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  1. For the record

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    Our pick of the best recent quotes and comments

    I think this was just an example of how not to do business

    Sean O’Keefe from Syracuse University quoted in the Times

    O’Keefe, a former NASA administrator, was commenting on the uncontrolled re-entry of the Chinese space station Tiangong-1, which crashed in the Pacific early last month.

    We’re caught up in a sort of no man’s land because of these technicalities

    Graham Peters, chairman of the trade association UKspace, quoted by Reuters

    Peters says that Britain is already losing work on the EU’s Galileo satellite programme as European consortia are starting to form without UK companies when bidding for new contracts.

    The art is a symbol of how he touched lives in the city and instilled a sense of pride in its residents

    David Sechur, senior bursar at the University of Cambridge’s Gonville and Caius College, quoted by the BBC

    Sechur was commenting on a mural that has appeared on a Cambridge bridge in tribute to the late Stephen Hawking.

    This result plants a flag

    Leslie Rosenberg from the University of Washington quoted in Symmetry

    Rosenberg was commenting on the latest results of the Axion Dark Matter Experiment, which recently showed that it had achieved the necessary sensitivity to detect axions – candidate dark-matter particles.

    I am a scientist. I am often wrong, and that’s okay

    Optical physicist Paulina Kuo from the National Institute of Standards and Technology, writing on the lab’s blog

    Kuo says that being wrong is part of the process of doing science, but the trick is catching errors before they “leave the lab”.

    It’s a nanomaterial solution to solve a chemistry problem

    Materials scientist Jiaxing Huang from Northwestern University quoted in the New York Times

    Huang and colleagues have discovered that a solution containing graphene could make a successful hair dye, which stayed on even after 30 washes.

  2. Seen and heard

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    Weird and wonderful stories from the world of physics

    (Cardiff University)

    The price of football

    With the 2018 FIFA World Cup kicking off next month, you’d better start collecting those Panini stickers now if you want a compete album. There are 682 stickers this time, but how much would it cost to collect them all? There are five stickers in a packet, which each costs 80p, so if you were incredibly lucky and had no duplicates it would take 137 packets, or £109.60, to complete. In reality, you will end up with lots to spare – probably of an obscure Panamanian right back – so Cardiff University mathematician Paul Harper has analysed the realistic cost of finishing the album. He found that, if you just bought packet after packet without swapping duplicates with friends, you would need to buy, on average, 4832 stickers or 967 packets to complete the book, at a whopping £773.60. But if you got together 10 friends in a swap group, filling the album would reduce the cost to a mere £247. Bargain.

    The rhythm of the beat

    Are music fans’ movements during a rock concert the same as those of fans during a football match? To answer that question, in 2016 seismologist Jordi Díaz from the Institute of Earth Sciences Jaume Almera in Barcelona installed a seismometer in the basement of the institute’s building, which is near to FC Barcelona’s stadium. Speaking at the European Geosciences Union general assembly in Vienna last month, Díaz revealed that he could pick up signals from football fans jumping up and down when their team scored – and even as they entered and left the ground. A rather large signal came in March 2017 when Barcelona were playing Paris Saint-Germain in a Champions League knock-out game. Trailing 4-1 from the first leg, Barcelona scored in the final minute of the match to win 6-5, taking them through to the next round and sparking wild celebrations. Díaz also studied the signal generated from a Bruce Springsteen rock concert in the city in 2016, finding that the seismometer could even be used to differentiate songs because fans danced differently depending on the rhythm of a tune. And as the music fans’ movements are more coordinated than those of the football fans, the seismometer could also differentiate between the two forms of activity. Yes, but what happens when football fans start dancing?

    Fake news

    Mathematical physicists Alexandre Bovet of Belgium’s University of Namur and Hernan Makse of the City College of New York have looked at how Twitter users interacted with purveyors of fake news during the 2016 US presidential elections. Using a “comprehensive” dataset of 171 million Tweets made during the five months before the election, they identified 30 million Tweets, sent by 2.2 million users, which were classified as spreading fake and extremely biased news. They found that “influencers” who spread centre- and left-leaning news largely determined the opinion of Hillary Clinton supporters. Yet they found the opposite for right-wing voters, who tended to influence the output of people producing fake-news Tweets. And who, according to the study, was one of the biggest spreaders of biased news? Yes, @realDonaldTrump.


