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‘Gigantic jets’ caught on camera

Lucky strike elusive lightning spotted above Duke University

Ever since the American polymath Benjamin Franklin braved electric storms with his scientific kites, the study of lightning has been associated with the Romantic explorer in search of scientific answers. The latest Romantics to shed light on this spectacular natural phenomenon are a team of physicists in the US who have managed to capture the most detailed images yet of a “gigantic jet” – a rarely seen form of high-altitude lightning that shoots upwards towards the heavens.

Gigantic jets are believed to initiate from the electric coupling between the lowest part of the atmosphere, known as the troposphere, and the upper atmosphere at altitudes of 90 km where lots of free ions and electrons exist. This form of lightning has been observed previously from the ground and from orbit. But, because it happens so high up in the atmosphere, no one has yet managed to get close enough to study its electric properties during a strike.

Braving the storm

To obtain a more detailed picture of the physics, the team at Duke University, North Carolina and Yucca Ridge Field Station, Colorado, set out to observe a gigantic jet in action during the tropical storm Cristobel in July 2008. To their surprise and good fortune, on 21 July, a gigantic jet struck within just a few kilometres of the researchers’ recording station near Duke University. The researchers established the exact location and dimensions of the bolt using low-light photography, and quantified the transfer of electric charge by observing the lightning’s radio signal using a series of ground-based radio sensors.

Presenting their findings in Nature Geoscience, the team recorded the total charge transfer from the troposphere to the ionosphere as 144 C for the estimated lightning bolt length of 75 km. This is about the same amount of charge that is transferred in strong cloud-to-ground lightning strikes but with the charge being transferred in the opposite direction – away from the Earth towards the upper atmosphere. “Knowing how far the jet was from our sensors, combined with the radio signals, enables us to say how strong the jet current was,” says Steven Cummer, an electrical engineer at Duke University and leader of the research team.

Gigantic jets have been captured on camera previously but in the past they had only been observed from many thousands of kilometres away. “We were lucky to capture on video a gigantic jet so close to our radio sensors and this meant that we could make high precision measurements with very little uncertainty,” Cummer told physicsworld.com.

Unanswered questions

While this research provides the most accurate picture yet of gigantic jets, it does not completely solve the mystery of how this phenomenon is initiated within clouds. “It appears that these gigantic jets are connected to layers that contain a lot of total charge, but really understanding this will require some measurements of the internal structure of lightning channels within the clouds during gigantic jets, which we don’t have yet,” says Cummer.

The researchers intend to develop their research by observing more gigantic jets in more detail. “One thing that we’d like to do is capture a gigantic jet with a higher speed camera that we are now running, in order to resolve in time how they actually develop,” Cummer continues. Documenting more jets would let them get a better idea of what can produce gigantic jets.

Fortunately for air passengers, almost all commercial planes fly below the top of the very tall thunderclouds – up to 15 km altitude – from which these gigantic jets emerge. However, there are a few high altitude aircraft that should take precautions. “Even though gigantic jets appear to be pretty uncommon, they could affect something that was not well protected from lightning,” warned Cummer.

The day Galileo brought astronomy to the masses

One of Galileo’s first telescopes

By Michael Banks

Today marks an important date in the calendar of the International Year of Astronomy (IYA2009.

400 years ago, on 25 August 1609, the astronomer Galileo Galilei presented his first telescope to policy makers from the Venetian Republic.

Galileo ushered the lawmakers into St Mark’s Campanile – a bell tower in St Mark’s Square — in the heart of Venice to present his latest invention.

Impressed with seeing objects such as ships from a great distance, the telescope obviously left its mark as Galileo’s salary was doubled and he was also awarded life tenure at the University of Padua.

Galileo probably made a lot of cash from selling the telescope to merchants who found them useful at sea and as items of trade.

However, Galileo is, of course, best known for the mark he has left on the history of astronomy. (As always Google have their own tribute to the anniversary)

To mark the IYA2009, earlier this year we published an interesting article about how one of Galileo’s early telescopes was being rebuilt by researchers in Italy to study what Galileo may have been able to see.

