Innholdsfortegnelse for EG17 i New Scientist - The Essential Guides

THE story started 4.6 billion years ago. A huge shock wave from the explosion of a massive star caused a cloud of dust and gas laced with heavier elements to begin to collapse in on itself. Eventually, this formed the sun, Earth, the other planets, moons, asteroids and, eventually, us. For decades, researchers have been hunting for pristine material from these turbulent times to better understand exactly how these processes occurred. Those pristine materials are meteorites – space rocks that fall to Earth. Meteorites are time capsules from the solar system’s birth. They are mostly fragments of asteroids that orbit between Mars and Jupiter, plus the occasional piece of the moon or Mars that has come unstuck and crossed Earth’s orbital path. These fragments have existed more or less untouched…

THE young Earth would have looked profoundly different from today. There was no oxygen in the air, which meant that lots of metallic iron was dissolved in the water, staining the oceans green. Levels of atmospheric methane were perhaps high enough to colour the sky orange. And any land would have been barren rock, mostly dark black and grey. Understanding when Earth first got dry land helps to shape ideas about how life began. Some scenarios for its origin require exposed surfaces, so they can’t be true if everything was underwater. The question of Earth’s first land is therefore also a question about the origins of every living thing, including us. There are almost as many hypotheses about the origin of life as there are scientists thinking about it. There…

EARTH’S core is made of iron, but that isn’t the end of the story. There is still much to learn about what Earth’s core is like and how it came to be. What we do know is that the core starts 2900 kilometres down and its diameter is 7042 km. It is comprised of two layers, the molten iron outer core and the solid inner core, which is made of nickel and iron and is roughly the size of the moon. It hasn’t always been this way. Initially, the planet was just one big jumble with no obvious structure. Then the heaviest elements, mostly iron and a little nickel, settled towards the centre and formed a core. On top of this is the mostly solid mantle, the bulk of Earth’s…

EARTHQUAKES are caused by the sudden movement of one tectonic plate against another. Between 1500 and 2500 earthquakes of magnitude 5 and above are recorded every year around the world. Measured on the Richter magnitude scale, earthquakes of below 5 are considered light to minor. Five is a moderate earthquake that will be perceptible to everyone in the vicinity. Anything above magnitude 8 is considered to be a severe earthquake, causing severe damage and claiming lives. We might be able to predict big earthquakes in the near future better than we thought, according to research that used machine learning to analyse decades of past earthquakes in California. There have been many attempts to predict earthquakes using real-world signals, such as changing water levels, or data catalogues, such as the time…

ON 1 January 1995, a gargantuan wall of water slammed into the Draupner oil platform in the North Sea. The 25-metre giant rose from a surrounding sea churned by waves averaging 12 metres high. Dubbed the New Year’s wave, it was the first official recording of a rogue wave. Since then, our understanding of the complex forces that drive water to create rogue waves has become clearer, propelled by more reliable measurements, advances in wave modelling and ramped-up computational power. But to protect ships and lives at sea, we need to predict when these rogues will occur. Given the complex patterns of waves across the vast reaches of the seas, making accurate forecasts is no simple task. Still, the need for such predictions may be getting more urgent: as climate…

IN NOVEMBER 1929, a huge earthquake in the Grand Banks off the south coast of Newfoundland in Canada sent tremors as far as New York. As the sea floor shook, a vast quantity of sand and mud began to stir up and flow down a canyon, gathering momentum as it went, creating a dramatic underwater avalanche. It involved enough material to make two Mount Everests and triggered a tsunami that killed more than 25 people. This is the biggest known example of an undersea avalanche, but it wasn’t a one-off. Beneath the waves, the largest avalanches in the world regularly occur in Earth’s coasts and oceans, carving out the deepest and longest canyons on our planet. Most of the time, they happen without anyone noticing. For hundreds of years, the…

What took you to NASA? [After the second world war] my main line of work was freezing whole animals and bringing them back to life to test resuscitation techniques. I discovered that if you wanted to find an animal that survives for a long time in the frozen state, you need one with a certain composition of fatty acids in its blood, and hamsters fit this. But we needed to check this to prove it. Two floors from where I worked, Archer Martin had just invented the gas chromatograph, which could analyse the fatty acids in the animal’s fat. So I went to see him with my sample, but he said he’d need 100 times more – it would mean a mass slaughter of hamsters. I was crestfallen. Then he…

