Researchers at Massachusetts Institute of Technology (MIT) are developing a revolutionary new computer interface that they refer to as a “responsive environment”. The group at MIT’s Media Lab has built a system called DoppelLab that is designed to create visualize and sonic environments based on data collected from networked sensors. In this video, the group’s leader Joe Paradiso introduces the project and lays out his vision of a future world where people and their environments are truly connected.
Measuring culture
Last February I was a panellist at a discussion on “Culture and metrics” at the Museum of Modern Art (MoMA) in New York City. The event was organized by Paola Antonelli, the museum’s senior curator of architecture and design and director of its new R&D department, which she founded last July. One of her goals is to identify ways to measure the museum’s impact on culture and the wider economy.
Antonelli, who originally studied economics before completing a Master’s in architecture, told me her idea for the department germinated after the 2008 financial crisis. “I had a chip on my shoulder,” she said. The crisis, in Antonelli’s view, revealed that traditional economic strategies were promoting investments that had a chaotic and even negative impact. Cultural institutions, on the other hand, offered “a slower but more dependable and effective key to long-term growth”. She felt sure that “more faith, attention and money would soon flow into cultural institutions”.
It didn’t happen. Disappointed, Antonelli sought to demonstrate to politicians and other prospective sponsors that cultural institutions exert a genuine and positive impact on growth. To do so, she recalled Lord Kelvin’s dictum: “When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be.”
Measuring muddles
The traditional quantitative measures of museum productivity – foot traffic, membership size, number of exhibitions and so on – do not quite capture the spectrum of a museum’s influence. Antonelli therefore organized February’s panel to explore ways of demonstrating a more complete and long-term impact. About 200 people attended the event, which raised probing issues about measurement. One panellist was Kate Levin, the commissioner of New York City’s Department of Cultural Affairs, who presented statistics that impressively confirmed the importance of culture to city life. Her department estimated, for example, that The Gates – an environmental artwork erected by Christo and Jeanne-Claude in New York’s Central Park in 2005 – had attracted four million visitors and resulted in an estimated $254m economic boon for the city. She cited last year’s World Cities Culture Report, which concluded: “What links world cities to one another is trade, commerce and finance. What makes them different from one another is culture.”
Andrew Ross, a social and cultural analyst at New York University, mentioned factors that cause economists using traditional methods to underestimate the value of the arts. One is “cost disease” – the fact that productivity does not behave in the arts as it typically does in manufacturing. It takes, for example, the same number of people to perform a quartet today as in Beethoven’s time, though musicians’ real wages have increased. Another factor is “psychic income” – the willingness of artists to accept low wages in return for intangible benefits such as exposure.
I cited a distinction (originally presented in my 2011 book World in the Balance) between measurement against standards – what the SI is about – and measurement against ideals. The first is procedural and conventional, while the second is experiential and involves goals such as justice and education. The irony, I said, is that just when civilization is on the verge of perfecting measurement against standards with the “New SI” (which replaces artefact standards, such as the kilogram in Paris, with natural constants), measurement against ideals is more controversial than ever. We often pretend we can turn measurements against ideals into measurements against standards – by representing justice as a blindfolded woman holding scales, for instance. But this is metaphorical wish fulfilment: what could go in that pan? Small wonder that when we try to measure goals quantitatively it can give rise to front-page fights.
One obstacle to measuring against ideals is Goodhart’s law, a kind of Heisenberg uncertainty principle for culture. Named after the British economist Charles Goodhart, who devised it in 1975, the law essentially says that once a measure is chosen for making policy decisions, it begins to lose value as a measure. Goodhart applied it to banking policy, but in other fields, too, measurement can distort not only the practice being measured, but also perception of the goal. As soon as you measure intelligence, say, with standardized tests, schools begin to teach to the test – and you begin to view intelligence as a child’s ability to be taught to the test. If you measure researchers’ quality by the number of papers they produce, they start churning out unnecessary numbers of low-quality papers.
The critical point
Goodhart’s law tempts us to regard quantifying cultural impact as hopeless. We may recall with nostalgia the physicist Robert R Wilson’s famous testimony before Congress in 1969, when he was challenged to justify Fermilab’s new accelerator if it had no practical value even for defending the country. Wilson refused to manufacture a fake utilitarian reason and defended the device on cultural grounds. “[It] has nothing to do directly with defending our country,” he said, “except to help make it worth defending.”
