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Home » Page 1054

Climate-friendly aircraft routing could cut environmental damage

Rerouting transatlantic flights to follow the most climate-friendly path could damage the climate 10% less for an increase in costs of just 1%. That’s according to a team from Germany, the Netherlands, Belgium, Norway and the UK.

“An attractive aspect of our approach is that it potentially enables some mitigation of aviation’s climate impact…using the current aircraft fleet,” Volker Grewe of the Deutsches Zentrum für Luft- und Raumfahrt, Germany, and Delft University of Technology in the Netherlands, explains. “Some mitigation options involve changes in aircraft or engine design, which would take decades to implement given the slow – and expensive – turnover of the global fleet.”

Volker and colleagues modelled routings for 800 daily flights across the Atlantic under five typical winter weather patterns and three typical summer patterns. The team combined the EMAC chemistry-climate model with an air-traffic simulator, choosing 85 variations for each flight path – 17 horizontal and five vertical. Then they picked the most “eco-efficient”, which is the path with the best ratio of climate-impact reduction to cost increase.

Multiple impacts

Aircraft have an impact on the climate by emitting carbon dioxide, water vapour, nitrogen oxide and particulates. These alter the concentration of the greenhouse gases ozone and methane, and also form contrails. Where and how high the plane is, as well as the time of day and season, all alter the size of its climate effect.

“It is now well established that – unlike the climate effects of CO2 – the non-CO2 climate effects such as contrail formation depend sensitively on when and where the aircraft emissions occur,” says Grewe, “and these sensitive regions vary in location and importance from day to day, as they are strongly influenced by the prevailing weather patterns.”

Contrails, for example, form if the hot, moist exhaust from the jet engine becomes saturated with respect to water when it mixes with the air in the atmosphere. And the trails only persist if the ambient air is saturated with respect to ice. Contrails affect both incoming radiation from the Sun and the exit to space of infrared radiation emitted by Earth and its atmosphere. On average, the trails cause warming, but close to sunrise and sunset they can result in cooling.

Ozone and methane

In general, aircraft emissions tend to boost the amount of ozone and decrease methane concentrations, with the warming from the extra ozone outweighing the cooling from the reduction in methane. But this varies a lot locally, and in some regions the emitted nitrogen oxides cause cooling.

“Put simply, if we can avoid those regions in the atmosphere where the non-CO2 emissions have the largest climate effect, we can reduce the climate impact significantly,” says Grewe. “Our modelling study showed that a large reduction of aviation’s climate impact is feasible at relatively low costs.”

Rerouting flights could cut their climate harm but may increase fuel and staff costs. Cost-efficient reductions in climate impact mostly resulted from avoiding the formation of warming contrails or from producing cooling contrails, Grewe and his colleagues found.

Close collaboration

Investigating such mitigation options requires close collaboration between atmospheric scientists and disciplines like air-traffic management, Grewe says. He believes all sectors must play a role in meeting the internationally agreed 2 °C target for the total climate effect of human activity.

“This is particularly challenging for the aviation sector, given the predictions of its continued growth over coming decades,” he says. “Hence, we need a combination of various mitigation options – technological, such as cleaner and more efficient engines, and operational, i.e. more eco-efficient routes. To make this happen, a political framework is required, which aims at limiting aviation impacts. It might be on an international or regional basis.”

Airlines would in all likelihood need regulations or a market incentive such as a price on climate impact to carry out such climate-friendly routing. While the International Civil Aviation Organisation (ICAO) has decided to implement the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), non-carbon-dioxide effects are still not considered in political decisions to limit the climate effect of aviation, Grewe says.

Reliable forecasts

“Implementing our proposed approach…is likely to be at least 5–10 years in the future – it should be considered ‘exploratory’ at present,” he adds. “We have to convince all stakeholders that the approach is worthwhile and feasible in practice, and that the costs associated with it are proportionate. And because the location of the climate-sensitive regions varies markedly from day to day, we also need to clearly establish that we can reliably forecast these areas sufficiently far in advance, so that re-routing aircraft to avoid them can be done with confidence.”

