12 週 PET 閱讀週考卷

Round the Moon and back

On 1 April 2026, four astronauts climbed into a spacecraft called Orion and left Earth for the Moon. Their mission, Artemis II, was the first time in more than fifty years that human beings had travelled that far from home.

The crew were Reid Wiseman, Victor Glover and Christina Koch of NASA, together with Jeremy Hansen of the Canadian Space Agency. None of them landed on the Moon; that was never the plan. Instead they flew a great loop around it and came home ten days after they had left. Hansen described the flight as "a test drive with the whole world watching".

The point of a test drive is to find out what does not work. Artemis II was designed to check the parts of Orion that cannot be tested properly on the ground: its air supply, its computers, and above all its heat shield, which has to survive temperatures of thousands of degrees when the spacecraft falls back into the Earth's atmosphere. Engineers had run thousands of computer models, but a model is not a journey.

At the furthest point of the loop, the crew were 252,756 miles from Earth — further than any human being had ever been. Koch said later that the strangest moment was not looking at the Moon, which she had seen in photographs all her life, but turning round and looking the other way. From out there, she said, the Earth was small enough to cover with a thumb, and it was impossible to see where one country ended and the next began.

The crew were not only sightseeing. They spent long hours photographing the lunar surface, testing how well they could fly Orion by hand, and sending video calls down to classrooms. Millions of students watched. For NASA that was part of the mission too: Artemis II was meant to be seen.

On 10 April the capsule dropped through the atmosphere and splashed down in the Pacific Ocean off the coast of San Diego. Ships reached it within minutes. The heat shield had held.

What happens next is harder. The plan is for a later Artemis flight to put astronauts back on the surface, this time near the Moon's south pole, where scientists believe there is frozen water. Water can be drunk, and it can also be separated into the gases that make rocket fuel. If that turns out to be true, a base on the Moon becomes something more than a flag and a photograph.

Nobody at NASA pretends the schedule is certain. Rockets are delayed, money runs short, parts fail. But for ten days in April 2026 four people went round the Moon and came back, and for the first time in half a century the question was no longer whether it could be done, but when it would happen again.

A bridge built for animals

Anyone driving along the highway in Colorado this summer may have noticed something unusual passing over the road: a wide green bridge, covered in grass, small trees and rocks. It was not built for cars. 16

Roads are a serious problem for wild animals. A deer that needs to reach water on the other side of a highway does not understand traffic, and neither do elk, bears or mountain lions. In the United States, hundreds of thousands of collisions between vehicles and large animals are reported every year. 17

The Colorado crossing, which opened in 2026, is the largest structure of its kind in North America. Engineers spread real soil across it and planted the same species that grow on the hillsides nearby, so that an animal walking towards it sees a continuation of its own landscape rather than a piece of engineering. Fences several kilometres long guide animals gently towards the entrance.

18 Elsewhere, cameras have shown that large animals often need two or three years before they will use a new crossing at all. Younger animals learn faster, and once a few individuals have crossed, the rest follow.

The idea itself is not new. The first wildlife bridges were built in France in the 1950s, and the Netherlands now has hundreds of them. 19 What has changed recently is the evidence. Studies of crossings in Canada and the western United States suggest that a well-placed structure, combined with fencing, can cut collisions on that stretch of road by more than eighty per cent.

That figure matters even to people who care nothing about wildlife. 20 Seen in that way, a crossing costing several million dollars pays for itself over a few decades.

Whether the Colorado bridge works as well as its designers hope will not be clear for years. For now the cameras are running, and the first hoofprints have already appeared in the soil.

A final that would not end

The 2026 World Cup final was not a beautiful game, but nobody who watched it will forget it. Neither side could 21 a goal in ninety minutes, and the match went into extra time.

Then, in the 105th minute, a substitute 22 a difference. Ferran Torres, who had come on less than twenty minutes earlier, reached a low cross and turned it past the goalkeeper. Spain had 23 the lead at last.

Argentina 24 everything they had at the Spanish defence in the time that remained, but the defence held. When the whistle went, Spain had 25 the World Cup for the second time in their history.

For the three host countries — the United States, Canada and Mexico — it had been the largest tournament ever held, with forty-eight teams instead of thirty-two. Whether so many matches really 26 the competition is still argued about.

Good news off the coast

The North Atlantic right whale is one of the rarest large animals in the world. Fewer 27 four hundred are thought to be alive today. So when researchers counted at 28 eighteen new calves during a single breeding season this year, the news travelled quickly.

