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Is this the world's smallest snowman?

“I’m riding in the midnight blue”

By James Dacey

Sizing up at just one fifth the width of a human hair, this must be a very strong contender for the smallest snowman in the world.

His body has been formed by welding together two tin microparticles (10 µm in diameter), which are usually used in the calibration of electron microscopes. A focused ion beam was deployed to etch out his eyes and mouth and a tiny fleck of platinum forms the nose.

The little fella’s creator is researcher David Cox who works at the National Physical Laboratory (NPL) in London. He was taking time out from his usual job of fabricating devices for the Quantum Detection Group. “I guess I was just born to make stuff,” Cox writes on his homepage.

There is a video on the NPL homepage showing just how Cox sculpted his miniture friend.

Fish swishing mixes the oceans

Fluid mixing processes in the oceans play a major part in governing the world’s heat and carbon balances as well as providing a food delivery service to a variety of organisms. The wind and tides play key roles in this process but several research groups have claimed that, perhaps surprisingly, the combined motion of marine organisms could also make a significant contribution to global mixing. Now, a pair of mathematicians in the US have developed a model, which they say suggests that this could indeed be the case.

The idea that marine swimmers are having a significant impact on ocean-mixing was first proposed in the 1960s by Walter Munk, a celebrated researcher in the oceanography community. “Munk set out to list all the factors that could influence mixing in the ocean, and he threw ‘biological processes’ in there, by which he meant the effect of swimming organisms such as fish or plankton,” says Jean-Luc Thiffeault of the University of Wisconsin, who was involved in this latest research.

Despite his insight, however, Munk did not have the data nor the means to establish the extent to which marine life is making a contribution. Due to a lack of experimental results and ongoing debates surrounding the complex interactions between the atmosphere and the oceans, Munk’s idea seemed to fall by the wayside. One of the major objections has always been the issue of scaling – researchers have been unable to see how organisms of the order of a few centimetres could have any significant impact over the thousands of kilometres of oceans.

Swimming into the 21st century

Earlier this year, however, physicsworld.com reported on how researchers in California had demonstrated an alternative mixing mechanism that could enable a significant contribution from smaller organisms. By studying the movement of jellyfish through a water column, the scientists looked at how marine animals drag water with them as they swim up and down. As water density increases with depth, the swimming fish affect the total potential energy of the fluid leading to further ambient fluid motions and eventually molecular mixing.

In this latest research, Thiffeault and his colleague Steve Childress from New York University take this mechanism as a starting point and develop a more complex physical model to gauge the effect this mixing could have on a global scale. They model marine organisms as spheres of 1 cm radius that are travelling at 1 cm/s because these are the parameters of krill, which is an exceptionally common species across the oceans.

In the model the spheres move around randomly without interacting, much like particles in an ideal gas. Thiffeault and Childress are interested in the displacement of water as a result of these moving spheres. Given the large number of spheres involved, tools from statistical physics are used to calculate an “effective diffusivity”, which is related to the flux of molecules triggered by the disturbed sea water.

By no means salt of the Earth

Based on well-established estimates of total biomass in the oceans, the researchers calculate an effective diffusivity triggered by marine swimmers of 6 × 10^–5 cm²/s. Significantly, this is four orders of magnitude larger than for the equivalent volume of salt, meaning that if all marine life behaved like grains of salt then their impact on mixing would be substantially reduced. Although it is still 100 times smaller than the effect caused by of heat redistribution in the ocean, it suggests that marine swimmers are indeed making a noticeable contribution to ocean mixing, say the researchers.

What is more, the researchers say that this figure is likely to be a lower limit on the true contribution that marine animals make to ocean mixing. If the model were to include the effect of vortices in the wake of a moving fish, or fish “sticking” due to the viscosity of seawater then the mixing effect could be enhanced. Fish travelling in large schools could also increase the effect as the mixing effect scales nonlinearly with size of body and water currents may also travel through the school.

