Matching features

Reading Passage 2 – Keeping the Same Time

A Before the nineteenth century, few people had any reason to know what time it was anywhere other than in their own town. Time was local: noon was the moment when the sun stood highest in the sky, and because the sun appears to travel from east to west, noon arrived a little later at every place further to the west. A town a hundred kilometres west of another would therefore keep time several minutes behind it. Public clocks on churches and town halls were set by sundials or by astronomical observation, and nobody was troubled by the fact that neighbouring towns disagreed.

B The railways changed this. When journeys that had once taken days could be completed in a few hours, differences of a few minutes began to matter. A passenger reading a timetable needed to know whether a departure time referred to the clock at the station he was leaving or at the one he was travelling to, and staff scheduling trains on a shared line needed a single reference if collisions were to be avoided. In Britain, individual railway companies began to run their trains according to London time, and within a decade most of the country's railways had adopted it.

C This so-called railway time did not win immediate acceptance. Many towns continued to keep their own local time on public clocks, and some clocks were fitted with two minute hands, one showing local time and the other railway time. Critics complained that an arrangement designed for the convenience of commercial companies was being imposed on everyone else. Nevertheless, the practical advantages proved hard to resist, and over the following decades the great majority of public clocks came into line. Parliament finally made Greenwich Mean Time the legal time throughout Great Britain in 1880.

D In North America, the problem was far greater. The continent was so wide that a single national time was impossible, and before the 1880s the railroads operated on dozens of different times, often each company's own. On 18 November 1883, the railroads of the United States and Canada introduced a system of standard time zones, each covering a broad band of territory and differing from its neighbours by exactly one hour. In many places, the change took effect at midday, and the occasion became known as 'the day of two noons', because in towns that had to turn their clocks back, noon arrived twice. Remarkably, the new zones had no legal basis in the United States until 1918; for more than three decades, they were simply an agreement among private companies.

E Meanwhile, astronomers and geographers were debating a related question: from which line of longitude should the world measure east and west? Different nations used their own capitals or observatories as the starting point on their maps and charts, which caused confusion for navigators. In 1884, delegates from more than twenty countries met at a conference in Washington, D.C., and voted to adopt the meridian passing through Greenwich, in London, as the world's prime meridian. One reason for the choice was practical: a large majority of the world's shipping already used charts based on Greenwich. Not every country accepted the decision at once, however; France, for example, continued to use the Paris meridian for many years afterwards.

F The conference did not establish a worldwide system of time zones, but it prepared the ground for one. Over the following decades, country after country adopted a standard time defined in relation to Greenwich, most commonly a whole number of hours ahead of it or behind it, although a few chose offsets that include an extra half hour or even three-quarters of an hour. In practice, zone boundaries rarely follow lines of longitude exactly; they bend around national and regional borders, and some large countries have chosen to use a single time across their entire territory.

G Today, the precise time is no longer set by the sun, or even by an observatory at Greenwich. Since the 1960s, the second has been defined by the vibrations of atoms, and the world's official time scale, Coordinated Universal Time, is maintained by combining the readings of hundreds of atomic clocks in laboratories around the world. Yet the basic idea remains the one that the railways made necessary: people in widely separated places agreeing to read the same hour from their clocks. It is easy to forget how recent that agreement is, and how much argument it took to reach it.

Reading Passage 2 – Second Lives Beneath the Waves

A When a ship reaches the end of its working life, it is usually towed to a breaker's yard, where it is cut up and its steel sold for scrap. A small number, however, meet a very different fate. Cleaned, stripped and then deliberately sunk, they come to rest on the seabed, where within months they begin to attract fish, corals and sponges. Artificial reefs of this kind have been created off the coasts of the United States, Australia, Malta and many other countries, and they have become popular destinations for divers. But the practice has always had its critics, and the question of whether a sunken ship is a gift to the ocean or simply a convenient way to dispose of waste has never been entirely settled.

B The idea of placing objects in the sea to attract fish is far from new. Fishermen in Japan were sinking wooden frames weighted with stones in the eighteenth century, and similar practices have been recorded in the Mediterranean. What has changed is the scale. In the second half of the twentieth century, governments began to sink not only ships but also old railway carriages, military vehicles and even concrete from demolished buildings. Some of these early projects were poorly planned: in one notorious case off the coast of Florida, around two million used car tyres were bound together and dropped into the sea in the 1970s, in the hope that they would become a reef. Instead, the bundles broke apart in storms, and loose tyres were thrown against existing natural reefs, damaging them. Clearing them up has cost millions of dollars.

C Lessons from such failures have shaped modern practice. Before a ship can be sunk today, it must be thoroughly cleaned of fuel, oil, paint containing toxic substances, and any loose material that could float away. Wiring and insulation, which may contain harmful chemicals, are removed, and openings are cut in the hull so that divers can enter and leave safely. This preparation is expensive and can take more than a year; in some cases it costs more than the value of the scrap metal the ship would otherwise have produced.

D Why do marine organisms colonise a wreck so quickly? Part of the answer is that, on much of the seabed, hard surfaces are scarce. Many coastal waters have floors of sand or mud, to which corals and sponges cannot attach themselves. A ship provides a large, stable structure rising from the seabed, with sheltered spaces of every size, from narrow gaps between metal plates to entire rooms. Small fish shelter in these spaces, and larger predators follow them. Biologist Elena Marsh, who has surveyed wrecks in the Gulf of Mexico for over a decade, has found that the number of fish around a ship can exceed that on a natural reef of similar size within five years.

