IELTS Academic Reading Practice Test 101

For centuries, sailors who ventured beyond sight of land had no reliable way of knowing where they were. They could estimate speed and direction, but ocean currents and winds made dead reckoning deeply uncertain. Latitude could be determined by measuring the height of the sun at noon or of a known star above the horizon, but doing so accurately on a moving ship required an instrument far better than those available before the eighteenth century.

Early instruments had serious drawbacks. The astrolabe, inherited from astronomers, was too heavy and unstable on a rolling deck. The cross-staff required the observer to look directly at the sun, which was both painful and inaccurate, while the backstaff allowed the sun to be sighted by its shadow but still demanded considerable skill. By the late seventeenth century, navigators needed a portable instrument that could measure angular distances precisely without hurting the user's eyes and without being thrown off by the ship's motion.

The principle of using mirrors to bring two images together had been suggested by Isaac Newton among others, but it was not turned into a practical navigational instrument until around 1730, when the English mathematician John Hadley and the American inventor Thomas Godfrey independently produced instruments based on double reflection. Hadley demonstrated his design to the Royal Society of London, and it was quickly recognised as a major advance. Because its arc was one eighth of a circle, it became known as an octant, and it could measure angles up to ninety degrees.

The octant was soon found to be insufficient for the method of determining longitude known as the lunar-distance method, which required measuring the angle between the moon and a star or the sun, sometimes more than ninety degrees. Instrument makers therefore extended the arc to sixty degrees, one sixth of a circle, which allowed angles up to one hundred and twenty degrees to be read. The new instrument took its name from the Latin word for a sixth, sextans, and it gradually replaced the octant during the second half of the eighteenth century.

A marine sextant is built around a rigid frame, traditionally made of brass, shaped like a sector of a circle. Pivoted at the centre is an arm, known as the index arm, which carries an index mirror at its top. A second mirror, the horizon mirror, is fixed to the frame in front of a small telescope. Half of the horizon mirror is silvered and half is clear, so that the observer can see the horizon through the clear part while also seeing the reflected image of a celestial body. Shade glasses of various densities protect the eye when the sun is being observed, and a micrometer drum on the index arm allows very fine adjustments.

To measure the altitude of the sun, for example, the navigator holds the sextant upright, looks through the telescope and finds the horizon through the clear part of the horizon mirror. The index arm is then moved until the reflected image of the sun appears in the silvered part and is brought down until it just touches the horizon. The arm is clamped in place, and the observer turns the micrometer drum to make a final precise adjustment. The angle is then read from the graduated arc, using a vernier scale to obtain fractions of a minute of arc.

The reading on the arc is not yet the true altitude. Small errors in the instrument, known as index error, must be allowed for, and the height of the observer's eye above the water, called dip, also affects the apparent horizon. Light from a celestial body is bent by the atmosphere, an effect known as refraction, which makes the body appear higher than it really is. When the sun or moon is observed, a further correction for its semi-diameter is needed because navigators normally measure the edge, or limb, of the body rather than its centre.

Despite its precision, the sextant has clear limitations. It requires a visible horizon, which means it cannot be used in fog or when low cloud obscures the horizon, and it is useless for measuring the altitude of stars during daylight, except for the brightest ones. On aircraft and in spacecraft, where no sea horizon exists, bubble sextants or other devices using an artificial horizon have been developed, but these are less accurate than a good marine sight.

The sextant became the defining instrument of the great era of oceanic exploration and trade. It enabled navigators to fix their latitude with accuracy and, when combined with a reliable chronometer and lunar tables, to determine longitude as well. The accurate charts produced during this period opened long-distance routes to regular commerce and made voyages safer and faster than ever before. By the nineteenth century, no ship undertaking a major voyage would sail without at least one sextant.

Today, satellite navigation systems provide continuous and highly accurate positions at the touch of a button, yet the sextant has not disappeared. Many national maritime academies still require trainee officers to learn celestial navigation, and regulations for ocean-going vessels usually require a sextant to be carried as a back-up in case electronic systems fail. The basic optical principle remains unchanged, and a well-maintained sextant can still tell a careful navigator where they are, even when every electronic device on board has stopped working.

