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Home » Page 1430

Australian climate researchers face death threats

Climate researchers in Australia have been rocked by revelations that several scientists have received aggressive e-mails and even death threats. The intimidation, which first came to light in the Australian press early last month, has resulted in some of the targeted researchers being moved into more secure offices. The abuse comes as the Australian minority Labor government led by Prime Minister Julia Gillard is framing legislation that would determine a price that businesses have to pay for releasing carbon into the atmosphere.

One scientist who has been under attack is marine biologist Ove Hoegh-Guldberg, who directs the Global Change Institute at the University of Queensland, Brisbane. He is known for speaking out about his research into the deadly effects of increased sea temperatures on corals. On 13 June he was sent five threatening e-mails from anonymous sources, which included the line “Eat shit and die to [sic] lying communist asshole”.

Another scientist who is affected is Will Steffen, head of the Climate Change Institute (CCI), based at the Australian National University (ANU) and a member of the Climate Commission that advises the Australian government. He has received a death threat and “a spate of obnoxious and nasty e-mails” after writing a commission report published on 24 May that recommends the country “strongly and urgently” curbs carbon emissions.

Completely intolerable

In response to the harassment, the ANU has now moved nine staff members of the CCI, including Steffen, to a more secure location, which requires card access. “It’s completely intolerable that people be subjected to this sort of abuse and to threats like this,” Ian Young, vice-chancellor of the ANU, told Physics World. The police have been advised but have not investigated so far.

Gillard is yet to determine a specific pricing for the carbon tax, with the government’s eventual decision promised for this month. However, the government has been publicly attacked on its policy, especially by the Conservative opposition led by Tony Abbott. He says the policy is a “great big new tax” on every citizen and that the nation’s lucrative coal, gas and iron-ore exporters will be forced to shed jobs as a result.

The more controversial the area, the more important that any researcher should feel free to argue a case based on evidence without fear of reprisalSuzanne Cory, president of the Australian Academy of Science

In a statement, Suzanne Cory, president of the Australian Academy of Science, defended the right of researchers to do their work free from abuse and threats of violence: “The more controversial the area, the more important that any researcher should feel free to argue a case based on evidence without fear of reprisal.”

Intimidation tactics

According to Susannah Eliott, head of the independent Australian Science Media Centre, scientists in Australia have been subjected to threats for a few years, but they are now becoming increasingly wary of talking to the media for fear of further intimidation. Indeed, David Karoly, a meteorologist from the University of Melbourne, says that every time he appears in the media he then gets threatened, which has now got “more highly offensive and abusive”. One such recent example he received was a message stating that “Global warming is the biggest fraud in the history of mankind. People that promote it need to be put down!”

Michael Mann, director of the Earth System Science Center at Pennsylvania State University and creator of the widely accepted “hockey-stick graph” showing the recent surge in temperatures caused by climate change, says he finds it disturbing that Australian climate scientists have been subjected to the same sort of intimidation tactics that he has had to contend with in the US. “It would seem to confirm a level of coordination and even orchestration to the attacks against climate science and climate scientists,” he says.

Introducing the ‘wrinklon’

A new quasiparticle called the “wrinklon” could help explain why materials as diverse as graphene and household curtains wrinkle in much the same way – despite their very different length scales. The particle has been introduced by researchers in Belgium, France and the US as a result of measurements on a wide range of materials on length scales from micrometres to metres. While the work may not lead to more attractive curtains, wrinkles do turn out to affect the electronic properties of graphene and the analysis could therefore influence the development of graphene-based devices.

Wrinkles can appear whenever a sheet of material is fixed along one or more edges. In the case of a fabric curtain, the wrinkles are close together at the top and the space between wrinkles increases continuously further down the curtain. The emergence of wrinklons – by Pascal Damman and colleagues at the universities of Mons, Paris and California Riverside, as well as the Massachusetts Institute of Technology – reflects this change and defines the patterns of wrinkles seen in such materials.

Self-similar patterns

Physicists have enjoyed great success in describing complex systems in terms of quasiparticles – collective excitations that behave much like discrete particles. This latest wrinklon quasiparticle describes a localized region with a high degree of stretching where two wrinkles merge into one (see figure). Indeed, if you happen to be sitting next to a curtain, then you can probably see a few wrinklons, which may appear depending on the tension in the material and its physical properties such as thickness and elasticity.