“The model is simplified but will allow future studies to probe a wide variety of scenarios of fish schooling and the corresponding fluid mixing that is achieved,” says John Dabiri of California Institute of Technology who carried out the earlier research on water displacement. “Water parcels can become trapped within the shoal and transported over large distances. This process can significantly enhance the stirring of the water, which ultimately leads to enhanced mixing”.

Dabiri also recognizes the significance of this latest research to climate science. “The model appears sufficiently flexible that one could simulate various scenarios of future animal population dynamics, perhaps including dynamics caused by climate change.

Thiffeault told physicsworld.com that he hopes to develop this research by making the model more sophisticated and testing the results through collaborations with experimental teams.

This research is available for free download on the arXiv preprint server.

Budget deficit threatens Japanese science

Researchers in Japan are expressing concerns that their research funds could be cut in half – or possibly even terminated – following the government’s decision to slash over $35bn from next year’s budget. A number of research labs in the country, including the Spring-8 synchrotron in Hyogo and the KEK particle-physics lab in Tsukuba, could see large cuts to their research budgets next year that, they say, would threaten the county’s competitiveness in science.

In a statement issued yesterday, Atsuto Suzuki, director general of KEK, said that it could take “years” for the country to recover from the cuts. “Neglect of the importance of fundamental research could result in a long-term stagnation of our national competitiveness,” he says.

The problems have been brewing since early November, when the new Japanese government, elected in August, announced plans to slash next year’s budget, which begins in April 2010. Some suggest the budget cuts are because the new government – led by Prime Minister Yukio Hatoyama from the Democratic Party of Japan – promised during the election campaign to make it free for students to attend public high schools. Such schools currently charge tuition fees and are not compulsory to attend even though most of the population do so.

If the government starts slashing funds it really hurts Japanese science and its credibility Hitoshi Murayama, University of Tokyo

However, this pledge significantly adds to the budget of the Ministry of Education, Culture, Education, Science and Technology (MEXT), which is dominated by elementary and middle school education. As a result, MEXT is seeking to cut its expenditure elsewhere, which means that science could be in the firing line.

In early November the Japanese government set up working groups to re-evaluate around 400 ongoing research projects in the country as well as university budgets for next year. These working groups report to the Government Revitalization Unit (GRU) – an 11-member panel chaired by Hatoyama himself) – that is mostly made up of politicians, industry leaders and a few academics.

This arrangement has caused concern in the scientific community that they are not being properly represented when deciding the fate of their projects. “We scientists do not have any opportunity to defend our programmes,” says Hitoshi Murayama, director of the Institute of the Physics and Mathematics of the Universe (IPMU) at the University of Tokyo and one of the leaders against the proposed budget cuts.

Worrying times ahead

The working groups have now evaluated the 400 projects and budgets for universities. “Only very few came out unscathed,” says Murayama. “Most of them were recommended for reduction, and quite a few for near termination.” Among those earmarked for cuts are the Spring-8 synchrotron in Hyogo, which could see its budget slashed by a third to a half, as well as no money going towards what would be the world’s fastest supercomputer to be built at the RIKEN lab.

At the end of November four Nobel laureates, including Makoto Kobayashi from Kyoto University, who shared the 2008 Nobel Prize for Physics with Yoichiro Nambu and Toshihide Maskawa for their work on broken symmetry in particle physics, took the unprecedented step of criticizing the government’s plan to cut the research budget. The laureates called on the government to listen to scientists when deciding to allocate funding for research projects.

Things were made worse in late November when the GRU finished looking at the overall budget for universities and national laboratories, like the KEK particle-physics lab in Tsukuba and the J-PARC experimental complex in Tokai. Although the GRU proposed having another review about the regular operating budget for personnel and infrastructure at universities, 50% of the members of the GRU voted to terminate the operating budget for projects such as the Superkamiokande neutrino experiment at J-PARC, the B-meson factory at KEK and Japan’s involvement in the Subaru optical and infra-red telescope in Mauna Kea, Hawaii.