Right whales are easy to tell apart, 29 makes them easier to count than most whales. Each animal has rough white patches on its head, and no two patterns are the same. Photographs taken from aircraft are compared 30 a catalogue that has been kept for decades.

Eighteen calves is not enough to save the species. Researchers estimate that the population needs considerably more than that each year 31 order to grow. Many young whales still die after becoming caught in fishing ropes or 32 struck by ships.

Still, it is the best season for several years, and it suggests that changes to shipping routes may be helping. Nobody is celebrating yet, but the numbers are moving in the right direction.

In September 2026 the European climate service Copernicus 1 that the previous month had been the warmest August ever recorded. Scientists who 2 out the study said that most of the extra heat came from human activity rather than from natural changes.

Records of this kind have been 3 so often in recent years that some readers no longer 4 attention to them. That worries researchers. A single hot month means very little on its own, they explain; what matters is the 5, and it has pointed upwards for decades.

The effects are not spread evenly. Southern Europe suffered weeks of extreme heat while other regions had an ordinary summer. That unevenness makes it easy for people to 6 that nothing unusual is happening where they live.

The eastern barred bandicoot, a small Australian animal about the size of a rabbit, was once 7 extinct in the wild. Foxes and cats had 8 rid of almost every population on the mainland.

In 2026 conservationists 9 up to a hundred of them onto Phillip Island in Victoria — the largest release of the species ever attempted. The island was chosen because years of work had already 10 it free of foxes.

Bandicoots make useful neighbours. A single animal can 11 dozens of small holes in the soil in one night while hunting for insects, and those holes help water and seeds reach the roots of plants.

Nobody can promise that the release will succeed. But the species has already returned from the edge once, and researchers now 12 it as one of Australia's few genuine conservation successes.

The 2026 Winter Olympics, held in February, were shared 13 two Italian places more than four hundred kilometres apart: Milan and Cortina d'Ampezzo. Spreading the Games out 14 organisers to use arenas that already existed instead of building new ones.

It also 15 problems. Athletes and spectators spent hours on trains, and some events 16 place in mountain villages that had never handled crowds of that size.

Organisers argued that the alternative was worse. Several recent host cities have been 17 with empty stadiums that cost millions a year to look after. Using old buildings, they said, was the only way to 18 the Games affordable for a country that had no wish to spend heavily.

The fish that came back

For most of the last century, the Russian River in northern California was a place where coho salmon used to live. Older residents remembered them; younger ones had only heard the stories. By the early 2000s the wild population had fallen so low that biologists could count the returning adults on their fingers.

Coho salmon are born in fresh water, swim out into the Pacific, spend two or three years at sea, and then find their way back to the exact stream where they hatched. It is an astonishing piece of navigation. It is also a weakness. A salmon cannot choose a different river. If the stream it was born in has been blocked by a dam, drained for irrigation, or warmed by the loss of the trees that once shaded it, that population simply ends.

All three of those things had happened along the Russian River. Vineyards replaced forest; water was taken out in exactly the months when young fish needed it most; and concrete crossings stopped the adults from reaching the upper streams.

The recovery programme, begun in the early 2000s, was not glamorous. Biologists raised young salmon in tanks and released them into carefully chosen streams. Landowners agreed to leave more water in the river through dry summers. Volunteers planted trees along the banks — not for beauty, but for shade, because a stream two degrees cooler holds noticeably more oxygen. Old crossings were rebuilt so that fish could pass through them.

For years, nothing happened. Then, slowly, fish began returning in numbers that made scientists check their equipment twice. In 2026 coho were recorded spawning in stretches of the Russian River system where they had been absent for decades.

It would be wrong to call this a victory. The numbers remain a tiny fraction of what they once were, and one severe drought could undo a decade of work. Conditions out in the Pacific, which nobody can control, matter as much as anything done on land.

What the story does show is how long this kind of work takes. Almost every person who designed the programme has now retired. The fish that returned in 2026 were the descendants of fish released by people who never saw this result and who, when they began, had no strong evidence that it would ever arrive.

That is an uncomfortable lesson in a world that prefers quick answers. It is also the reason the biologists on the Russian River keep going into schools. The children listening now are the ones who will find out whether it worked.

The law that stopped at the horizon

Draw a line in the sea about 370 kilometres from any coast, and something strange happens. Inside that line, a country makes the rules. Outside it lie the high seas — nearly two thirds of the ocean, and, for most of human history, almost nobody's responsibility. 16

That does not mean the high seas were empty of law. Ships had rules; fishing fleets had agreements; deep-sea mining had its own authority. 17 A fish protected under one agreement could be caught under another, and an area important to whales might be studied by scientists, fished by three countries and crossed by shipping lanes, with no single body able to say that it should be left alone.

