IELTS Academic Reading Practice Test 62

At its height in the late fifteenth and early sixteenth centuries, the Inca state, known to its subjects as Tawantinsuyu, governed a territory that stretched for more than 4,000 kilometres along the Andes, from what is now southern Colombia to central Chile and Argentina. This was the largest empire ever established in the pre-Columbian Americas, and its survival depended on the ability of distant provincial administrators to move people, goods and information quickly across some of the most difficult terrain on Earth. Two inventions above all made that possible: an extraordinary network of roads and a system of knotted cords called the quipu.

The road system, called Qhapaq Ñan in Quechua, was not a single highway but a web of routes that linked mountain highlands with the Pacific coast and the eastern foothills of the Andes. Although the Spanish later called it the Great Inca Road, modern estimates put its total length at more than 30,000 kilometres. The network was planned and maintained by the state, and it reflected a clear hierarchy: broad stone-paved causeways radiated from the capital, Cusco, while narrow trails and stepped paths served more remote settlements.

For a society that used no wheeled vehicles and had no horses until the Spanish arrived, the road system was a remarkable achievement in civil engineering. Llamas served as pack animals, but they were limited in the loads they could carry, and most goods moved on the backs of human porters. Engineers cut paths into steep rock faces, built low stone walls to mark the route across high plateaus, and laid paving over marshy ground. Along the coast, where the desert is often covered by drifting sand, they used stone markers to keep travellers on course; in the highlands they constructed suspension bridges of braided grass and fibre across deep gorges. These bridges had to be replaced every year or two because the plant material rotted, and their maintenance was assigned to nearby villages.

The roads did not serve ordinary travel. Most people who moved along them were soldiers, officials, porters or labourers travelling on state business, and communities near the roads were required to provide them with food and shelter. A system of tambos, or way stations, was established at intervals of roughly a day's walk. These structures stored grain and other supplies and offered lodging for travelling officials. They also made it possible for armies to move rapidly through the empire and for tax goods, such as textiles, maize and dried potatoes, to be carried to provincial storehouses.

Communication was even faster than travel. Relay runners known as chasquis were stationed in pairs at small huts along the roads, often within sight of one another. When a message arrived, one runner would receive it, announce the contents to his partner and then run with it to the next post, while the first received a rest. Messages could reportedly travel more than 200 kilometres in a single day, though such figures come from later Spanish accounts and may be exaggerated. The chasquis carried oral messages and quipus, and they were selected for fitness and trained from childhood.

In 2014 UNESCO inscribed the Qhapaq Ñan as a World Heritage site, describing it as a network of roads that once connected the Inca capital with the far reaches of the empire. The listing crosses six modern countries: Argentina, Bolivia, Chile, Colombia, Ecuador and Peru, and it includes not only road sections but also associated structures such as tambos, bridges and administrative centres. The inscription recognised both the engineering skill required to build the roads and the organisational capacity of a state that had no writing in the European sense.

What the Inca state used instead of writing was the quipu, a device made of cords and knots. A typical quipu consists of a main horizontal cord from which a series of pendant cords hang. Many quipus have secondary branches attached to the pendants, and some have more than a thousand cords. The cords themselves were spun from cotton or from the wool of llamas and alpacas, and dyed in a wide range of colours. Researchers believe that colour, the direction of twisting and the spacing of the cords all contributed to the information encoded in a quipu.

The clearest use of quipus was for numbers. Knots tied in the pendant cords recorded quantities using a base-10 positional system: a cluster of knots at the bottom of a cord stood for units, the next cluster for tens, then hundreds and so on, while the absence of knots in a position represented zero. Scribes known as quipucamayocs used these records for censuses, tax assessments and inventories of storehouses. Spanish administrators in the early years after the conquest accepted quipus as legal evidence in disputes over tribute, precisely because they were so systematic.

Whether quipus could record more than numbers remains a subject of debate. Early Spanish witnesses wrote that the cords contained histories, laws, poems and songs, and some modern researchers have argued that certain quipu patterns may encode words or syllables. The difficulty is that very few quipus survive, and those that do lack the oral context that once accompanied them. Most experts agree that the numerical content can be read, but the possible narrative dimension remains largely undeciphered. This uncertainty makes quipus among the most tantalising artefacts of the ancient Americas.

