IELTS Academic Reading Practice Test 6

Paper is so common today that it is easy to forget how recently it became cheap. For most of human history, people wrote on materials that were either costly or cumbersome: clay tablets in Mesopotamia, papyrus in Egypt, parchment made from animal skin in medieval Europe, and strips of bamboo or silk in early China. Each had its drawbacks.

Papyrus grew in only a few places, parchment required the skins of large numbers of animals, and bamboo was heavy – a single book written on bamboo strips could fill a cart. The invention of paper, a thin sheet formed from plant fibres that have been broken down in water and then dried, offered a material that was light, flexible and, eventually, inexpensive.

Chinese tradition attributes the invention of paper to Cai Lun, an official at the imperial court, who in the year 105 CE is said to have presented the emperor with sheets made from the inner bark of the mulberry tree, hemp, old rags and worn-out fishing nets. Archaeologists have since discovered fragments of paper in China that are considerably older, including one bearing part of a map that dates from the second century BCE, so Cai Lun is now generally regarded not as the inventor but as the person who improved the process and promoted its official use. Whatever its precise origins, papermaking spread steadily across East Asia, reaching Korea and then Japan by the early seventh century.

Westward expansion took longer. According to a frequently repeated story, Chinese prisoners captured after a battle in Central Asia in 751 taught the craft to papermakers in Samarkand, although many historians now regard this account as a convenient simplification of a gradual process. What is certain is that by the end of the eighth century paper was being produced in Baghdad, and that the Islamic world rapidly became the centre of paper production. Paper helped to support an extraordinary expansion of scholarship, administration and book production across the region, and from there the techniques passed to Muslim Spain and Sicily, and later to Christian Europe.

Medieval European papermakers made their product almost entirely from linen and cotton rags. The rags were first sorted according to their quality and colour, and then left to soak and partially rot in water for several weeks, a process that softened the fibres. Next, they were pounded into a thick pulp by heavy hammers; in Italy, where the town of Fabriano became famous for its paper in the thirteenth century, these hammers were driven by water wheels, greatly increasing output. The pulp was poured into a large vat and diluted with water.

A worker then dipped a mould – a wooden frame holding a fine screen of wire – into the vat and lifted it out horizontally, shaking it gently so that the fibres interlocked as the water drained away. The wet sheet was turned out onto a piece of felt, and stacks of sheets and felts were squeezed in a press to remove as much water as possible. Finally, the sheets were hung up to dry and dipped in a solution of gelatine, which made the surface less absorbent so that ink would not spread.

Fabriano's papermakers also introduced the watermark, a design produced by attaching a shape made of wire to the screen of the mould. Because the pulp settled slightly less thickly over the wire, the design became visible when the finished sheet was held up to the light. Watermarks allowed mills to identify their products, and for historians today they provide valuable evidence for dating documents and tracing where the paper was made.

The arrival of the printing press in Europe in the fifteenth century created enormous demand for paper, and by the eighteenth century rags were in short supply. Papermakers experimented with substitutes, including straw and various plants, but the decisive solution was wood. In the 1840s the German weaver Friedrich Gottlob Keller developed a method of grinding wood into fibres, and later in the century chemical processes were introduced that dissolved the substances binding wood fibres together, producing a stronger pulp. At the same time, machines invented in France and developed in England at the beginning of the nineteenth century made it possible to produce paper in a continuous roll rather than one sheet at a time.

These changes made paper astonishingly cheap, contributing to the spread of newspapers, mass literacy and modern bureaucracy. They also had an unexpected cost. Much of the paper produced between the mid-nineteenth and late twentieth centuries contained acidic chemicals that cause it to become brittle and yellow over time, and libraries and archives around the world now spend considerable sums trying to preserve books and documents from this period. Rag paper made centuries earlier, by contrast, often remains in excellent condition.