    (iStock / CopterAnansak)

    Subatomic vote

    What’s your favourite particle? Physics labs around the world were championing their favourites in March for the title of “Most Awesome Subatomic Particle”. CERN backed the proton with the SLAC National Accelerator Laboratory in California putting its weight behind the photon. The electron, meanwhile, was championed by the National High Magnetic Field Laboratory in Tallahassee, Florida, while the Institute for Quantum Matter at Johns Hopkins University in Baltimore, Maryland, supported the neutron. After some intense canvassing, in late March people took to Twitter to pick their favourite. The winner, with 36% of the vote, was the photon. Second was the proton with 26%. The electron came third with 22% followed by the neutron with a lowly 16%. One wonders why the neutrino was left out; after all, it could be the only particle to offer physics beyond the Standard Model.

  3. Quasicrystal seen to superconduct

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    Cool stuff Diffraction pattern from the first superconducting quasicrystal alloy. (Keiichiro Imura, Noriaki K Sato and Tsutomu Ishimasa)

    Superconductivity has been observed for the first time in a quasicrystal – a solid with atoms arranged in an ordered pattern, but without any translational symmetry. The discovery was made by Keisuke Kamiya and Noriaki Sato at Nagoya University in Japan and colleagues, who created the quasicrystal from an alloy of aluminium, zinc and magnesium. They found it conducts without resistance when cooled below 0.05 K.

    The researchers began with their alloy of aluminium, zinc and magnesium in an “approximant crystal” phase, which is a bit like a quasicrystal, but has a lattice that repeats in space. They then reduced the aluminium content of the alloy while keeping the magnesium content almost constant. In doing so, the critical temperature marking the onset of superconductivity fell gradually from 0.8 K to about 0.2 K.

    When the alloy had just 15% aluminium, it transformed into a quasicrystal. The specific heat of the material jumped dramatically when cooled below 0.05 K, while the magnetic flux inside the material was almost entirely blocked – both signs that a transition to a superconducting phase had occurred. The team says that this “extraordinarily low” critical temperature explains why it had previously been difficult to observe superconductivity in quasicrystals.

    The conventional theory of superconductivity says it is due to correlated electrons forming “Cooper pairs” that flow without resistance. Closer inspection of the properties of the quasicrystal superconductor, however, suggests that the Cooper pairs arise from the weak coupling of electrons. Although relatively uncommon, weak coupling is seen in other materials including the approximant crystal phase of the alloy in the study. Sato says this similarity could mean that the observed superconductivity is not related to the quasicrystalline nature of the alloy – but is rather “dirty superconductivity” that occurs in imperfect crystals.

    However, he adds, the theory of quasicrystals also predicts another form of superconductivity, based on fractal geometry in quasicrystals. “There is a strong possibility that fractal superconductivity makes at least some contribution, and we would be excited to finally measure it,” Sato says. The team is now examining the interplay between this fractal geometry and the weakly coupled electron pairs (Nature Comms 9 154).

    Sam Jarman

  4. Nanowire arrays boost nuclear fusion

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    Fire me up The target chamber used to achieve laser fusion in deuterated polyethylene nanowires. (Advanced Beam Laboratory / Colorado State University)

    Smaller, cheaper neutron sources and new opportunities for simulating the extreme conditions at the centre of stars are two possible benefits of new work carried out by physicists in the US and Germany. Led by Jorge Rocca of Colorado State University, the researchers directed rapid-fire pulses of intense blue light from a compact laser at arrays of nanowires. The process generated a dense plasma yielding lots of neutrons from nuclear fusion.

    Most attempts to show nuclear fusion’s feasibility as an energy source involve huge, energetic lasers. The National Ignition Facility (NIF) in California, for example, is three football pitches big and generates pulses with an energy of 1.8 MJ, which compress tiny pellets of deuterium and tritium until the nuclei fuse and emit neutrons. NIF’s aim is ignition, with the alpha particle released by the fusing nuclei providing heat for a self-sustaining reaction – and the energy of the neutrons being tapped to produce electricity.

    However, NIF fires only a few times a day and some researchers are instead working on less energetic but more rapid-fire lasers. These will never near ignition, but can still achieve exceptionally high intensities – thanks to the extreme brevity, and hence power, of their pulses. In the latest work, Rocca and colleagues used a titanium-sapphire laser to generate pulses lasting just 60 fs with up to 1.65 J of energy.