Research concerns

Murayama is also concerned about the threat to the IPMU. The institute is part of Japan’s World Premier International Research Center Initiative (WPI programme), which founded five institutes from nanoscience to immunology in 2007 to attract researchers from abroad to work in Japan. The five institutes are funded for 10 years and each receive $10m per year and Murayama is bracing himself for 50% cuts to the WPI programme.

As the IPMU’s costs mostly go on salaries, this could potentially mean cutting staff numbers in half. “Previously there had not been many jobs for non-Japanese scientists,” says Murayama, “so this hurts the case for science in Japan.”

Negotiations will now take place in the Ministry of Finance with a finalized budget for 2010 set to be made at the end of December. “I am very worried at the moment,” says Murayama. “If the government starts slashing funds it really hurts Japanese science and its credibility.”

Taking the pulse of the Vulcan laser

For a view of what it’s like to work on a giant laser, tune in to this interview with fusion scientist – and Vulcan laser user – Kate Lancaster, as she talks about the basic physics research that is taking place there.

Laser fusion gets HiPERactive

These are exciting times for laser fusion. In the next couple of years, the US National Ignition Facility (NIF) should reach “ignition” – the point at which a fusion device starts to kick out more energy than it takes in. But what happens after that? After all, releasing the energy of the stars is one thing; releasing it in a form that could actually turn on some lights is another.

One project that aims to bridge this gap is called the European High Power Laser Energy Research Project – HiPER for short – and it’s the subject of Physics World‘s latest video feature. In the first video, HiPER director Mike Dunne describes how the project will work, and outlines some of the technological hurdles that need to be overcome to transform laser fusion into a practical power source.

When he’s not co-ordinating the efforts of researchers at HiPER’s 26 member institutions, Dunne is also head of the UK’s Central Laser Facility (CLF) in Oxfordshire. The CLF is home to a number of lasers – including Vulcan, one of the highest-intensity lasers in the world – that provide possible templates for the high-power, high-repetition-rate system that HiPER will need. For a view of what it’s like to work on these giant lasers, tune in to our interview with fusion scientist (and Vulcan laser user) Kate Lancaster, as she talks about the basic physics research taking place there.

Are quasars star-making machines?

A quasar is a black hole that draws in matter from the surrounding space. Its strong gravitational field imposes a huge kinetic energy on this matter, causing it to radiate across a wide range of wavelengths. According to new research, however, quasars do more than consume matter – they can also create stars. Indeed, David Elbaz, of the CEA in Saclay, France, and colleagues believe that quasars might in fact be capable of building entire galaxies.

Supermassive black holes, up to hundreds of millions times more massive than the Sun, are found in the centre of most large galaxies. The black holes inside nearby galaxies – and in the Milky Way – do not consume matter and in these galaxies stars are known to form when gas and dust particles cool and collapse due to gravitational instabilities. However, the star-forming process and therefore the relative ordering of black hole and galaxy creation is less clear-cut in the early universe. “Some models suggest a tightly linked co-evolution between black holes and the stars around them,” says Elbaz. “It is possible that the black holes grow faster in the beginning and then the galaxies catch up, but astronomers have no real grasp yet on the exact physics involved in this mechanism.”

In 2005 astronomers carried out a detailed study of 20 quasars about four billion light years from us and discovered that 19 of these, as expected, consisted of supermassive black holes surrounded by a galaxy. However, one of them, HE0450-2958, contained no trace of an accompanying galaxy. Elbaz and colleagues have now studied this quasar at infrared wavelengths using the Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope in Chile, in order to look for dust that might be obscuring the galaxy. However, although they found evidence for dust heated near to the quasar itself, they found no sign of a hidden galaxy. Instead, they found that an apparently unrelated galaxy some 22,000 light-years away from the quasar is producing stars at the equivalent of about 350 Suns per year – some 100 times faster than typical galaxies in the local universe.