In the interior of Antarctica, snow rarely melts. Each year's snowfall is buried by the next, and over thousands of years the accumulated layers are compressed into solid ice that can be more than three kilometres thick. Because this ice preserves information about the conditions in which the snow fell, it forms one of the most valuable archives available to climate scientists. By drilling vertically through the ice sheet and extracting long cylinders of ice, known as cores, researchers can read a continuous record of past climate that extends back far beyond the beginning of human history. Cores from Greenland in the Arctic provide a similar record, but the ice there is thinner and generally younger. Antarctica, with its vast and largely undisturbed interior, therefore offers the longest archive of all.

The most remarkable feature of ice cores is that they contain samples of the ancient atmosphere itself. As snow is gradually transformed into ice, the spaces between the snow crystals are sealed off, trapping tiny bubbles of air. When a section of core is crushed or melted in a laboratory under carefully controlled conditions, the gases released from these bubbles can be analysed directly. This allows scientists to measure the concentration of carbon dioxide and methane in the atmosphere at times long before any instruments existed to record them. Direct measurements of atmospheric carbon dioxide only began in the late 1950s, so without ice cores our knowledge of earlier concentrations would be largely guesswork.

Temperature, by contrast, must be calculated indirectly. Water molecules contain different forms, or isotopes, of hydrogen and oxygen, some of which are slightly heavier than others. The proportion of heavier isotopes in snow depends on the temperature at which it formed: the colder the climate, the smaller the proportion of heavy isotopes that reaches the interior of Antarctica. By measuring these proportions through the length of a core, scientists can reconstruct how temperatures changed over time. Other substances in the ice add further detail. Layers containing sulphate particles mark major volcanic eruptions, while the quantity of dust reveals how dry and windy the climate was, since deserts expanded during cold periods and winds carried more dust towards the poles.

The scale of the record has grown steadily. In the late 1990s a core drilled at the Russian Vostok station provided a record of around 420,000 years. A few years later, the European Project for Ice Coring in Antarctica, known as EPICA, drilled more than 3,200 metres into the ice at a site called Dome C and extended the record to about 800,000 years. Over that period, the core showed eight complete cycles of ice ages separated by shorter warm periods, and throughout these cycles the concentration of carbon dioxide rose and fell closely in step with temperature, ranging between roughly 180 and 300 parts per million. Today's concentration, above 420 parts per million, lies far outside that range.

Obtaining such records is extraordinarily demanding. Drilling sites are often more than 3,000 metres above sea level, where summer temperatures average around minus thirty-five degrees Celsius, and the drilling season lasts only a few weeks each year. The ice must be extracted in sections a few metres long, carefully logged and kept frozen throughout its journey to laboratories on other continents, since any melting would destroy the information it contains. A single deep core can take several field seasons to complete, and the analysis of its contents may continue for decades. Parts of each core are also stored in reserve, so that future researchers using techniques not yet invented will be able to return to the same ice.

One question that the existing cores could not answer concerns a puzzling change in the rhythm of the ice ages. Evidence from ocean sediments indicates that, until around a million years ago, cold and warm periods alternated roughly every 41,000 years; after that, the cycles lengthened to around 100,000 years. Why this transition occurred remains one of the central mysteries of climate science. The amount of sunlight reaching the Earth, which varies with regular changes in the planet's orbit, did not change in a way that would obviously explain it. Because the cause may be connected to changes in greenhouse gases, scientists have long hoped to find ice old enough to record the atmosphere before and during the transition.

In January 2025, a European project known as Beyond EPICA announced that it had drilled 2,800 metres down to the bedrock at a site called Little Dome C, retrieving ice that initial analysis suggests is at least 1.2 million years old. In the deepest part of the record, many thousands of years of climate history are compressed into a single metre of ice, so extracting precise information will require particularly sophisticated laboratory techniques. Researchers nevertheless hope that the core will reveal whether changes in carbon dioxide played a role in the shift to longer ice-age cycles – evidence that could also improve predictions of how the climate will respond to the greenhouse gases being added to the atmosphere today.

