IELTS Academic Reading Practice Test 171

Few household products were discovered so completely by accident as the adhesive sold around the world as superglue. In 1942, with the United States at war, chemists at the research laboratories of Eastman Kodak in Rochester, New York, were looking for a clear plastic that could be moulded into gun sights for military aircraft. Among the hundreds of compounds they prepared were the cyanoacrylates, liquids that dried into hard, transparent solids. Yet the material behaved in a way the researchers found infuriating: it set within seconds, sticking together anything it touched, including the glass instruments used to measure it.

The explanation lies in the shape of the molecule. A cyanoacrylate monomer is a small molecule containing a carbon–carbon double bond. When it meets even a trace of moisture — the invisible film of water present on almost every surface and in the air itself — that bond opens and the molecules join into long chains. This process, polymerisation, happens with remarkable speed and requires no heat, pressure or solvent to start it. The product is a rigid plastic that holds the two surfaces together. Because the reaction needs moisture, a very dry or acidic surface slows it down, while skin, which is always a little damp, sets it almost instantly.

For nearly a decade the discovery was shelved. Then, in 1951, Harry Coover, who had worked on the original project, was supervising a search for materials that could withstand the heat inside aircraft cockpits. A colleague, Fred Joyner, was measuring the refractive index of a series of cyanoacrylates in a refractometer, an instrument that identifies a liquid by the way it bends light. He found that the two glass prisms inside it had become permanently bonded together. The compound responsible was not a nuisance after all but a product, later marketed as Eastman 910.

Coover, who was granted patents on the chemistry, became the public face of the new adhesive. He demonstrated its strength on American television by gluing together two metal bars with a single drop and then suspending a heavy weight from them. Commercial production began in 1958, and the glue was soon used in factories to assemble loudspeakers, cameras and components for cars. Early advertising made extravagant claims about the weight that one drop could support, claims that held true only for a carefully prepared joint placed under the right kind of stress.

Despite its speed, the adhesive has obvious weaknesses. The cured plastic is brittle and resists peeling and impact poorly, so a joint that survives a direct pull may fail easily if the parts are bent or struck. It cannot fill gaps, and it soaks into porous materials such as paper or unglazed pottery before it can set, which is why it is rarely used on them. Its habit of bonding skin instantly has caused countless small accidents. Manufacturers have responded by thickening the liquid into a gel, by adding rubber particles to absorb shocks and by selling solvents that dissolve the hardened glue.

Measuring the strength of a glued joint is less straightforward than it sounds. Cyanoacrylates perform impressively when the two surfaces are made to slide past one another, but poorly when one is levered away from the other, and the figures quoted by manufacturers usually refer to the most favourable arrangement. Surface preparation matters as much as the adhesive: a trace of grease or dust can halve the strength of a bond. Standard methods for testing adhesives are designed to make results comparable between laboratories, but no laboratory test can predict how a repair will behave on a vibrating machine or a leaking pipe.

Household superglue arrived later, in small tubes sold through ordinary shops. The tube is a clever piece of packaging, because the liquid sets on contact with moisture in the air and would otherwise harden inside its container. A sealed tube keeps for about a year, after which it becomes too thick to pour. Gels, thickened with silica, stay where they are put and are preferred by many users for vertical surfaces, though they fill gaps less readily and set more slowly. Labels warn that the product bonds skin in seconds, and hospitals treat a steady trickle of patients who have glued their fingers together.

The medical uses turned out to be more valuable than anyone had expected. Ordinary household glue is unsuitable for the body because it cures too rigidly and its breakdown products irritate tissue. Modified versions, made from longer-chain cyanoacrylates, set more slowly into a flexible film that the body can eventually break down. These are now used to close surgical incisions and small wounds instead of stitches. Accounts from the Vietnam War describe cyanoacrylate sprays being used to slow bleeding in soldiers before they could reach hospital, and this experience pointed towards the later medical products.

Coover continued to work on the chemistry for decades and held more than 400 patents by the end of his career. Recognition came late. He received the National Medal of Technology and Innovation in 2010, when he was in his nineties, and died the following year.

