The first person to use gas for illumination was a French engineer by the name of Philippe Lebon. In 1801 his revolutionary system of methane pipes and jets lit up the Hôtel de Seignelay so brilliantly that ordinary Parisians paid three francs apiece just to marvel at it. Overnight guests may have been less enthusiastic. Although methane itself is colourless and odourless, Lebon’s process for extracting it left the gas heavily contaminated with hydrogen sulphide, which – as Mark Miodownik cheerfully reminds us in his latest book – is a chemical that “smells of farts”.

The often odorous and frequently dangerous world of gases is a fascinating subject for a popular-science book. It’s also a logical one for Miodownik, a materials researcher at University College London, UK, whose previous books were about solids and liquids. The first, Stuff Matters, was a huge critical and commercial success, winning the 2014 Royal Society Winton Prize for science books (and Physics World’s own Book of the Year award) on its way to becoming a New York Times bestseller. The second, Liquid, drew more muted praise, with some critics objecting to a narrative gimmick that shoehorned liquid-related facts into the story of a hypothetical transatlantic flight.

Miodownik writes about the science of substances such as breath, fragrance and wind as well as methane, hydrogen and other gases with precise chemical formulations

Miodownik’s third book It’s a Gas avoids this artificial structure and is all the better for it. It also adopts a very loose definition of “gas”, which leaves Miodownik free to write about the science of substances such as breath, fragrance and wind as well as methane, hydrogen and other gases with precise chemical formulations. The result is a lively, free-associating mixture of personal, scientific and historical anecdotes very reminiscent of Stuff Matters, though inevitably one that feels less exceptional than it did the first time around.

The chapter on breath shows how this mixture works. It begins with a story about the young Miodownik watching a brass band march past. Next, we get an explanation of how air travels through brass instruments. By the end of the chapter, Miodownik has moved on, via Air Jordan sneakers and much else, to pneumatic bicycle tyres and their surprising impact on English genetic diversity.

Though the connection might seem fanciful at first, it seems that after John Dunlop patented his air-filled rubber bicycle tyre in 1888, many people (especially women) were suddenly able to traverse bumpy roads cheaply, comfortably and without assistance. As their horizons expanded, their inclination to marry someone from the same parish plummeted: between 1887 and the early years of the 20th century, marriages of this nature dropped from 77% to 41% of the total.

Miodownik is not the first to make the link between bicycle tyres and longer-distance courtships. (He credits the geneticist Steve Jones for the insight, building on work by the 20th-century geographer P J Parry.) However, his decision to include the tale is a deft one, as it illustrates just how important gases and their associated technologies have been to human history.

Anaesthetics are another good example. Though medical professionals were scandalously slow to accept nitrous oxide, ether and chloroform, these beneficial gases eventually revolutionized surgery, saving millions of patients from the agony of their predecessors. Interestingly, criminals proved far less hide-bound than doctors, swiftly adopting chloroform as a way of subduing victims – though the ever-responsible Miodownik notes that this tactic seldom works as quickly as it does in the movies, and errors in dosage can be fatal.

Not every gas-related invention had such far-reaching effects. Inflatable mattresses never really caught on; as Miodownik observes, “beds were for sleeping and sex, and neither was enhanced by being unexpectedly launched into the air every time your partner made a move”.

The history of balloons is similarly chequered. Around the same time as Lebon was filling the Hôtel de Seignelay with aromas, an early balloonist, Sophie Blanchard, was appointed Napoleon’s “aeronaut of the official festivals”. Though Blanchard went on to hold a similar post under the restored King Louis XVIII, Miodownik notes that her favourite party trick – launching fireworks from a balloon filled with highly flammable and escape-prone hydrogen – eventually caught up with her. In 1819, aged just 41, her firework-festooned craft crashed into the roof of a house and Blanchard fell to her death.

Miodownik brings a pleasingly childlike wonder to his tales of gaseous derring-do

The lessons of this calamity were not learned. More than a century later, 35 passengers and crew on the hydrogen-filled Hindenburg airship (which included a smoking area among its many luxuries) met a similarly fiery end.

