Seriously Curious

by Tom Standage

  How shoelaces untie themselves

  Engineering brings great benefit to humanity, from bridges to computer chips. It has, though, had difficulty creating a shoelace that does not accidentally come loose. This was, in part, because no one truly understood why shoelaces come undone in the first place. But that crucial gap in human knowledge has now been plugged. Christopher Daily-Diamond, Christine Gregg and Oliver O’Reilly, a trio of engineers at the University of California, Berkeley, have worked out the mechanics of shoelace-bow disintegration. They have finally solved the mystery of how shoelaces untie themselves.

  Technically, a shoelace bow is a type of slip knot that has, at its core, a reef knot. Like conventional reef knots, bows can be mistied as “granny” knots, which come undone more easily than a true reef does. But even a shoelace bow with a true reef at its core will fail eventually, and have to be retied. That is because walking involves two mechanical processes, both of which might be expected to exert forces on a shoelace bow. One is the forward and back movement of the leg. The other is the impact of the shoe itself hitting the ground. Preliminary experiments carried out by Mr Daily-Diamond, Ms Gregg and Dr O’Reilly showed that neither of these alone is enough to persuade a bow to unravel; both are needed. So they had to devise experiments which could measure and record what was going on while someone was actually walking. The “someone” in question was Ms Gregg, who endured numerous sessions on a treadmill so that the behaviour of her shoelaces could be monitored. Using cameras, and tiny accelerometers attached to the laces, the researchers realised that two things are important. One is how the act of walking deforms the reef at the centre of a bow. The other is how the different inertial forces on the straight-ended and looped extremities of the bow conspire to pull the lace though the reef in the way a wearer would when taking a shoe off.

  During walking, the reef itself is loosened by the inertial forces of the lace ends pulling on it. This occurs as a walker’s foot moves first forward and then backward as it hits the ground during a stride. Immediately after that, the shock of impact distorts the reef still further. This combination of pull and distortion loosens the reef’s grip on the lace, permitting it to slip. In principle, the lace could slip either way, giving an equal chance of the bow eventually undoing completely or turning into a non-slip knot of the sort that long fingernails are needed to deal with. In practice, the former is far more common. The reason turns out to be that the free ends of the bow can swing farther than the looped ends do. The extra inertial force this causes favours slippage in the direction of the longer of the free ends. To start with, the effect is small. But as the free end in question continues to elongate, the disparity in inertial force gets bigger – and, eventually, only two or three strides are needed to take a shoe from being apparently securely tied to being untied.

  Probably, nothing can be done about this differential elongation. But it might be possible to use the insights Mr Daily-Diamond, Ms Gregg and Dr O’Reilly have provided to create laces that restrict the distortion of the reef at a bow’s centre, and thus slow the whole process down. Understanding how laces untie themselves is, you might say, an important step on the way to inventing a solution.

  Why the sea is salty

  Seen from space, the Earth is a pale blue dot. Two-thirds of its surface is covered by water. But most of that water by far – around 97% – is salty. Of the 3% that is fresh water – which is the kind humanity needs to drink, wash, make things and (most of all) produce food – about two-thirds is locked up in glaciers, ice caps and permafrost. That leaves less than 1% of the planet’s water easily accessible in rivers, lakes or aquifers. In short, the salinity of the oceans means useful water is scarce, while the less useful kind is abundant. So why is the sea salty?

  The salt in the ocean mostly got there as the result of a process called weathering, which transfers mineral salts from rocks on land into the sea. Rain is not pure water, but contains small amounts of carbon dioxide absorbed from the air, which makes rainwater very slightly acidic. When this weak acid falls on land, tiny traces of minerals are dissolved from rocks into the water, and these minerals separate into charged particles called ions. These ions travel along with the water into streams, rivers and eventually into the ocean. Many of these mineral ions are subsequently removed from the sea water by marine plants and animals, but others remain in the water, and their concentration builds up over millions of years. Over 90% of the ions in sea water, accounting for about 3% of the ocean by weight, are sodium and chlorine ions, which are the chemical constituents of common salt. Other processes also play a role. Underwater volcanoes and hydrothermal vents discharge mineral salts into sea water. And isolated bodies of water with insufficient drainage may become increasingly salty through evaporation, which carries water away while leaving dissolved minerals behind. The Dead Sea (which contains about 30% mineral salts by weight) is the best-known example.