The road network and the quipu were complementary technologies. The roads allowed chasquis and officials to carry quipus from regional centres to Cusco, where they could be consulted by the ruler and his advisers. The quipu, in turn, gave the state a memory that did not depend on any individual. Together they helped the Inca govern a mountainous empire without horses, wheels or alphabetic writing, and they continue to attract the attention of archaeologists, historians and textile specialists.

Nuclear fusion is the process that powers the Sun and other stars. In a star, enormous gravitational pressure squeezes hydrogen nuclei together until they combine, or fuse, to form helium, releasing vast amounts of energy. Reproducing this process on Earth is difficult because the repulsive electrical force between positively charged nuclei is very strong. To overcome it, scientists must create conditions far more extreme than those inside the Sun, where the density of matter is immense. On Earth, where such density cannot be achieved, the favoured approach is to heat a gas of hydrogen isotopes to temperatures of around 100 million degrees Celsius. Inside the Sun, fusion occurs at about 15 million degrees, but the enormous pressure allows it to proceed; on Earth the lower density forces researchers to seek far higher temperatures.

The most commonly discussed fuels are deuterium and tritium, two heavy isotopes of hydrogen. Deuterium is found in seawater and is effectively abundant, while tritium is rare in nature and must be produced artificially. In a future reactor, tritium would be bred from lithium inside the machine itself, using neutrons from the fusion reaction. A small quantity of these fuels contains a remarkable amount of energy; one gram of deuterium-tritium mixture could, in principle, release roughly the same energy as several tonnes of coal. Moreover, the lithium required to breed tritium is also relatively common in the Earth's crust.

At the temperatures required for fusion, atoms lose their electrons and form a plasma, an electrically charged gas. No solid material can contain such a plasma, because it would instantly melt or vaporise. Engineers therefore use magnetic fields to hold the plasma away from the walls of the reactor vessel. The field acts like an invisible container, guiding the charged particles in circular paths and preventing them from touching the surfaces. Because the plasma is electrically charged, it can be shaped and steered by magnetic forces, a principle used in everything from small research devices to the largest reactor projects. This technique is known as magnetic confinement, and the most advanced device based on it is the tokamak.

The tokamak was developed in the Soviet Union in the 1950s and has since become the leading design for fusion experiments. It is a doughnut-shaped vacuum chamber surrounded by powerful magnets. The magnets produce a field that both confines the plasma and drives a current through it, helping to heat the gas to extreme temperatures. Many of the world's largest fusion machines are tokamaks, including the Joint European Torus, which operated in the United Kingdom until 2023, and the experimental reactor JT-60SA in Japan. Experimental results from these machines have steadily improved, though no tokamak has yet produced more energy than it consumed.

The most ambitious international project is ITER, a huge tokamak under construction at Cadarache in southern France. It is funded by a partnership of 35 countries, including the European Union, China, India, Japan, Russia, South Korea and the United States. When completed, ITER aims to produce about 500 megawatts of fusion power from 50 megawatts of heating power, a tenfold return. If the project succeeds, it will be the first fusion device to maintain a burning plasma for long pulses, a crucial step toward a power plant. Construction has been accompanied by delays and rising costs, but the project remains a central test of whether fusion can be a practical energy source.

An alternative to magnetic confinement is inertial confinement, in which a small pellet of fuel is compressed so quickly that it reaches fusion conditions before it can fly apart. The most prominent experiments have been conducted at the National Ignition Facility in California, where 192 powerful lasers focus intense energy onto a fuel capsule. In December 2022 researchers there announced that a reaction had released 3.15 megajoules of energy, more than the 2.05 megajoules delivered to the target. This was a scientific milestone, though it represented energy delivered to the pellet rather than a net gain for the facility as a whole.

Even after fusion is demonstrated, substantial challenges remain. The fusion reaction produces high-energy neutrons, which damage the structure of the reactor and make materials radioactive over time. Engineers must develop materials that can withstand decades of bombardment. Tritium breeding, plasma stability and the removal of waste heat are also unsolved engineering problems. In addition, fusion machines consume large amounts of electricity during operation, and any commercial plant would need to produce far more energy than it uses throughout its life cycle. These problems are not insurmountable, but they help explain why fusion has repeatedly been described as being decades away from commercial use.