Now the scientists, who included a road map in their paper in Environmental Research Letters (ERL), are looking for more funding. They are also participating in ATM4E, a European project investigating whether it’s possible to avoid climate-sensitive regions in areas with high traffic density, as well as how the approach can be made operational, included in a weather forecast system, and verified.

New graphene-like material could have a band gap

A new 2D material just one atom thick has been made by an international team of researchers led by Axel Enders. Dubbed hexangonal boron–carbon–nitrogen (h-BCN), the material could offer many of the benefits of graphene, which is a hexagonal lattice made of just carbon. But unlike graphene, h-BCN has a direct electronic band gap, which could make it useful for creating electronic devices.

First isolated in 2004 by Andre Geim and Konstantin Novoselov, who shared the 2010 Nobel Prize for Physics for their discovery, graphene is blessed with a wealth of potentially useful mechanical and electronic properties. Despite being so thin and flexible, graphene is much stronger than steel and is an excellent conductor of heat. Graphene also conducts electrons at extremely high speeds. As a result, it could be the ideal material for making electronic devices that are ultrafast, high-density and even bendable.

Mind the gap

Many of graphene’s electronic properties arise from the fact that it is a semiconductor with a zero-energy gap between its valence and conduction bands. This is not ideal for making transistors and other electronic devices because such circuits need semiconductors, such as silicon, that have a band gap. In an attempt to make a modified version of graphene that does have a band gap, device developers have therefore explored various schemes – including applying an electric field, adding chemical impurities or modifying the structure of graphene. None, however, has proved ideal.

Now, Enders and colleagues at the University of Bayreuth, University of Nebraska-Lincoln, University of Krakow, State University of New York at Buffalo, Boston College and Tufts University have developed a graphene-like material that could fit the bill. The team made h-BCN by heating an organic molecule containing boron, nitrogen and carbon on an iridium substrate. The result is an atomically thin layer of h-BCN that is corrugated because of the lattice mismatch between the layer and substrate.

Multiple techniques

The team studied the structure and electronic properties of the film using molecular-resolved scanning tunnelling microscopy imaging, X-ray photoelectron spectroscopy and low-energy electron diffraction. The researchers also used density functional theory and first-principles calculations to further understand h-BCN.

An important result of the measurements and calculations is the prediction that h-BCN should have a direct electronic band gap of a size that falls between that of gapless graphene and hexagonal boron nitride, which is an insulator. According to the researchers, this band gap could make the material better suited than graphene for electronics applications.

“Our findings could be the starting point for a new generation of electronic transistors, circuits and sensors that are much smaller and more bendable than the electronic elements used to date,” says Enders. “They are likely to enable a considerable decrease in power consumption.”

The study is described in ACS Nano.

Flash Physics: Atoms mimic each other, QCD cracks five loops, metamaterial bricks shape sound

How atoms can impersonate each other

An atom could be made to emit an optical signal that is usually associated with another type of atom, according to calculations done by Andre Campos, Denys Bondar, Herschel Rabitz and Renan Cabrera at Princeton University in the US. When an atom is illuminated with light it can absorb energy and give off light at a set of frequencies distinct to that type of atom – which forms the basis of optical spectroscopy. However, if the atom is illuminated by an intense and complex optical signal it should be possible – in principle – to control the quantum states of the atom and cause the emission of light at frequencies not normally seen from that atom. Unlike conventional spectroscopy, a measurement of such a spectrum would not reveal the type of the atom – unless the experimenter knew the precise nature of the complex optical signal. Previous attempts to calculate the exact nature of such an optical signal has proven very difficult. But now, the team has come up with a successful scheme that involves both bound and ionized quantum states of an atom. Writing in Physical Review Letters, the team points out that some of the experimental techniques needed to carry out its scheme have already been demonstrated in the lab.