Although the quasar is still ‘naked’, it will eventually be ‘dressed’ David Elbaz, CEA Saclay

Combined with earlier observations showing that HE0450-2958 is injecting radio jets and accompanying gas into the galaxy, the researchers concluded that the quasar might be responsible for this rapid star formation and therefore creating its own host galaxy. They point out that the quasar is moving towards the galaxy relatively slowly – at a few tens of thousands of kilometres an hour – and that it should therefore merge with it at some point in the future. “Although the quasar is still ‘naked’,” says Elbaz, “it will eventually be ‘dressed’ when it merges with its star-rich companion. It will then finally reside inside a host galaxy like all other quasars.”

More powerful jets

Elbaz and co-workers maintain that their hypothesis could explain a well-established correlation between the mass of a black hole and the mass of the stars that surround it (it is always smaller by about a factor of 700) because more massive black holes would produce more powerful jets, leading to more star formation. The researchers acknowledge that HE0450-2958 might still be found to sit within a galaxy – such a galaxy would just have to be much fainter or much smaller than the galaxies typically found around quasars. But they maintain that even if such a galaxy were found this would not fundamentally change their conclusion. “We would still have found that a quasar can drive the formation of stars, and given that the companion galaxy will eventually merge with the quasar it will still make up a significant fraction of the final galactic mass.”

Abraham Loeb, an astronomer at Harvard University, believes that Elbaz’s team “provides interesting new data on the environment of HE0450-2958”. However, he cautions that the rapid star formation in the neighbouring galaxy might be explained using a different mechanism – galaxy merger – if the quasar is indeed found to be already immersed in a galaxy. “Numerical simulations of galaxy mergers indicate that during close passage, cold gas is driven towards the centres of the interacting galaxies and that this leads to star formation” he says, adding that “one should also keep in mind that this is only one system, and generalizing the conclusions to all quasars is premature”.

Elbaz agrees on the importance of searching for similar systems in the distant universe – in other words looking for quasars and star-forming regions separated by significant gaps – using the next generation of ground- and space-based telescopes. He acknowledges that until they do this their hypothesis is likely to remain controversial because the universe contains huge amounts of gas that could be used to create new stars and yet galaxies have been creating ever fewer stars, leading many researchers to believe that gas-guzzling quasars in fact suppress star formation. “It may well be that quasars first help star formation, then in a second stage quench it,” he adds.

The research is published in the journals Astronomy and Astrophysics and The Astrophysical Journal.

Physics takes the wobble out of rowing

Every year, teams of rowers from Oxford and Cambridge universities sweep along the Thames river at close to 15 miles per hour in one of the world’s most famous boat races. In each boat, the oars lie alternately left and right to generate – one might assume – an even push. But is this the most effective rig?

Possibly not, according to John Barrow, a theoretical physicist at Cambridge. While not a rower himself, Barrow has produced a formula that shows which rigs will naturally travel in a straight line, without a finite mechanical moment that causes them to wiggle left and right. For an eight-oared boat there are several possible zero-moment rigs – and the traditional Oxbridge “eight” isn’t one of them.

“If you tinker with the way you seat the oarsmen it is possible to have a zero moment,” he explains. “For a four there’s only one way to do it, but for the eight, I discovered, there’s four ways to do it…Then I could show that this was equivalent to an interesting little combinatorial problem.”

Starboard to port

Barrow approached the problem by considering the simplified mechanics of rowing. The action of each oarsman, he assumed, generates a force in the rowlock that can be split into two perpendicular components: one in the backwards (bow to stern) direction, and the other in the sideways (starboard to port) direction. He calculated the individual moments by multiplying each of these sideways forces with their distance from the stern, and then added all the products to give the total moment.

The four best eights

As it turns out, this summation has a neat general formula, where the individual moments get incrementally bigger with distance from the stern and have opposite signs for starboard and port. So, for example, a traditional Four, which is arranged alternately, would give a total moment of 1 – 2 + 3 – 4 = –2. To get a zero moment and avoid wiggling, the rig would instead need the second and third rowers on the same side – or, in Barrow’s formula, 1 – 2 – 3 + 4 = 0.

