirements with difference, in fact.
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Physics World June 2013 53 The Hamburg Centre for Ultrafast Imaging (CUI) is a Cluster of Excellence funded by the German Federal Government. The Cluster is based on the unique research environment of Hamburg AWE plays a crucial role in the and involves the University of Hamburg and its partners, the MPG, DESY, XFEL and EMBL. We invite applications for defence of the United Kingdom, by providing and maintaining Ph. D. and Postdoc Positions the warheads for the country’s in the core areas of CUI: nuclear deterrent. A. Imaging and Control of Quantum Systems B. Atomically Resolved Structural Dynamics We are a centre of scientific, engineering C. Dynamics of Order Formation on the Nanoscale and technological excellence, with some of the most advanced research, design CUI combines research projects in physics, chemistry, and biology and production facilities in the world. Our at the forefront of international research and offers a rich and unique expertise also assists the UK comprehensive course programme. Government in developing and delivering a range of innovative and integrated support ;IMRZMXILMKLP]UYEPM½IHERHQSXMZEXIHGERHMHEXIWXSETTP]4L( services, including national nuclear applicants should hold a Master of Science in Physics, Chemistry, or security and counter-terrorism solutions. Biology depending on the project. The university intends to increase AWE has an on-going requirement for the number of women amongst its academic personnel and expressly high-quality candidates for a diverse range IRGSYVEKIWUYEPM½IH[SQIRXSETTP]-RGSQTPMERGI[MXLXLI of Science roles across the company. ,EQFYVK)UYEP3TTSVXYRMX]0E[TVIJIVIRGI[MPPFIKMZIRXSUYEPM½IH female applicants. 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54 Physics World June 2013 Physics World June 2013 55 Lateral Thoughts: Aaron Leonard physicsworld.com Some overlooked basic principles
In a collision between objects A and B in an isolated system, the momentum lost by object A will be equal to that gained by object B. So says the principle of momen- tum conservation. This fundamental law of physics has become so embedded in our psyche that it seems natu- ral to apply it to situations outside physics. Muggings, for example. Object A is walking home when object B confronts it with the words “Give me all your money.” Horrocks iStockphoto/Justin The outcome, per the conservation law, is that object B leaves with the money, while object A goes home empty- handed. Yet many other principles with applications to daily life have been sadly overlooked by physicists, despite their omnipresence. As a corrective, here are a few examples. The first new principle is the ubiquitous Was That My Exit Principle. To understand how this principle works, imagine you are cruising down the motorway on your way to the town where your Aunt Sarah lives, the nearby laboratory of one of your collaborators, Was that your more embarrassing than your own intended acquisition. or a pleasant bit of countryside. Seated next to you is exit? Pinning Within seconds, the situation collapses into a black hole – depending on your destination – your spouse, your of mutual humiliation and you are both forced to quit colleague or your pet goat. You know you need to get down the the aisle entirely. off at Junction 2B; indeed, your cousin William, your exit’s precise While the paralytic power of that principle is impres- collaborator’s website or your map (which the goat is, location adds sive beyond measure, it has stunningly few practical unfortunately, eating) has told you as much. But as you up to an hour applications, so let us conclude with something more approach the region where you know the junction must useful: the Narcissistic Accidental Causality Principle. be, the only sign you can see is obscured by trees. Was to your trip. Not to be mistaken for its close cousin, the causality that your exit? 2B, or not 2B? But there is no principle, this law holds that no matter where you are Your human companions are unsure, and the goat, remedy. It is in space or time, if something goes wrong, it will surely despite its incessant bleating, is not giving up any infor- be your fault. mation. Pinning down the exit’s precise location adds simply a law The word narcissism is, admittedly, a bit misplaced somewhere between an extra 20 minutes and an hour of nature here, because rather than indicating a loving preoccu- to your trip. During this time, your spouse threatens pation with self, it is more an indictment of the same. you with divorce, your colleague pretends to re-read a Say, for example, you went shopping and forgot to buy paper from 1987, and your pet goat starts munching on the necessary butter, milk or other key ingredient for the car manual. But there is no remedy. It is simply a dinner. You have an excuse in the form of a magni- law of nature, and the best we can do is to allow for it. tude-6.0 earthquake, which happened to strike while Moving on to a more sensitive area of social interac- you were at the market. Nevertheless, dinner is still tion, let us look at the Confounded Browsing Principle. ruined, and your spouse, partner or friend is livid. You It is a little-acknowledged fact that in any bookshop, can argue that the earthquake was out of your hands, chemist’s or novelty store there exists a positive corre- but that line of argument is beside the point. You for- lation between the desirability of the item you wish to got, so you caused the ruination of a perfectly good buy and the probability that someone else will be stand- meal. It is your fault. ing right in front of it, obscuring your view. It does not Of course, I could go on. The truth is, there are matter if the shop is grand or humble, full or empty, almost as many principles as there are ways humanity but preliminary evidence does suggest that the correla- has found to undermine the millions of years of evolu- tion becomes stronger if the object you seek is of an tion that have led us to our current state of exquisite embarrassing nature. consciousness. I could, for example, write about the I The scenario plays out thusly. You are in the chem- Really Wish I Hadn’t Kept Humming “Take Me to the ist’s, searching for that perfect “family planning” prod- River” at a Crocodile Survivors Anonymous Meeting uct. In front of you, apparently gazing intently at an Principle, or the Did I Really Just Send that E-mail to array of laxatives, is your neighbour from down the my Boss Principle or even the Principles, Schminciples street – a sweet old lady you know by sight, but with – Dismissing a Revolutionary Insight Through Smug whom you have only a nodding acquaintance. There Arrogance Principle, among many others. But as we all you are, joined by your mutual interest in aisle C. You struggle to keep our heads above the ever-rising waters wait, whiling away the time by reading the labels on the of cascading principles, the Conservation of Space laxatives. But it is no use. She does not budge. After Principle prevents me from completing the list. some minutes, it dawns on you that the Confounded Browsing Principle is universal: if your neighbour is Aaron Leonard is a freelance writer based in New York City, e-mail confounding you, you must also be preventing her from [email protected] completing her purchase. You look up and find to your O Readers are invited to submit their own Lateral Thoughts. Articles horror that you are standing in front of something even should be 900–950 words, and can be e-mailed to [email protected]
56 Physics World June 2013
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