    Capable of being fired three times a second at arrays of deuterated polyethylene nanowires, each about 5 μm long, the pulses rip electrons from the wires’ surfaces. The electrons then get accelerated to very high energies within the void between the wires, which heat up rapidly and explode. The resulting plasma accelerates deuterons to energies up to several megaelectronvolts, causing the deuterons to fuse and generate rapid bursts of neutrons.

    Rocca and colleagues were able to generate up to two million fusion neutrons per joule. While these efficiencies were higher than those from similar-sized lasers, they were lower than those at NIF, which recently yielded some 8 × 1015 neutrons per pulse, or about four billion neutrons per joule. The plasma, which has a high energy density, could, however, be ideal for studying extreme astrophysical environments (Nature Comms 9 1077).

    Edwin Cartlidge

  5. Physicists dish the dirt on clothes washing mystery

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    Rinse cycle The top row shows fabric that is rinsed in fresh water, while in the bottom row it was rinsed in a detergent solution. (S Shin et al., Phys. Rev. Applied (2018))

    A fresh water rinse is just as important as washing in detergent for getting your clothes clean, according to physicists in the US and UK. They claim that the rinse cycle plays a key role in removing dirt from deep within textiles, by setting up chemical and electrolyte gradients that draw it out. This insight could lead to the development of more efficient and environmentally friendly washing machines.

    Washing machines clean clothes using water mixed with detergent, followed by a fresh-water rinse and then a spin-cycle. The detergents contain surfactants – compounds that lower the surface tension between liquids and other substances. They are usually ionic and can attach to particles (such as dirt) in the solution, therefore causing a neutral particle to become charged.

    When washing clothes, the lowered surface tension makes it easier for the water to mix with and loosen dirt on the fabric. Conventional understanding is that the detergent draws out the dirt and the water rinse then washes the dirt away. But there is a problem with this idea – most fabrics contain tiny pores that do not allow any significant fluid flow inside them. According to Sangwoo Shin at the University of Hawaii, Patrick Warren of Unilever in the UK and Howard Stone of Princeton University in the US, it should take several hours for micron-sized particles to diffuse out of these micron-sized pores. Yet lots of particles do leave these pores on much faster time scales. The question as to how this is possible is known in the washing industry as the “stagnant core problem”. The researchers hypothesized that it is related to diffusiophoresis – the directed motion of particles up or down a chemical gradient.

    To investigate, the team mimicked stagnant cores in detergent-saturated fabrics by using microfluidic channels with dead-end pores filled with polystyrene particles (the dirt) in a surfactant solution. They found that if they flushed the pores with detergent-filled water, the flow did not remove the particles from within – there was no concentration gradient to encourage diffusiophoresis.

    In contrast, a fresh water rinse washed away most of the detergent except for deep within the pores, where the surfactant concentration, now attached to particles, remained high. As the surfactants are ionic, the resulting gradient created an electric field that encouraged diffusiophoresis to such an extent that the pores nearly emptied over 10 minutes of rinsing.

    The team repeated the tests using stained cotton and found that rinsing a detergent-saturated fabric with fresh water cleaned it much faster than a detergent solution rinse. (Phys. Rev. Appl. 9 034012).

    Michael Allen

  6. Persistent storms

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    (NASA / JPL-Caltech / SwRI / ASI / INAF / JIRAM)

    Rather than a representation of an organized fiery hell, this is an image of Jupiter’s north pole. Based on infrared data collected by Juno’s Jovian Infrared Auroral Mapper (JIRAM), it shows the pole’s odd arrangement of cyclones, which scientists have now discovered are remarkably persistent. The north pole has nine storms – with eight circling one that sits at the pole and each one being around 4000–4600 km in diameter. Meanwhile, the south pole is home to five cyclones circling a sixth, each around 5600–7000 km across. In both cases, the position and shapes of the cyclones remained more or less the same over hundreds of days of observation. The finding has the team baffled, as fluid dynamics cannot explain how the cyclones and patterns do not appreciably change over time, or why the storms do not interact with each other (Nature 555 216).

    Hamish Johnston

  7. {box: analysis – a decade of disappointment}

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    The launch of the James Webb Space Telescope (JWST) was starting to feel within touching distance. Set to blast off next year, excitement was brewing in the community with astronomers writing proposals for observing time on the JWST’s four scientific instruments. But following the telescope’s delay until May 2020 at the earliest, once again it feels a distant prospect (see above).