In fact, the formula shows that, so long as the total number of oarsmen is divisible by four, any rowing boat be arranged to have a zero moment. It means there are 29 non-wiggling twelves, 263 sixteens and 2724 twenties. The eights have a mere four, of which just two – so-called “Italian” and “German” rigs – have ever been put into common practice (see figure).

Switching around oarsmen

Nick Caplan, a biomechanist at Northumbria University, thinks Barrow has tackled an “interesting and relevant” topic in rowing mechanics. However, he says that coaches and biomechanists will attempt to balance boats themselves by switching around oarsmen, who tend to exhibit subtle differences in their “force-time profile” or the way they sweep the oar. “The paper assumes that the force-time profile is the same on all oars,” he adds. “[But] if coaches could use the information presented in the paper in conjunction with knowledge of the shape of the force–time profile for each member of the crew, then it may be possible to improve boat balance and thus improve performance.”

It’s certainly not enough to turn an average crew into a winning crew Anu Dudhia, Oxford University

Anu Dudhia, a rower and physicist from Oxford University, thinks Barrow’s conclusions might not work in practice. He points out that three of the zero-moment eights have the front and back rowers on the same side, which would mean the back rower has to put his oar into the “dirty” water left from the front. He also says the effect of the wobble is usually small: “It’s certainly not enough to turn an average crew into a winning crew, as [Barrow] rather implies. While some top-level eights adopt unconventional rigs, it’s not for this reason.”

Barrow admits that his study is idealized. Still, he thinks it would be straightforward to create a model that would test the different rigs, and is keen to see if his formula can be modified for the analysis of other systems, such as insects with many legs.

The research is under review at the American Journal of Physics, and is available online on arXiv.

Lasers simulate magnetic field in a BEC

Physicists in the US have become the first to use laser light to make neutral, ultracold atoms behave like charged particles in a magnetic field – even though the atoms have no charge. The set-up could be used as a “quantum simulator” to gain a better understanding of how electrons in solid materials respond to magnetic fields. In particular, it could shed further light on the fractional quantum Hall effect (FQHE), which could someday be exploited in quantum computers.

Neutral atoms of integer spin are now widely used to simulate the quantum behaviour of condensed-matter systems, such as superconductivity, by cooling them to such low temperatures that they form a Bose–Einstein condensate (BEC), in which the atoms settle in the same quantum state and move coherently as though they are a single entity. The interactions between the atoms can then be adjusted by external magnetic fields, thereby allowing physicists to “dial up” interactions that mimic those between electrons in a solid.

But because the atoms in a BEC are neutral, it has been hard to simulate the effects of a magnetic field on electrons and other charged particles, which is critical for understanding superconductivity and other effects related to the charge and spin of the electron. Physicists had got around this problem by physically rotating a BEC, because the coriolis force has a similar effect to a magnetic field. Researchers have had some success in creating vortices in rotating BECs – vortices that are similar to those that occur when certain superconductors are exposed to a magnetic field.

Fiendishly difficult

However, these experiments are fiendishly difficult, particularly at the large angular velocities needed to simulate magnetic fields strong enough to bring out the FQHE. The new research, carried out by Yu-Ju Lin and colleagues at the Joint Quantum Institute of NIST and the University of Maryland in the US and the National Polytechnic Institute of Mexico, allows a magnetic field to be simulated in a BEC, without rotating the condensate itself.

The experiment involved first forming a BEC of about 250,000 rubidium-87 atoms held at about 100 nK in an optical trap before firing perpendicular laser beams at the atoms. An atom can absorb a photon from one of the beams, and then be stimulated by the second beam to emit a photon in a specific direction. The net effect is a change in the canonical momentum of the atom.