Staff at the Institute and Museum of the History of Science in Florence, Italy, together with the Arcetri Observatory, also in Florence built an exact replica of the device that Galileo gave to his patron the Grand Duke of Tuscany, Cosimo II, in about 1610 that could magnify distant objects by up to a factor of about 20.

The Galileo anniversary is, however, not the only one in astronomy on this day.

Today also marks the 20th anniversary of NASA’s Voyager 2 craft coming closest to Neptune on its grand tour of the outer planets. (click here for the article we will be publishing in the September issue of Physics World about the anniversary)

The two Voyager craft — named Voyager 1 and Voyager 2 — launched on 5 September and 20 August 1977, respectively, (yes, the dates are the right way round) and completed their grand tour of the solar system 20 years ago.

Possibly one of the most successful space missions, the two craft are now on their way to the boundaries of the heliosphere – the ‘bubble’ of space blown by the solar wind into the interstellar medium.

So if you are feeling inspired by the Galileo anniversary and want to see for yourself what he could have observed 400 years ago, then you can always get your hands on your very own Galileoscope.

Voyager heads for interstellar space

Two decades ago today — 25 August 1989 — an extraordinary spacecraft took its final, stunning photos of the distant planet Neptune, before heading towards the edge of the solar system and the interstellar void beyond. Voyager 2 was launched by NASA in 1977 to take advantage of a rare alignment of the planets that occurs only once every 176 years. The alignment allowed the craft — and its sister ship Voyager 1 — to take a “grand tour” of the outer planets of the solar system, picking up speed at each planetary rendezvous via so-called gravity-assist manoeuvres.

Voyager 2, launched on 20 August 1977, crossed the ring plane of Saturn, then headed on to Uranus and Neptune, returning the most spectacular pictures ever taken of those distant, giant planets. Voyager 1, meanwhile, blasted off on 5 September 1977 on a faster orbit that would allow it to do a fly-by of Titan — one of Saturn’s four moons. After its cloud-skimming encounter with that moon, Voyager 1 headed upwards at an angle of 35° to the plane of the ecliptic, leaving the solar system behind forever.

The two sister craft now form the Voyager Interstellar Mission (VIM). Although it was never certain when the Voyager craft blasted off in 1977 that they would survive for so long, VIM is still an official NASA mission. It receives some $4.7m each year — with funding planned through until at least 2012 — and employs 40 staff at NASA’s Jet Propulsion Laboratory.

Both craft are currently investigating the physics of the outer solar system and will continue to do so until they cross over into interstellar space. Five instruments are running on the spacecraft, transmitting data about the strength of the local magnetic field as well as the speed, temperature and density of the solar wind — the stream of particles from the Sun — and the intensity of energetic ions and cosmic rays.

Asymmetric bubble
VIM is led by veteran California Institute of Technology physicist Edward Stone, who has been involved with the Voyager programme since 1972. Having originally co-ordinated the 11 teams of scientists that were involved in the planetary phase of the mission, the 73 year old remains as excited as ever about the science that the Voyager craft are doing, particularly now that they are in the most distant part of the “heliosphere” — the bubble of space blown by the solar wind into the interstellar medium.

“It was our message saying ‘We, as a civilization, now can do this!'” Edward Stone, California Institute of Technology, leader of the Voyager Interstellar Mission (VIM)

Voyager 1 entered this region, known as the “heliosheath”, in December 2004 after crossing the “termination shock”, which is where the solar wind — normally travelling at about 400 km s^-1 — is abruptly slowed down to subsonic speeds as it presses against the hydrogen and helium ions of interstellar space. Voyager 2 followed its sister craft into the heliosheath in August 2007. What Stone and his colleagues are now trying to do is understand how the solar wind gets deflected as it interacts with the interstellar wind, which is proving more complex than models suggest.

One of the first surprises, as Stone and colleagues reported in Nature last year (454 71), was that the heliosphere is not spherical but asymmetric. Indeed, the southern boundary was found to be some 1500 million kilometres closer to the Sun than the northern boundary. “[This] tells us that there is something outside that is pressing more strongly on the south than on the north — most likely a magnetic field,” says Stone. “So we’re very interested in working with the models of the heliosphere to interpret and predict the direction of the local interstellar magnetic field and its strength.”