SOFAR, geothermal energy hasn’t taken off like other renewables. More than a century after humans started using Earth’s hot water and steam to produce power, geothermal provides less than 1 per cent of global electricity. There is no problem with supply: the depths of our planet still smoulder from its violent formation and the slow burn of radioactive decay. See chapter 1 for more on the formation of Earth The core is a searing 6000°C, and the heat contained in the upper 3 kilometres of the crust would be enough to meet the world’s energy demand thousands of times over. Geothermal energy also sidesteps the problems that plague so many other clean sources of energy. It is always available, regardless of whether the wind blows or the sun shines. Alongside…

CURRENTLY, we know of more than 5000 planets in the universe. A handful are in our solar system, but the majority are exoplanets: worlds that orbit distant stars. So far, at least, the only one which we know for certain to be habitable is Earth – but that doesn’t preclude other life-bearing planets from existing out there. The search for these other worlds is complicated by our ignorance of what other forms life might take, and so what conditions would make a planet habitable. But if life on Earth is anything to go by, it can’t exist without liquid water. Organisms ranging from bacteria to blue whales rely on water for their survival, making it likely that extraterrestrial life forms would have similar needs. Because liquid water can only exist…

OUR PLANET IS OUR HOME. IT’S THE SOLID GROUND BENEATH OUR FEET. WE BREATHE IN ITS AIR AND SWIM IN ITS OCEANS. IT’S SO FAMILIAR TO US, AND HAS BEEN STUDIED FOR SO LONG, THAT YOU MAY BE ASTOUNDED TO DISCOVER HOW MANY MYSTERIES REMAIN ABOUT WHERE IT CAME FROM, WHAT IT IS MADE OF AND HOW IT IS CHANGING. THAT’S BEFORE WE BEGIN TO ASK WHAT MAKES OUR PLANET SPECIAL, WHETHER WE WILL SUCCEED IN LOOKING AFTER IT AND WHETHER THERE IS ANYTHING OUT THERE TO RIVAL IT AS A REFUGE FOR LIFE. THIS ESSENTIAL GUIDE WILL CAST THE FAMILIAR INTO A WHOLE NEW LIGHT, INCLUDING: ❶ Why Earth is right for life ❷ The mysteries deep beneath our feet ❸ Rivers in the sky ❹ The story of…

EARTH is the only planet we know of that has plate tectonics. So what went right? Models have shown that for plate tectonics to get going, a planet has to be just the right size: too small and its lithosphere – the solid part of the crust and upper mantle – will be too thick. Too big and its powerful gravitational field squeezes any plates together, holding them tightly in place. The conditions also have to be just right. The rocks making up the planet can’t be too hot, too cold, too wet or too dry. Yet even if these conditions are met, there is one more crucial factor that needs to be introduced. Somehow, the lithosphere has to be cracked in such a way that one piece will dive…

SINCE the late 19th century, geologists have used vibrations called seismic waves, normally generated by earthquakes, to map the interior of our planet. These waves move slowly in less dense and rigid rock, but faster through more tightly packed matter, and have revealed the four layers found inside our planet. Turn back to page 24 for a-description of these layers In the 1980s, seismic waves hit on something odd: two giant clumps inside the planet’s mantle, making up about 8 per cent of the mantle’s volume. These lumps sit on top of the liquid core, one below the Pacific Ocean, one beneath Africa. As wide as ocean basins, they also seem to rise almost 1000 kilometres vertically, into the mantle. They are uneven and misshapen, like the waxy blobs of…

THE solid inner core of our planet may be slowing its rotation and getting ready to switch spin directions relative to the rest of the planet. This seems to be part of a cycle lasting about 60 years in which the core periodically speeds up and slows back down again. Beneath Earth’s mantle is a churning layer of molten iron and nickel, with a dense inner core of iron kept solid by the intense pressure at the centre of the planet. The movement of the inner core relative to the mantle and surface has been under debate for decades, and measurements of earthquakes are now helping researchers to understand it better. Yi Yang and Xiaodong Song at Peking University in China and their colleagues have analysed the seismic waves from…

