IELTS Academic Reading Practice Test 176

For most of the nineteenth century, a wheel was a rigid circle of wood with a band of iron shrunk onto its rim. On a smooth surface such a wheel rolls easily enough, but on the broken stone and mud of contemporary roads every bump was transmitted directly to the vehicle and its passengers. Carriages were heavy, horses were expensive and a long journey was exhausting. Engineers understood that a cushion of air would absorb shocks far better than iron, but no one had found a way to keep such a cushion inside its container.

The first person to solve the problem was Robert William Thomson, a Scottish engineer. In 1845 he took out a patent for what he called an aerial wheel: a hollow rubber tube, enclosed in a leather jacket and bolted to the rim of a carriage wheel, then inflated with a pump. Thomson tested it on a heavy carriage and reported that the vehicle ran more smoothly and needed noticeably less effort to pull. The invention worked, but it did not sell. Rubber was costly, the roads were poor, and solid tyres were adequate for the slow vehicles of the period.

Rubber itself was part of the difficulty. Vulcanisation, the process that makes rubber strong and elastic by heating it with sulphur, had been patented only a year or two before Thomson's, and the material was still produced in small batches from wild trees in the Amazon basin. It was expensive, variable in quality and hard to shape into a thin, seamless tube that would hold air under pressure. A hollow tyre demanded rubber of a consistency that manufacturers could not yet supply, and this, as much as the state of the roads, explains why the idea was shelved.

Within a few years the patent lapsed and the aerial wheel was forgotten. For four decades wheels remained solid. The coming of the bicycle changed the calculation, because a bicycle is light, fast and entirely dependent on its rider's comfort. The high bicycles of the 1870s and 1880s, with a large front wheel and a small rear one, were notorious for throwing their riders over the handlebars at the first stone.

The second inventor was John Boyd Dunlop, a veterinary surgeon who had moved from Scotland to Belfast. In 1887 he watched his young son struggle to pedal a tricycle over the cobbled streets and decided to improve the tyres. He wrapped a sheet of rubber around the wheel, inflated it with a football pump and glued the ends together; according to the family story, his son was soon beating his friends in races. Dunlop filed a patent in 1888 and, with the help of a local businessman, began to make tyres for cyclists.

Then came the demonstration that made the pneumatic tyre famous. In 1889 a Belfast cyclist named Willie Hume fitted Dunlop's tyres to his machine and won a series of races against riders on solid tyres. The victories were widely reported, and orders followed. A company was formed to exploit the patent, with the Dublin businessman Harvey du Cros at its head, and within a few years pneumatic tyres had become standard equipment on racing bicycles.

Success brought legal trouble. When the new company tried to defend its patent, lawyers found Thomson's specification of 1845, which described much the same device, and Dunlop's claim to be the inventor was weakened. The historical record now gives Thomson priority. Commercially it made little difference: the company held the market through manufacturing skill and the purchase of rival patents rather than through the exclusive right to the idea.

The early tyre had a serious practical flaw. It was glued to the rim, so a puncture meant cutting the tyre off, repairing the tube and cementing it back, a job that took hours. In 1890 a British inventor, Charles Kingston Welch, patented a tyre held on the rim by a wire bead, which could be removed with levers, and in the same period the Michelin brothers in France developed a detachable tyre with a separate inner tube. Within a few years a cyclist could mend a puncture at the roadside in minutes.

Motor cars posed a greater challenge, since they were much heavier and travelled much faster. In 1895 the Michelin brothers entered a car fitted with pneumatic tyres in the Paris–Bordeaux–Paris race, a distance of more than a thousand kilometres, to show that the idea could survive at speed. Thereafter the tyre industry grew alongside the car industry. In the 1910s manufacturers found that adding carbon black to rubber greatly increased its resistance to wear, and the useful life of a tyre rose from a few thousand kilometres to tens of thousands.

Fabric and steel cords replaced cotton canvas as the reinforcing material, and in the late 1940s Michelin introduced the radial tyre, in which the cords run across the tyre rather than diagonally. The radial design gave a longer life, lower fuel consumption and better grip, and it gradually displaced the older cross-ply construction in most of the world. The principle that Thomson patented in 1845, a thin cushion of air between vehicle and road, has never been improved upon.