Stone claims to already have some information about the direction and strength of the magnetic field of interstellar space based on the fact that the heliosphere is distorted. But to measure the field directly, the Voyager spacecraft will have to cross the final frontier of the solar system — the heliopause — where the pressure of the interstellar wind and of the solar wind balance. Nobody knows for sure when Voyager 1 — the more distant of the two spacecraft — will enter interstellar space because no-one knows exactly where it begins, but Stone estimates that it will be within the next five or six years.

Beyond the final frontier
Telltale signs that Voyager 1 has left the heliosphere will, Stone thinks, be a change in the magnetic field and ion flow, and an increase in energetic particles from the Milky Way hitting the craft, which will no longer be protected by the heliosheath. “The radiation environment will be much more intense from supernovae that have occurred in the Sun’s region over the last 10 million years or so,” he says.

“Voyager represents the benchmark for outer solar-system exploration” John Zarnecki, The Open University, UK

Stone and his colleagues have also been surprised by the physics of the termination shock. Models assumed that the energy of the solar wind, which has to go somewhere when it slows down, would heat the wind from, say, 104 K before the shock to 106 K afterwards. But instead Voyager found that the temperature of the wind after the shock was only 105 K.

“We now believe that that energy went into heating ions that actually came in as atoms from interstellar space,” Stone says. “So once again we are trying to improve the models to understand this interaction.”

To Stone, the Voyager legacy is alive and well — a human adventure as much as a scientific one — and he applauds the original decision of a committee led by Carl Sagan to place two golden discs on the sides of the craft, containing sound and images about life on Earth, that may one day be our calling card to another civilization. “It was our message saying ‘We, as a civilization, now can do this!’,” he says.

But the craft have also inspired others too, such as space scientist John Zarnecki from the Open University in the UK, who was a principal investigator of the Huygens probe that landed on the surface of Titan on 14 January 2005. “To my generation, [Voyager] represents the benchmark for outer solar-system exploration,” he says. “Everything that we have done since then is built on it. There is no question that the success of the Voyager 1 fly-by of Titan in 1980 inspired me to believe that it was possible to send a probe there.”

Arm dentists with lasers, urge researchers

Shiny teeth Ultrasonic measurement goes dental

Your dentist’s verdict on the health of your teeth could be made more accurate, thanks a new physics-based technique developed by scientists in Australia and Taiwan. Developed by a team led by Simon Fleming at the University of Sydney, the technique involves using laser-generated ultrasound to probe tooth enamel elasticity without needing to scratch the surface of teeth. Writing in Optics Express, the researchers say that their method could also detect decay at an earlier stage than your dentist would by just peering and poking in your mouth.

In Fleming’s new technique, an area of tooth is illuminated and heated with a laser, which causes it to rapidly expand and initiate an ultrasonic surface acoustic wave (SAW) that then propagates outwards. The SAW vibration only penetrates around one wavelength deep into the material, and the velocity at which it travels along the surface is governed by the material’s elasticity. The elasticity of a tooth, which indicates its level of mineralization, and hence its healthiness, decreases as the tooth decays. Therefore, measuring the speed of the SAW vibration in a tooth can indicate how healthy it is.

Laser sound

Fleming concedes that at first he had his doubts that this technology would be suitable in dentistry. “I asked myself, ‘Are we really going to fire lasers into someone’s mouth and make their teeth ring like a wine glass?'” he said. However, after carrying out a series of trials, the researchers soon realized that the technique would be safe. “As a remote, non-destructive technique it is applicable in vivo and opens the way for early diagnosis of tooth decay,” he added.

The introduction of a non-destructive technique for probing teeth is likely to be warmly welcomed by squeamish patients. At present, the most commonly used method for measuring enamel elasticity, called “nano-indentation”, involves scratching the surface of teeth to gauge the mechanical response of the surface layers. Although the SAW method has only performed on extracted teeth, Fleming and Wang hope to develop the technique to make it suitable for use in the mouth. “We’re envisioning a probe about a centimetre in diameter,” Fleming said.