Vortices in a BEC

A magnetic-field gradient was then applied across the BEC, which changes the energy levels of the atoms – and therefore the momentum transfer process. The result is that the momentum change acts in one direction on one side of the BEC and in the opposite direction on the other. This can be described mathematically as a vector potential, the “curl” of which is identical to a magnetic field.

Lin and colleagues confirmed the simulation of a magnetic field by looking for a matrix of vortices in the BEC. Because the vortices are tiny – just nanometres in size – they cannot be spotted using light. So the team switched off the optical trap, causing the BEC to expand and magnifying the vortices until they were large enough to see using visible light. As there are no atoms at its centre, the vortex appears as a black dot against the lighter background of the atomic gas.

“The vortices are proof that we have simulated a magnetic field,” Lin told physicsworld.com. Furthermore, the vortices appeared to be arranged in a regular lattice – something that is also predicted by theory.

More work to be done

Martin Zwierlein of the MIT-Harvard Center for Ultracold Atoms, who was not involved with the research, agrees with Lin and colleagues that more work needs to be done before the system can be used to study quantum effects like the FQHE, which is of particular interest because it could some day be exploited in quantum computers.

To observe this effect a very thin sheet containing a small number of strongly interacting electrons is cooled to very low temperature and a strong magnetic field is applied. At certain field strengths, the electrons condense into a liquid-like collective state containing quasiparticles, each of which carries a fraction of electrical charge and a quantized amount of magnetic flux. Some physicists believe that these quasiparticles could be used to store and process information in a topological quantum computer.

One challenge will be to boost the strength of the simulated magnetic field. According to Lin, the simulated field is not significantly stronger than fields created by rotating a BEC. In addition, an optical lattice must be created to divide the BEC into very thin slices, each containing a small number of atoms.

The research is reported in Nature.

Puppetry of quantum mechanics

The Bohr-Einstein Debates, With Puppets from Chad Orzel on Vimeo.

By Hamish Johnston

A few months ago physics blogger (and Physics World contributor) Chad Orzel promised his readers that if they stumped up at least $2000 for a charitable appeal, he would put on a puppet show about the famous debate over the interpretation of quantum mechanics between Niels Bohr and Albert Einstein.

He raised over four grand…so raise the curtain and enjoy…

The action opens at the 1929 Solvay conference with Einstein (played by a bichon stuffed toy) expressing his concerns with quantum theory in an appalling German accent — ‘if vee detect zee electrons vun at a time…’

Bohr — a black Labrador retriever — responds and the debate is underway.

The supporting cast includes Paul Ehrenfest as a hedgehog and Paul Dirac as a “disinterested” elephant.

Oh, and Orzel’s dog (a real dog) plays the role of a sceptical audience.

The show is a delight — but I’m left wondering how Orzel got through it without contracting a serious case of the giggles! I suspect many takes were involved.

Why the canine obsession? Orzel has just published a book called How to Teach Physics to your Dog.

And you can read Orzel’s Physics World article on measuring the electron’s electric dipole moment here.

Fancy a flutter on the Higgs?

By Hamish Johnston

Alexander Unzicker wants you to place a bet on the Higgs boson — or more precisely whether it will be discovered at the LHC.

He has set up a site called www.bet-on-the-higgs.com, where he explains how you can bet on the discovery of the Higgs at intrade.com — which is a ‘prediction market’ based in Ireland.

If you are tempted to place a bet, please make sure that doing so is legal where you live.

Here in Dirac House I can’t even look at intrade’s Higgs pages — they are ‘forbidden’ — but Unzicker has posted a screen shot of his intrade account, which I have reproduced below.

Buy low, sell high

Sorry about the fuzziness, but if you squint you can see that he is wagering on the ‘Observation of the Higgs Boson Particle’.

What’s not clear from the screen shot is whether Unzicker — who teaches maths and physics in Munich — is betting for or against the discovery…you’ll have to check his website to find out.

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Is this the world's smallest snowman?