IELTS Academic Reading Practice Test 115

Radar is the use of radio waves to detect objects and to measure how far away they are. The idea rests on a simple observation: a radio wave, like a sound wave, is partly reflected when it strikes something solid. The German physicist Heinrich Hertz, who first produced and detected radio waves in the laboratory between 1886 and 1888, noticed that they bounced off metal surfaces, and he used the effect to show that his invisible waves behaved in the same way as light.

The first person to patent a device based on the principle was Christian Hülsmeyer, a German engineer. In 1904 he obtained a patent for an apparatus he called the Telemobiloskop, which sent radio waves across the water and detected the returning signal when a ship lay in their path. It could show that a vessel was present and roughly in which direction, but it could not measure distance, and its range was too short to interest the navies of the day. In 1922 Guglielmo Marconi, whose wireless telegraphy had already transformed communication, publicly suggested that radio might be used to detect ships in fog.

Serious development began in the 1930s, when several countries feared that an enemy might build a beam capable of destroying aircraft. In Britain, the Air Ministry asked its scientific advisers whether such a death ray was feasible. The task of answering fell to Robert Watson-Watt, a physicist at the National Physical Laboratory.

He calculated that no radio beam could carry enough power to harm a crew, but he pointed out that radio waves reflected from an aircraft could reveal its presence. In February 1935 a trial was hurriedly arranged in a field near the village of Daventry, using the BBC's powerful short-wave transmitter there and a receiver brought from the laboratory. An aircraft of the Royal Air Force was flown across the beam, and the reflected signal appeared on the receiving set almost exactly as predicted.

The demonstration convinced the government, and money was found for a chain of stations along the east and south coasts of Britain. The resulting network, known as Chain Home, was largely complete by the time war broke out in 1939. Its masts, some more than a hundred metres tall, stood on cliff tops and farmland. The system used comparatively long wavelengths, around ten metres, which allowed it to detect aircraft far out over the sea. It could give the range and bearing of a formation and a rough estimate of its height, but it struggled to detect aircraft flying low, and a second chain of stations had to be added to fill the gap.

Radar works by timing. A transmitter sends out a short burst of radio energy, called a pulse, which travels outward at the speed of light. When the pulse meets an object, some of its energy is scattered, and a small fraction returns to the station as an echo. A sensitive receiver picks up this echo, and the interval between the outgoing pulse and the returning one is measured. Because the pulse has to travel to the object and back, the range is half the distance obtained by multiplying the speed of light by that interval. On the earliest sets the answer appeared as a spike on the glowing trace of a cathode-ray tube.

A decisive advance came in 1940, when two physicists at the University of Birmingham, John Randall and Harry Boot, built a new kind of valve called the cavity magnetron. Earlier transmitters could produce only modest power at very short wavelengths; the magnetron generated far more at a wavelength of about ten centimetres. Short waves allow a compact aerial to form a narrow beam, which is essential for radar carried in an aircraft. In the same year a British mission took a magnetron to North America, where the information was shared with American scientists, and a large laboratory was established at the Massachusetts Institute of Technology.

Wartime radar took many forms. Airborne sets searched the sea for submarines and surfaced ships, while others, operating at microwave frequencies, allowed bombers to find targets at night and through cloud. On the ground, controllers used radar to guide fighters towards incoming raids, a method known as ground-controlled interception, and the network gave the defenders of Britain information their opponents lacked. Germany and Japan built their own radar systems, but neither country matched the microwave equipment produced in Britain and the United States.

After 1945 the military technology was adapted for peaceful use. Airports installed radar to track aircraft on approach and to keep them apart in the air, and the growth of air travel would have been impossible without it. Ships used it to avoid collisions in fog, and meteorologists discovered that rain and hail return strong echoes, which led to weather radar. Later sets measured the change in frequency of the returning signal caused by a moving object, an effect named after the Austrian physicist Christian Doppler, and this Doppler shift made possible everything from police speed guns to systems that warn drivers of obstacles.