The High Seas Treaty was written to close that gap. 18 It is the first agreement that allows nations to create protected areas in international waters and to require environmental checks before new activities begin there.

Reaching that point took almost twenty years of negotiation. 19 Poorer nations argued, reasonably enough, that they should not be shut out of places they had never had the ships to reach. Richer nations worried about their fishing industries. The compromise satisfied nobody completely, which is often what a workable treaty looks like.

Signing, however, is not the same as doing. 20 Enforcement is the real question: the high seas are vast, patrol vessels are few, and a satellite can show where a ship is but not always what it is doing.

Even so, something has changed. For the first time, the answer to "who is responsible for that part of the ocean?" is not simply "nobody".

A season nobody wanted

By the end of the summer, more than eight million acres had burned across the western United States — one of the worst fire seasons in years. At least seven firefighters 21 their lives.

Fire itself is not the enemy. Many western forests have 22 on regular, low fires for thousands of years; those fires clear dead wood without ever reaching the tops of the trees. The problem is what happens when small fires are prevented for decades. The fuel builds up, and the fire that eventually 23 out is far harder to control.

Hotter, drier summers 24 matters worse. Fire crews now speak of a season that begins earlier and refuses to end.

Some states have begun lighting careful fires themselves in cool, damp weather, on the argument that a forest which burns a little cannot burn a lot. It is slow work, and it 25 on public support, because smoke from a planned fire looks exactly like smoke from a disaster. Persuading people to 26 the difference may matter as much as any new equipment.

Fewer nests taken

On the Kei Islands in eastern Indonesia, leatherback turtles have been hunted for generations. The meat was eaten and the eggs 27 collected from the beaches, 28 threatened a species that is already in danger.

A project run together 29 the local communities has now cut the number of turtles and nests taken by about eighty-five per cent. It did not work by banning anything. Instead, villagers were employed 30 guards and monitors, so that protecting the turtles became a source of income 31 than a cost.

Leatherbacks are the largest turtles alive, and some of them swim right across the Pacific. A female may not come back to lay eggs 32 two or three years, which is why a beach that looks empty is not necessarily a beach without turtles.

Local leaders say the change came about because the project asked what the villages needed first, and talked about turtles second.

The 2026 World Cup was the largest in the tournament's history. Forty-eight teams took part instead of thirty-two, and the matches were spread across the United States, Canada and Mexico. 1

The distances were the first problem. A group containing teams based in Vancouver and in Monterrey meant journeys of more than four thousand kilometres between matches. 2 Coaches complained that recovery time, rather than skill, would decide some results.

Heat was the second. Several stadiums in the southern United States recorded temperatures above forty degrees at midday, and organisers were criticised for scheduling matches at the hottest hours in order to suit television audiences in Europe. 3 In two matches the referee stopped play so that the players could drink.

Not everything was harder, though. 4 Mexico City's stadium, which had already hosted two World Cup finals, needed very little work, and most of the American venues had been built for American football and already existed. Only a small number of new facilities were required, which is unusual for a tournament of this size.

The final, held in New Jersey, ended with Spain beating Argentina by a single goal in extra time. 5 For the three hosts, though, the more satisfying figure was the attendance: more people watched matches in person than at any World Cup before it.

Hail is not simply frozen rain. A hailstone begins as a tiny piece of ice carried upwards inside a storm cloud by rising air. 6 Each time it rises, another layer freezes onto it. Cut a large hailstone in half and the layers are visible, like the rings of a tree.

The size a hailstone can reach therefore depends on one thing above all: how strongly the air inside the storm is rising. 7 When the rising air finally weakens, the stone falls.

A study published in 2026 used a global climate model to ask what warming will do to this process. The answer was not what many people expected. 8 Warmer air near the ground holds more moisture and produces stronger updraughts, and stronger updraughts can hold heavier stones in the air for longer.

The effect is not the same everywhere. 9 In some tropical regions the freezing level is expected to rise so high that small hailstones melt before they reach the ground, and hail may actually become rarer there.

For anyone who has to pay for the damage, the distinction matters. 10 A single severe hailstorm over a city can destroy thousands of roofs and vehicles in twenty minutes, and insurance companies have begun reading these models as carefully as the scientists who built them.

The mountains and high plateaus of central Asia are sometimes called the Asian Water Tower. Snow and ice collect there, and the rivers that flow out of them — the Ganges, the Indus, the Yangtze, the Mekong and others — supply water to well over a billion people. 1

Most reporting about the region concentrates on glaciers, because a shrinking glacier is easy to photograph. 2 Research published in 2026 put that loss at roughly twenty-four billion tonnes a year, with the sharpest declines in crowded farming areas.