    Initially expected to cost $500m with a launch date of 2007, since then the JWST has had its departure rescheduled on more than 10 separate occasions. To adapt a term widely used by critics of nuclear fusion, the launch always seems a year away and who is to say that it won’t be postponed yet again. And while the US Congress capped the cost of the mission at $8.8bn last year, that figure is likely to be surpassed given the most recent hold-up.

    The engineering challenge to build the JWST is huge. The behemoth can easily be categorized as a “civilization-class” mission – pushing the forefront of engineering. The JWST’s sunshield, for example, which keeps the instruments cool and in a stable environment, is a massive 20 × 14 m while its 6.5 m mirror is made up of 18 hexagonal segments, giving the telescope a collecting area of 25 m2. Both the mirror and the sunshield are folded away for launch and will then unfurl following take-off.

    NASA has been burnt before when launching similar civilization-class projects. Weeks after the Hubble telescope was launched in April 1990, images from it were blurred. The culprit was spherical aberration due to the telescope’s primary mirror having been polished to the wrong shape. Given that Hubble was in orbit around the Earth, astronauts were fortunately able to repair the probe in December 1993. But it still wasn’t easy – it took 11 days and five space walks, a record at the time.

    Like Hubble, the JWST is expected to open a new vista on the cosmos. Yet the problem for NASA is that the JWST will instead be placed at Lagrange Point 2 – a place 1.5 million kilometres from Earth in the opposite direction to the Sun. No astronauts will be making a trip there if the telescope encounters any problems.

    Space science has seen some incredibly successful and daring missions in recent years, including the landing of the Curiosity rover on Mars in 2012 and the European Space Agency’s Philae lander touching down on comet 67P/Churyumov–Gerasimenko in 2014. The JWST will add to that list. Given the amount of money already spent and the delays, NASA can’t afford to get it wrong. This is especially so if the agency wants Congress on its side to fund future large-scale missions such as the Wide Field Infrared Survey Telescope, which US president Donald Trump has already tried to defund in his 2018 budget request (see ‘US science set for record spending boost’).

    The JWST is a mission too big to fail. It seems wise to delay the launch until NASA can do all it can to make it a success.

    Michael Banks

  8. NASA delays James Webb Space Telescope

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    Testing times ahead The James Webb Space Telescope has now been delayed until May 2020. (NASA / Desiree Stover)

    NASA has announced that it will delay the launch of the James Webb Space Telescope (JWST) to May 2020. The mission was expected to launch in mid-2019 but continuing issues in testing and combining the observatory’s components have pushed it back a year.

    The decision to delay the launch, which was made before Republican Congressman Jim Bridenstine from Oklahoma was confirmed as NASA’s new boss, will likely mean that the project exceeds the $8bn budget mandated by Congress in 2011.

    NASA has said it will now establish an independent review board, chaired by NASA veteran Thomas Young, to investigate the impact, with the agency expected to send a revised budget to Congress in late June. “The primary issue will be getting congressional authorization or a funding measure passed in fiscal year 2019 to get relief for Webb,” says NASA spokesperson Bob Jacobs.

    Developed by NASA along with the European and Canadian space agencies, the JWST will feature a mirror three times the diameter of the Hubble space telescope. Astronomers believe that the JWST will revolutionize their understanding of early star formation and exoplanets. The news of the delay comes after the US Government Accountability Office released a report in late February stating that the JWST was unlikely to meet its 2019 launch date.

    One of the issues facing the JWST is the craft’s huge 21 × 14 m sunshield that will provide a cold and thermally stable environment for the mirror and science instruments. Deployment tests of the sunshield took much longer than anticipated and engineers discovered tears in the ultrathin fabric, which have now been fixed.

    “Webb is the highest priority project for the agency’s science mission directorate, and the largest international space science project in US history,” says acting NASA administrator Robert Lightfoot, who has been in temporary charge for more than 15 months. “All the observatory’s flight hardware is now complete, however, the issues brought to light with the spacecraft element are prompting us to take the necessary steps to refocus our efforts on the completion of this ambitious and complex observatory.”

    Indeed, it is crucial that there are no issues once JWST launches. Unlike Hubble, which is in orbit around the Earth, JWST will instead be placed out of reach for astronauts at Lagrange Point 2 – a gravitational balance point some 1.5 million kilometres beyond the Earth’s orbit around the Sun. “Webb is a really complex machine and rigorous testing is required to have a high confidence of success,” notes Thomas Zurbuchen, associate administrator for NASA’s science mission directorate. “We have one shot to get this into space. Failure is not an option.”

    Michael Banks