Modern radar looks very different from the equipment tested at Daventry. Warships and airliners carry sets that steer their beams electronically rather than by turning a dish, and satellites map the surface of the Earth with pulses of a similar kind. The underlying principle, however, has not changed since Hertz noticed that his waves bounced off metal. A pulse is sent out, an echo comes back, and the time between the two tells the operator where the object is.

A surgical robot is not, in spite of the name, a machine that operates on its own. The systems in use today are tools that extend a surgeon's hands, and every movement they make is directed by a person at a console a few metres away. The best known is the da Vinci system, made by the American company Intuitive Surgical, which received approval from the United States regulator, the Food and Drug Administration, in 2000 for use in keyhole operations on the abdomen. By the early 2020s several thousand of these machines were installed in hospitals around the world, and they are used most often for the removal of the prostate and for surgery on the kidney, the womb and the bowel.

The equipment has three parts. The surgeon sits at a console and looks into a viewer that shows a three-dimensional image from a camera inside the patient. The hands are placed in grips that pass on their position to a computer, which then instructs the arms of a cart standing beside the operating table. Those arms hold fine instruments, no thicker than a pencil, which are introduced into the body through small cuts. Because the computer sits between surgeon and instrument, it can filter out the slight tremor that every human hand has, and it can scale movements down, so that a movement of several centimetres at the console produces one of a few millimetres inside the patient.

The instruments themselves are more dexterous than the human hand in one respect: the tips bend and rotate, giving seven independent directions of movement, a range that no straight rod passed through a small opening can offer. This matters because keyhole surgery, in which the surgeon works through cuts of a centimetre or so rather than a single large incision, is otherwise performed with long, rigid tools that pivot awkwardly against the wall of the body. The camera, meanwhile, magnifies the operating area many times over, so that structures a millimetre across can be distinguished.

For patients, the advertised benefits follow from the size of the openings. Less tissue is cut, so there is less bleeding and, in principle, less pain and a shorter stay in hospital. For the surgeon, the console is comfortable and the view is steady, and the machine does not become tired or distracted. Operations on the prostate, deep in the pelvis and surrounded by nerves that control continence and sexual function, are particularly demanding, and it was here that robotic assistance was first widely adopted.

Robotic assistance has spread fastest in urology and in gynaecology. In the United States most radical prostatectomies, the removal of the prostate for cancer, are now carried out with the help of a machine, and the technique has been adopted widely for the removal of the womb and for operations on the bowel. Hospitals often advertise the technology, and patients may ask for it by name, even where the evidence of benefit over ordinary keyhole surgery is slight.

There are, however, real drawbacks. The most surprising is the absence of touch. In conventional surgery a doctor feels resistance through the instrument and knows how much force is being applied; in most robotic systems the console offers no such feedback, so the surgeon must judge pressure from the appearance of the tissue alone. The machines are also large, they take time to set up and to attach to the patient, and they cost well over a million dollars each, to which the price of instruments and maintenance must be added. Surgeons need specific training, and the early part of that training is associated with longer operations.

The clinical evidence is more cautious than the marketing. Few would dispute that robotic operations are feasible and safe, and that blood loss and recovery time are often better than after open surgery. Compared with standard keyhole surgery, however, the picture is less clear. A large international randomised trial of rectal cancer surgery, published in 2017, found no significant difference in the main measure of success between robotic and ordinary keyhole operations. Reviews of prostate surgery have reached similar conclusions. The strongest, most consistent finding is that outcomes depend far more on the skill and experience of the operating team than on the machine.

Research is now directed at the weaknesses. Several groups are working on force sensors that would let the console reproduce the feel of tissue, though the engineering is difficult because the sensors must be sterilised and small enough to fit inside a fingertip-sized instrument. Others are shrinking the tools: flexible robots that travel through the mouth or the bowel, and capsule devices that could be swallowed, are being tested. The most successful example of greater machine independence is orthopaedic surgery, where a robot guided by a three-dimensional scan can cut bone for a knee replacement with an accuracy that is hard to achieve by hand.