Weather forecasting was transformed in April 1960, when the United States launched TIROS-1, the first satellite designed to observe clouds from orbit. Its pictures were crude by modern standards, but they showed for the first time the pattern of cloud over the oceans, where observations had previously come only from the occasional ship. Within a decade no weather service could operate without satellite images, and today dozens of satellites supply a continuous stream of measurements that are fed into the numerical models on which every forecast beyond a few hours depends.

Weather satellites occupy two kinds of orbit. Placed roughly 36,000 kilometres above the equator, a geostationary satellite takes exactly as long to complete an orbit as the planet takes to rotate, and so seems to remain fixed above one spot. From there it can photograph a whole hemisphere every ten or fifteen minutes, which is ideal for watching storms develop. A polar-orbiting satellite flies much lower, at about 800 kilometres, passes over the poles and sees the entire globe twice a day, but at a much finer resolution.

The two systems are complementary, and no single country operates enough of them. Satellites are owned by national meteorological agencies and by EUMETSAT, the European organisation, and their data are exchanged through a framework coordinated by the World Meteorological Organization, so that a forecaster in one country routinely works with images from a satellite owned by another. The arrangement has a weakness: when an old satellite fails before its replacement is in orbit, a gap in coverage can open, and forecasters must manage without it.

The instruments that do this work are radiometers, which measure the intensity of radiation arriving from the Earth in a number of wavelength bands known as channels. A visible channel records sunlight reflected from cloud and surface; a thermal infrared channel records the radiation emitted by the surface or by the top of a cloud, and therefore indicates its temperature; a water-vapour channel, centred on a wavelength at which water molecules absorb strongly, reveals the moisture in the middle of the troposphere. Each channel is sensitive to a different feature of the atmosphere, and the combination is far more informative than any single image.

Infrared observations have an obvious limit. The radiation that reaches the satellite comes from the highest cloud top, so a thick layer of cloud hides everything beneath it, and the internal structure of a storm remains invisible. Microwave sounders overcome this. They measure weak emission from oxygen and water molecules at wavelengths that pass through cloud, and from those measurements computers derive vertical profiles of temperature and humidity through the depth of the atmosphere, including the layers inside a storm. A microwave imager can also estimate rainfall over the ocean, where no rain gauges exist.

Satellites also measure wind, though not directly. By tracking the movement of cloud features from one image to the next, computers produce atmospheric motion vectors, estimates of wind at the height of the cloud. A scatterometer, a radar that bounces pulses off the sea, infers the wind at the surface from the roughness of the water, since a windy sea is a choppy one. An altimeter, meanwhile, times a radar pulse reflected from the sea surface to measure its height, revealing waves, storm surges and slow changes such as El Niño.

The volume of data is enormous, and forecasters do not simply look at pictures. Radiances, the raw measurements of radiation, are fed directly into numerical models in a process called data assimilation, which combines them with conventional observations from ships, aircraft and ground stations to estimate the state of the atmosphere at a given moment. Because the models are chaotic, small improvements in that estimate can produce large improvements in a forecast several days ahead, and satellite data are now the largest single input to the process.

The results are visible in forecast skill. Since the 1980s, errors in predictions of where a tropical storm will travel three days ahead have fallen substantially, and satellite data are widely credited with much of the improvement. Forecasters can also distinguish low cloud and fog from the ground beneath by comparing two infrared channels, because the two behave differently at those wavelengths, and over deserts, where ground stations are sparse, this is often the only evidence available before dawn.

Satellites detect volcanic ash, which is invisible to ordinary radar but dangerous to aircraft engines, and they track the movement of dust, smoke and pollution across continents. There are limits, however. A geostationary satellite sees the high latitudes at a shallow angle, and above about sixty degrees of latitude its view becomes too distorted to be reliable, so polar-orbiting satellites carry the burden there. Instruments also degrade in the harsh environment of space, and combining readings from an ageing satellite with those from its replacement, without introducing an artificial jump into the record, is a demanding technical task.