Along the dry coasts of Chile, Peru, Namibia and Morocco, there are places where rain rarely falls yet fog rolls in from the ocean for much of the year. These regions are often among the world's driest, yet their skies can be damp for months at a time. For centuries, plants and animals have taken advantage of this moisture, and for at least a few decades people have done the same. By stretching a fine mesh in the path of the wind, communities can collect droplets of fresh water that would otherwise drift inland and disappear. This technique, known as fog harvesting, is attracting renewed attention as water supplies tighten in many dry regions.

The principle is simple. Fog is composed of countless tiny water droplets, typically between one and forty micrometres in diameter, that are carried horizontally by the wind. When this wind passes through a mesh, some of the droplets collide with the fibres and stick to them. As more droplets are captured, they combine into larger drops, which then run down the mesh under gravity into a gutter. From the gutter the water is piped to a storage tank, where it can be allowed to settle before use. The process relies entirely on natural air movement, so it consumes no fuel and produces no waste.

A standard fog collector is a low-technology structure. Two vertical posts support a rectangular frame carrying a double layer of mesh, usually made from a plastic such as polypropylene or polyethylene. The mesh is stretched flat and facing the prevailing wind, with cables holding the structure steady so that it does not flap in strong gusts. Beneath the mesh, a narrow trough collects the water that drains from the fibres and carries it to a tank or a small reservoir. The entire system has no moving parts and requires no electricity, which makes it suitable for remote areas where maintenance skills and spare parts are scarce.

The amount of water a collector yields depends on several interacting factors. Droplet size is a crucial factor, since larger droplets are easier to capture than very small ones. Wind speed also matters, because stronger winds push more fog through the mesh, though at very high speeds some droplets may be blown straight through. The physical properties of the mesh are equally important. A mesh with very small openings may capture a high proportion of droplets, but it also resists airflow, causing wind to flow around rather than through it. Conversely, a mesh with large openings allows the fog to pass through almost unimpeded but catches very little. The wettability of the fibre surface also matters: water spreads more readily on some materials, making it easier for droplets to slide down before being blown away. In addition, the angle of the mesh and its height above the ground can influence how much water is collected.

Fog harvesting has been practised most famously in Chile, where researchers began systematic experiments in the 1950s and later built collectors on hills such as El Tofo to supply water to nearby settlements. In Morocco, the non-governmental organisation Dar Si Hmad has operated a large project on Mount Boutmezguida since 2015, providing water to villages in the Anti-Atlas mountains. Smaller schemes have been tested in South Africa, Namibia, Guatemala, Ecuador and the Canary Islands, among other places. The yields are modest by the standards of a city supply, but for dispersed rural communities they can make a critical difference, especially in months when springs and wells run low.

The attractions of fog collection are obvious. It runs on wind alone, uses inexpensive materials and can be maintained by local people with basic training. However, the method has real limits. Yields vary daily and seasonally, and only certain coastal or mountainous locations have enough fog and wind to justify a project. The collected water is generally suitable for drinking after filtration or disinfection, but because it starts as atmospheric moisture it may contain dust, sea salt or micro-organisms, so treatment is often recommended. Furthermore, storage can be a challenge, because demand is highest in dry periods when fog may be least reliable.

In recent years, researchers have tried to make fog collection more efficient. One promising design replaces the woven mesh with an array of vertical wires, sometimes described as a fog harp. Because the wires are not crossed, droplets can run down without being trapped at intersections, and the open structure allows air to pass through more freely while still catching droplets. Laboratory tests suggest that such designs can collect more water per unit area than a conventional mesh, although their cost and long-term durability under real outdoor conditions remain to be demonstrated. The fog harp is not yet widely used, but it illustrates how small changes in geometry can alter performance.

Fog harvesting will never replace dams, rivers or desalination for large populations, but it offers a valuable supplementary source in places where those options are impractical or unaffordable. The most successful projects tend to be those in which the community is involved in construction and management from the start, so that local knowledge guides the choice of site and the distribution of water. As climate change makes rainfall less predictable in many dry regions, gathering water directly from fog may become an increasingly useful part of the mix, alongside rainwater harvesting, wastewater recycling and careful demand management. In such communities, fog water is rarely seen as a cure for water scarcity, but as one reliable element in a broader strategy.

