IELTS Academic Reading Practice Test 31

A The invention of paper money in China is widely considered to be one of the most consequential innovations in the history of finance. Before its appearance, the great economies of Asia and Europe had relied for several thousand years on metallic coinage struck from gold, silver, bronze or copper. These coins were robust and difficult to counterfeit, but they were also heavy, awkward to transport and limited in supply to the output of mines. Paper, by contrast, was relatively light, abundant and easy to print in any required denomination. Its widespread use as money required, however, not only the technological prerequisites of papermaking and woodblock printing but also a degree of public confidence in the issuing authority that took several centuries to develop.

B The earliest documented predecessors of paper money are said to have been the jiaozi, deposit receipts issued from around 1024 by a consortium of merchants based in the Sichuan region of southwest China. Sichuan at the time used heavy iron coins that were inconvenient for large transactions; the receipts could be redeemed for fixed quantities of these coins at the issuing offices and quickly came to circulate as a substitute for the coinage itself. When the merchant consortium began to fail under the weight of poor lending decisions, the imperial government of the Northern Song dynasty took over the system and from 1024 issued the receipts as official currency, with a fixed three-year expiry and a stated reserve of metallic coinage to back each issue.

C Over the following two centuries, the use of paper money expanded steadily. The Southern Song dynasty, which followed the loss of northern China in 1127, relied heavily on paper notes called huizi to finance its lengthy military confrontations with the Jurchen and Mongol powers to the north. The notes were issued in three denominations, were redesigned periodically to deter forgery and were withdrawn after a set period in exchange for a new issue. As military costs mounted, the temptation to print beyond the reserves of metallic coinage proved difficult to resist, and successive Southern Song governments allowed the value of huizi against silver to fall by roughly nine-tenths between 1190 and the fall of the dynasty in 1279.

D The most ambitious paper currency system of the medieval world is widely regarded as that of the Yuan dynasty, which united China under Mongol rule from 1271. Kublai Khan's government issued a single nationwide note, the chao, redeemable in principle for silver, and prohibited the private use of gold and silver in transactions on pain of severe penalty. For roughly half a century the system worked impressively; the Venetian traveller Marco Polo described in his memoirs how "all the people of these lands willingly take these papers, since wherever they go they pay in this same money for whatever they buy." By the 1340s, however, the Yuan government's growing military and ceremonial expenditures had so far outstripped its silver reserves that the chao lost most of its purchasing power, contributing to the social unrest that ushered in the founding of the Ming dynasty in 1368.

E The early Ming dynasty attempted to restore paper currency under the name daming baochao, but a series of large unbacked issues swiftly produced a similar collapse of confidence. By the middle of the fifteenth century, China had effectively reverted to silver as its principal medium of large-scale exchange — a substance which, unlike paper, could not be issued at will by a hard-pressed government. The Ming experience cast a long shadow: for the next several centuries, Chinese officials regarded paper money as a temporary expedient suitable only for emergencies, and the technology that the country had pioneered came to be developed instead by European banks and national treasuries.

F Several lessons of the Chinese experience are now widely accepted. The first is that paper money depends on confidence, and that confidence in turn depends on the discipline of the issuing authority. The second is that the temptation to over-issue appears to be a recurring feature of paper currencies, particularly under conditions of military stress. The third is that, once trust has collapsed, it is exceedingly difficult to rebuild. These observations remain a staple of central-banking discussion to the present day, and help to explain why currency issuance has so often been entrusted, in modern states, to authorities deliberately insulated from immediate political pressures.

A Nuclear fusion, defined as the process by which light atomic nuclei combine into heavier ones with the release of vast amounts of energy, is widely regarded as the engine that powers the Sun and every other main-sequence star. Reproducing it on Earth has been a recognised scientific ambition since the 1930s, when Hans Bethe is said to have worked out the reactions by which hydrogen is fused into helium in stellar cores. Unlike its sister process, nuclear fission, fusion produces no long-lived radioactive waste and apparently cannot run away into an uncontrolled chain reaction. Its potential benefits as a source of limitless, low-carbon electricity have kept it on research agendas for more than seventy years.