Five-loop QCD calculated at long last

A quantum chromodynamics (QCD) calculation involving five loops has been made for the first time by physicists in Russia and Germany. QCD describes the strong nuclear force between the quarks that make up protons, neutrons and other heavy particles. It is notoriously difficult to calculate the properties of systems governed by QCD because of the enormous strength of the strong nuclear force and the fact that calculations must consider large numbers of virtual quark–antiquark pairs that pop into and out of existence. As a result, physicists have struggled to calculate the properties of even simple objects such as the proton. Since the early 1970s, physicists have shown that QCD calculations can be made as a series of corrections to a leading-order calculation. These corrections are called loops, and physicists had been able to calculate one-, two-, three- and four-loop corrections. However, progress had been stuck at four loops since 1997. Now, Pavel Baikov at the Skobeltsyn Institute of Nuclear Physics in Moscow and Konstantin Chetyrkin and Johann Kühn of the Karlesruhe Institute of Technology have extended calculations to five loops. Writing in Physical Review Letters, the trio use five loops to calculate several properties of the Higgs boson.

Metamaterial bricks shape sound

Photograph of metamaterial bricks
These metamaterial bricks can be placed together to create a new supermaterial that can manipulate sound. (Courtesy: Interact Lab / University of Sussex)

A new “supermaterial” has been made that can bend and shape sound waves using specially designed bricks. Scientists at the University of Sussex and the University of Bristol in the UK have developed an acoustic device that can transform incoming sound waves into any required sound field. Sound manipulation is useful for many applications including ultrasound imaging, loudspeaker design and acoustic levitation. Current approaches use fixed lenses and expensive phased arrays. In contrast, this latest device comprises small, 3D-printed metamaterial bricks. These slow down incoming sound by directing it through meandering channels. The tailored geometries of the channels delay the wave phase to create the desired sound field. Gianluca Memoli from the Sussex team describes the device as a “do-it-yourself acoustics kit”, as the bricks are easily made and can be arranged in arrays specific to the application requirements. The new material could be used on a large scale to direct and focus sound to form an audio hotspot. It could also be suitable for small-scale applications such as focusing high-intensity ultrasound waves to destroy tumours within the body. The material is presented in Nature Communications.

 

  • You can find all our daily Flash Physics posts in the website’s news section, as well as on Twitter and Facebook using #FlashPhysics. Tune in to physicsworld.com later today to read today’s extensive news story on a new graphene-like material.

A laser-bubble mermaid, ode to seven exoplanets, metallic hydrogen is lost

Tiny bubbles: laser-made mermaid (Courtesy: Kota Kumagai, Utsunomiya University)
Tiny bubbles: a laser-made mermaid. (Courtesy: Kota Kumagai/ Utsunomiya University)

By Hamish Johnston

A popular way of melding science and art is to create an image of a mythical being in your lab. Yoshio Hayasaki and colleagues at Utsunomiya University in Japan have made a pretty good likeness of a mermaid using a laser that forms tiny bubbles inside a liquid. “In our display, the microbubble voxels are three-dimensionally generated in a liquid using focused femtosecond laser pulses,” explains team member Kota Kumagai.

(more…)

Nanoparticles give super-resolution microscopy a boost

A new way of beating the diffraction limit in optical microscopy has been unveiled by physicists in Australia and China. The technique makes use of nanoparticles to improve the efficiency of stimulated emission depletion (STED) microscopy, allowing it to be used with lower levels of illumination than previously possible.

STED microscopy was developed by the Germany-based physicist Stefan Hell, who won one third of the 2014 Nobel Prize for Chemistry for his work on the technique. The technique allows features much smaller than the wavelength of light to be observed with a microscope – something that is impossible with conventional microscopes.

Doughnut’s hole

STED involves tagging regions of interest in a sample with fluorescent molecules and using a beam of light to cause the molecules to emit light. A second “depletion” beam of light is focused to a doughnut shape in the sample and suppresses the fluorescence everywhere in the focal region – except at the doughnut’s central hole. By scanning the beams jointly over the sample, the spatial distribution of the fluorescent molecules can be determined at resolutions much smaller than the wavelength of the light used.

The resolution of STED improves as the intensity of the depletion beam increases. However, if the depletion beam is too powerful it will heat up the sample and destroy it – and this puts a practical limit on the resolution that can be achieved.

Now, Peng Xi, Dayong Jin and colleagues at Macquarie University and several other institutes in Australia and China have got around this problem by using lanthanide-doped upconversion nanoparticles (UCNPs) in place of fluorescent molecules. UCNPs are tiny crystals – as small as 13 nm across in this particular study – that absorb two or more long-wavelength optical photons and then emit one shorter wavelength photon.