E Not everyone is convinced that this represents a real benefit. A central question, raised by the fisheries scientist Tom Akers among others, is whether artificial reefs actually produce new fish or merely attract existing ones from the surrounding area. If the latter is true, a wreck may do more harm than good, because concentrating fish in one place makes them easier for fishing boats to catch. Akers argues that the answer probably varies from one species to another, and that without careful long-term monitoring it is impossible to know which effect dominates in any particular case.

F There are also concerns about what happens as a wreck ages. Steel corrodes in seawater, and while a large ship may remain structurally sound for many decades, its upper decks will eventually collapse. The engineer Rosa Lindqvist points out that the rate of corrosion depends heavily on depth and water temperature, and that ships sunk in shallow, warm waters may deteriorate much faster than their planners expected. As the structure breaks down, the habitat it provides changes too, and divers who enter older wrecks face increasing risks.

G Supporters respond that, whatever its effect on fish numbers, a well-managed artificial reef can relieve pressure on natural ones. Popular natural reefs suffer damage from the anchors and fins of large numbers of visiting divers. By offering an attractive alternative nearby, a sunken ship can draw some of these visitors away. The marine economist David Okoro has calculated that a single wreck off the coast of South Australia generates several million dollars a year in tourism, much of it for small businesses such as dive schools and guesthouses. For coastal communities, he suggests, this income may matter as much as any ecological argument.

Reading Passage 2 – Farming Upwards

A At first sight the concept appears to belong to science fiction: lettuces, herbs and strawberries cultivated in tiers inside windowless warehouses, illuminated by pink and blue light and entirely without soil. Over the past fifteen years, however, so-called vertical farms have progressed from architects' sketches to functioning commercial operations. Their advocates portray them as a response to several of agriculture's most persistent difficulties, ranging from the depletion of freshwater resources to the lengthy supply chains on which urban populations depend. The sector's track record, nevertheless, has been strikingly inconsistent: a handful of profitable enterprises coexist with a series of costly and widely reported collapses.

B The underlying technology is relatively straightforward. In the majority of installations, crops are cultivated hydroponically, their roots immersed in a solution of water and dissolved minerals; in others, which rely on a technique termed aeroponics, the roots are left suspended in the air and periodically sprayed with a fine mist. Since the water is captured and recirculated rather than lost through evaporation and drainage, operators maintain that consumption can be as much as 95 per cent lower than on a conventional farm producing an equivalent crop. Because the growing environment is sealed, insects have considerable difficulty gaining access, with the result that pesticides are seldom required. Illumination is supplied by light-emitting diodes (LEDs), and it is here, according to the plant physiologist Professor Ines Duarte, that much of the real ingenuity resides. 'Photosynthesis does not respond equally to every wavelength,' she observes. 'LEDs allow us to tune the spectrum to the requirements of each species at each stage of its development – a degree of control that natural sunlight cannot provide.'

C For food retailers, though, the principal appeal lies less in resource efficiency than in freshness. A field-grown lettuce may spend several days in transit and storage before it is displayed for sale, deteriorating in both flavour and shelf life along the way. A vertical farm, by contrast, can be sited on the periphery of a city or even within it, so that produce picked in the early morning may be on supermarket shelves the same day. 'Consumers are not buying technology,' remarks Marcus Feld, who founded one of the earliest commercial vertical farms in northern Europe. 'What they are buying is a salad that keeps for a week in the fridge rather than three days.' Output is also highly predictable: an indoor facility is insulated from drought, flooding and unseasonal frost, and can therefore supply an identical volume throughout the year.

D The fundamental obstacle is energy. Whereas sunlight costs nothing, electricity does, and every hour of illumination received by an indoor crop must be paid for, as must the cooling required to dissipate the heat generated by the lamps. It is for this reason that vertical farms produce little apart from leafy greens, culinary herbs and a limited range of soft fruit – crops that mature rapidly, are harvested in their entirety and command a comparatively high price per kilogram. Staple cereals such as wheat and rice present an altogether different case. The agricultural economist Dr Hannah Kessler has estimated that the electricity needed to grow enough wheat indoors for a single loaf would cost many times the retail price of the loaf itself. 'For any crop, the decisive question is how much revenue each unit of light can generate,' she argues. 'In the case of basil, a considerable amount; in the case of grain, virtually none.'

E The consequences of these economics became painfully apparent when energy prices rose steeply in the early 2020s. A number of well-capitalised companies, some of which had attracted hundreds of millions of dollars in investment, were obliged to close facilities or file for bankruptcy. Critics contended that, in many instances, business plans had rested on unduly optimistic cost projections and on the assumption that rapid expansion would in itself generate economies of scale. Feld is frank about the industry's misjudgements. 'Many of us, quite simply, designed our operations for an era of cheap power,' he acknowledges. 'Once that era ended, the figures no longer added up.'

F Few commentators now anticipate that vertical farming will supplant conventional agriculture, yet this need not imply that it lacks a future. Some producers are adopting hybrid models, notably greenhouses that exploit natural daylight and activate supplementary LEDs only when sunlight is insufficient. Others are drawing on solar or wind generation, or on surplus heat from neighbouring industrial plants. Duarte, for her part, suspects that the technology's most significant contribution may lie in a different direction entirely. 'Consider polar research stations, cities in arid regions or, eventually, a lunar base,' she suggests. 'Where conventional cultivation is impossible, a vertical farm is under no obligation to compete with a field. It merely has to function.'