B The fundamental challenge is widely said to be heat. To overcome the electrostatic repulsion between positively charged atomic nuclei, the fuel must be raised to temperatures of around 150 million degrees Celsius — broadly ten times hotter than the centre of the Sun — at which point matter exists in a fourth state, plasma, that no solid container can withstand. Two principal strategies have so far been pursued. Magnetic confinement uses powerful magnetic fields to suspend the plasma in a vacuum chamber, typically a doughnut-shaped device called a tokamak. Inertial confinement, by contrast, uses high-energy laser pulses to compress a tiny fuel pellet so rapidly that fusion occurs before the pellet has time to fly apart.

C The tokamak design, first developed in the Soviet Union in the late 1950s by Lev Artsimovich and his colleagues, is reported to have achieved a decisive early breakthrough. By 1968, the T-3 tokamak at the Kurchatov Institute in Moscow had reached temperatures of around 10 million degrees Celsius, an order of magnitude higher than any rival device. Within a decade the tokamak had largely become the dominant approach to magnetic-confinement fusion worldwide. The Joint European Torus (JET) in the United Kingdom, which began operating in 1983, set successive records throughout the 1990s, including a single pulse in 1997 in which 16 megawatts of fusion power were briefly generated.

D The pivotal milestone widely known as scientific breakeven — defined as producing more fusion energy from a single reaction than the energy delivered to the fuel — was reached in December 2022 at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California. Using 192 high-power lasers focused on a millimetre-sized pellet of deuterium and tritium, the NIF team is said to have achieved a fusion energy output of 3.15 megajoules from 2.05 megajoules of laser energy delivered to the fuel — a ratio of approximately 1.5 to 1. Critics observed that the total electrical energy required to power the lasers and operating systems amounted to roughly 300 megajoules, meaning that the experiment remained far from the point at which fusion would yield surplus electricity.

E The most ambitious magnetic-confinement project currently under construction is widely held to be ITER, an international collaboration between 35 nations being built at Cadarache in southern France. When completed, ITER will be the largest tokamak ever constructed, with a plasma volume some ten times larger than that of JET. The project aims to demonstrate the production of 500 megawatts of fusion power for sustained periods of at least 400 seconds, from an input heating power of 50 megawatts — a gain factor of ten. Initial first-plasma operation, originally scheduled for 2025, has slipped to the latter half of the decade. The total cost has risen from an initial estimate of around 5 billion euros to more than 22 billion.

F While government-led projects have dominated the field for decades, private investment in fusion has surged in recent years. According to the Fusion Industry Association, total private capital committed to fusion startups rose from approximately $300 million in 2018 to over $6.2 billion by the end of 2023. Companies such as Commonwealth Fusion Systems in the United States, Tokamak Energy in the United Kingdom, and TAE Technologies in California are pursuing approaches that range from advanced tokamak designs using high-temperature superconducting magnets to more exotic concepts based on field-reversed configurations and stellarators.

G Significant practical obstacles arguably remain. The tritium fuel required for the deuterium-tritium reaction, considered the most accessible fusion pathway, is extremely scarce; current world stocks apparently amount to only around 20 kilograms, much of it produced as a by-product of Canadian heavy-water fission reactors that are nearing the end of their service lives. Future fusion reactors will probably need to breed their own tritium by allowing neutrons released during fusion to react with lithium blankets surrounding the reaction chamber, a process that has been demonstrated only at small scale.

H Despite these challenges, the rhetorical climate around fusion has shifted markedly in the past five years. Several governments, including those of the United Kingdom and the United States, have set explicit national targets for prototype fusion power plants by 2040, and the International Atomic Energy Agency has begun the development of regulatory frameworks for future commercial deployment. Whether fusion will arrive in time to play a significant role in mid-century climate strategy remains uncertain, but the field has, for arguably the first time in its long history, begun to attract the seriousness of investment and policy attention that its potential has always seemed to warrant.

A The neolithic settlement of Catalhoyuk, in the Konya plain of south-central Turkey, is regarded as among the largest and longest-occupied prehistoric sites known to archaeology. Inhabited continuously from about 7100 to 5950 BCE, the site grew into a densely packed mound covering some 13 hectares and housing, at its height, an estimated 3,500 to 8,000 people. Its discovery in the early 1960s and the spectacular finds that have emerged from it have made Catalhoyuk a central reference point in debates about the transition from hunter-gatherer life to settled agricultural society.