Groundwater is harder to worry about because it is invisible. A farmer whose well still produces water has no obvious reason to think anything is wrong. 3 By the time a well fails altogether, the water that fed it may have taken centuries to collect.

The causes are not mysterious. Far more land is irrigated than fifty years ago, pumps are cheaper and more powerful than they were, and in several countries the electricity used for pumping is paid for by the government. 4

Solutions exist, and none of them is popular. Charging for water, limiting the depth of new wells and changing to crops that need less of it all cost somebody something immediately, while the benefit arrives slowly and is shared by people who did not pay. 5

Clouds do not simply appear. Water vapour needs something to condense onto — a speck of dust, salt from sea spray, a particle of smoke. 6 Without them there would be very few clouds anywhere.

For years, climate models have struggled with the Arctic. The region is warming faster than anywhere else on Earth, yet the models have never agreed on how much of the sky there should be covered by cloud. 7 Cloud can either warm the surface by trapping heat beneath it or cool the surface by reflecting sunlight, so getting the amount wrong affects everything else a model predicts.

In 2026 researchers described a process in the Arctic atmosphere that had been missing from those models. 8 The result is a sharp increase in the number of particles available for cloud formation — in some conditions many times more than the models had assumed.

9 It also explains why measurements taken from aircraft have sometimes found far more particles than anybody expected.

None of this means the Arctic is safe, and none of it changes the direction of the warming. 10 A model that produces roughly the right amount of Arctic cloud for the wrong reason will sooner or later produce the wrong answer somewhere else.

The crew of Artemis II were not chosen at random. Reid Wiseman had commanded 1 International Space Station. Christina Koch held the record for the longest single spaceflight by 2 woman. Victor Glover had piloted a crewed capsule into orbit, and Jeremy Hansen was the first Canadian 3 had been given a mission beyond low Earth orbit.

What they shared was experience of long periods in small spaces. The Orion capsule, 4 carried them round the Moon and back, has less room inside than a family car once all its equipment is fitted.

They trained for years for problems 5 never happened. That is the nature of the work: most of what an astronaut learns is intended 6 be useless.

Every year, farms around the world produce enormous quantities of stalks, husks and straw. Most of it is burned or left to rot, 7 is a waste of material that took a whole season to grow.

Much of that waste is made of lignin, the tough substance 8 gives plants their stiffness. Lignin is hard to break down — that is exactly 9 it exists — and for decades chemists could separate it only by using high temperatures and strong acids.

In 2026 a research group described 10 new catalyst that breaks lignin into useful chemicals under far milder conditions. If the method can be scaled 11, material now treated as rubbish could become the raw ingredient 12 paint, glue and medicines.

More and more schools around the world now ask students to hand 13 their phones at the start of the day. Some lock them in pouches; others simply collect them in a box at the door.

Supporters say the effect is obvious within a week. Break times get noisier, they report, 14 is exactly the point: children talk to each other again.

Critics argue that a ban teaches nothing. A student 15 phone is taken away learns only that adults can take things away — not 16 to manage a device they will carry for the rest of their lives.

The research so far is mixed. Studies have found improvements in concentration, but the schools 17 introduced bans were often changing several other things at the same time, so the effect of the phone rule alone is very hard 18 measure.

The school that moved its clock

Ask a fifteen-year-old why they are tired and they will usually blame their phone. Sleep researchers think the answer is a good deal older than any phone.

At some point in early adolescence, the internal clock that tells a human being when to feel sleepy shifts later — typically by one to two hours. The change is biological. It happens to teenagers all over the world, in countries with very different attitudes to screens and homework. A thirteen-year-old who used to fall asleep at nine may now find it genuinely difficult to sleep before eleven, however early the alarm has been set for the morning.

School timetables were not designed with this in mind. In many countries lessons begin between seven and eight, which, for a teenager whose body believes it is still the middle of the night, is an odd hour to be asked to think clearly.

Over the last twenty years a number of schools and districts have tried the obvious experiment: start later. The results have been consistent enough to be interesting. Students in schools that pushed the first lesson back by an hour tended to sleep longer overall — not, as sceptics had predicted, simply go to bed an hour later. Attendance improved. In several studies, the number of road accidents involving young drivers in the surrounding area fell.