Surface probe

To test their technique, the researchers fired 266 nm ultraviolet light from a solid-state laser through a cylindrical lens at two teeth. The beam pulses once per second for 5 ns, creating an ultrasonic SAW vibration. Wang measured the changes in SAW velocity by shining a second laser at the tooth up to 10 mm from the original beam. The laser interacts with the SAW and then a proportion of light reflects back into an optical fibre, where it is collected and used to evaluate the properties of the surface.

“The ability of this technology to provide quantitative information and detect changes in the re-mineralization of enamel provide a unique opportunity not available using existing technologies in the dental clinic,” said Michael Swain, a dental and biomaterials researcher at the University of Sydney, who was also involved in the research.

Brian Culshaw, who performs research into laser-generated ultrasound at the University of Strathclyde, UK, agrees that it could be relatively straightforward to produce a probe for direct dental measurements. He points out, though, that no actual measurements of elastic modulus are presented in the paper, so the method cannot be compared with previous assessments of the mechanical properties of tooth enamel. “Much has to be done, probably in vitro, before the real usefulness of the tool can be evaluated,” Culshaw said.

'Nondiscovery' creates media ripple

Gravitational waves could be detected using interferometry Credit: NASA

By James Dacey

Big physics projects like the LHC that tackle some of the most fundamental questions in science are clearly a double-edged sword for journalists. On the one hand, it is relatively easy — and can be very enjoyable — to “sell” the sheer enormity of the research questions and the infrastructures involved in the projects themselves. On the other hand, it can be very difficult to pin down and explain the actual “news” when these things start to slowly churn out results.

One project that falls into this category is the search for gravitational waves that has been taking place over the past few years. Gravitational waves are vibrations of space-time predicted by Einstein’s general theory of relativity. A number of interferometery experiments are currently trying to detect gravitational waves by measuring tiny changes in the separation of two masses that are expected to occur when the waves traverse a detector.

As gravitational waves have been able to propagate freely since the beginning of the Universe, the hope is that direct detection could yield significant information about the first 380, 000 years after the Big Bang when the Universe was opaque to electromagnetic radiation.

In this week’s edition of Nature, a cohort of researchers report the latest findings from two of the major players in this search for gravitational waves – The LIGO Scientific Collaboration located in the US and the Virgo Collaboration in France and Italy. The paper reports the latest data from these two experiments collected 2005 – 2007, and discusses the implication of these results for the standard picture of cosmology.

The bottom line with this new paper is that both collaborations are yet to find evidence for the existence of gravitational waves — although, obviously, these results provide important limits on the amplitude of the gravitational-wave background and the energy density of gravitational waves in the Universe. The wider significance to cosmology is that this data is starting to constrain models of how the early Universe evolved as well as placing limits on some of the more specific theories like the idea “cosmic superstrings”.

Coming across this paper, it seemed pretty obvious that these results will be of great importance to the gravitational wave community, but I was pleasantly surprised to see such an abstract area of science make it into one of the UK’s national papers. The Times ran an enthusiastic news analysis piece with the headline “Warp factor zero:how scientists followed Einstein back to the first minute of the Universe”.

The fact that a mainstream newspaper would choose to cover such a “nondiscovery” of this kind must have also made enjoyable reading for the press team at CERN. Following the media bonanza surrounding last September’s launch of the LHC there must have been more than a few fears of a potential backlash when the project inevitably takes a good few years before it starts churning out results.

Long live big physics!

DNA scaffolds could make nano-circuits

A new method for folding DNA into a range of useful shapes and for positioning these “origami” pieces onto industrial materials has been developed by researchers at IBM and the California Institute of Technology (Caltech). The resulting nanostructures could be used to create electronic and optical devices for cheaper, speedier and more powerful computer chips, say the researchers.

The origami method for manipulating DNA was developed originally in 2006 by Paul Rothemund at Caltech. It involves forcing a large viral genome to bend by the addition of small synthetic DNA sequences in a solution. The shorter segments attach to the main genome and act as “fastening posts” that hold the DNA in a range of shapes such as squares, triangles and stars that measure just 100–150 nm across.

