IELTS Academic Reading Practice Test 188

In 1898 two British chemists, William Ramsay and Morris Travers, were searching for further members of a family of chemically inert gases. By evaporating a large quantity of liquid argon and collecting the most volatile part, they isolated a gas that glowed with a brilliant crimson light when an electric current passed through it. They named the new element neon, from the Greek word for new. For more than a decade it remained a laboratory curiosity, with no obvious practical use.

The person who changed that was Georges Claude, a French engineer and chemist whose company liquefied air to supply industry with oxygen and nitrogen. Neon was one of the gases left over from that process, and in 1910 Claude demonstrated a lamp consisting of a sealed glass tube filled with neon, shown publicly at the Paris Motor Show that December. His design was simple in principle: two electrodes sealed into the tube, a gas at low pressure, and a supply of high voltage. Claude also took out patents on improved electrodes that made the tubes durable enough to be sold, and he was the first to bend the discharge into the shapes of letters.

When the voltage is applied, free electrons are pulled through the gas and collide with neon atoms, lifting the atoms' own electrons to higher energy levels. As these electrons fall back, the energy they release appears as light. Because every gas has its own set of energy levels, each produces a characteristic colour: neon glows a strong orange-red, while argon, another inert gas, gives a paler blue. There is no filament to burn out, as there is in an incandescent bulb, and a tube will therefore run for many thousands of hours.

Claude's system reached the United States in 1923, when a Packard car dealership in Los Angeles ordered two signs. In a city lit by incandescent bulbs the effect was startling, and the signs, which the company advertised as liquid fire, drew crowds. Within a decade neon had become the standard way of advertising along commercial streets and in districts such as Times Square in New York. Much of the early industry was built on cheapness as well as spectacle: a sign could be assembled in a small workshop from glass tubing, a burner and a transformer.

Colour was not confined to the gases themselves. By coating the inside of a tube with fluorescent powders, makers could convert the invisible ultraviolet light produced by mercury vapour into almost any hue, so that a single sign could combine several colours. The glass itself could be tinted, and the tubing bent to follow the curves of a brand's lettering. Skilled glassblowers became the most valuable workers in the trade, since their craft largely determined what a sign could look like.

The electrical demands were considerable. A tube of any length needs a high voltage to start the discharge, so a transformer was built into each sign to raise the ordinary mains supply to several thousand volts. Because the gas inside is at low pressure, the tube is fragile, and because the discharge produces heat, the fittings must allow the glass to expand. Installers therefore needed both electrical skill and a practical understanding of how glass behaves out of doors.

Making a reliable tube was a matter of cleanliness as much as design. Each tube was heated and connected to a vacuum pump for hours to remove traces of air and moisture, since impurities shorten the life of a lamp, and was then filled with neon and sealed. The finished tube was usually run for some time before installation, so that early failures happened in the workshop rather than above a shop door. Old tubes can be refilled, which is one reason why restorers prefer to repair a sign rather than replace it.

Neon's dominance did not last. Fluorescent lamps, first marketed in 1938, gave a cooler, whiter light and were cheaper to run, and from the 1950s onwards illuminated plastic boxes displaced the glass tube from shopping centres and highways. Some towns passed rules limiting the size or brightness of signs, and many older installations were removed when buildings were altered. By the 1970s the craft was in steep decline in Europe and North America, and workshops that had trained generations of glassblowers began to close.

Yet the signs themselves acquired a value their makers had not expected. Photographers had been drawn to them since the 1930s, and from the 1970s campaigns to preserve historic examples gathered strength. Museums devoted to the medium opened, among them the Museum of Neon Art in Los Angeles, and restored signs were reinstalled as public artworks, while in Las Vegas a boneyard was created to keep discarded examples. Collectors now pay high prices for working pieces, and a few workshops still bend glass by hand using techniques that have changed little since Claude's day.

Today many glowing signs are not neon at all. Light-emitting diodes use far less energy and can be programmed to change colour, and they have replaced discharge tubes in most commercial display, so that a sign which appears to be a classic design may well be an imitation. That has not ended the story. Neon remains in use where its saturated colour and faint flicker are wanted, and artists continue to explore what a sealed tube of gas can do.