The objections are practical rather than scientific, and they are not trivial. School buses often serve primary and secondary schools one after the other, so moving one timetable moves several. Sports fixtures, after-school jobs and parents' own working hours are all built around the existing day. Teachers point out, reasonably, that a later finish eats into their evening as well as everybody else's.

There is also a limit to what the research shows. Most studies compare the same school before and after a change rather than assigning students at random, and almost all of them come from a small number of countries. A teenager in Taipei and a teenager in Minnesota do not face the same pressures, and it would be careless to assume that one timetable suits both.

What the evidence does suggest is that the tiredness adults so often read as laziness has a measurable cause. That reading matters. A student who is told to go to bed earlier and cannot is being asked to solve a problem they did not create.

None of this argues that phones are harmless or that homework should disappear. It argues something narrower and more useful: that before blaming a teenager for being half asleep in a lesson at half past seven, it is worth asking who chose half past seven, and why.

The animal that builds its own wetland

Beavers were hunted out of most of western Europe centuries ago, for their fur and for their meat. By 1900 only a few hundred were left on the whole continent. 16

A beaver does not simply live beside a river; it rebuilds it. Using branches and mud, it dams small streams to make ponds deep enough to hide the entrance to its home. 17 Water slows down, spreads out and soaks into the ground instead of rushing on towards the nearest town.

That last point has changed the argument. 18 A landscape full of beaver ponds holds water during heavy rain and lets it go slowly through dry weeks — which is precisely what many European rivers, straightened and deepened over two centuries, no longer do.

Not everyone is pleased. 19 A flooded field is a real loss to the farmer who owns it, and telling that farmer about flood protection thirty kilometres downstream is not much of an answer.

Several countries now pay compensation, or fund simple devices that hold a dam at a chosen height without destroying it. 20 Whether that patience lasts will decide how far the beaver's return actually goes.

The machine in the classroom

Within three years, software that can write essays has gone from a curiosity to something most secondary students have 21 use of. Schools have had to 22 up their minds quickly about what is allowed.

The easy answers have not 23 well. Banning the tools outright is hard to enforce, since a student can simply use a phone at home. Allowing everything 24 away the reason for setting written work at all.

Most schools have settled somewhere in the middle. Many now ask for work to be produced in class, under supervision, when the aim is to 25 out what an individual can do unaided, and allow the software openly when the aim is to plan or to check.

Teachers report one unexpected effect. Explaining why an answer produced by a machine is weak 26 students to read far more carefully than marking their own work ever did.

Two wheels, one battery

Electric bicycles have changed who cycles. A hill that once kept older riders at home, or made arriving at work in ordinary clothes impossible, is 27 longer a barrier. In several European cities, e-bikes now outsell ordinary bicycles.

The effect is largest in places 28 the distances are slightly too far to walk but not far enough to make a car convenient. Surveys suggest that many e-bike journeys replace car trips, 29 is exactly the result cities were hoping for.

There are new problems. Riders travel faster than they used to, and as 30 result a path shared with pedestrians feels less comfortable than it did. Cheap batteries, especially those bought online and charged indoors, have caused fires.

Most cities have responded 31 setting speed limits for shared paths and by introducing rules about 32 batteries may be sold.

The reef gardeners

Off the coast of Florida, in shallow water, there are rows of what look like plastic trees. Hanging from their branches are fragments of coral, each about the length of a finger. This is a coral nursery, and it is one answer — a partial one — to the loss of the world's reefs.

A coral reef is built by animals. Each polyp is a soft creature a few millimetres across which builds a stone case around itself; a reef is millions of them, together with the limestone left behind by their ancestors. Inside the tissue of most reef-building corals live tiny algae. The algae make food from sunlight and pass most of it to the coral; the coral gives them a safe place to live. Neither does well without the other.

When the water becomes too warm, that arrangement breaks down. The coral pushes the algae out and turns white — bleaching. A bleached coral is not dead, and if the water cools quickly enough the algae come back. If it does not, the coral slowly starves.

Marine heatwaves have become longer and more frequent. In recent years much of the Caribbean has recorded the highest sea temperatures ever measured there, and reefs that had survived earlier events did not survive those.

Coral gardening is one response. Fragments are broken from healthy colonies, grown in nurseries where they can be cleaned and protected, and then fixed onto damaged reef. Corals grow faster as fragments than they do as whole colonies, so a nursery can multiply a rare individual many times over.

The people doing this work are clear about its limits. A team can replant a few hectares in a year; the Caribbean has thousands of square kilometres of reef. Nor does planting deal with the cause. A restored reef sits in the same warming ocean as the one it replaced.