Blue light

When illuminated with near-infrared light at 980 nm, the team’s UCNPs emit blue light at 455 nm. However, when a near-infrared depletion beam at 808 nm is also fired at the nanocrystals, a stimulated emission process causes the UCNPs to stop emitting blue light and emit near-infrared light instead.

To see if the UCNPs are appropriate for STED, the nanocrystals were dispersed in a medium that was specifically formulated for fluorescence microscopy. The team then used STED to image the UCNPs at a spatial resolution of about 28 nm, which is much shorter than the wavelengths of the light used by the microscope. To achieve similar resolution using traditional STED techniques would require a much more intense depletion beam, say the researchers. Another benefit of using the UCNPs is that the near-infrared light can be supplied by two simple diode lasers.

However, the technique does have some downsides. The intensity of blue light given off by the UCNPs is much lower than the light produced in conventional STED, which means that it takes about 10 times longer to acquire an image. Further work must also be done to ensure that the nanoparticles will only tag specific regions of a sample. The researchers must also ensure that the UCNPs do not stick together when dispersed in a sample.

The technique is described in Nature.

Flash Physics: Frozen droplets explode, biophysicist wins Emmy Noether prize, galaxy glows with gamma rays

Frozen droplets explode on camera

Exploding frozen water droplets have been filmed at high speed. As a droplet of water freezes from the outside in, it can explode in a shower of ice shards. Although the phenomenon is known to be caused by the self-confinement of the initial ice shell and expansion of the water inside as it solidifies, the mechanisms leading to the explosion are mostly unknown. A team from the University of Twente in the Netherlands has used high-speed cameras and computer modelling to study the event from the formation of the first ice crystals to the moment the droplet bursts. To do so, they supercooled millimetre-size droplets in a specially designed chamber. This meant that the water was below freezing point but free from ice crystals – which ensured a reproducible starting point for the experiments. Sander Wildeman and colleagues then triggered the freezing process by touching the droplet with a small tip. This caused a shell of ice to encapsulate the drop within microseconds. As the liquid water within the centre becomes compressed by the shell expanding inwards, the shell itself undergoes intermediate fracturing and healing. Furthermore, the scientists observed that some of the pressure is released as an “arm” of ice that extends from the droplet. Within about 2 s, the droplet shatters and sprays ice shards at a velocity in the order of 1 m/s. Using computer modelling, the team concluded that the droplets only explode if their diameter is larger than 50 μm. Below this, the surface tension of the ice shell is strong enough to balance the internal pressure and keep the droplet intact. The study, described in Physical Review Letters, could help in understanding how hail and other precipitation form.

Patricia Bassereau wins Emmy Noether physics prize

Photograph of Patricia Bassereau
Innovative and inspiring: biophysicist Patricia Bassereau. (Courtesy: Institute Curie Research Centre)

The Autumn-Winter 2016 Emmy Noether Distinction for Women in Physics prize has been given to Patricia Bassereau of the Institute Curie Research Centre in Paris, France. Awarded by the European Physical Society, the prize was given to Bassereau for “her important and innovative work on the studies of soft matter and in vitro biological systems at the forefront of biophysics. Her rich and fruitful career is an inspiration for young women researchers.” Bassereau leads the Membrane and Cell Functions research group at the Institute Curie, where she is currently working on the physics of biological membranes including non-equilibrium systems, molecular motors and biomimetic systems. Describing the importance of mentorship for women embarking on careers in science she says: “I have been lucky to meet great scientists who gave me advice, helped me gain self-confidence and also believed I could perform interesting science.”