By studying images of wrinkled materials, the team led by Damman found that the patterns are self-similar. This means that the same pattern occurs in different regions of the material but on different length scales. As Damman explains, “If you look at a photograph of a region of the curtain without knowing the length scale, you can’t know where it was taken.”

The team demonstrated the universal nature of wrinkling by studying materials as diverse as graphene (a sheet of carbon just one atom thick), curtains made of fabric and rubber, as well as paper and plastic sheets. For each material the team measured the distance between neighbouring wrinkles (the wavelength) as a function of the distance from the fixed edge of the material (the top of a curtain, for example). They also measured the tension on the material – in the case of curtains this is supplied by the downward pull of gravity. The Young modulus (or elasticity) and thickness of the material were also measured.

One power law for all

The team found that the “normalized wavelength” (the wavelength divided by the thickness of the material) of ripples in a number of materials have the same power-law relationship with the “normalized distance” from the fixed edge. This distance includes a term that is a function of the tension, thickness and elasticity of the material.

When plotted on a log–log graph, measurements on materials ranging from graphene to fabric curtains fall on the same line. “This is the best evidence yet that wrinkling occurs in the same way over a wide range of length scales,” says Benjamin Davidovitch of the University of Massachusetts, Amherst, who was not involved with the experiment. “It has never been demonstrated with such clarity,” he adds.

According to Damman, the findings could be important to those studying graphene. As the wrinklons are affected by the thickness of the material, it should be possible to determine the thickness of a sample simply by looking at its wrinkles. Researchers could therefore distinguish between graphene that is one atom thick and samples that are two or three atoms thick – something that can be difficult to do.

These latest results could also be used to ensure that graphene devices are made wrinkle-free, or with specific patterns of wrinkles. This could be important for those developing electronic devices based on graphene, because the electronic properties of the material are affected by wrinkles. According to Damman’s colleague Chun Ning Lau of the University of California, Riverside, devices with desirable properties could be created by “straintronics” – whereby specific wrinkle patterns are created by controlling the strain on graphene.

The work is describe in Phys. Rev. Lett. 106 224301.

Top cosmologist to teach at humanities dream school

USPS.jpg
Krauss will bring cosmology into the humanities

By James Dacey

The physicist and popular-science author, Lawrence Krauss, will join a star-studded array of academics to teach at a private university in London called the New College for the Humanities.

The new university is the brainchild of A C Grayling, a philosopher at the University of London, who is well known in the UK through his regular appearances in the media. Grayling says the university will bring a much needed boost to the arts and humanities in the UK, which are being squeezed in state-supported universities due to budget cutbacks. Its business model takes inspiration from the US Ivy League universities as students will pay £18,000 a year for tuition fees – double the maximum that most UK universities can charge.

Students will be offered a very broad syllabus and will be encouraged at every turn to take a critical outlook. They will be treated to lectures by world-leading academics including Richard Dawkins who will teach evolutionary biology and science literacy, and Stephen Pinker who will cover philosophy and psychology.

Among this dream team will be Lawrence Krauss, the author of Physics of Star Trek and several other popular-science books. He told me that he plans to give an introduction to the modern view of the universe, and he will touch on other subjects, including quantum mechanics. “Science literacy will play a large part in the program, as it should,” he said. “A literate person should have the same kind of fluency in the ideas of science that they have in the arts and humanities.”

Krauss says that he will pitch the course to be understood by students with little scientific background. “Based on my teaching experience at a variety of US institutions, I believe one can proceed rather far in this regard with minimal background – with motivated students it should be fun” he said.

But not everybody in the UK has been as enthusiastic as Krauss about Grayling’s new venture. Since the philosopher announced his plans for the new university at the beginning of June, he has been attacked by critics who have dismissed the venture as elitist or opportunistic. Last week, both Grayling and Dawkins were both confronted by angry protesters during public lectures, with Grayling’s talk being evacuated after a smoke bomb was let off. Even the Mayor of London, Boris Johnson, has chirped in with a letter to the Telegraph in which he labels the university as “rejects college” – for rich kids who weren’t bright enough to get into Oxford and Cambridge.