Sticky shapes

One of the main limitations of the technique is that the DNA shapes need to be formed in a saltwater solution, which can damage surfaces such as silicon wafers. In addition, the DNA structures tend to arrange themselves randomly onto a substrate surface, which makes it difficult to integrate them into electronic circuits afterwards.

Now, Rothemund and colleagues have overcome this problem by developing a novel approach to DNA origami that could also enable researchers to position DNA shapes with improved accuracy. The researchers first “draw” an outline of the desired DNA origami shape onto a silica substrate using a combination of electron-beam lithography and oxidative etching. The negative-charge of these patches makes them “sticky”, so that when a solution of DNA and magnesium chloride is poured onto the surface, the positively charged magnesium ions draw DNA strands into these patches, causing them to fold.

To demonstrate the new technique, Rothemund and his team created a series of sticky triangles on a silica substrate and filled 95% of the sites, etching the sites to within 10° of a designated orientation. “Not only can we put origami where we want them, but they can be oriented in the direction we want them,” says Rothemund. He adds that he was “completely thrilled” with IBM’s contribution to the work. “I honestly thought it might take 10 years to solve the problem, if it was ever going to be solved at all.”

Nano-scaffolding

The resulting nanostructures might be used as scaffolds or as miniature circuit boards for precisely assembling components like carbon nanotubes and nanowires. Such circuits would be much smaller than those possible using conventional techniques to fabricate semiconductors. Indeed, the resolution of the process is roughly 10× higher than those currently used to make computer chips because the spacing between the components can be as small as just 6 nm, explains Rothemund.

An added bonus is that the process is not simply limited to organizing structures like electronic components but could come in handy for biological studies too. For example, it might be used to study how groups of proteins interact by placing the proteins in patterns on top of the DNA origami.

The Caltech-IBM team will now develop its technique by trying to position and orient asymmetric shapes as well as symmetric ones, like triangles. “Making multiple shapes that can all be used at once without interfering with each other so that we can construct more complex patterns on surfaces will also be important,” says Rothemund.

Eventually, the researchers will look at industrial applications – for example, using the origami to organize nanoelectronic components for use in computer chips.

This research was published in Nature Nanotechnology.

Metamaterials learn to remember

Materials best known for their use as invisibility cloaks and super-lenses can now have their properties fixed with external stimuli, thanks to research performed in the US and the South Korea.

The new “memory metamaterials”, made by Tom Driscoll of the University of California at San Diego and colleagues, can have their electromagnetic properties temporarily modified depending on the level of applied voltage or light. According to the researchers, such tuning could allow for a “set-and-forget” approach to complex metamaterials for applications where it is impractical to maintain an external stimulus.

Harry Potter physics

Metamaterials are engineered structures that respond to electromagnetic waves in unusual ways. For example, they can be designed to have a refractive index that varies throughout, even taking on a negative value in some cases. This particular ability of metamaterials led to them being used in 2004 to make the first super-lens, which can beat the so-called diffraction limit, and the first invisibility cloak for microwaves in 2006.

One of the problems with most metamaterials is that they can only be designed to operate at a single “resonant” frequency. Although there are “frequency agile” metamaterials that allow their resonant frequency to be tuned with a certain stimulus, the tuning is lost as soon as the stimulus is taken away. Driscoll – whose group includes others from San Diego, Duke University in North Carolina, US, and ETRI in Daejeon, South Korea – solves this issue by creating memory metamaterials that can remember the new frequency that they should operate at.

Like many other metamaterials, memory metamaterials contain an array of conductive rings, called split-ring resonators (SRRs), which provide the basic electromagnetic properties. However, in memory metamaterials the SRRs are patterned onto vanadium dioxide, which has a metal-to-insulator phase transition that can be controlled with light or an applied voltage.

A new phase

It is the phase of vanadium dioxide, which can last for long periods after the light or voltage is withdrawn, that provides the “memory”. The specific phase alters vanadium dioxide’s capacitative properties, which in turn control the SRRs’ resonant frequency. Until the phase changes back, the resonant frequency is set.