Occasional tragedies aside, Miodownik brings a pleasingly childlike wonder to his tales of gaseous derring-do. He often opens chapters with stories from his actual childhood, and while a few of these (like the brass band) are merely cute, others are genuinely jaw-dropping. Some readers may recall that Miodownik began Stuff Matters by describing the time he got stabbed on the London Underground; while there is nothing quite so dramatic in It’s a Gas (and no spoilers in this review), he clearly had an eventful youth.

At times, it becomes almost a game to guess which gas these opening anecdotes will lead to. Though some readers may find the connections a little tenuous, Miodownik is a good enough writer to make his leaps of logic seem effortless even when they are noticeable. The result is a book as delightfully light as its subject matter, and a worthy conclusion to Miodownik’s informal phases-of-matter trilogy – although if he wants to write about plasmas next, I certainly won’t stop him.

• 2024 Viking 304pp £22.00hb

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Mechanical watches and clockwork toys might seem like relics of a bygone age, but scientists in the US and Japan are bringing this old-fashioned form of energy storage into the modern era. By making single-walled carbon nanotubes (SWCNTs) into ropes and twisting them like the string on an overworked yo-yo, Katsumi Kaneko, Sanjeev Kumar Ujjain and colleagues showed that they can store twice as much energy per unit mass as the best commercial lithium-ion batteries. The nanotube ropes are also stable at a wide range of temperatures, and the team say they could be safer than batteries for powering devices such as medical sensors.

SWCNTs are made from sheets of pure carbon just one atom thick that have been rolled into a straw-like tube. They are impressively tough – five times stiffer and 100 times stronger than steel – and earlier theoretical studies by team member David Tománek and others suggested that twisting them could be a viable means of storing large amounts of energy in a compact, lightweight system.

Making and measuring nanotube ropes

To confirm this, the team needed to overcome two challenges. The first was finding the best way of making energy-storing ropes from commercially-available SWCNT materials. After testing various methods, the team settled on a yarn-like rope treated with thermoplastic polyurethane, which accelerates the elastic deformation of individual nanotubes and improves their ability to “share the load” with others.

The second challenge was to measure energy stored in ropes which, at only microns in diameter, are much thinner than a human hair. “This small size made it hard to handle and measure them accurately,” says Kumar Ujjain, an assistant research scientist at the University of Maryland-Baltimore County’s Center for Advanced Sensor Technology (UMBC-CAST) who began the project while working with Kaneko at Shinshu University.

The team’s solution was to develop an instrument that combines a motor for twisting the sample with a laser displacement gauge to measure how much torque the strained rope exerts. By adding a microscope and high-speed camera, the scientists could track how much force and twisting the ropes experienced in real time. “This precise measurement was crucial for determining how much energy the ropes could store,” Kumar Ujjain says.

To measure the stored energy, the scientists added a load to the twisted rope and monitored its rotation as the rope unwound. The maximum gravimetric energy density (that is, the energy available per unit mass) they measured was 2.1 MJ/kg (583 Wh/kg). While this is lower than the most advanced lithium-ion batteries, which last year hit a record of 700 Wh/kg, it is much higher than commercial versions, which top out at around 280 Wh/kg. The SWCNT ropes also maintained their performance over at least 450 twist-release cycles, and Kumar Ujjain says they have other advantages, too.

“Storing energy in mechanically twisted carbon nanotube ropes is generally safer than using chemical energy storage, such as in lithium-ion batteries, which can pose risks like fires or explosions,” he explains. “The energy in these twisted ropes is purely mechanical and doesn’t involve hazardous chemicals.”

Managing and exploiting stored energy

One possible application for a chemically safe, biocompatible energy-storage system would be in medical sensors. The UMBC-CAST team is developing a stretchable, porous CO₂ sensor that can be applied directly to a patient’s skin, and Kumar Ujjain says that a micro-generator based on twisted nanotube ropes could be a good way of powering it. Getting to that point will, however, require additional research focused on scaling up the nanotube ropes, integrating them with existing devices, and above all, developing mechanisms for releasing the stored energy in a controlled, predictable way.