Bright gamma-ray sources spotted at centre of Andromeda

The centre of the Andromeda galaxy as seen by the Fermi Gamma-ray Space Telescope
The centre of the Andromeda galaxy as seen by the Fermi Gamma-ray Space Telescope. The yellow and white regions have the most intense gamma-ray emissions. (Courtesy: Credit: NASA/DOE/Fermi LAT Collaboration and Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF)

Most gamma rays emanating from the Andromeda galaxy come from its centre, rather than throughout the galaxy, as previously expected. That is the conclusion of astronomers who have used NASA’s Fermi Gamma-ray Space Telescope to study Andromeda, which at 2.5 million light-years distance is the nearest major galaxy to Earth. The result is reminiscent of the previous – and unexpected – observation by Fermi that there is an excess of gamma rays coming from the centre of the Milky Way. The astronomers have proposed several explanations for the Andromeda observation. One is that the gamma rays are produced by the decay of hypothetical dark-matter particles, which are expected to concentrate at galactic centres. Another is that there may be an unexpectedly high concentration of pulsars at the centre. These are spinning neutron stars that emit copious gamma rays. The next step for the team is to look at X-ray and radio emissions, which could help scientists work out if the gamma rays are indeed produced by pulsars. The observations are described in The Astrophysical Journal.

 

  • You can find all our daily Flash Physics posts in the website’s news section, as well as on Twitter and Facebook using #FlashPhysics. Tune in to physicsworld.com later today to read today’s extensive news story on a new fluorescence microscopy technique.

Nuclear energy may come from the sea

Uranium has been extracted from seawater using electrochemical methods. A team at Stanford University in California has removed the radioactive material from seawater by using a polymer–carbon electrode and applying a pulsed electric field.

Uranium is a key component of nuclear fuel. On land, there are about 7.6 million tonnes of identified uranium deposits around the world. This ore is mined, processed and used for nuclear energy. In contrast, there is 4.5 billion tonnes of the heavy metal in seawater as a result of the natural weathering of undersea deposits. If uranium could be extracted from seawater, it could be used to fuel nuclear power stations for hundreds of years. As well as taking advantage of an untapped energy resource, seawater extraction would also avoid the negative environmental impacts of mining processes.

Tiny concentrations

Scientists are therefore working on methods to remove and recover uranium from the sea. However, the oceans are vast, and the concentration of uranium is only 3 μg/l, making the development of practical extraction techniques a significant challenge. “Concentrations are tiny, on the order of a single grain of salt dissolved in a litre of water,” says team member Yi Cui. Furthermore, the high salt content of seawater limits traditional extraction methods.

In water, uranium typically exists as a positively charged uranium oxide, or uranyl, ion (UO2+2). Most methods for extraction involve an adsorbent material where the uranyl ion attaches to the surface but does not chemically react with it. The current leading materials are amidoxime polymers. The performance of adsorbents is, however, limited by their surface area. As there are only a certain number of adsorption sites, and the concentration of uranium is extremely low compared with other positive ions like sodium and calcium, the uranium-adsorbent interaction is slow and sites are quickly taken up by other ions. Furthermore, the adsorbed ions still carry a positive charge and therefore repel other uranyl ions away from the material.

Electrochemical answer

Cui and his team turned to electrochemistry and deposition for a solution to this problem. In a basic electrochemical cell, there is an electrolyte solution and two submerged electrodes connected to a power supply. By providing the electrodes with opposite charges, an electrical current is driven through the liquid, forcing positive ions to the negative electrode, and electrons and negative ions to the positive electrode. At the negative electrode, called the anode, the positive ions are reduced, meaning they gain electrons. For most metallic ions, this causes the precipitation of the solid metal and is often deposited on the electrode surface.

In their electrochemical cell, the team used an anode made of carbon coated with amidoxime polymer, and an inert partner electrode. The electrolyte was seawater, which for some tests contained added uranium. By applying a short pulse of current, the positive uranyl, calcium and sodium ions were drawn to the carbon–polymer electrode. The amidoxime film encouraged the uranyl ions to be preferentially adsorbed over the other ions. The adsorbed uranyl ions were reduced to solid, charge-neutral uranium oxide (UO2) and once the current was switched off, the unwanted ions returned to the bulk of the electrolyte. By repeating the pulsed process, the researchers were able to build up the deposited uranium oxide on the electrode surface, no matter what the initial concentration of the solution was.