What gardening can do is buy time and keep options open. If particular colonies survive heat that kills their neighbours, those individuals are worth multiplying, and several projects now select for heat tolerance in exactly this way. A few are experimenting with moving heat-adapted corals to cooler reefs that will warm later.

Ask the divers whether they expect to save the reefs and the honest ones say no — not like this, and not alone. What they say instead is that a reef with a few thousand surviving colonies can rebuild itself when conditions allow, and a reef with none cannot. The nurseries are not a cure. They are an attempt to make sure that something is still there if a cure ever arrives.

Paper, screen, and what changes between them

Most students now read more on screens than on paper, and for a long time it was assumed that this made no difference at all. 16

The clearest finding concerns length. For short texts — a message, a headline, a set of instructions — studies find almost no gap between the two. 17 Readers of long texts on screen tend to score slightly lower on questions about structure and sequence: what came before what, and how the argument was built up.

Several explanations have been offered. 18 A book gives the hand a constant physical signal of how far through it you are; a scroll bar does this far less well.

Another explanation has nothing to do with the device at all. 19 People approach a screen expecting to skim, because most of what they read on screens is designed to be skimmed, and they carry that habit into texts that deserve slower attention.

The practical conclusion is not that screens should be avoided. 20 Reading a long article on a screen deliberately — slowly, with no other tabs open, perhaps taking notes by hand — appears to close most of the gap.

Farming upstairs

In a warehouse outside a European city, lettuces grow in stacked trays under pink light, without soil and without sunshine. Vertical farms like this one 21 a great deal of attention a few years ago, and a great deal of money.

The appeal is easy to understand. A vertical farm uses a small 22 of the water a field needs, produces no run-off, and can be built close to the shops it supplies, which 23 down transport costs. Nothing depends on the weather.

The difficulty is electricity. Plants that would otherwise 24 free sunlight have to be lit artificially, and lighting is expensive. Several well-funded companies have 25 out of business as energy prices rose.

Those that survive have mostly narrowed their range. Herbs and salad leaves, which are light, fragile and sold at high prices, 26 sense in a vertical farm. Wheat does not.

Looking further back

The James Webb Space Telescope was launched at the end of 2021 and began sending back images 27 following summer. It sees in infrared, so it can look straight through the clouds of dust 28 hide young stars from ordinary telescopes.

Because light takes time to travel, looking far away is the same 29 looking far back. Webb has photographed galaxies as they were when the universe was only a few hundred million years old.

Some of what it found was not expected. Several of those early galaxies appear brighter and more developed 30 the standard models had predicted, 31 has sent theorists back to their calculations.

That is not a failure. A telescope built only to confirm what we already believed would hardly be worth 32 cost.

The return of the night train

For most of the twentieth century, the sleeper train was the ordinary way to cross Europe. You boarded in one capital in the evening, ate badly, slept unevenly, and stepped out into another capital while it was still cool. Then cheap flights arrived, and by the early 2000s most of these services had been quietly withdrawn. Carriages were sold or scrapped.

In the last few years they have begun coming back. New routes have opened between cities that had not been joined by a night train for decades, and several operators have ordered new sleeping carriages — the first built in Europe for a generation.

Three things explain the change. The first is climate. A night train produces a small fraction of the emissions of the equivalent flight, and for passengers who have decided to fly less it is often the only realistic way to make a long journey.

The second is time, and this argument is more interesting than it sounds. A flight of two hours is rarely a journey of two hours: there is the trip out to the airport, the waiting, and the trip in from the airport at the other end. A night train takes the hours you would have spent asleep anyway and uses them for travelling. Passengers describe arriving rested and in the centre of the city, which no airport can offer.

The third reason is simply that people enjoy it. Operators report that a surprising number of passengers book a sleeper for a journey they could have made faster by day.

The difficulties are real. Sleeping carriages carry far fewer passengers than a seated train of the same length, so tickets have to cost more. The trains cross borders, which means different electrical systems, different safety rules and different national railway companies, each with its own priorities; a single route can require agreements with five separate organisations. And a night train occupies the track at exactly the hours when engineers want to close the line for maintenance.

None of these problems is new, and none has been fully solved. What has changed is that governments now see a reason to help. Several countries have cut the fees charged to night-train operators, or funded new carriages directly, on the grounds that the alternative — more short flights — costs the public more in the end.

Whether the revival lasts is an open question. It has happened before: night trains were declared finished in the 1990s, came back briefly, and disappeared again. This time the economics are different, but not obviously easier. What is certain is that a generation which had never seen a sleeper carriage is now booking them, and discovering that a journey can be part of the holiday rather than the price of it.