THE Mariana trench lies in the west of the Pacific Ocean, south of Japan. Its depth varies along its 2500-kilometre length, but its deepest point confirmed so far, known as Challenger Deep, reaches a depth of 10,984 metres (36,037 feet). To put that in context, you could submerge Mount Everest and the summit would still be 2 kilometres underwater. Its depth is roughly the same distance that a commercial airliner cruises at above the ground. Investigations into the trench by the Vernadsky Institute of Geochemistry in the 1950s recorded a maximum depth of 11,034 metres, but this has never been verified. In fact, nobody knows for sure how far down the deepest part of the trench is, as no comprehensive survey has ever been conducted. The Mariana trench is the…

THE Atlantic Ocean conveyor belt, also known as the Atlantic meridional overturning circulation, or AMOC, is part of a global network of currents that push all the water in the oceans up and down the length, breadth and depth of the various interconnected basins. From the tropical Atlantic off the coast of South America, warm surface water flows north towards Greenland and western Europe, bringing with it an uncharacteristically warm climate, carried by the Gulf Stream. The water becomes saltier as it evaporates and cools as it moves north. Both factors make it denser, so that by the time it reaches the Norwegian and Greenland seas, it has sunk by 2 or 3 kilometres. From there, it makes its way back south at depth (see map, right). Changes in salinity…

Some 8000 years ago, a massive chunk of Norway’s continental shelf collapsed. Known as the Storegga Slide, around 3200 cubic kilometres of sediment plummeted to the ocean floor. The resulting tsunami travelled as far as Greenland and Canada, with waves more than 20 metres high crashing over the Shetland Islands in the UK. Some propose the event may have drowned Doggerland, an area once above the waves but now submerged by the North Sea, cutting the UK off from Europe. As opposed to the flow of a turbidity current, submarine landslides shift a coherent lump of sediment in one single, dramatic movement. But, like turbidity currents, submarine landslides hadn’t been measured until recently. Wenyuan Fan, a seismologist at the Scripps Institution of Oceanography in California, wasn’t looking for landslides when…

IT IS easy to picture a planet without oxygen. It looks like Mars. Our nearest planetary neighbour was probably once a water world too, primed for life to evolve. But it lacked a vital ingredient: a protective shield of ozone derived from oxygen. Without an ozone layer, the sun’s rays slowly atomised the Martian water. The hydrogen floated off into space while the oxygen oxidised the iron-rich Martian topsoil, turning it rust-red. Perhaps there is – or was – life on Mars. But if so, it never progressed beyond the bacterial stage. So how did Earth get lucky? Ten years ago, when I was writing my book Oxygen, it didn’t seem too big a deal. Photosynthesising bacteria were the magic ingredient. These tiny organisms popped up in Earth’s oceans early…

What does the circular economy mean to you? I think the nicest definition was given decades ago by one of the founders of this idea, Walter Stahel, who said a linear economy is like a river and a circular economy is like a lake. More specifically, it’s about keeping resources in production and keeping consumption cycles going for as long as possible, and keeping their value high. I see the circular economy as an instrument, a way of decoupling economic growth from resource use and environmental impacts. How important is it in your work? At the IRP, our focus is on managing natural resources in the most sustainable way. Sometimes, people talk about “resource efficiency”, but that’s really just about how to improve the current economic model. The circular economy…

THE diversity of life on Earth is astonishing, but extremely difficult to define. As soon as scientists come up with a definition of what makes a living creature, it seems that something comes along to challenge it. You don’t need a brain to be alive, or a heart, or a spine. You can survive without oxygen, without sunlight, even without two cells to rub together. You can live without feeling the effects of ageing, or in total isolation, or through centuries of hibernation. But in the absence of a robust definition, there are a few things that most biologists agree all life forms must have. They should all be capable of passing on their genetic material to a new generation of organisms through reproduction, as well as being able to…

The basic energy source driving large-scale geological changes is heat: the immense reservoir of thermal energy in Earth’s interior, augmented by the decay of radioactive elements, induces convection currents in the mantle, the 3000-kilometre-thick layer of silicate rock between the core and the crust. Around 330 million years ago, all the landmasses on Earth came together to form a single supercontinent called Pangaea. It was the most recent supercontinent on Earth and began to split apart roughly 180 million years ago. But the details of the process remained elusive until 1993, when John Baumgardner at Los Alamos National Laboratory in New Mexico developed the first three-dimensional computer model that begins from a small set of basic principles and accounts for the main features of this geophysical drama. As well as…