Grayling has since struck back by emphasizing the fact that 30% of students will be offered financial support, funded largely by the fees of the wealthier students. He also argues that foreign students at state-funded universities already pay in the region of £18,000, and many universities have been increasing their overseas student intake for some time. You can read Grayling’s full arguments expanded in this opinion piece published in the Independent yesterday.

So I bid Lawrence good luck. But with continuing criticism, including a big thumbs down from the president of the National Union of Students, it may not be plain-sailing. The celebrity professors will have to use all their brain power to win the hearts and minds of the British public.

Hackers steal quantum code

While in principle unbreakable, quantum cryptography is known to have weaknesses in practice. One shortcoming has now been graphically illustrated by physicists in Singapore and Norway, who have been able to copy a secret quantum key without revealing their presence to either sender or receiver. The researchers are now working to remove the loophole they have exposed.

Quantum cryptography involves encoding messages using a key that is rendered secret by a quantum-mechanical principle – that the act of measuring affects the system being measured. In one popular scheme, the sender “Alice” sends a key in the form of a series of polarized single photons to the receiver “Bob”. Alice polarizes each photon at random using either a horizontal–vertical polarizer or a polarizer with two diagonal axes. Bob detects each photon by also randomly selecting one of the two different polarizers.

If Bob happens to pick the same polarizer as Alice, then he will definitely measure the correct polarization of a given photon. Otherwise, as the uncertainty principle dictates, there is a 50% chance he will get it wrong. Once he has made all the measurements, Bob asks Alice over an open channel which polarizers she used for each photon and he only keeps the results for those measurements where he happened to pick the correct polarizer, and this series of results becomes the secret key.

Catching Eve

An eavesdropper, “Eve”, who seeks to measure the polarization of the photons sent by Alice would reveal her presence because, given a long enough string of photons, the probability of her correctly guessing Alice’s sequence of polarizers becomes practically zero. When she makes incorrect measurements, she randomizes the polarization. This means that in some of the cases where Bob should make a correct measurement, he makes a wrong one. So, again speaking openly with Alice and comparing a small subset of the key, Bob realizes there is an intruder if that subset contains errors.

Now Christian Kurtsiefer and colleagues at the National University of Singapore and researchers at the University of Trondheim have found a way to hide Eve’s eavesdropping by exploiting a weakness in the single-photon detectors used in many commercially available quantum-cryptographic receivers. This involves Eve using a bright light to “blind” the four avalanche photodiodes that Bob uses to detect photons in each of the four different polarization states.

The blinded photodiodes are no longer sensitive to single photons, but instead behave like classical detectors that generate a current proportional to the intensity of the incoming light and respond to pulses of light above a certain intensity threshold. “The detectors are like human eyes, which at night can almost distinguish single photons but during the day are unable to do so because they are flooded with light,” says Vadim Makarov of the Trondheim team.

Alice and Bob are oblivious

Eve intercepts each of the photons sent by Alice and measures them using randomly chosen polarizers. With each measurement Eve sends a bright pulse of light, above the intensity threshold and with the same polarization as the photon measured, to Bob’s detectors. This removes Bob’s ability to randomly assign polarizers for each measurement. Instead he is constrained to the same sequence of polarizations as obtained by Eve. This means that when Bob and Alice publicly compare the subset of the key, they find no errors. In other words, Eve has found out the key and has remained hidden while doing so.

Kurtsiefer and colleagues attacked an existing 290 m-long fibre link on the campus of the National University of Singapore. Using equipment that fits inside a suitcase, they intercepted single photons travelling along the fibre and then re-emitted the corresponding bright light pulses. During a 5 min interval they intercepted more than eight million photons and then forwarded the corresponding bright pulses, with every single pulse being registered by Bob in the correct detector.

Now we have shown that that vulnerability can be practically exploitedVadim Makarov, University of Trondheim

This is not the first experiment to reveal that a quantum key can be surreptitiously copied. In the past three years Hoi-Kwong Lo of the University of Toronto and colleagues have demonstrated a number of loopholes in a commercial quantum-cryptographic system, while last year Makarov’s research group showed that commercial systems can be disabled using bright light. But, says Makarov, this latest work represents the first time that anyone has built a complete quantum eavesdropper and actually stolen a key. “Previously, we showed that quantum-cryptography systems were vulnerable,” he explains, “and now we have shown that this vulnerability can be practically exploited.”