To test their memory metamaterials, Driscoll and colleagues examined them with terahertz spectroscopy before and after they applied an electrical pulse. They found that the resonant frequency shifted from 1.65 THz by as much as 20%, and persisted for at least 10 minutes. “Such persistent tuning is likely to be useful in reconfigurable metamaterial devices, enabling a kind of set-and-forget approach to the reconfiguration process,” says Driscoll.

The researchers suggest that materials other than vanadium dioxide could push the effect to higher frequencies, and perhaps even the visible part of the spectrum.

This research was published in the latest edition of Science.

Producing tiny inorganic LEDs in bulk

A team of researchers in the US has developed a new technique to shrink the size of inorganic LEDs so they can be used as pixels in display screens. The novel process could allow these tiny light sources to be easily mounted on a range of materials – such as glass, plastic and rubber substrates – for the first time. This breakthrough could lead to affordable and eco-friendly applications, including computer screens and flexible displays, claim the researchers.

LEDs emit light across a narrow band of frequencies when their electrons combine with holes to form “excitons”. Conventional LEDs are made using inorganic materials and are usually created from a stack of thin semiconductor layers that are grown onto circular substrates that are diced up to form thousands of small chips. Blue and green LEDs are made from gallium nitride (GaN) and indium gallium nitride (InGaN) layers, and red equivalents are based on aluminum indium gallium phosphide (AlInGaP).

The bottom layers of these LEDs contain intentional impurities that create an abundance of electrons in this region. Positively charged holes are formed in the top layers by including a dopant and when an appropriate voltage is applied across the device these two carriers are drawn together so that they recombine to emit a photon.

Pros and cons

Inorganic LEDs are bright, reliable and last a long time, which is why they are used as back-lights in a range of applications from watches to advertising boards. The production of inorganic LEDs, however, is laborious because manufacturers must saw up wafers, remove the diodes and then relocate the diodes into specific applications. What is more, the lateral dimensions of LED chips at present can be no smaller than 200 μm, which is too large for many displays.

Organic LEDs, in contrast, are made by sandwiching carbon-based molecules between an indium tin oxide-coated substrate and a metal contact. Applying a voltage across this structure brings electrons from one side of the device together with holes from the other, and the recombination of these carriers generates a photon. In recent years, this process has been used to create arrays of parallel organic LEDs for use in display panels.

Producing displays that feature small inorganic LEDs arranged in parallel is a tougher challenge, but the US team led by John Rogers at the University of Illinois, Urbana-Champaign, has managed to do just that. The hope is that these tiny lights could eventually be produced en mass in parallel to act as the pixels of a display screen, rather than just forming the back-light.

In a small-scale demonstration of the technique, the researchers deposited an aluminium arsenide (AlAs) layer and a red LED onto a gallium arsenide (GaAs) substrate. They then selectively removed parts of the film using photolithography and etching to define square “LED islands” of length 50 μm on this wafer. Subsequent exposure to hydrofluoric acid removes most of the surrounding AlAs layer to leave an array of LEDs that are weakly bound to the substrate.

Printing light

An automated printing tool with a soft stamp picks up an array of these tiny LED chips and deposits them onto a substrate, such as glass, plastic or rubber. A thin metallic mesh on this substrate provides one contact to the LEDs, before a second contact is applied with a lithographic technique to complete the process.

Although the technique can currently be used to make red displays, Rogers now plans to develop full colour displays by working out a way to produce blue and green LEDs as well. “We are preparing a manuscript on that content now,” Rogers told physicsworld.com.

Another potential application is white-light systems for general illumination, which are being developed by a spin-off company, CoolEdge. “We are also exploring flexible and stretchable infra-red and ultra-violet devices for certain applications in biomedicine,” says Rogers.

The researchers reported their work in the latest edition of Science.