“There is a risk if the ropes are twisted too tightly,” Kumar Ujjain explains. “In such cases, the tension could suddenly release, like an over-tightened spring in a clockwork watch, potentially causing damage.” Proper handling and safety measures should, he says, make this risk manageable.

The study is described in Nature Nanotechnology.

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My home state of Kansas is famous for being very flat and having lots of tornadoes, so when I read that scientists in nearby Indiana have found a connection between flatness and tornado risk, I was intrigued.

Turns out, it’s not Kansas’ own flatness that’s to blame. Instead, scientists at Purdue University say that its exciting weather is due to the flat surface of the Gulf of Mexico. Together with other geographic factors, they argue, the ocean’s smoothness is what turns Kansas and neighbouring states into an ideal setting for films like the 1996 summer blockbuster Twister and its just-released sequel Twisters.

The scientists’ argument begins with a piece of conventional wisdom. The “tornado alley” of the North American Great Plains is commonly attributed to two geographic features: the Rocky Mountains to the west and the Gulf of Mexico and the Caribbean Sea to the south. When trade winds hit the east slope of this north–south mountain range, they turn northward and increase in speed while developing what meteorologists call “anticyclonic shear vorticity” – a fancy way of saying that the air starts to rotate counterclockwise. At the same time, southerly winds from the tropical Gulf pump warm, moist air into the lowest layer of the atmosphere. Together, these phenomena create conditions that favour severe thunderstorms and the tornadoes they spawn.

There’s just one problem with this story. The central region of South America (Uruguay and parts of Argentina, Paraguay and southern Brazil) is also next to a prominent north–south mountain range: the Andes. It also has a ready source of warm, moist air: the Amazon basin. And it also experiences a lot of severe thunderstorms – more thunderstorms, in fact, than central North America, with thunderclouds that extend further into the atmosphere. But tornadoes are much less common there, and the conventional wisdom can’t explain why.

An extra factor

In their study, which is published in PNAS, Purdue’s Dan Chavas and his then-PhD student Funing Li, together with colleagues at the US National Center for Atmospheric Research, Stony Brook University, and Colorado State University, sought an explanation in a previously overlooked difference between North and South America. While the surface of the Gulf of Mexico and Caribbean Sea is smooth, they noted, the similarly warm-and-moist Amazon basin is heavily forested and contains terrain such as plateaus and highlands. Might this roughness explain the absence of a South American tornado alley?

To test this hypothesis, the scientists performed experiments using a global climate model. In the first experiment, they flattened a computerized version of the Amazon basin to ocean-like smoothness and modelled the resulting tornado potential in central South America. In the second experiment, they did the opposite, filling in the digital Gulf of Mexico and observing how this affected tornado potential in central North America.

The results were striking. The smoothed-out version of South America experienced around twice as many tornadoes as the real-world version. Northeastern Argentina was particularly hard-hit. Conversely, a filled-in Gulf in the model version of North America reduced the number of tornadoes by up to 41%, with the biggest drops seen in the Great Plains and the southeastern US.

As a solution to Kansas’ tornado problem, this finding isn’t terribly useful. Human geoengineers are not going to start filling in the Gulf of Mexico any time soon, and the natural processes that might do it would be cataclysmic. (Let’s just say that a few extra twisters would be the least of our problems.) But the research does have some practical implications. Rampant deforestation is making the Amazon basin smoother. Forest regrowth is making the eastern US slightly rougher. According to the researchers, such changes could affect tornado frequency, though the exact nature of the effect is hard to predict.

“An important question is how terrain and land cover may alter the response of tornadoes in the future, as climate change may shift the large-scale atmospheric circulation and the geographic patterns of severe thunderstorm and tornado activity that it produces,” they write. “We hope our study motivates future research exploring those additional factors.”

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