  The natural processes that make the seas salty can be reversed by desalination technologies that turn sea water into fresh water. This involves either boiling and then recondensing water, or pumping it at high pressure through reverse-osmosis membranes that allow water molecules to pass, but are impermeable to larger mineral ions. Both processes are energy-intensive, however, though reverse osmosis has become far more energy-efficient in recent years. Accordingly, desalination plants are generally found in places where water is scarce but energy is cheap, such as the Middle East.

  As climate change causes “global drying” – making some wet parts of the world wetter, and dry parts drier – demand for fresh water will intensify in the coming years; half the world’s population is expected to live in water-stressed areas by 2050. Better water-management policies and more water-efficient agricultural practices (such as drip irrigation) are needed. Improvements to desalination technology would help too, by allowing mankind to tap the oceans’ inconveniently salty water. “If we could ever competitively – at a cheap rate – get fresh water from salt water,” observed President John F. Kennedy in 1961, “that would be in the long-range interests of humanity, which would really dwarf any other scientific accomplishment.”

  Why diamond production may be about to peak

  In the frozen tundra of northern Canada, miners work day and night to extract diamonds from beneath the ground at Gahcho Kué. Owned by De Beers, it is the biggest new diamond mine to open in more than a decade. It may also be the company’s last – De Beers has no plans to open another. Other companies have a few mines planned, but Bain, a consultancy, expects diamond production to peak in 2019, then begin a slow decline. Why is the world about to reach peak diamond production?

  The modern diamond industry got going about 150 years ago, when a farmer’s son found a diamond near the Orange River in South Africa. A diamond rush followed, causing a surge of production that threatened to send prices plummeting; the high price of diamonds depends on their scarcity. In 1888 Cecil Rhodes founded De Beers to consolidate the area’s mines. The company would retain a stranglehold on supply for more than a century, limiting availability in order to maintain high prices. “Our only risk,” Rhodes later declared, “is the sudden discovery of new mines, which human nature will work recklessly to the detriment of us all.”

  Much has changed since then. De Beers now controls only about one-third of the market. It regards any big discoveries, by itself or anyone else, to be unlikely. Explorers have sampled nearly 7,000 kimberlite pipes, the extinct volcanoes that brought most gem diamonds to the surface. Of these just 15% held diamonds and only 1% (about 60) contained enough to justify the cost of building a mine. Though exploration continues, most analysts reckon that the best deposits have now all been found.

  For those who dig up diamonds, waning supply is a relief; it will help prop up prices. Brides continue to want diamond engagement rings: in America, De Beers reports, a quarter of young brides dreamed of their rings years before beginning a relationship. But there are signs that demand might falter. Those in the mille
nnial generation earn less than their parents did at their age and are less interested in material luxury. They grew up as awareness of “blood diamonds”, which are mined to fund conflict and are illegal, entered popular culture. Brides who want a diamond now have alternatives in the form of synthetic diamonds, which have improved in quality and become less costly to produce. De Beers and other miners are working to boost demand, with new advertising campaigns and slogans. But it helps that supply is not forever.

  Why Boko Haram prefers female suicide-bombers

  Boko Haram has used more female suicide-bombers than any other terrorist group in history. Of the 434 bombers the group deployed between April 2011 and June 2017, 244 of them, or more than half, have been definitely identified as female. More may have been. The Tamil Tigers, the previous holders of the gruesome record, used 44 female bombers over a decade, according to a study by Jason Warner and Hilary Matfess for the Combating Terrorism Center at West Point, an American military college. Boko Haram, whose insurgency has killed more than 30,000 people in north-east Nigeria and neighbouring countries since 2011 and displaced 2.1m, is therefore the first group to use a majority of female bombers.