The problem that will not sink

Almost everything made of plastic since the 1950s still exists in some form. It may be buried, burned or broken into pieces too small to see, but the material itself does not rot. 16

For years the public image of the problem was a single photograph: a turtle, a straw, a beach covered in bottles. 17 Most of the plastic entering the ocean is not bottles and straws at all. Lost fishing gear, packaging that was never collected, and fibres washed out of clothing make up far more of it.

The pieces that worry scientists most are the ones nobody photographs. 18 They have been found in rain, in soil, in the bodies of animals at every level of the food chain and in human blood. What they do there is not yet well understood, which is not the same as saying they do nothing.

Countries have spent several years negotiating a global agreement on plastics. 19 Some governments want limits on how much new plastic is produced; others, particularly those whose economies depend on making it, want the agreement to concentrate on collection and recycling instead. The gap between those two positions is the whole negotiation.

Recycling on its own cannot close it. 20 Most plastic can be recycled only once or twice before the material becomes too weak to use, and much of what is collected is never recycled at all, because sorting it costs more than making new plastic does.

None of this means that individual effort is pointless. It means that the size of the problem and the size of the usual solutions do not match.

The cheapest air conditioning

On a hot afternoon, the difference between a street with trees and an identical street without them can 21 as much as ten degrees. Trees do not simply 22 shade. Water evaporating from their leaves 23 heat out of the air, in the same way that sweat cools skin.

Cities have begun to 24 this seriously. Several have set targets for the proportion of the city covered by tree canopy, and a few now 25 a tree as a piece of public equipment, like a drain or a street light, with a budget for looking after it.

Getting the trees to survive is the hard part. A young tree planted in a narrow hole in a pavement, surrounded by traffic and rarely watered, often 26 within five years. Planting is easy to photograph; keeping alive is not.

Cheaper than expected

Forty years ago, electricity from sunlight was so expensive that it was used mainly on satellites, 27 nothing else would do. Since then the cost of a solar panel has fallen further and faster 28 almost anyone predicted — by more than ninety per cent in two decades.

The reason is not 29 single breakthrough. It is the effect of building the same thing over and over again: each time the total number of panels ever made has doubled, the price has fallen by roughly a fifth.

Solar power now has a different problem. It produces most 30 its electricity in the middle of the day, when demand is often low, and none at all at night. Storing it is 31 the cost of batteries has become the question that matters.

Nobody in 1985 expected any of this. The lesson, 32 economists still argue about, is how badly experts can underestimate something that gets slightly cheaper every single year.

The bees nobody counts

Mention bees and most people picture a honeybee in a wooden hive. 6 Britain alone has more than two hundred and fifty species, most of them solitary: a single female digs a hole, lays her eggs, stocks each one with pollen, seals it, and dies before her young emerge.

These wild bees do a large share of the pollination that agriculture depends on. 7 Some crops are pollinated better by wild species than by honeybees, because different bees work at different temperatures, at different times of day, and on flowers of different shapes.

The trouble is that almost nobody counts them. 8 Wild bees have no keeper, no address and no value that appears in anybody's accounts, so a decline is noticed late, or not at all.

What evidence there is gives no comfort. 9 The causes are the familiar ones: fields without flowers, hedges removed, pesticides, and a climate that brings flowers out before the insects that feed on them have appeared.

Some remedies are surprisingly small. 10 A strip of wild flowers along the edge of a field, a patch of bare soil left undug, a hedge allowed to flower — each of these costs very little and supports species that no hive will ever house.

Made to be mended

Until recently, a broken appliance usually 11 up in one of two places: a repair shop or a skip. Over the last twenty years most of the repair shops have closed, partly because manufacturers stopped 12 spare parts available and partly because new products became cheap enough simply to replace.

New rules in several countries are trying to 13 that. Makers of certain goods must now supply parts for a set number of years, publish repair instructions, and design products that can be 14 apart without being destroyed.

The rules are not popular with everybody. Some companies argue that they will 15 up prices and slow down design. Repairers reply that a product which cannot be opened was never really sold to the customer — only lent to them.

Whether the rules 16 a difference depends on whether repair becomes cheaper than replacement. For many small appliances, it still is not.

Where your old phone goes

There are more mobile phones on Earth 17 people, and most households keep several that no longer work. Together they contain a surprising amount of valuable material: a tonne of old phones holds far more gold 18 a tonne of rock from a gold mine.

Recovering it is difficult. The metals are present in tiny quantities and are glued, soldered and coated 19 place. Doing the job safely needs equipment that only a few plants in the world possess.