Distance has also been overcome. In 2001 a surgeon in New York removed the gallbladder of a patient in Strasbourg, in France, while watching a video link; the operation showed that the physical presence of the operator is no longer strictly necessary. Whether such operations become routine depends less on technology than on the reliability of the connections between the two places. Meanwhile the ordinary robot remains what it has always been: a very good tool, and not a replacement for the person holding it.

The word detox was borrowed from medicine, where it refers to the treatment of a person who is dependent on a drug. Applied to screens and social media, it carries an obvious message: our devices are a kind of poison, and the cure is to stop using them for a while. Retreats now advertise days without wifi, and apps exist to stop us opening other apps. I share the unease that lies behind these experiments, but I doubt that the metaphor points towards an answer.

That unease is not imaginary. Something is happening to attention. Studies of how people actually spend their time suggest that a large share of adults check a phone within minutes of waking, and many do so repeatedly through the day. There is a growing body of evidence linking heavy use of social platforms with poorer sleep and, among adolescents, with anxiety. A study at the University of Pennsylvania, published in 2018, asked undergraduates to use each of three social platforms for no more than ten minutes a day for three weeks; compared with a control group, they reported feeling less lonely and less depressed. The effect was modest, but it was real.

Yet the detox framing gets several things wrong. First, it treats a social and commercial problem as a private one. The platforms are not neutral pipes through which content arrives; they are engineered to hold attention, with endless scrolling, notifications timed to bring us back and recommendations chosen to keep us watching. When a system is designed to be hard to leave, telling individuals to leave it is rather like blaming a pedestrian for the design of a road. Second, the metaphor of poison suggests that the only safe dose is none. Most people cannot and would not want to abandon the tools by which they arrange their work, keep in touch with family and find their way across a city.

Third, there is the question of evidence. Detox retreats are not research studies, and the claims made for them are rarely tested. What is tested tends to be less dramatic. Reviews of the literature on screen time and adolescent well-being find small associations, and some find none at all after other factors are taken into account. A teenager who is unhappy may spend more hours online, rather than spending hours online making themselves unhappy; the direction of cause is difficult to establish. Campaigners on both sides have been quick to present weak findings as decisive.

The strongest argument for a break is not that it purifies the body but that it reveals a habit. Anyone who has tried a week without a phone knows the odd, phantom sensation of reaching for it, and that sensation is informative: it shows that the behaviour had become automatic. In this respect a temporary retreat may be useful, in the way that a holiday can reveal how much of one's working life is unnecessary. As a permanent solution, however, it fails, because it treats the symptom in an individual while leaving untouched the system that produced it.

There is also a matter of justice. A retreat in the countryside is available to those with money and free time; a ban on phones in the office is a luxury that a worker expected to answer messages at midnight does not have. Advice to switch off therefore falls hardest on the people with least control over their own hours. Some of the proposed remedies are, by contrast, collective: France prohibited the use of mobile phones by pupils in primary and middle schools in 2018, and several other countries have since restricted them in classrooms.

What might a better approach look like? It would begin by accepting that the technology is here to stay and that the interesting question is what it is designed to do. Regulation of persuasive design — limits on autoplay, on features aimed at children, on the collection of data about attention — is likely to achieve more than any number of individual pledges. Schools can teach pupils how the systems work, which is more useful than telling them to use them less. Default settings matter too: a phone that asks whether a notification should be allowed, rather than assuming that it should, hands the choice back to its owner. And adults can make rules for themselves that are sustainable rather than heroic: keeping the phone out of the bedroom, turning off notifications by default, deciding in advance when to look.

None of this is to deny that some people need to stop altogether. For a minority, the pull of a platform is strong enough to justify quitting it, in the same way that some drinkers must abstain rather than moderate. But that is a clinical judgement about an individual, not a model for the rest of us. The detox industry has taken a real concern and sold it back as a consumer experience: pay to be deprived for a weekend, then return to the same arrangements.

My conclusion, then, is that the question is wrongly posed. We are asked whether we should give up our devices, when we should be asking who benefits from the way they are built and who has the power to change it. A walk without a phone is pleasant and occasionally revealing, but it will not alter the incentives of an industry whose revenue depends on our attention. If the aim is to make that attention less easily captured, the change will have to be made where the systems are designed, not where they are used.