  Nigeria’s government likes to say that Boko Haram has been “technically defeated”. The group split into two factions in 2016, after Islamic State (IS) declared a preference for a more moderate leader, Abu Musab al-Barnawi, over Abubakar Shekau. The latter’s tactics include using suicide-bombers to blow up mosques and markets, inevitably killing fellow Muslims. (Some analysts dispute the idea of factions, arguing that Boko Haram has always been made up of different cells.) But the group is far from vanquished, even though it has been forced out of towns since Muhammadu Buhari, a former military dictator, reclaimed the presidency in 2015. In July 2017 the branch affiliated to IS killed 69 members of an oil-exploration team. Indeed, the group’s suicide-bombings were especially lethal in 2017, after a relative lull in 2016. During June and July alone they killed at least 170 people, according to Reuters, a news agency. The jihadists are sending more children to their deaths too: the UN counted 83 used as human bombs in 2017, four times the total for 2016. Two-thirds of them were girls.

  The suicide-bombers sent by Boko Haram are, however, less lethal than those used by other groups, say Mr Warner and Ms Matfess. This is partly because around a fifth of them detonate their explosives when confronted by soldiers, killing only themselves. Yet still the group sends attackers to Maiduguri, the city where the insurgency began, to target the university, markets and camps for the displaced. It is no coincidence that its use of female bombers rose sharply after the kidnapping of the 276 “Chibok Girls” from their school in April 2014. Boko Haram realised the propaganda value of women: the use of supposed innocents as lethal weapons has a powerful shock factor. They arouse less suspicion (at least they did when the tactic was first deployed, if no longer) and can more easily hide explosives underneath a voluminous hijab. And by sending women to blow themselves up, Boko Haram also saves its male fighters for more conventional guerrilla-style attacks.

  Some of the women may be willing, if brainwashed, jihadists. Many, though, are believed to be coerced into strapping on bombs. One did so with a baby on her back. Some may see it as a way out of an abusive life as one of Boko Haram’s “wives”, plenty of whom are raped by their “husbands”. Those who give themselves up to the authorities rather than detonating their bombs often face a lifetime of stigma, as their families and communities may be unwilling to take them back. So whether the women kill anyone or not, Boko Haram sows fear and division – exactly as it intends.

  Move over, oil. Which countries have the most lithium?

  Lithium is a coveted commodity. Lithium-ion batteries store energy that powers mobile phones, electric cars and electricity grids (when attached to wind turbines and photovoltaic cells). Demand is expected nearly to triple by 2025. Annual contract prices for lithium carbonate and lithium hydroxide for 2017 have doubled, according to Industrial Minerals, a journal. That is attracting investors to the “lithium triangle” that spreads into Argentina, Bolivia and Chile. This region holds 54% of the world’s “lithium resources”, an initial indication of potential supply before assessing proven reserves.

  Despite having similar-sized lithium resources, there are vast differences in output between the three countries. Chile produced 76,000 tonnes in 2016, more than twice as much as Argentina. Bolivia only managed to sell a measly 25 tonnes. Such differences are emblematic of how the South American trio treat enterprise and investment more generally. Market-friendly Chile is far ahead in rankings for ease of doing business, levels of corruption, and the quality of its bureaucracy and courts. Even so, production growth has flattened, allowing Australia to threaten its position as the world’s top producer.

  Below the salt

  Lithium resources, tonnes, m

  January 2017

  Sources: US Geological Survey; Roskill Information Services; Comibol; World Bank; Transparency International

  *Lithium carbonate equivalent

  It has been decades since anyone thought of Argentina as business-friendly. Cristina Fernández de Kirchner, a populist president who governed until December 2015, made things harder. But under her successor, Mauricio Macri, Argentina has been hastening to make up lost ground. Bolivia has barely begun to exploit its resources. Its investment regime suffers from “lack of legal security, weak rule of law, corruption and murky international arbitration measures”, according to America’s State Department. In the battle for lithium-triangle supremacy, it has a long way to go.