There are many types of waves flowing across the oceans, from small ripples to huge walls of water, 30 metres high peak to trough. They are mainly caused by winds and, if unimpeded, can travel for thousands of kilometres. Waves occur when the wind blows over the surface of the water, transferring its energy and causing the water to move in a circular motion. The rise and fall of water molecules creates a wave that moves in the direction of the wind. The wave transports energy, not water. An analogy is a crowd of people doing a Mexican wave in a stadium: the people stay in the same location, but the wave they create travels around the arena. As waves reach the shore, the shallow floor begins to impede the…

The Gulf Stream is famous for the warm glow it brings to the UK and the rest of western Europe. But if the Atlantic meridional overturning circulation (or AMOC) were to collapse, the Gulf Stream would vanish, cooling Europe and possibly beyond. Some have painted this as a good thing. After all, as temperatures soar because of climate change, surely a bit of fresh air can’t hurt? Not so fast. For starters, a weaker AMOC would shift water around the Atlantic, leading to extremely rapid sea level rise along the US east coast – adding 15 to 21 centimetres at New York City by 2100, according to one estimate. This would bring more severe flooding whenever storms hit. It also isn’t certain that there would be cooling. A recent study…

If, as seems increasingly likely, photosynthesising cyanobacteria first made an appearance in Earth’s oceans around 2.7 billion years ago, why did they take so long to make a difference to Earth’s air? One possibility is that the oxygen’s first chemical mission was to oxidise all the iron and compounds like hydrogen sulphide in the oceans. Only after it had done that was it free to escape into the atmosphere. Perhaps the most persuasive answer, though, is purely geological. It comes from geologist Heinrich Holland at Harvard University. He points the finger at gases such as methane and hydrogen sulphide that are constantly spouted by volcanoes. They would have reacted with the first free oxygen to form carbon dioxide and sulphur dioxides, effectively removing the oxygen from circulation. Holland proposes that…

As the nitrogen cycle is disrupted, it has knock-on effects across the planet. OCEAN DEAD ZONES Rain can wash nitrates into watercourses and oceans. This nitrogen-based pollution feeds algal blooms that suck up oxygen as they decompose, choking aquatic life. The result is a watery “dead zone”, of which there are more than 400 in the world’s oceans, including a huge one in the Gulf of Mexico. AIR POLLUTION Cars and power plants emit nitrogen oxides, which are one of the principal precursors to a type of air pollution called particulate matter. These tiny particles can be breathed into our lungs, where they cause tissue damage associated with a range of health problems. SOIL ACIDIFICATION The same nitrate that can sneak into waterways can also pull key nutrients out of…

JAMES LOVELOCK’S Gaia hypothesis is that life on Earth acts to preserve its own existence by stabilising conditions on the planet. Popularised in the 1970s, it inspired a generation of scientists who study Earth’s many systems, from the climate to forests, and how they interact as a whole. But for the first time in geological history, the planet has conscious beings at the controls and humans are now pushing Earth’s systems out of whack. For instance, we have released more greenhouse gases than other living organisms can mop up, and these are heating up the planet. Turn overleaf for an interviewwith James Lovelock The evidence that our impact on Earth is harmful is overwhelming. At a conference celebrating Lovelock’s 100th birthday in 2019, Ricarda Winkelmann at the Potsdam Institute for…

THE Arctic is setting new records for the speed and area over which its ice is melting. What’s more, the Greenland ice sheet, which alone contains enough water to raise global sea levels by six metres, is disappearing. The frozen Arctic soil and sediment (or permafrost) is melting, releasing more and more carbon dioxide and methane into the atmosphere. In 2019, vast wildfires in the peatlands of Siberia blazed for more than a month, and the Arctic warming is playing havoc with weather systems in the northern hemisphere too. If you prefer to think simply in terms of money, in 2019, a report in the journal Nature estimated that the economic impact of Arctic warming by the end of this century could be as high as $67 trillion. As the…

WE ALL know the ending: everybody dies. Since our sun’s birth 4.6 billion years ago, its core has been getting ever denser and hotter. It is now 30 per cent more luminous than it was at birth and it is only going to get brighter. Ultimately, life’s fate is sealed – it will be fried by the sun’s intense energy. Earth will once more become a dead rock before being swallowed as the sun expands into a red giant star. But let’s not jump ahead quite that far. Take a few minutes to think about Earth’s final chapter. What will be the last organisms to survive as the planet fries and where will they hide? What will our blue marble look like in its swansong millennia? Humanity will have vanished…