Removal and recovery

In tests comparing the new method to plain adsorptive amidoxime, the electrochemical cell significantly outperformed the more traditional material. Within the time it took the amidoxime surface to become saturated, the carbon–polymer electrode had extracted nine times the amount of uranium. Furthermore, the team demonstrated that 96.6% of the metal could be recovered from the surface by applying a reverse current and an acidic electrolyte. For an adsorption material, only 76.0% can be recovered with acid elution.

Despite the researchers’ success, there is a long way to go before large-scale application. To be commercially viable, the benefits of the extracted uranium must outweigh the cost and power demands of the process. Furthermore, the process needs to be streamlined to treat large quantities of water. “We have a lot of work to do still but these are big steps toward practicality,” Cui concludes.

The extraction method is described in Nature Energy.

Flash Physics: Rhodium breaks up carbon dioxide, UK invests £229m in new institutes, ions sense rotation

Illuminated rhodium breaks up carbon dioxide

Simulation of rhodium nanocubes breaking down carbon dioxide into mainly methane when illuminated with ultraviolet light
Cubic breakdown: rhodium nanocubes break down carbon dioxide when illuminated. (Courtesy: Chad Scales)

Carbon dioxide has been converted to methane by illuminating rhodium nanoparticles with ultraviolet light. Using light to break down carbon dioxide (CO2) in the atmosphere is a long-sought-after mechanism. Not only could it start reducing the environmental impact of human CO2 emissions, the methane could be used as a renewable source of energy. Scientists at Duke University in the US have broken apart CO2 using tiny, cubic rhodium particles and ultraviolet light. Rhodium is a rare, inert metal that is already used in small amounts to speed up chemical processes in industry. To catalyse such reactions, an extra energy input is required and heat is typically used. Using rhodium nanoparticles, Jie Liu and team compared the breakdown of CO2 using heat and ultraviolet light. They found that not only is the reaction more efficient when using light, it almost exclusively produced methane rather than a mix with carbon monoxide. The group suggests that the light generates energetic electrons that activate the necessary intermediates for methane production, while barely affecting chemical bonds involved in carbon-monoxide production. Next, the team hopes that tweaking the size of the nanoparticles will mean that sunlight can power the reaction. The work is presented in Nature Communications.

UK invests £229m in new research institutes

Artist's impression of the Sir Henry Royce Institute for Advanced Materials
The Sir Henry Royce Institute for Advanced Materials will open in 2019. (Courtesy: University of Manchester)

The UK government has announced it will provide £129m for a new materials centre located at the University of Manchester. Once open in 2019, the £150m Sir Henry Royce Institute for Advanced Materials will perform research in a range of areas from 2D materials to advanced metals processing, nuclear materials and energy storage. The institute was first mooted in 2014 by former UK Chancellor George Osborne and in late 2015 it was revealed that Julia King, a former chief executive of the Institute of Physics, which publishes Physics World, will chair the new centre. Meanwhile, the UK government has also announced that it will invest £103m in the Rosalind Franklin Institute – a new hub for life and physical sciences. Based at Harwell in Oxfordshire, it will be led by optical physicist Ian Walmsley from the University of Oxford. The institute, together with seven other partner sites, will aim to develop new technologies to tackle major challenges in health and life sciences, such as developing new treatments for chronic diseases.

Rotation sensor could be made from interfering ions

A proposal for a compact yet highly sensitive device that detects rotation using ions has been unveiled by physicists in the US. The sensor, which has yet to be built in the lab, is based on a Sagnac interferometer. This involves splitting a wave into two signals and sending the signals in opposite directions around a ring before recombining the signals at a detector. A change in how the interferometer is rotating will affect how the two signals interfere at the detector. This Sagnac effect is already used in optical gyroscopes in which light is sent in opposite directions around a coil of optical fibre. Now, Wes Campbell and Paul Hamilton of the University of California, Los Angeles, have proposed a scheme that uses ions to make an accelerometer that should combine high sensitivity with very small size. The wave–particle duality of quantum mechanics means that the ions behave like waves as they travel through the interferometer – which is based on an ion trap. Crucial to the success of the design, according to Campbell, is that the matter waves complete many circuits of the interferometer – much like light in a fibre coil. This would allow a practical device to be made much smaller than existing matter-wave gyroscopes, which are based on beams of atoms. If built, their device is expected to be as sensitive as existing commercial optical gyroscopes. However, writing in Journal of Physics B: Atomic, Molecular and Optical Physics, Campbell and Hamilton say that the performance could be improved. Although the device is only sensitive to changes in rotation, Campbell says it could be possible to use an ion trap to create a linear accelerometer. This could be paired with a rotation sensor to create GPS-free navigation systems that could be used on spacecraft and other vehicles used in locations where GPS is not available.