However, Makarov, believes this vulnerability could be corrected. One possible solution, he says, is to place a small single-photon source just in front of Bob’s detectors and switching it on at random intervals to ensure that the detectors can still register individual photons. If the detectors repeatedly fail, then the operators would be alerted to Eve.

“The whole purpose of our research is to try and make quantum cryptography more secure,” says Makarov. “All security technologies go through this proving phase.”

Nicolas Gisin, a physicist at the University of Geneva in Switzerland and co-founder of quantum-cryptographic manufacturer ID Quantique, welcomes the latest research, pointing out that his company has now developed counter-measures to deal with such attacks. “The only way to guarantee good implementation of quantum cryptography is by independent tests,” he says. “In this sense, quantum hackers do a very useful job.”

The research is published in the online journal Nature Communications 10.1038/ncomms1348.

‘Plasmon ruler’ measures tiny distances in 3D

The first ever 3D “plasmon ruler” has been unveiled by researchers in the US, Germany and France. Until now, such nanoscale measuring devices were limited to measuring distances in just 1D, which meant that they could not be used to monitor 3D processes in biological and soft matter. The new sensor could prove useful for monitoring structural changes in biological samples, such as protein folding and DNA interactions.

Metals can absorb light by creating plasmons, which are particle-like collective excitations of conduction electrons at a metallic surface. A 1D plasmon ruler exploits the fact that the plasmon resonances of two metallic nanoparticles couple with each other when they are close together. The spectrum of light associated with the plasmons is strongly shifted toward the blue or red depending on how close or far apart the nanoparticles are to each other.

For example, in previous studies two gold nanoparticles were connected together via a single strand of DNA. When complementary double-stranded DNA was then added, researchers observed a significant blueshift in the light spectrum of the plasmon resonances. Since double-stranded DNA is much stronger than single stranded, the nanoparticles are pushed apart – that is, the distance between them becomes larger. By continuously monitoring the spectrum of the gold particles, the dynamics of the DNA “hybridization” could be recorded.

Stack of gold nanorods

Now, Laura Na Liu of the Lawrence Berkeley National Laboratory and colleagues at the University of Stuttgart and the University Blaise Pascal in Aubière have extended this concept so that it works in 3D. In their new plasmon ruler, the researchers employed a stack of five gold nanorods arranged in a “H” shape with the central rod acting as the horizontal bar of the H (see image). The other two pairs of rods were chosen so that they acted as quadrupolar “antennas” for visible lightwaves. When biological molecules are attached to the structure, the central rod or quadrupole antennas move relative to each other, which results in a shift of the plasmon resonances of the system that can be measured, just like the 1D ruler. The researchers fabricated their set-up using high-precision electron-beam lithography and layer-by-layer stacking nanotechniques.

“Compared with its 1D counterpart, our ruler offers additional degrees of freedom – such as rotating, twisting and tilting – to detect the dynamic behaviour of bioentities,” Liu told physicsworld.com.

New generation of plasmon rulers

According to the researchers, the concept can be applied to single metallic nanocrystals joined together by oligonucleotides or peptides. This could lead to a new generation of plasmon rulers capable of monitoring events occurring during a wide variety of macromolecular transformations in 3D. Such transformations include DNA interacting with enzymes or proteins, protein folding and the dynamics of peptide motion, and the elastic vibrations of cells membranes in situ and in vivo, to name but a few.

“Metallic nanoparticles of different sizes could also be attached at different positions on DNA or proteins and each metallic element may move individually or collectively in three dimensions,” explains Liu.

The team now hopes to make 3D plasmon rulers using biochemical linkers. The concept might even be extended to even more complicated plasmon structures, according to Carsten Sönnichsen of the Johannes Gutenberg University of Mainz in Germany.

The research is described in Science 332 1407.