Despite these difficulties, fusion retains an almost unique appeal. The fuels are available in huge quantities, the reaction produces no greenhouse gas emissions, and there is no risk of a runaway chain reaction or meltdown, because the plasma would simply cool if conditions were disrupted. A number of private companies are now developing smaller tokamaks using new high-temperature superconducting magnets, and some claim that demonstration plants could appear within a decade. Most cautious observers, however, say that commercial fusion power remains at least two or three decades away.

Most wealthy societies are ageing rapidly. In countries such as Japan, Italy and Germany, more than one person in five is already aged 65 or over, and the proportion is still rising, while the number of younger workers available to provide care is shrinking. This demographic shift, combined with a chronic shortage of nurses and care assistants, has led governments and technology companies to look for ways of using robots in homes, hospitals and residential institutions. The debate is no longer whether robots can perform useful tasks, but what kind of care older people actually need.

One group of robots is designed to address loneliness. The best known is Paro, a robotic baby harp seal developed in Japan, which responds to touch, sound and movement. It has been used in care homes and dementia units in several countries, and some studies report that it reduces anxiety, encourages conversation and increases social interaction among residents. However, most trials have been small and of short duration, and the observed effects are often modest. Researchers in this field caution that Paro and similar robots should be seen as tools rather than as replacements for human company.

Robot animals are particularly common in dementia care. Robot cats and dogs can provide the comfort of a pet without the demands of feeding, walking or veterinary visits. Supporters argue that they calm agitation and give people with severe cognitive impairment something to care for. Critics reply that they risk substituting a mechanical imitation for a genuine relationship, and that if used mainly to keep residents quiet, they may reduce rather than increase human contact. The line between assistance and deception is, in practice, not always easy to draw.

Telepresence robots, consisting of a screen mounted on a mobile base, allow relatives and health professionals to visit an older person remotely. The person at the other end can steer the robot through a house or care home, see the resident and talk in real time. During the COVID-19 pandemic, such robots were used to maintain some contact when physical visits were impossible. They are most valuable for families separated by distance and for specialist medical consultations, though no one argues that a video call can fully substitute for the presence of a person in the room.

Other robots offer physical assistance. Lifting devices and exoskeletons can help older people stand, walk or move between bed and chair, and they can reduce the back injuries suffered by human caregivers. Service robots can fetch objects, deliver meals or carry laundry along hospital corridors. The potential benefits are obvious, but the robots are expensive, require training, and often struggle in cluttered, unpredictable home environments. Real dwellings contain loose rugs, narrow doorways and uneven floors, which present difficulties that laboratory demonstrations rarely capture.

Monitoring technologies are perhaps the least visible form of robot care. Sensors, voice assistants and wearable devices can track movement, remind people to take medication and alert relatives or emergency services if someone falls. These systems may extend the period during which an older person can live independently. At the same time, they raise privacy concerns, because constant monitoring can feel like surveillance. Older adults may accept such devices only if they trust that the information is used for their benefit and that they can switch it off.

The evidence base for care robots is developing but still thin. Systematic reviews have found many pilot studies with positive results, but few large randomised controlled trials, and the outcome measures vary widely. It is therefore difficult to say which robots produce lasting benefits and for whom. I believe that the current enthusiasm for robot care has run ahead of the evidence, and that robots should not be routinely introduced into services without rigorous evaluation. Innovation is welcome, but it should be paired with independent research into costs, safety and effects on well-being.

Ethical questions are inseparable from technical ones. A robot pet that an older person believes to be alive raises concerns about honesty and dignity. Using robots to perform intimate tasks such as bathing or lifting may reduce a person's sense of autonomy. There is also a risk that robots will be used to cut staffing costs rather than to improve care, leaving older people with less human contact than before. Designers are increasingly advised to involve older people in the development process, so that the technology serves their preferences rather than imposing a uniform solution.

In my view, the most sensible role for robots is as supplements to human care, not substitutes for it. Robots can monitor falls, remind patients to take medicine, move heavy loads and help families stay in touch; these are tasks where reliability and repetition matter more than emotional understanding. But the core of good care is a relationship between people.

A robot cannot replace a nurse who listens, a volunteer who holds a hand or a family member who remembers a birthday. Policy should therefore strengthen the care workforce and use robots to free staff for the relational work that only humans can do.