But in today’s world, MoMA’s panellists agreed, Kelvin’s dictum prevails. Politicians, policy-makers and sponsors are measurement-driven, even with cultural matters. We therefore have to be more ingenious in devising metrics for cultural institutions. But to circumvent Goodhart’s law, we also have to recall that measurement involves not only an “it” – something measured – but also a “who” – the measurer. In measuring against an ideal, the measurer must not be anonymous; we have to be clear who is measuring and why.
As Antonelli put it: “The problem of measuring cultural impact cannot be resolved by numbers alone.”
Old-school cosmological calculations
By Tushna Commissariat
The next time you need to quickly convert the redshift of some distant cosmic object to parsecs or kilometres, and find that your laptop and phone have both run out of charge (the horror!), the “Paper-and-pencil cosmological calculator” might be just the thing for you. More of a chart than a “calculator”, the new table – that is based on the ΛCDM cosmological model of the universe – has been drawn up by Sergey Pilipenko from the Lebedev Physical Institute in Moscow. And here’s the best bit – all the parameters that Pilipenko has plugged into his table are from the latest Planck results unveiled last month.
Topological insulator created for light
An optical analogue of a topological insulator has been created by physicists based in Israel and Germany. Consisting of an array of helical waveguides, light cannot propagate between waveguides in the bulk of the array but it can move unhindered along its surfaces – even when the light encounters significant surface defects. According to the team, these properties could allow the material to be used to simulate quantum phenomena or be used in photonic circuits.
Since they were first predicted in 2005 and subsequently identified in the lab, topological insulators have been a hot topic in condensed-matter physics. Electrical insulators in the bulk, these materials have surface states that conduct electrons extremely well. The robust nature of the surface conduction is a result of the topology of the system. The energy difference between the surface states and the bulk states is so large that an electron moving along the surface cannot scatter into the bulk.
Maintaining momentum
Even more importantly, a surface electron with a certain momentum is unable to scatter into a state with opposite momentum because doing so would involve flipping its spin – which it is forbidden from doing in ordinary materials. So the electron has no choice but to keep moving in the same direction. As a result, topological insulators show great promise for applications such a quantum computing, where scattering from defects will destroy quantum information carried by electrons.
Now a team – including Mikael Rechtsman, Yonatan Plotnik and Mordechai Segev of Technion and Julia Zeuner and Alexander Szameit of the Friedrich-Schiller University – has created an optical material that behaves much like a topological insulator. The researchers came up with the idea in 2011 when they read a theory paper that argued that a topological insulator could be created in a material by subjecting it to time-varying electromagnetic fields. They realized that the 2D Schrödinger equation of such a material is identical to the equation that describes the 3D propagation of light through an array of light guides – if the direction along the waveguides is treated as time rather than the z component of space.
Leaking light
If the waveguides are simply straight cylinders, light can leak from one waveguide to the next, which makes the array analogous to an electrical conductor in the x–y plane – indeed, the array is a honeycomb and its properties are similar to the electrical properties of graphene. But to simulate the time-varying fields, the waveguides would need to be helical as this opens up a gap in the x–y conduction band and stops light from moving between waveguides – creating a bulk insulator. However, as the surface propagation states endure, light would be free to propagate in the x–y direction on the surface.
To test the idea in the lab, the team took a piece of fused silica and used a femtosecond-laser-writing method – which modifies the local refractive index – to create the array of helical waveguides. The nearest-neighbour spacing between waveguides is 15 μm and the structure is 10 cm long. The researchers then fired a beam of light at an edge of the hexagonal face of the array and found, as expected, that the light propagated in the x–y direction on the surface of the structure – but not in the bulk. Furthermore, when the light reaches an edge of the array, it was found to propagate easily around the corner and keep going along the adjacent face – an example of how robust the surface propagation is.
To further test how persistent the surface propagation is, the team created arrays that are missing waveguides at the surface. Again, the researchers found that the light moved seamlessly through such defects, just as expected of a topological insulator.
Sub-wavelength materials
The team told physicsworld.com that such photonic topological insulations could find use in silicon photonics – circuits that use pulses of light to transmit information rather than electronic signals. A key challenge in creating tiny photonic circuits is preventing light from reflecting or leaking into places where it should not be – which can cause crosstalk between circuits. Ideally, this could be done using topological insulators that confine light to regions smaller than the wavelength of the light itself.