  Why the global arms trade is booming

  In February 2017 the emirate of Abu Dhabi held the International Defence Exhibition and Conference (IDEX), the Middle East’s largest arms fair. The four-day event was a roaring success, playing host to 1,235 exhibitors and a record number of delegates. On the last day, the United Arab Emirates announced $5.2bn worth of weapons purchases from suppliers including France, Russia and America. The Gulf state’s hunger for big guns is hardly exceptional. A study by the Stockholm International Peace Research Institute (SIPRI), a think-tank, found that transfers of big weapons from 2012 to the end of 2016 reached their highest volume for any five-year period since the end of the cold war. Why is the global arms trade doing so well?

  The frail security balance of an increasingly multipolar world has many countries worried. Since the end of the cold war, scholars have found that greater instability – both internal and external – has tended to be correlated with a rise in military spending, as intuition would suggest. What has changed in recent years is that a larger share of the money is going towards imports: in contrast with the 2000s, when the West’s armies undertook the bulk of the fighting in Afghanistan and Iraq, many nations sucked into this decade’s disputes lack military muscle and have no domestic industry capable of building it up. With America less eager to be the world’s policeman, they see a greater need for buying their own kit. Vietnam, which borders the South China Sea, imported three times more weaponry in the period from 2012 to the end of 2016 than in the previous five years. Saudi Arabia’s purchases grew by 212% and Qatar’s by 245%.

  But the trade is also underpinned by a push on the supply side. America, which sells arms to more than 100 countries, dominates the market. As technology improves, it is helping to retool developing nations’ arsenals with modern gadgets, such as GPS guidance and automated systems. Its exports grew by 42% from 2008 to 2015. Other exporters see a lucrative market too. China, known in the 1990s for its knock-offs of Western equipment, has emerged as a top-tier supplier. South Korea sells aircraft and warships to Latin America. Russia is building on its cold-war legacy business.

  The proliferation of conventional weapons is a source of volatility in itself. Yet measures to contain them have been feeble. Unlike nuclear treaties, conventional-arms-control regimes focus on making sure weapons are not sold to irresponsible users, rather than promoting disarmament. Even within this narrower scope, the effi
cacy of such measures remains unproven. The UN-led Arms Trade Treaty, the first global attempt at regulating the business, came into force in December 2014. China and Russia are not signatories; America has yet to ratify it. Together, these three countries account for more than 60% of exports. Existing regional control instruments, such as the EU Code of Conduct on Arms Exports, have a patchy record of blocking controversial sales. In some regions, including Asia and the Middle East, there are no such treaties. Meanwhile, America’s plans to increase military spending may prompt others to go shopping again. Expect arms trade shows – along with the arms trade – to continue to boom.

  What do think-tanks do?

  “According to such-and-such, a think-tank,” is a phrase familiar to readers of any newspaper, not least The Economist. Sharp quotes, intriguing facts and bold new policy proposals are attributed to the mysterious tanks (as is plenty of rubbish). What exactly are these outfits, which churn out reports on everything from Brexit to badgers?

  The “think-tank” label became popular in the 1950s, by which time there were already plenty of such organisations in existence. Many of America’s most venerable examples, including the Brookings Institution and the Carnegie Endowment for International Peace, were founded in the early 20th century. Britain’s Royal United Services Institute, a military-analysis outfit, was created in 1831 by the Duke of Wellington. But think-tanks really blossomed in the second half of the 20th century. Researchers at the University of Pennsylvania reckon there are now nearly 7,000 of them worldwide.

  In essence, think-tanks aim to fill the gap between academia and policymaking. Academics grind out authoritative studies, but at a snail’s pace. Journalists’ first drafts of history are speedy but thin. A good think-tank helps the policymaking process by publishing reports that are as rigorous as academic research and as accessible as journalism. (Bad ones have a knack of doing just the opposite.) They flourished in the 20th century for two reasons. Governments were expanding everywhere, meaning there was lots of demand for policy expertise. And the arrival of 24-hour news created an insatiable appetite for informed interviewees. The same trends are now causing think-tanks to take off in developing countries.