The lunar eclipse as Physics World readers saw it

By James Dacey

Skygazers in many parts of the world were treated yesterday to the longest total lunar eclipse in over a decade. Sadly, here in the south-west of England almost complete cloud cover meant that I saw precisely none of it. It was rotten luck and Google’s “live coverage'”of the eclipse felt like a very poor second best.

But thankfully my spirits were lifted this morning when I saw these two splendid photographs sent to us by readers via the Physics World Facebook page. The first image was taken by Pedram Esfahani, an engineering physics student based in Tehran, Iran, who captured this shot of the Moon just before the total eclipse.

eclipse1.jpg

This second photo taken by Jawaid Siddiq in Lahore, Pakistan, also shows the Moon just before the total eclipse at 0910 GMT (0110 local time).

eclipse2.jpg

In the second image you can see that the shadowy region takes on a slightly red hue. This effect (as I’m sure you’ve all been explaining to your non-physicist friends) is due to the way light interacts with the Earth’s atmosphere. To reach the Moon during an eclipse, light has to pass around the Earth and light at the blue end of the spectrum tends to be scattered by the atmosphere. But light at the red end of the spectrum, with its relatively longer wavelengths, has a much better chance of sneaking through and reaching the Moon, before it is then reflected back to Earth.

Totality – when the lunar face is completely blocked – lasted from 1922 GMT until 2102 GMT, making it the longest total eclipse since July 2000. The diagram below was created by NASA to show the extent to which the eclipse was observable across the planet.

nasadiagram.jpg

You can see a larger version of this diagram with the different eclipse stages explained at NASA’s official eclipse website. The site also gives details of the eclipses coming up during the rest of the year, with the next event to add to your calendar being a partial solar eclipse on 1 July.

Peer pressure keeps young planets growing

Two US astrophysicists claim they have answered an important question about how planets form: why don’t young planets get pushed into their companion stars before they have a chance to grow? It turns out that a little company is enough to keep them there, say the researchers, who argue that multiple planets moving through a rocky disk can prevent one another from falling into the star.

“All young planets are subject to migration,” says Scott Kenyon of the Smithsonian Astrophysical Observatory in Massachusetts, who did the work with Benjamin Bromley of the University of Utah. “Migration for gas or ice giants is more commonly discussed, but migration is also an issue for terrestrial planets with masses ranging from that of Pluto to the Earth.”

Astronomers believe that planets form in a disk of gas and dust surrounding a young star. The first step towards planet formation is the planetesimal – a small rocky body with radius of roughly 1–10 km. As the dust condenses into planetesimals during the first few million years of a star’s life, larger rocks begin to emerge that grow much more rapidly than the rest. These bodies, termed oligarchs, are on their way to young planethood, using their gravitational pull to attract and pack on more planetesimals.

Pushy planetesimals

In addition to providing a means for growth, planetesimals can also push an oligarch towards its doom in the central star. A lone oligarch orbiting through the disk of planetesimals clears a path much like a stick being dragged through sand. The planetesimals on either side of the trench press on the oligarch, says Kenyon, and as the outer ring has more mass, the planetesimals deliver a net inward push.

In the past, magnetic fields, turbulence and thermodynamics have been used to explain how rocky planets are prevented from falling into their stars. However, Bromley and Kenyon say that the wake patterns created by multiple oligarchs circling a star are enough to prevent structures from forming in the planetesimal disk that would push the young planets in.

Once the oligarchs account for about half of the material in the disk, a few tens of millions of years after the birth of the star, they begin making even more material gains by combining with one another. Rather than hollowing out a series of trenches, the oligarchs are now randomly scrawling in the planetesimal “sand”, which also prevents the planetesimals from settling into patterns that would feed the oligarchs to the star.

Real, but not clear

“This is a real effect,” says John Papaloizou of the University of Cambridge in the UK. “However, its extension to interactions with gas is not clear.”

Making direct calculations of the movements of multiple planets through a more realistic disk of gas and planetesimals raises the complexity significantly, requiring more computing power than is practical today. Instead, Bromley and Kenyon extended their simulation to gas disks.