The physicists also believe that the materials could be useful as photonic simulators of quantum effects. These could be used, for example, to gain a better understanding of electrons in real materials. Finally, the group points out that those trying to build quantum computers that use photons as qubits could be interested in developing photonic topological insulators, because scatter-free propagation may aid in the development of a robust quantum computer.
The work is described in Nature.
Are there signs of SUSY in Planck data?
Evidence of supersymmetry (SUSY) could be lurking in the cosmic microwave background (CMB), according to a UK-based physicist who has calculated how the theory could affect fluctuations in the CMB. The claim comes just a few days after the latest CMB observations were released by the team running the Planck space telescope – results that suggest that evidence for SUSY may not be forthcoming from the CMB. However, if these latest calculations are correct, the CMB could offer a window into dark matter and complement the search for SUSY at the Large Hadron Collider (LHC) when it starts up again in 2015.
Back in March, the team behind the European Space Agency’s Planck telescope released the most accurate map to date of the cosmic microwave background (CMB) – the relic radiation left over from the Big Bang. As well as putting tighter constraints on the age of the universe and its contents, the findings also strongly support the idea that the early universe underwent a rapid growth spurt known as inflation. In the first tiny fraction of a second, the infant universe swelled by a factor of 1078. Physicists’ simplest explanation is that a single field – the inflaton – provided the mechanism for this exponential increase. Natural quantum fluctuations within the inflaton would have been blown up too and are now imprinted as the speckled temperature variations seen in Planck’s CMB map.
Imprinted by sparticles?
However, some researchers working on theories that go beyond the Standard Model of particle physics believe that the inflaton would have had other fields for company. SUSY encompasses one such family of theories and postulates that every known particle has an as-yet-unseen partner known as a “superparticle” or “sparticle”. Each sparticle has a corresponding field that should have been present in the universe’s first moments, and therefore could also be imprinted in the CMB.
Now, Anupam Mazumdar of Lancaster University has set out to explore this idea further, telling physicsworld.com, “A natural question one can ask is what do these [additional] fields do in the early universe?”
In trying to answer this, he hit upon a new idea. “It is possible the extra fields play the role of spectators, unable to modify the dynamics of inflation but still leaving an imprint,” he explains. He calculates that fluctuations within these spectator fields would have been much larger than those of the inflaton. As the universe swelled, they got taken along for the ride. It could be, then, that it is these spectator fields, and not the inflaton, that are responsible for the speckles in the CMB map. The key test is in how the speckles are distributed. “If they are caused by fluctuations in multiple fields then their distribution [throughout the CMB map] would not be exactly Gaussian,” says Mazumdar, referring to the bell-shaped curve ubiquitous in statistics.
Still room for new physics
However, there is a snag. Mazumdar’s initial work was published in Physical Review D prior to the release of the Planck findings, which have since shown the distribution to be closer to Gaussian than ever previously measured. Re-examining his work in light of Planck, he posted a new paper on the arXiv pre-print server. “I had to rule out some parameters, but there is still space in there for new physics,” he argues. Speaking to physicsworld.com ahead of a recent Planck conference in the Netherlands, he says he will present evidence that “multiple fields might play the same role as a single field, within the range that Planck has shown”.
Currently, it is difficult to tell one way or the other, but any departure from a Gaussian distribution in the CMB would leave the door open to SUSY. “Planck has diminished the possibility of a link, but it hasn’t destroyed it,” explains Andrew Pontzen of the University of Oxford, who was not involved in the research. “We’ll need future experiments like the Square Kilometre Array, but if a link can be teased out between inflation physics and supersymmetry that would be tremendously exciting,” he said.
Whither the WIMPs?
Part of the excitement stems from the possibility of explaining dark matter, the shadowy entity that the Planck result revealed to make up almost 27% of the mass/energy of the universe. Although physicists do not know exactly what dark matter is, some supersymmetry theories predict the existence of weakly interacting massive particles (WIMPs), which are a leading candidate for dark matter. “We’re closing in on WIMPs with experiments like the Large Hadron Collider, so if you could also make a link to the period of inflation, that would allow us to tackle the problem from two angles,” explains Pontzen.
But, with the Square Kilometre Array not due to come online until 2020, and the LHC recently shut down for refurbishment, Mazumdar’s idea of physics beyond the Standard Model playing a role in inflation may, for now, remain a tantalizing possibility.