The human eye has several features that make it attractive to engineers. The cornea, the transparent front surface, has no blood vessels, which is why it stays clear; it takes its oxygen from the air and its nutrients from fluid inside the eye. Tears, which keep the surface moist, carry proteins, salts and sugars whose composition changes with the state of the body. A lens resting on the cornea is therefore in contact with a fluid that can be sampled continuously, and it sits only a few centimetres from the retina, the light-sensitive layer at the back of the eye.

Contact lenses themselves are much older than electronics. Leonardo da Vinci sketched ways of altering the refraction of the eye with water around 1508. Practical lenses appeared in the 1880s, when Adolf Fick, a German-born physician working in Zurich, had glass shells ground to cover the whole eye, including the white, and wore them for short periods. The decisive change came in 1961, when the Czech chemist Otto Wichterle produced the first soft lens from a water-absorbing plastic. His early lenses were made in a spinning mould, and the apparatus was assembled from a child's construction kit and a bicycle dynamo in his kitchen.

A smart lens is built around a thin, curved piece of polymer, and its electronics must follow the same curve. The active part usually consists of a sensor, a small integrated circuit and an antenna, embedded near the edge of the lens so that they do not interfere with vision. Power normally arrives from outside the eye: a coil worn on the skin nearby, or built into a pair of spectacles, transmits radio waves to the antenna, which turns them into the small currents the circuit needs. Some designs add a thin-film battery, but batteries remain bulky and rigid, and any source of power generates heat that must be kept away from the cornea.

The application that has attracted most attention is the measurement of glucose, because people with diabetes must check their blood sugar several times a day, usually by pricking a finger. Glucose is present in tears, and a lens can carry an enzyme-based sensor whose output current depends on how much glucose it meets. The attraction is obvious: a reading every few minutes, with no needle. Concentrations in tears are far lower than in blood, so the sensor must be extremely sensitive, and the relationship between the two is not fully understood. The amount of fluid on the eye also varies with blinking and with temperature, and a device that reports a number is of little use unless that number can be trusted.

Pressure inside the eye offers a second target. In glaucoma, damage to the optic nerve is associated with raised pressure, yet a measurement taken in a clinic is only a snapshot. The Swiss company Sensimed developed a lens containing a strain gauge which records tiny changes in the shape of the cornea as the pressure rises and falls over twenty-four hours, and the device received European approval in 2009. Recordings of this kind have shown that pressure behaves quite differently at night, or when a patient is lying down, from the way it behaves during a clinic appointment.

None of this makes the engineering easy. The cornea has no blood supply of its own and relies on the air for oxygen, so any lens must be permeable enough to avoid suffocating the tissue beneath it. Modern soft materials that incorporate silicone transmit far more oxygen than the hydrogels available in Wichterle's day, but circuits, metal tracks and adhesives tend to block the surface. The eye is also a hostile environment for delicate components: it is wet, it moves, and the eyelid sweeps across the lens with every blink. Proteins and lipids from tears settle on the surface, so the device must survive regular cleaning and the warmth of the body.

A different line of research uses the lens as a display. Several companies have built prototypes in which a micro-light-emitting diode, together with focusing optics, is embedded in a rigid section of the lens and projects an image onto the retina. The image might be a route instruction, or an outline marking the edge of a step for someone with impaired vision. Because the light is directed into the eye rather than out into the room, the display can be bright enough to read in daylight yet invisible to everyone else. The electronics such a lens needs, however, are far more complex than those required by a sensor.

Lenses can also deliver medicine. Soaking a soft lens in a solution of a drug allows it to absorb the drug, which then diffuses slowly onto the eye, keeping the concentration on the surface steadier than drops do and sparing patients the need to remember four doses a day. The weakness is that the drug is often gone within a few hours; one solution is to add a layer of vitamin E, an oily substance that slows the diffusion and spreads the release over several days. Lenses loaded with drugs for glaucoma and for bacterial infection have been tested in animals.