Music is found in every known human culture, yet its purpose has long puzzled scientists. Unlike language, it conveys little precise information; unlike food or shelter, it is not obviously necessary for survival. Charles Darwin speculated that musical ability might have evolved as a means of attracting partners, while others have suggested that it strengthened bonds within groups or helped parents to soothe their infants.

None of these explanations has been proved, but over the past three decades advances in brain imaging have allowed researchers to investigate more directly what happens in the brain when people listen to or perform music – and whether musical activity has effects that extend beyond the enjoyment it provides. Such questions matter for educational policy as well as for science, since schools must decide how much time and money to devote to music.

The most famous claim of this kind began with a short paper published in the journal Nature in 1993. Frances Rauscher, Gordon Shaw and Katherine Ky reported that college students who had listened to a sonata by Mozart performed better on a test of spatial reasoning than those who had listened to relaxation instructions or sat in silence. The effect was small and lasted only a few minutes, and the authors made no claims about general intelligence. Nevertheless, the finding was rapidly transformed in popular culture into the idea that classical music makes people – and especially babies – cleverer. Recordings marketed to parents sold in large numbers, and in 1998 the governor of the American state of Georgia proposed giving every newborn child a recording of classical music.

Subsequent research was far less encouraging. Many attempts to reproduce the original result failed, and a comprehensive analysis published in 2010 by researchers at the University of Vienna, which combined the results of around forty studies involving more than three thousand participants, found no reliable evidence that listening to Mozart specifically enhanced spatial ability. The analysis also found that the effects reported by the original research group were noticeably larger than those reported by other laboratories. Where small improvements did occur, they appeared to reflect a general increase in alertness or mood, which could equally be produced by other music the listeners enjoyed – or by an interesting story.

A more plausible version of the claim concerns active musical training rather than passive listening. Several studies have found that children who take music lessons perform slightly better on tests of intelligence and academic achievement than those who do not. The difficulty lies in interpreting this association. Families who can afford lessons tend to have higher incomes and more educated parents, and children who persist with an instrument may already possess greater concentration or motivation.

When researchers have randomly assigned children to music lessons or to other activities, the benefits for general intelligence have usually been small or absent, and some recent analyses have concluded that well-controlled studies show no meaningful transfer from music to unrelated skills. This does not mean that music lessons are worthless; it means only that their value should be judged by what they teach directly, rather than by supposed benefits elsewhere.

Brain-imaging research has nevertheless revealed that music has powerful effects of a different kind. In a study published in 2011, researchers in Montreal asked volunteers to bring recordings of music that gave them intense pleasure – sometimes experienced as 'chills' down the spine. Scans showed that the moments of peak emotion were accompanied by the release of dopamine, a chemical messenger involved in the brain's reward system, in a region associated with pleasure. Strikingly, dopamine was also released in a different region in the seconds before the peak, as listeners anticipated what was coming. Music, in other words, appears to engage the same reward mechanisms that respond to food and other basic pleasures, partly by creating expectations and then fulfilling or delaying them.

Other research has examined the long-term effects of intensive musical practice. Professional musicians, particularly those who began training in early childhood, show differences in the structure of brain regions involved in hearing, movement and the coordination of the two hands. Because it is impossible to assign people at random to decades of practice, however, researchers cannot be certain how much of this difference is caused by training and how much reflects characteristics that led people to become musicians in the first place. Studies that follow children over several years of lessons have found some changes developing during training, which suggests that practice plays at least some part.

Perhaps the most promising applications lie in medicine. Rhythmic music can help some people with Parkinson's disease to walk more steadily, apparently because a regular beat provides an external cue that compensates for damage to the brain's own timing systems, and music therapy is increasingly used to reduce anxiety in patients undergoing surgery. These benefits are more modest than the claims once made for the 'Mozart effect', but they rest on firmer evidence. The history of music research thus offers a lesson that extends beyond music itself: an appealing idea, repeated often enough, can easily run ahead of the science on which it was supposedly based.