When will quantum communications blast off?
By Hamish Johnston
I think it’s safe to say that quantum communications between satellites and ground-based stations should be possible. Optical signals have already been sent 144 km through the air between ground stations at sea level. More recently, quantum communications have been achieved between an aircraft in flight and a ground station 20 km distant.
While quantum communications have been sent comparable distances via optical fibre, it’s unlikely that the fragile single photons used in such missives would survive an ocean crossing unscathed. Therefore if technologies such as quantum key distribution cryptography are to become truly practical, satellites must be involved.
Listen to the sound of the Big Bang
By James Dacey
Hearing the Big Bang
It sounds like a Kraftwerk track, but this is in fact an audio representation of the Big Bang based on scientific measurements. The physicist John Kramer has produced the sounds using the new data from the ESA’s Planck Mission analysis of the cosmic microwave background (CMB) radiation.
ATRAP nails down the antiproton’s magnetic moment
Researchers working on the Antihydrogen trap (ATRAP) experiment at CERN have made the first single-particle measurement of the magnetic moment of the antiproton. Achieved with an uncertainty of 4.4 parts per million, the magnetic moment is exactly opposite to that of the proton, as predicted. This result is 680 times more precise than previous measurements made on exotic atoms containing antiprotons and is an important step towards understanding why the universe contains more matter than antimatter.
Physicists are keen to capture and compare antimatter to its matter counterpart in order to conduct precision tests of charge–parity–time (CPT) symmetry. Understanding this symmetry could help explain why the universe contains so little antimatter. To do this, researchers make very accurate measurements of properties such as the magnetic moment and the spin of antiprotons to look for inherent differences between these and the properties of the proton.
Precise comparisons
"By comparing the antiproton's tiny magnetic moment to that of the proton, we test the Standard Model and its CPT theorem at a high precision," says ATRAP spokesperson Gerald Gabrielse of Harvard University in the US. To carry out the study, the researchers use a Penning trap to capture and suspend single antiprotons so that their charge, mass and magnetic moment can be precisely measured. The antiprotons themselves are supplied by CERN's Antiproton Decelerator. "We detected the response of the suspended antiproton to radio signals that we sent in its direction. The size of the [magnetic moment] in the antiproton is determined by the ratio of the two frequencies that made the antiproton respond most energetically," explains Gabrielse.
Challenging experiments
Gabrielse points out that the measurements were difficult to make and presented the team with many challenges. He tells physicsworld.com that the antiprotons available at CERN are moving at nearly the speed of light, so the researchers essentially need to slow each one down to a near-stop to capture them. "Also, detecting the motion of a single particle is a bit challenging, as you might expect, since the many particles in the nearby apparatus are also moving and their motion makes a noise signal that competes with the signal from our single antiproton," explains Gabrielse. He also points out that the magnet moment of the antiproton is very small – about 500 times smaller than that of an electron – making measurements even more difficult.
Nevertheless, the team found that the magnetic moments of the antiproton and proton are "exactly opposite" – that is, equal in strength but opposite in direction with respect to the particle spins. "Here, exactly opposite means that the direction that the [magnetic moment] points with respect to the particle's internal spin is opposite to that of the proton, but the size of the [magnetic moment] is the same," says Gabrielse. "Our measurement is thus consistent with the prediction of the Standard Model of particle physics to a precision 680 times better than what could be determined in earlier measurements. As such, this measurement is a notable success of the Standard Model," he says.
Despite the accuracy of these measurements, the ATRAP collaboration feels that much more precise and accurate measurements of the magnetic moment of the antiproton will be necessary to test the Standard Model prediction much more stringently. Gabrielse urges us to "stay tuned, since we believe that this is only the first step". The team feels that, given time, it will "have the new quantum ideas and methods to eventually test this prediction of the Standard Model nearly 1000 times more precisely".
The research is published in Physical Review Letters.
What is the anthropic principle?
In less than 100 seconds, Roberto Trotta explains this often-misunderstood philosophical idea: why it seems so unlikely that conditions in the universe are so perfectly tuned for life to exist.
Watch more from our 100 Second Science video series.
Honey at the asymptotic limit
By Hamish Johnston
What’s the buzz in physics this week? Forget dark matter, it's honey – or rather the strange properties of this tasty fluid.
If you have a sweet tooth (or an interest in the Rayleigh–Plateau instability) check out this paper in Physical Review Letters.
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