Much of the world's electronic waste therefore ends 20 being taken apart by hand, often by people with no protection at all, in places 21 the burning of cables releases substances nobody should breathe.

Designing devices that can be opened easily would help, 22 would collecting them properly in the first place. Neither is technically hard.

The room inside the mountain

On a Norwegian island a thousand kilometres from the North Pole, a concrete entrance leads into the side of a mountain. A tunnel runs a hundred and thirty metres into the rock, and at the end of it are three rooms kept at eighteen degrees below zero. Inside are boxes, and inside the boxes are seeds: more than a million samples, from almost every country on Earth.

The Svalbard Global Seed Vault is not a seed bank in the usual sense. It lends nothing and studies nothing. It is a backup.

Around the world there are roughly seventeen hundred seed banks, most of them attached to universities or agricultural institutes. They hold the varieties that farmers have developed over ten thousand years: wheats that tolerate salt, beans that ripen early, rices grown in one valley and nowhere else. These collections are working libraries — researchers borrow from them constantly. They are also fragile. A seed bank can be lost to a power failure, a flood, a war, or simply to a government that stops paying for it.

That is why the vault exists. Any institution may deposit duplicates of its collection free of charge, and the depositor remains the owner: nobody else may open those boxes. Svalbard was chosen because it is cold, politically stable, and high enough above sea level to stay dry. The rock itself would keep the seeds frozen for weeks even if every machine failed.

The vault has been used for its intended purpose once. An international collection held in Aleppo, in Syria, became unreachable during the war there. Researchers who had moved to Lebanon and Morocco asked for their duplicates back from Svalbard, grew them, and returned fresh seed to replace what they had withdrawn. The system worked exactly as designed — which is not something that can often be said of insurance.

Not everyone is comfortable with the idea. Some argue that storing seeds in a freezer treats crops as museum objects, when a crop variety is really a relationship between a plant, a place and the people who grow it. A seed kept at minus eighteen degrees stops adapting. The farmers' fields where these varieties developed are still disappearing, and no vault prevents that.

The people who run Svalbard do not disagree. They describe the vault as the last copy, not the only one, and they say that the work which matters is happening in the seed banks and in the fields, not in the mountain.

Still, the mountain is there. It takes no electricity to stay cold, it asks nothing of anybody, and once a year, when new deposits arrive, someone opens the door and adds a few more boxes to a collection that exists entirely for a future nobody wants to need.

How a word gets in

People often say that a word is "not in the dictionary", as though a committee somewhere had considered it and refused. 16

Modern dictionaries are built from evidence. Lexicographers work from enormous collections of real language — billions of words of newspapers, novels, transcripts, websites and recorded speech — and search them for patterns. 17 The question is not whether a word is good, but whether it is used: widely, over time, and by people who are not stopping to explain it.

That last condition matters more than it sounds. 18 A word that always appears in quotation marks, or followed by "as they call it", has not yet settled. When writers begin using it plainly, assuming the reader knows, it has.

Speed varies enormously. 19 Others take decades, or never arrive at all: for every word that enters, many more appear briefly and vanish, which is why dictionaries are careful.

Removing a word is rarer than adding one. 20 Most dictionaries keep obsolete words and simply mark them as such, because a reader who meets one in an old book still needs to be able to look it up.

What happens while you sleep

A night's sleep does more than rest the body. While you are unconscious, the brain appears to 21 through what happened during the day, strengthening some connections and letting others fade.

This is why students who sleep after studying tend to 22 better in a test than students who study for the same length of time and then stay awake. The information has not simply been stored; it has been sorted.

The effect is strongest for material that was studied with full 23. Facts read once while half listening to music do not benefit much.

It also explains why the last hours before an examination are rarely the most useful. A candidate who 24 up all night may feel prepared, but the brain has been 25 of the very process that turns study into memory.

None of this is an argument for studying less. It is an argument for finishing earlier and 26 the rest to the night.

Older than writing

High in the mountains of the western United States grow bristlecone pines, some of 27 are more than four thousand years old. They were already ancient when the first alphabets were being invented.

They survive by growing slowly. In conditions 28 would kill a faster-growing tree — thin soil, little water, constant wind — a bristlecone adds almost nothing each year, and its wood becomes so dense that insects and fungi can make little impression 29 it.

Much of a very old tree is dead. A strip of living bark may run up one side of a trunk that is bare everywhere 30, and that strip alone is enough to keep the tree alive.

The oldest individuals are not marked, and their locations are kept secret. In 1964 a researcher cut down what turned out 31 be the oldest tree then known, in order to count its rings. Nobody wants that 32 happen again.