Cloud watching goes hi-tech

On cloud nine New device will help ESA to monitor the Earth

Researchers in Northern Ireland have built an instrument that could significantly improve the imaging of clouds from space, leading to more accurate weather forecasts and climate models. The electronic device will give meteorologists and climate scientists access to previously undetectable thermal emissions from clouds, which could reveal valuable information concerning the formation of rainfall and the Earth’s energy budget. The researchers have filed for a patent for the device, which will be used by the European Space Agency (ESA) in a number of upcoming missions.

With the continued uncertainty surrounding the effect of clouds in climate models, satellite instruments are playing an increasingly important role in climate science. Space-borne remote sensing instruments, however, have been limited by the fact that they can only detect either vertically or horizontally polarized components of thermal emissions from gases in the Earth’s atmosphere – but not both at the same time.

Head in the clouds

Robert Cahill and his colleagues at Queen’s University have overcome this problem by designing an electronic filter that can detect thermal emissions up to a very high frequency, regardless of how they are polarized. It consists of two rectangular loops of highly conductive metal embedded into the surface of a silicon wafer. The outer loop begins to conduct when excited by horizontally polarized waves, while an inner loop will only conduct when excited by vertically polarized waves.

The instrument, called a dual-polarized Frequency Selective Surface Filter (SSF), was constructed using silicon rather than metal due to the material’s higher tensile strength. It is designed to operate in the 250–360 GHz range but the researchers are also developing an SSF to operate at 664 GHz – the highest dual-polarization detector ever produced. One of the main advantages of SSF over alternative detectors is that it is freestanding, which means that it can be transferred between instruments in a range of different missions.

Cahill told physicsworld.com that, having tested the device under a range of physical conditions, his team is about to begin the first high altitude trials later this year. “We have spent the past few years working on the engineering aspects of the device and we are confident that the present design can withstand very extreme physical conditions, such as those experienced at a space launch,” he says.

In developing the SSF to function at much higher frequencies, the Queen’s University researchers have been working with the UK Centre for Earth Observation Instrumentation – an organization with the broad goal of improving the quality of instrumentation in Earth observation. The researchers have also secured a contract with the ESA to provide filters for a series of meteorological satellites that it plans to launch between 2018 and 2020.

Top 25 physics films unveiled

CERN featured in the recent blockbuster Angels and Demons, which did not make it into a new list of top physics films, but the European physics facility will play host to an international film festival in February Credit: Sonypictures

By Matin Durrani

If you’re a film buff — and even if you’re not — you’ll no doubt be interested to learn that a website called Online Engineering Degree has posted a list of its “top 25 movies for physics geeks”.

Top of the charts for us physics geeks is October Sky. It’s a film I’ve never seen – but then my colleagues often accuse me of living under a cultural stone – but it is, apparently, a “feel-good movie about boys launching their own rockets”. Hmm, can’t say I’m desperate to watch it.

In second place is Apollo 13 — the Tom Hanks blockbuster that has that scary bit where our hero almost carks it on his way back to Earth. Now I have seen that one.

Third is Infinity, a bio about the Manhattan project, featuring Feynman et al. Now you’re talking.

There follow a couple of others I also hadn’t heard of before – Stargate and Parralel Worlds, Parallel Lives — before we reach a quartet of definite blockbusters: Deep Impact, Armageddon, Star Wars and Star Trek. The full list can be found here.

I’m not quite sure what Goldeneye is doing on the list though. The compilers, however, reckon that Brosnan’s first Bond film has “its share of physics conundrums”, such as his ability to catch up with a falling plane — by jumping off a cliff, of course.

I emailed Suzane Smith, who alerted me to the list, to ask how the films were picked — was it a mysterious cabal of physicists or just her and her chums musing one lunchtime? Sadly she has not yet got back to me so I cannot say what criteria they used, if any.

No doubt you’ll have your own view so take a look at the top 25 and let us know what you think of the list by commenting below.

Meanwhile, genuine filmmakers with a science-fiction or science documentary film in the can might be interested to know that entries are now being invited for the next Cinėglobe International Short Film Festival, which is to be held at CERN from 16-20 February 2010.

Entry is free and review copies can be sent on DVD or uploaded to the festival website. The festival rules can be downloaded here.

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