B Catalhoyuk was identified in 1958 by the British archaeologist James Mellaart during a survey of the Konya plain. Mellaart began formal excavations in 1961 and continued them until 1965, when he was barred from working in Turkey after a controversy concerning unpublished finds. In his four seasons of work, Mellaart and his team uncovered roughly 160 mudbrick dwellings, decorated with vivid wall paintings, bull's horn arrangements known as bucrania, and modelled plaster heads of leopards and other animals. His preliminary publications presented Catalhoyuk as a town centred on a goddess cult; the case rested largely on a number of clay figurines, including the celebrated "seated woman of Catalhoyuk" found inside a grain bin, which Mellaart interpreted as a representation of a mother goddess.

C Excavations resumed in 1993 under the British archaeologist Ian Hodder, working with an international team. The new project deliberately combined intensive on-site analysis with what Hodder called a "reflexive" methodology, in which the assumptions guiding interpretation were continually re-examined. Over the following twenty-five years, the project recovered an extraordinary range of material: human and animal bones, plant remains, lithic and bone tools, fragments of textiles, residues on grinding stones and traces of pigments in the painted plaster. The richness of the data has allowed Catalhoyuk to be reconstructed in remarkable detail, while obliging archaeologists to question several of Mellaart's bolder hypotheses.

D The houses of Catalhoyuk were entered through openings in their flat roofs, by means of wooden ladders. Doorways at ground level appear to have been essentially absent. Roofs served as the main thoroughfares of the settlement, and the houses were so closely packed that residents would have walked across the roofs of their neighbours to reach their own homes. Inside, each dwelling consisted of a single multi-purpose room with a hearth, storage bins, sleeping platforms and a small antechamber used for food preparation. Beneath the platforms, the inhabitants buried their dead, sometimes more than thirty individuals over the life of a single house. Each generation deliberately replastered the walls and floors many times, building up layers that have proved an exceptional record of household activities.

E The diet of the people of Catalhoyuk was based on cultivated cereals, principally emmer wheat and barley, supplemented by lentils and other pulses. Domesticated sheep and goats provided most of the meat; cattle, frequently shown in art, appear to have been hunted in the wild during the earlier phases of occupation and were domesticated only later. Isotopic analysis of human bones conducted in 2014 indicated that men and women consumed broadly similar diets, suggesting that differential access to food was not a marked feature of life at the site. Microscopic analysis of dental calculus has further shown that residents consumed small quantities of milk products, fish and a wide variety of plant foods.

F Particular interest has surrounded the social and religious life of the settlement, where many of Mellaart's most striking claims have been moderated. Hodder's team examined the figurines and found that the great majority depicted animals or stylised abstract forms rather than female humans. The most famous of the human figurines, including the seated woman from the grain bin, remained important objects but were now interpreted within a broader iconographic context in which ancestry, hunting, the bull and the leopard were at least as prominent as motherhood or femininity. Hodder has argued that what unified the settlement was not a single overarching cult but a dense web of household-level ritual.

G A particularly striking discovery of the Hodder era was the apparently systematic plastering of human skulls. Several adult skulls had been removed from their graves below the house platforms, painted with red ochre and then carefully replastered to reconstruct the face. They appear to have been kept in the houses for some time before being reburied. Similar plastered skulls have been recovered from the contemporary site of Jericho in the Levant, and their occurrence at Catalhoyuk suggests that ideas about the dead circulated over a wider region than was once supposed.

H The end of Catalhoyuk has also drawn scholarly attention. From around 6500 BCE, the inhabitants began to abandon the dense roof-entrance layout in favour of more dispersed houses with ground-level doorways and individual courtyards. The transformation took roughly five centuries and culminated in the abandonment of the eastern mound by about 5950 BCE. The reasons remain debated: climatic shifts, the exhaustion of nearby resources, growing inequalities and the social tensions of a maturing agricultural society have all been proposed. In recognition of its importance, Catalhoyuk was inscribed on the UNESCO World Heritage list in 2012.