 

  • You can find all our daily Flash Physics posts in the website’s news section, as well as on Twitter and Facebook using #FlashPhysics. Tune in to physicsworld.com later today to read today’s extensive news story on extracting uranium from seawater.

A tour de force of the cosmos

There is something rather strange about how physicists, both young and old, perceive science. I am sometimes confronted with the realization that I too am susceptible to a host of strange, if not pathological, notions: that science is pure and logical; that it is distant from the apparent caprice of more human-centred realms such as art or politics or sociology; and that this difference somehow makes science clean and ideal. However, the more I engage with the infrastructures of science – its reliance on both individuals and groups; its continuous need for advancing technologies; and the indelible effects of human rivalries, camaraderie and oversights – the more my notions of scientific idealism give way to a better understanding of scientific realism.

It is through this lens that I find Priyamvada Natarajan’s book, Mapping the Heavens: the Radical Scientific Ideas that Reveal the Cosmos, to be an instructive and thought-provoking exploration of the connections, tensions and mishaps that so often accompany scientific venture. The book delves into some of the most important and influential discoveries in cosmology – from exoplanets to dark energy and other universes. Through the stories of individuals and collaborations that have transformed cosmology, Natarajan – an astrophysicist at Yale University – attempts to blur the lines between the products of science and its human creators.

In doing so, she effectively renders modern physics and cosmology as an inherently anthropological search for answers to deep, fundamental questions. What is the Earth’s place in the universe? Is there a beginning and an end to all things? Is there more to our universe than we currently know? Indeed, Natarajan’s contemplations on various historical parables serve as a useful reference for today’s early-career scientists, who may find themselves in a state of uncertainty as they navigate the realms of “big science”, with its large collaborations and complex social structures.

On starting my first postdoctoral position at Cardiff University in the UK as part of the Laser Interferometric Gravitational-Wave Observatory (LIGO) collaboration, on 1 September 2015, I could not have predicted the historical observation we were to make a mere 13 days later. A gravitational wave, resulting from the collision of two black holes some 1.3 billion light-years away, rippled through the Earth and caused LIGO’s twin interferometers – in Livingston, Louisiana and Hanford, Washington – to squeeze and stretch by an infinitesimal but measurable amount.

It is expected that LIGO’s future observations will empower us to make novel contributions to many of the topics in astronomy and cosmology that the book explores. However, just as Natarajan traces the historical passage of astronomy and cosmology from fringe topics to venerated research fields, LIGO and its supporting communities are currently undergoing the process of mapping out an entirely new scientific subfield: gravitational-wave astronomy.

As LIGO scientists seek to define gravitational-wave astronomy with the insights gained from new observations, the field’s inherent ties to cosmology make Natarajan’s exploration valuable for any gravitational-wave enthusiast. This is perhaps not the most surprising claim, as gravitational physics – founded by Isaac Newton, and then reprised and strengthened by Albert Einstein – is the nexus for many stories in astronomy and cosmology. From the existence of black holes, to dark matter and dark energy, the impact of Einstein’s theory of gravity cannot easily be downplayed.

However, scientists may also often forget (either in exuberance over Einstein’s legacy or due to the seemingly deterministic nature of scientific progress) what Natarajan goes through a mildly repetitive exercise to reinforce: that not only do human biases impact the execution of science, but also they often impede and even obscure its progress as a whole.

Indeed, bias affects even the best of scientists, as Natarajan points out – Einstein’s long-held, incorrect belief in a static universe perfectly elucidates this point. The initial stubbornness of the astronomy community to accept the idea of dark matter, despite considerable observational evidence, shows how bias can affect entire groups. At the same time, Natarajan also describes how academic tensions and scientific scepticism go hand in hand with theory and evidence, to give way to and powerful consensus. Such agreement is the precursor to crucial, paradigm-changing discoveries that inevitably impact a scientific field, as well as the lives of every individual scientist.