Research now concentrates on sampling the atmosphere more often and in finer detail. Hyperspectral infrared sounders, which measure thousands of narrow channels at once, provide temperature and humidity profiles approaching those of a radiosonde, the instrument package carried aloft by a balloon. Constellations of small satellites offer a different route: NASA's TROPICS mission, a set of small microwave instruments launched in 2023, was designed to observe tropical cyclones far more frequently than a few large satellites can. A further goal is to capture the rapid intensification of a storm, a process that current models often miss. Data must also reach forecasters within minutes to be useful, which places heavy demands on the ground systems that process it.

A small tube arrives in the post. The customer spits into it, seals it and sends it back, and a few weeks later receives a report on ancestry, on distant cousins and on a handful of genetic variants associated with disease. Testing of this kind, sold directly to the public rather than ordered by a doctor, has become a mass-market product, advertised with the promise of self-knowledge. What the advertisement rarely explains is what happens to the sample once the report has been generated, and what the company is entitled to do with the information it contains.

The benefits are real and should not be dismissed. Adopted people have found biological relatives; families have discovered a shared risk of a condition that can be treated; couples have learned, before starting a family, that they both carry the same recessive mutation. A test that costs little more than a dental check-up can set in motion a conversation with a physician that would otherwise never have taken place, and in medicine prevention is almost always cheaper than treatment. To those who argue that the tests are merely entertainment, it is worth replying that a proportion of them are not.

Yet genetic information is unlike other personal data in three respects. It is permanent: a password can be changed, a genome cannot. It is shared: half of it belongs to each parent, and a meaningful fraction to every sibling and cousin. And it is predictive, in a way that is easily misread. A statistical elevation of risk is not a diagnosis, but a customer who reads that they have 'a raised chance' of an illness may hear something quite different.

The business model explains much of the anxiety. A test costing a few tens of pounds cannot by itself fund a laboratory, a website and a marketing campaign. Companies have therefore sought other sources of value, including subscriptions and partnerships with pharmaceutical firms, which pay for access to large sets of genetic and survey data. The terms that customers accept are long, and they change; a clause that seems acceptable at the point of sale may look very different after an update.

Nor is interpretation straightforward. A variant that has been studied mainly in people of one ancestry may carry a different meaning in another, and the same raw data analysed by different services can produce different conclusions. A customer who takes a report to a doctor may therefore be told either that the result is unremarkable or that it deserves further investigation, depending on who is reading it and which studies are being consulted.

Companies generally remove names and other obvious identifiers before passing data to researchers, and describe the result as de-identified. Anonymity, however, is harder to guarantee than the word suggests. Researchers have shown that a surname can sometimes be recovered from a modest number of markers on the male line, combined with freely available records, and that the number of markers required falls as databases grow. Adding a postcode and a year of birth to a genetic profile narrows the field dramatically.

The most visible collision between this industry and the state came in 2018, when police in California announced that they had identified a suspect in a long series of violent crimes by uploading a crime-scene profile to a public genealogy website and building family trees from partial matches. No warrant was needed, because the site was open to anyone willing to upload a file. The suspect had never submitted his own DNA; a distant relative had.

This is the heart of the problem. Consent is the usual justification for collecting and sharing data, but consent given by one person licenses inferences about others who have agreed to nothing. When a company alters its terms to permit law-enforcement searches, the decision is taken not by the people whose data will be searched but by strangers who happen to share some of their DNA. The individual at the centre of the transaction is not the only person affected by it.

Regulation has been uneven and has concentrated on accuracy rather than on privacy. Some authorities have required companies to show that a health claim is meaningful, and a few have restricted the direct sale of certain tests. Privacy law, where it exists, was written for a world of credit cards rather than genomes, and the protection a customer receives therefore depends heavily on the country of purchase.

What should be done? Banning the tests would be a mistake, since it would deny genuine benefits and drive the market underground. The remedy is to shift the burden from the individual to the firm: clear statutory limits on secondary use, independent oversight of research partnerships, a requirement that police access be authorised by a court, and a real right to have data deleted. Consent should be the beginning of the argument, not a complete defence.

Sequencing will become part of ordinary medicine. The question is not whether our genomes will be read but who will read them, for what purpose and on what terms. The industry's own answer, that a customer can always decline to buy, is too thin to protect the relatives of the customers who do.