Progress towards everyday use is slow, and not only for technical reasons. A lens containing a sensor is a medical device, and regulators reasonably demand evidence of safety, accuracy and reliability before it can be sold; trials are expensive and take years. Approval has been granted for a few specialist products, but none of these devices is yet a consumer item. Whether the public wants one is another question. A lens that must be removed and cleaned nightly, and whose electronics will eventually fail, is a demanding product to live with, however elegant the science behind it.

Ask a group of thirteen-year-olds how they signed up for social media, and most describe the same ritual: they typed a date of birth that made them old enough, and clicked accept. For nearly twenty years this has been the whole of age verification on the largest platforms. The rule exists in the terms of service, and in many countries in law, but the check is performed by the person the rule is meant to protect. It is as if a cinema asked children at the door to confirm they were eighteen and waved through anyone who said yes.

That arrangement is now being dismantled. In November 2024 Australia passed legislation obliging platforms to take reasonable steps to prevent anyone under sixteen from holding an account; the duty begins in December 2025, with penalties running to tens of millions of dollars. The United Kingdom's Online Safety Act, passed in 2023, takes a different route. Rather than naming an age, it requires services likely to be accessed by children to protect them, and the regulator's codes demand highly effective age assurance before certain material is shown. Other jurisdictions are drafting similar rules.

The case against self-declaration is not that children lie about everything, but that a single field offers no resistance. Regulators have repeatedly found that a large share of children with accounts gave a false year of birth, and that many hold several profiles, so that closing one leaves others open. A prompt is not a check; it is a request, and it is addressed to the one person with an interest in answering it wrongly.

What would a genuine check look like? The bluntest instrument is an identity document: the user photographs a passport or a driving licence, software reads the date of birth and sometimes compares the face with the portrait. Banks and gambling operators have done it for years. It is also the most intrusive option, because it requires every user, whatever their age, to hand over a document that carries a name, a number, a nationality and a photograph. A credit card check is cheaper, but it excludes adults without a card while admitting any child whose parents' card is to hand.

Other methods estimate rather than verify. Facial age estimation takes a short video or a photograph and returns a number: this face appears to be twenty-three. No document is required and no identity is established: the software does not ask who the person is, only how old they look. Trials commissioned by the Australian government tested several such systems, and the results were encouraging enough for regulators to take the approach seriously. Accuracy falls for some faces, particularly young ones and some demographic groups, and an estimate is a probability, not a fact.

Privacy is where the argument becomes difficult. Verifying an age and identifying a person are different tasks, but the systems that perform one can easily perform the other. If every user must prove an age, the platform must handle sensitive material about everyone, and a single breach exposes the documents or biometric templates of millions. Facial age estimation is less demanding, because a template can be discarded as soon as an estimate is made, but only if the company chooses to discard it. Campaigners point out that the safest database is the one that was never built.

There is also the question of who is shut out. Identity documents are not universal: some adults have no passport, and homeless people, refugees and the very poor are the least likely to hold one. A system that admits only the documented creates a new inequality in access to services that have become ordinary. Anonymity raises a related difficulty. People who use a pseudonym to discuss a medical condition, to escape a violent partner or to speak in a country where their sexuality is criminalised depend on not being named. Age assurance need not destroy anonymity, but a badly designed scheme would.

None of these objections is an argument for doing nothing. It is an argument for deciding precisely what has to be proved, to whom, and for how long the record is kept.

Designers have begun to answer that question. The least intrusive systems keep the check on the device or in a separate app, confirm nothing beyond the fact of age, and pass a token to the platform that says 'over sixteen' and no more. The platform learns the answer, not the birth date, and no central register of identities is created. Age estimation can be combined with this, so that most users never show a document and only doubtful cases are escalated. Where a document is required, it should be deleted once the check is complete, and the arrangement should be audited independently of the company that profits from it.

So the obligation should be imposed, but carefully. Platforms should carry the legal duty, because they control the design and hold the data. The state should set the standard, insist on the least intrusive method that will work, and pay for the independent audits. Firms that collect more than they need should be penalised, and the penalties should exceed whatever they save. The alternative — a decade more of children typing a false year — is not neutrality. It is a decision, taken by default, that the present arrangement is good enough. It is not.