The shift to remote work during the pandemic was often described as a giant, unplanned experiment. Millions of people who had never worked from home began doing so, and employers who had previously resisted the practice were forced to allow it. Several years later, the results of that experiment remain contested. Some companies have insisted that their staff perform better in an office, while others have closed offices altogether. My own view is that the question 'does remote work make people more productive?' has no single answer: it depends on the task, the worker, the technology and the way productivity itself is measured.

The research literature is consistent with this uncertainty. Studies conducted before the pandemic found a mixture of benefits and costs. A well-known experiment at a Chinese travel agency, for example, found that call-centre employees who volunteered to work from home handled more calls per shift than a comparison group in the office, and reported higher satisfaction. However, the same study also found that home-based workers were promoted at a lower rate, a finding that its authors interpreted as a warning about invisibility. Other studies have linked remote work with reduced commuting and greater flexibility, but also with professional isolation and weaker team identity.

Part of the difficulty is that 'productivity' means different things in different jobs. For tasks that are largely independent and measurable, such as processing claims or writing code, a quiet home office can bring genuine gains; workers avoid interruptions, control their schedules and often finish more in less time. For work that depends on intense collaboration, creative problem-solving or the exchange of half-formed ideas, however, remote arrangements may be less effective. The informal conversations that occur in corridors, before meetings and around shared spaces are hard to reproduce online, and their absence may not be felt until a project stalls.

A second problem is measurement. In factory and clerical work, output is easy to count, but in many knowledge jobs the product is intangible and emerges over months. Managers may therefore fall back on proxies such as hours logged, response times or the number of messages sent, which reward visible activity rather than genuine contribution. Remote work can worsen this tendency, because managers cannot see what people are doing and may grow anxious, while employees feel pressure to appear constantly available, a phenomenon sometimes described as digital presenteeism. This can create a culture in which people are judged by how quickly they reply to messages rather than by what they accomplish.

The blurring of boundaries between work and home is another well-documented risk. Without the physical separation of an office, many remote workers find it difficult to switch off at the end of the day. Surveys conducted during the pandemic found that average working hours increased in several countries, and that many employees experienced higher levels of stress and burnout. Autonomy, which should be one of the great advantages of remote work, can turn into an obligation to be always on. Organisations that introduce remote work therefore need to pay explicit attention to workload, rest and the right to disconnect.

Collaboration and innovation present particular challenges. Video calls are good at transmitting information, but they are less effective at building the trust and weak social ties that often support knowledge sharing. During the pandemic, some researchers observed that communication within teams became more siloed: people interacted more with close colleagues and less with those in other departments. It is too early to say whether this narrowing was a temporary response to crisis conditions or a lasting feature of remote work, but it suggests that simply moving meetings online does not replicate the social texture of an office.

In practice, many organisations have moved towards a hybrid model, in which employees spend part of the week in the office and part at home. The success of such arrangements depends less on the number of days spent in each place than on deliberate design. Teams need clear agreements about which tasks are best done where, which hours require synchronous availability and which communication can be asynchronous. Documentation becomes more important, because fewer decisions are made in the same room, and meetings should be reserved for genuine discussion rather than routine updates.

There are also equity concerns. Not every worker has a spare room, a fast internet connection or the freedom to work without interruption. Younger employees may miss the informal learning that comes from watching more experienced colleagues, and those caring for children or other relatives may face constant distractions even when they are technically at work. If remote work is treated as a privilege rather than as one option among several, it can deepen existing inequalities inside an organisation. A blanket requirement that everyone work from home for most of the week may therefore suit some employees far better than others.

The question posed at the start, then, is better replaced by a different one: not whether remote work is good or bad for productivity, but how, and for whom, and under what conditions. A mature approach would focus on outcomes rather than hours, give employees as much choice as possible, and support that choice with equipment, training and clear expectations. Remote work has not settled the productivity debate; it has made that debate more honest by exposing how little we know about what people actually do all day.