They looked for scenarios in which a gas cloud behaves like a disk of planetesimals, and they found two key requirements: the gas must have low viscosity; and the planets must be small. A denser, high-viscosity gas has a stronger tendency to smooth itself out after the oligarch runs through – like the wake of a canoe in water. This means that the disruptions to the patterns do not last as long. If the gas in the disk is dilute, the researchers argue that these conditions are met well enough that rocky planets should not fall into the star.

“Our results tell us that growing terrestrial protoplanets cannot migrate through a disk of planetesimals, allowing protoplanets to grow into the planets we see in our and other planetary systems,” says Kenyon. If the generalization to gaseous disks is realistic, then Kenyon believes that “we are a step or two closer to understanding the origins of the Earth and other planets”.

This research appears in the Astrophysical Journal 735 29.

Closing in on dark matter

In part one of the interview Hooper discusses the strong evidence for the existence of dark matter. This includes various astrophysical observations such as the dynamics of large-scale structures in the universe. “When we look at clusters of galaxies we find that they are much more massive, and have much more gravity associated with them, than their visual counterparts can account for,” he says.

Part one
Part one

Hooper explains that the favoured candidates for a dark-matter particle are “weakly interacting massive particles”, or WIMPs. As the name suggests, these particles appear to keep a low profile in the universe by interacting very little with all other matter. “They were created in the first fraction of a second after the Big Bang and more or less have existed without doing much of anything ever since.”

Hooper goes on to discuss the different types of experiment that have been created to try to detect dark-matter particles. One approach involves designing highly sensitive equipment capable of spotting WIMPs directly as they interact with detectors that are buried deep underground to shield them from background radiation. The other approaches Hooper describes look for indirect evidence of these particles using telescopes, or try to create dark matter at particle accelerators such as the Large Hadron Collider (LHC) at CERN.

Prospects for discovery

In the second part of the interview, Hooper speaks his mind about the prospects of discovery for these dark-matter experiments and some of the results to emerge so far. He believes that the scientific community is yet to see indisputable evidence for a discovery of dark matter, but some interesting “positive results” are starting to emerge.

Part two
Part two

Hooper shares his thoughts on one collaboration known as DAMA/LIBRA, which has been claiming for over a decade that it has detected dark matter, even though many in the community have remained highly sceptical of those claims. DAMA/LIBRA researchers have been reporting for 13 years that their experiment in Italy records a seasonal oscillation in its detections. This, they say, is caused by the Earth moving with (and against) a cosmic flow of dark matter.

Hooper believes DAMA/LIBRA’s claims could be strengthened if another experiment called CoGeNT, based in a mine in Minnesota, can observe a similar annual modulation in its detector. Since the interview was recorded early last month, CoGeNT has released new findings that seem to corroborate tentatively with the DAMA results.

But whatever comes of these claims, Hooper is confident that a verified discovery of dark matter could be just around the corner. “If I didn’t think it could happen then I would work on something else,” he says. “Any scientific goal has to have a plausible positive outcome or it’s not interesting and not worth doing.” What is more, Hooper is a scientist who puts his money where his mouth is. He tells the story of how four years ago he placed a bet with a colleague that dark matter would be discovered within five years. Despite there being just one year to run, Hooper still believes this is a good bet.

To change the world

I recently read a book with remarkable insights about what it is to be a scientist, the plight of science in the modern world and the challenge of maintaining its values. Before I tell you the name of the book – no peeking, or it will destroy the effect! – let me summarize the argument, specifying key passages.

Scientists, the book observes, tend to be attracted not only by the joy of practising science, but also by the beauty and wonder of nature (p3). Many know that science plays an indispensable part in solving pressing social problems, and are eager to help.

Yet, strangely, the cultural position of science is beleaguered. On the one hand, viewed from the local perspective of universities and labs, research exhibits an "extraordinary and genuine vitality" (p91). On the other hand, science does not have the cultural influence that it should; from a global and social perspective, science is not only marginalized but a "weak culture". Despite the vitality of science, "the whole (in terms of its influence in the larger political economy of cultural production) is significantly less than the sum of its parts" (p92). Furthermore, though science is vital to our personal, economic and political wellbeing, it "has become highly politicized" (p109).