The story is usually told as a discovery made twice: once by chemists who regarded a sticky liquid as a failure and once by researchers who could see a use for it. Not every accident follows that pattern, and most useful materials are found in the course of systematic research rather than by chance. What made the difference in this case was not luck alone but the persistence of a chemist who saw, at the second encounter, what an awkward substance might be good for, and kept working on it.

Optical computing is an old ambition that has repeatedly been declared imminent and repeatedly postponed. The idea is simple to state: instead of pushing electrons through transistors, use beams of light. In one sense the world already runs on photonics, because the internet is carried across oceans and between cities by laser pulses travelling through glass fibres, and photonic devices already outperform electronics at moving large quantities of data over distance. Yet at the end of every fibre sits a computer in which the actual work of calculation is done by electrons. Light transports information superbly; it is the processing that remains stubbornly electrical. This article explains why light appeals to engineers, what it can already do, and why a machine that calculates entirely with light is still a distant prospect.

Light has several properties that make it attractive as a computing medium. A photon carries no electric charge, so beams do not repel one another and do not meet the resistance that turns an electric current into heat; a photonic circuit can therefore, in principle, carry signals with very little loss. Two beams can also cross in the same piece of glass without interfering, which allows many connections to share one physical space. Because the information each beam carries can be encoded in a different colour — that is, a different wavelength — a single fibre can hold dozens of independent channels at once. Electronics has no equivalent: two wires cannot occupy the same place, and narrow copper tracks must be kept apart. Optical fibres are also largely unaffected by the electromagnetic interference that can corrupt electrical signals in factories and other electrically noisy places.

Some operations are naturally suited to optics. A simple lens, for instance, forms at its focus an image that is mathematically a Fourier transform of the object in front of it, and it does so for every point of the image simultaneously. Optical systems therefore perform certain kinds of pattern recognition and image filtering at great speed, because the processing happens as the light passes through the components rather than in a sequence of steps. Photonic links have also become indispensable inside data centres, where they carry signals between racks of servers, and engineers are now placing them between chips, and even between the cores of a single chip, to relieve the bottlenecks that copper wiring creates. Long-distance links rely on the same advantage, since a signal that stays inside glass does not pick up the electrical noise that affects copper cables.

During the 1980s optical computing attracted serious money and energetic optimism. Researchers designed arrays of microscopic switches that would let one beam control another, and in 1990 a team at AT&T Bell Laboratories in New Jersey demonstrated a processor built from such devices, using light rather than electricity to carry out a sequence of logical operations. It was a landmark, and it was also the high-water mark. Electronic chips continued to shrink and to become cheaper at a pace that optics could not match, and by the mid-1990s most industrial research programmes in optical computing had been closed or redirected into optical communications, where the physics was more forgiving. The lesson was that a technology can be excellent at transmission and still be poor at computation.

The central obstacle is that photons barely interact with one another. In a vacuum, or in ordinary glass, two beams of light pass straight through each other and nothing else happens. That is exactly what a communications engineer wants and exactly what a computer cannot tolerate, because logic requires one signal to switch or modify another; a transistor exists precisely because the current flowing through one part of it controls the current flowing through another. Making light behave in this way demands a nonlinear material, one whose optical properties change when light passes through it. Such materials exist, but the effects are weak: they need high intensities, and the devices are slow by electronic standards.

Two further difficulties are often underestimated. The first is memory. A computer must hold intermediate results, and there is no practical photonic equivalent of the transistor's tiny capacitor or of magnetic storage; light must either be trapped in a loop of fibre, which is bulky, or converted into an electrical signal, which costs time and energy. The second is size. Light cannot be squeezed into a space much smaller than half its wavelength, and the wavelengths used in communications are measured in micrometres, so a photonic component is far larger than a modern transistor, whose features are measured in nanometres. Optical circuits are therefore thousands of times less dense, and every conversion between light and electricity consumes power.

Recent research has concentrated on partnerships rather than replacements. Silicon photonics, in which light is guided through structures of silicon a few hundred nanometres wide, allows optical components to be manufactured on wafers in the same plants that make electronic chips. The most visible applications are connections rather than calculations: co-packaged optics places optical transceivers within the same housing as the processor, shortening the electrical path to a few millimetres. More ambitiously, several groups have built arrays of interferometers that perform matrix multiplication, the basic arithmetic of machine learning, by passing light through a network of channels. The largest computations still require electronics for control, storage and precision, and most researchers now expect optical and electronic circuits to work side by side rather than one replacing the other.