Indeed, during my time at Cardiff, I have witnessed first-hand the changing trajectory of belief in a theory that results when heavy scepticism meets robust evidence. Looking back at an early staff meeting, a particular individual doubted the detectability of gravitational-wave signals and openly mocked the decades-long efforts of the group. It was quite interesting to see both heckler and advocate toast with champagne a few months later, after all arguments had been put to rest. Although I am certainly biased by my experiences as a gravitational-wave astronomer, I would recommend Mapping the Heavens to readers from middle-school level onwards and from a wide range of backgrounds. Any minor wrinkles in the text’s construction and style are outweighed by insights gained into modern physics’ history via Natarajan’s skilful writing.

  • Yale University Press 288pp £16.99hb

Web life: ParticleBites

So what is the site about?

As you may guess from its name and strapline, ParticleBites – “The high-energy physics reader’s digest” – presents the latest research updates in high-energy particle physics. The blog, which serves as an online particle-physics journal club, covers both experimental and theoretical research, with each post based on a recently published research paper that is available on the arXiv preprint server. ParticleBites’ main aim, much like its sister website AstroBites, is to make research more accessible to those starting out in academia, by simplifying research papers and making the science more accessible to undergraduate students. “For most people, it takes years for scientific papers to become meaningful. Our goal is to solve this problem, one paper at a time,” claim the creators. Each post is written such that not only is the new research explained, but its importance in the field at large is also provided, giving some much-needed context to current research, especially for those who are new to particle physics. The website has about six to eight posts a month and topics range from dark matter and supersymmetry to neutrinos and nuclear physics. There is also the odd post about outreach, science policy and rumours, all with a particle-physics twist.

Who is behind it?

By particle physicists and for particle physicists, the posts are written and edited by a team of graduate students and postdoctoral researchers, including 10 regular authors and the occasional guest author. ParticleBites was founded in 2013 by Flip Tanedo, the website’s editor, following the Communicating Science 2013 workshop, which was organized by Harvard University’s Nathan Sanders, who co-founded AstroBites. Tanedo – an assistant professor in theoretical physics at the University of California, Irvine – also serves as director, together with Julia Gonski – a PhD student in the high-energy experimental group at Harvard. Tanedo also created the ParticleBites logo, which depicts a gauge boson (a force carrier) “eating” a Goldstone boson (spinless particles associated with the spontaneous symmetry) and becoming longitudinally polarized. According to Tanedo, the cartoon “represents the part of the phenomenon of electroweak symmetry breaking, which plays a central role in the Standard Model of particle physics.”

Can I get involved?

Yes – if you are a PhD student or postdoc in particle physics. The website has a “Write for us” section, which says that “if you’re a particle physicist (broadly defined) with a passion for writing and science outreach, feel free to contact us about writing opportunities with ParticleBites”. Potential authors are expected to have a solid background in particle physics and are selected on the basis of a sample blog post. Authors are expected to write a new post every two to four weeks, as well as edit fellow writers’ posts. The team is also looking for undergraduate and graduate students who can get involved in editing and proofreading posts.

Can you give me a sample quote?

From a post published in September 2016, titled “Horton hears a sterile neutrino?”: “Neutrinos, like the beloved Whos in Dr Seuss’ Horton Hears a Who!, are light and elusive, yet have a large impact on the universe we live in. While neutrinos only interact with matter through the weak nuclear force and gravity, they played a critical role in the formation of the early universe. Neutrino physics is now an exciting line of research pursued by the Hortons of particle physics, cosmology and astrophysics alike. While most of what we currently know about neutrinos is well described by a three-flavour neutrino model, a few inconsistent experimental results such as those from the Liquid Scintillator Neutrino Detector (LSND) and the Mini Booster Neutrino Experiment (MiniBooNE) hint at the presence of a new kind of neutrino that only interacts with matter through gravity. If this ‘sterile’ kind of neutrino does in fact exist, it might also have played an important role in the evolution of our universe.”

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