Three coping strategies

Scientists tend to cope by adopting one of three postures, which might be called the progressive, "neo-Anabaptist" and conservative attitudes (p109). Progressives actively seek to use science for social agendas, running the risk of compromising its ideals and distorting its otherwise rigorous standards and practice. Neo-Anabaptists hold an opposing view. They find politics corrupting to science and keep their distance from it. They maintain that science belongs in the laboratory, and distrust attempts to use it for political ends. Conservatives – the vast majority – blame the schools, media and politicians for encouraging irrationalism and pseudoscience, and for spreading "misinformation and fear" (p117), which is causing great harm to humanity and to the planet. Scientists, the conservatives claim, "have been under-represented, ridiculed and outright ignored by our political leaders for much too long" (p117), and that it is time to reassert reason in cultural discourse.

But none of these three approaches has managed to improve the cultural status of science. The principal reason is a failure to understand culture. Most scientists – understandably, for they are untrained in social theory – have a deeply flawed working theory of culture and how it changes (p24). This theory, a form of idealism, assumes that culture is ultimately a matter of ideas: to change culture you change ideas, and therefore "the autonomous and rational individual is the key actor in social change" (p26). Scientists, for instance, tend to assume they can change deeply ingrained ideas about science simply by speaking up loudly and articulately enough. But this is naive, ignores how culture "is generated, coordinated and organized", and "mistakenly imputes a logic and rationality to culture where such linearity and reasonableness does not exist but rather contingency and accident" (p26).

To make science seem not just a set of true facts, but symbolically and culturally vital, requires creating and developing new means of exhibiting the value of scientific research in its own right, and of showing its value for addressing social problems. "The only way to change culture is to create more of it," according to the author (p28).

This is not as formidable as it sounds; science has plenty of resources. First, nearly everyone is implicitly and informally a scientist because they possess certain scientific qualities (let's say knowing how to inquire, test and discover) even if only "in fragments or in corrupted form" (p232). Nearly everyone therefore has a proto-scientific attitude that can be fostered. This fostering should not have as its goal changing people into scientists, but rather encouraging their appreciation of its value in understanding and coping with the world (p242). Another means to improve science's cultural role would be to build institutions that give "tangible expression" (p78) to scientific culture alongside the existing social environment.

Science is fated to have a dual destiny. It is a rigorous discipline with its own norms and vitality independent of the general culture – but it is also historically and practically important to that general culture. Thus the book counsels a practice of "scientific presence" in which scientists engage the world by exhibiting "the exercise of leadership in all spheres and all levels of life and activity" oriented to "the flourishing of the world around us" (p260–261).

The critical point

How accurate and insightful did you find this characterization? I find it spot on. But let me now confess that my description was not entirely above board. It was instead a thought-experiment because the book I have been quoting from is To Change the World: The Irony, Tragedy, and Possibility of Christianity in the Late Modern World by James Hunter, Distinguished Professor of Religion, Culture and Social Theory at the University of Virginia. I was alerted to the book by a newspaper editorial. While my summary of its key portions was on the whole accurate, I have changed a handful of words, substituting "scientists" for "Christians", "scientific" for "Christian" and "science/ research" for "Christianity", "the church", "faith" and so forth.

Conservatives can imagine this book as a sophisticated strategy manual that has been captured from an enemy combatant: while the goals radically differ from your own, it is a must-read for strategy tips. To keep science robust and healthy, it is not enough to conduct scientific research; we also have to promote those values that allow research to be effectively and wisely conducted, and seen as relevant to current social problems. Yet because of our flawed theory of culture, the way scientists promote such values has been haphazard, incompetent and often even counter-productive. If we have not studied culture seriously, a first step is to learn from those who have.

Catching sight of the elusive wavefunction

In the orthodox interpretation of quantum mechanics, the wavefunction contains the maximal knowledge that is available about the state of a system. It determines the probabilities that various results will be obtained when measurements are made on the dynamic variables of the system such as its position or momentum.

However, measuring the wavefunction is no easy task. Thanks to Heisenberg's uncertainty principle, measuring a quantum system without effectively destroying it before the wavefunction is fully known has seemed impossible. Now, by taking a new approach to quantum measurement, Jeff Lundeen and his team from the National Research Council, Canada, have directly measured the wavefunction of identical single photons for the first time.