Ask a politician in almost any country what the economy needs and the answer will include the word start-up. Ministers compete to be photographed with young founders, universities advertise their incubators, and schoolchildren are taught that the founders of famous technology companies began in garages. The vocabulary of venture capital — pitching, scaling, pivoting, exiting — has leaked into ordinary speech, and a business that has existed for a few months is discussed with more respect than one that has traded profitably for fifty years. Some of this enthusiasm is well founded. Much of it, I will argue, is not.

The case for new firms rests on a real observation. Established companies are good at improving what they already sell and notoriously bad at abandoning it, and the managers whose careers depend on an existing product are rarely the people who invent its replacement. New entrants can explore ideas that incumbents have dismissed, and a small number of them grow into large companies that reshape whole industries. The possibility of building such a company also draws talented people away from safer careers, and the competition it creates can jolt established firms into changing. These are substantial benefits, and nothing in the rest of this article is meant to deny them.

The claim that is heard most often, however, is that new firms create most of the jobs, and here the evidence is more awkward than the slogan suggests. Careful work on firm dynamics shows that young companies do account for a disproportionate share of net job creation, but that this total is dominated by a very small group of fast-growing firms. The typical start-up stays small, employs a handful of people and never hires at all. Counting the number of businesses registered in a year tells a government almost nothing about future employment, because the distribution is so extremely skewed.

Failure, moreover, is far more common than the celebratory literature implies. A large share of new firms close within a few years, and the founders we hear from are, by definition, the survivors. This produces a systematic distortion in the lessons on offer. Advice drawn from successful companies is advice filtered through an invisible selection process, and the habits that appear to explain a triumph may equally have been present in hundreds of businesses that collapsed. The founder who ignored expert advice and succeeded is memorable; the thousands who ignored expert advice and failed are not interviewed.

The culture surrounding start-ups also distributes risk in ways that deserve more scrutiny than they receive. Failure is described as a learning experience, which it may be for an investor with a portfolio of twenty bets, but is a different matter for a young person who has spent their savings and several years of their working life on a single attempt. Encouraging people to accept such odds is easier when the person offering the encouragement bears none of the loss. The romance of the garage conceals how much of the risk is carried by individuals, and how much of the reward is captured by those who funded them.

Some costs fall on people who never chose to take part. The instruction to grow quickly, and the assumption that rules are obstacles rather than protections, has repeatedly produced harms that become visible only after the company is too large to ignore. A service that disregards taxi licensing, planning rules or safety standards does not necessarily innovate; it may simply move an existing business into a space where its costs are lower because nobody is enforcing them. The word disruption is used to describe this, but disruption of a regulated market and improvement of a service are different achievements, and only one of them is difficult.

A further problem is that policy has concentrated on the beginning of the process rather than on what follows. Many countries have succeeded in increasing the number of firms founded; far fewer have created the conditions in which such firms can grow. Scaling requires patient capital willing to wait years for a return, managers with experience of large organisations, and often a long programme of research that no quarterly report will reward. Governments that copy the visible style of a start-up culture, the incubators and the competitions, without the less glamorous institutions behind it, obtain the appearance of an innovative economy and little else.

None of this is an argument for fewer experiments, still less for protecting incumbents. It is an argument for measuring what we actually value. A country that counts registrations will get registrations; one that counts durable companies, well-paid jobs and useful products will get more of those. Reliability, maintenance and careful incremental improvement are treated in this vocabulary as the work of the unambitious, which is both untrue and expensive, since the firms that keep water systems running and aeroplanes flying rarely appear on magazine covers.

The start-up is a remarkable invention, and a society that makes it easy to begin a business is a fortunate one. But a culture that treats founders as heroes and legislation as an inconvenience has confused energy with judgement. We should keep the experiments and lose the mythology. That means admiring a company that is still trading after forty years as much as one that has just raised money for the second time.