Making a measurement on just one copy of a system – such as just a single photon – gives us part of the wavefunction. However, the measurement must be repeated many times on an ensemble of identical photons to gain enough information to construct the entire wavefunction. This indirect form of measurement is known as "quantum tomography" and has been used for some time.

Recording ripples

Lundeen likens tomography to mapping the shape of a ripple on the surface of a pond (the wavefunction) by taking snapshots of the shadows of the ripples on the bottom. By combining information from many snapshots, the shape of the ripple can be inferred. In quantum tomography, however, each snapshot measurement is so "strong" that it destroys the ripple and the process must be repeated with identical ripples. Beyond the destructive nature, certain wavefunctions such as atomic or molecular orbitals cannot be determined using tomography.

Instead of focusing on the shadows, the team has worked out a way to directly probe both the real and imaginary parts of the wavefunction of an ensemble of photons. The method relies on the concept of "weak measurement", which has been used recently to measure some quantum systems – and does not destroy the wavefunction.

"Our understanding of the wavefunction is rather abstract and there is no official textbook definition," says Lundeen. "We decided to look into the method of weak measurements irrespective of how wary scientists seem to be of it," he continues, explaining that, although the theory of weak measurements was developed in the 1980s, it was dismissed by many researchers because it produced rather "odd results" that were much larger than expected. The reason for the unexpected results, explains Lundeen, is that a weak measurement gives a complex number – it has a real part and an imaginary part.

Gentle measurements

The theory of weak measurement says that it is possible to "gently" or "weakly" measure a quantum system and to gain some information about one property (say, position) without appreciably disturbing the complementary property (momentum) and therefore the future evolution of the system. Though the information obtained for each measurement is tiny, an average of multiple measurements gives an accurate estimation of the measurement of the property without distorting its final value.

For a generic quantum measurement, the system to be measured is coupled with another state that can be thought of as a "pointer". Information about a measured property is gained by observing a change in the position of the pointer. Generally, this is considered to be a strong measurement because there is little overlap between the original and final positions of the pointer. The detection of a photon in a CCD, for example, would swing the pointer from zero photons to one but result in the destruction of that photon.

In a weak measurement, it is just the opposite, with the final position of the pointer overlapping to a large extent with its initial position. In the measurement carried out by the team, the real part of the wavefunction is given by a small shift of the pointer related to the position of the photon. The imaginary part of the wavefunction is given by a shift of the pointer related to the momentum of the photon. So the position is weakly measured while the momentum is strongly measured.

Four basic steps

The experiment has four basic steps. The first is to generate a stream of single photons with identical wavefunctions. "It is virtually impossible to measure a wavefunction with just one copy of a quantum system (i.e. one photon), this we are almost sure of," explained Lundeen. The team either used an attenuated laser beam or a process known as spontaneous parametric down-conversion (SPDC) to produce its photon stream.

The next step is to set up the weak measurement of the transverse position of the photon by inducing a rotation in each photon's polarization by a very small amount – 10° – using a quartz crystal. Because the polarization change is small, the system is not greatly disturbed.

The photons are then collimated and only photons travelling in a specific direction are detected – a process called post-selection. This is the strong measurement. In the final step, the weak measurement is carried out by measuring the two types of polarization that have actually occurred in the photons post-collimation. This is two-fold because the real part of the measurement is the actual amount of linear rotation that has occurred and the imaginary part is given by the circular rotation or the "ellipticity" of the polarization that has occurred. Together, these values give the weak measurement of the wavefunction. The researchers repeated the measurement for photons with different wavefunctions to confirm the accuracy of the results.

Better than tomography?

Lundeen points out that the signal-to-noise ratio of his team's experiment was rather good. Indeed, he says that an important benefit of the weak measurement technique is that the results are amplified. Therefore it could prove to be especially useful for studying systems that are currently very hard to measure.

While he believes that there will still be a place for quantum tomography, Lundeen feels that certain systems will benefit from the technique used by his team. "While tomography is a global measurement that is more a reconstruction of the wave function, our measurement is local and direct." he explained. "The simple benefit of our research is that we now have an operational textbook definition of a wavefunction...something that is essential."

The research was reported in Nature.

A preprint of the paper can be found at arXiv: 1112.3575.

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