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Seven years on Mars

Extinct human face revealed!

The continuing adventures of the Curiosity rover

AU ST RALIAN

Meet the Denisovans

DINOSAUR

MOMENT

BY MOMENT from asteroid to tidal wave

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MIND-READING BRAIN CHIPS Elon Musk plugs into thought power

EVERYONE WORKS FOR THE RAT QUEEN Why do mole-rats choose to live like ants?

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Break the Code PROBLEM 2: Atlas. Order from left to right: Prometheus, Helios, Perses, Atlas.

PROBLEM 1: Mercury. Each dot corresponds to a letter's location in 9 fields:

LOGIC

CODE-BREAKING

NUMERACY

CODE WORD Mercury-Atlas 6

PROBLEM 3: 6. There is more than one answer, but 6 will always be located in the yellow circle.

PROBLEM 7: 50/50.

At least two of the coins will always fall with the same side facing upwards. As the chances of heads or tails are the same, the chance is 50%.

PUBLISHED 20TH FEBRUARY 2020

LOGIC PROBLEM 6: $5.

Pumpkin = $2. Bananas = $3.

Make two equations: 5G + 2B = 16 and 2G + 3B = 13. Multiply them by 3 and 2: 15G + 6B = 48 and 4G + 6B = 26. Deduct them: 11G = 22, i.e. G = 2. So B = 3.

ISSUE 73 # AUSTRALIAN SCIENCE ILLUSTRATED

Mercury-Atlas 6 is the name of the NASA space mission that placed astronaut John Glenn in orbit around Earth as the first American aboard the Friendship 7 spacecraft.

NUMERACY PROBLEM 4: 14. The total of all horizontal and vertical rows is 36.

PROBLEM 5: 2 is the number of all six fields.

The total of the pie pieces is 9, and the total of the circles is 24.

Test yourself Answers to p82. No peeking!

The asteroid hit – but then what?

New discoveries have revealed exactly what followed in the next seconds, minutes and hours of the day which marked the beginning of the end for the great lizards.

DINOSAUR DOOMSDAY

Contents

24

CO STO VER RY

40 THE HUMAN BODY Scientists are discovering hundreds of previously unknown human cell types, suggesting new ways to fight disease.

REGULARS AND OTHER FEATURES 6 MEGAPIXELS Ants, sprites and eco-farming in our look at science in pictures

12 SCIENCE UPDATE

How gut bugs can get you drunk, and other new discoveries.

50 HOW BIG IS THE UNIVERSE? After a century of debate, we’re still not sure of the size of the universe. But the search for answers has created a new ‘Big Bang’ in our own conceptions of space and time.

62

18 ASK US How do plants grow towards light?

Why do shower curtains stick to us?

36 INVERTED SOLAR CELLS 48 FOR QUEEN & COLONY Mole-rats, ants and termites give up the good life for their love of a queen.

58 MIND READING Elon Musk’s company Neuralink has a brain chip which can read thoughts.

70 CELL DEATH Many of our cells are programmed to commit suicide, for good reasons.

In our ongoing climate series, we look at ways to reduce greenhouse gases not by reducing emissions, but by removing some of the carbon dioxide already in the atmosphere.

ROLL OUT THE BARRELS From herring to human bodies, everything travelled in wooden barrels for hundreds of years until technology superseded the ancient art of coopering.

DESIGN Art Director Malcolm Campbell ADVERTISING ENQUIRIES Advertising Manager ph: 02 9901 6100 Production Manager Peter Ryman Circulation Director Carole Jones INTERNATIONAL EDITION Editor-in-Chief Sebastian Relster International Editor Lotte Juul Nielsen BONNIER INTERNATIONAL MAGAZINES International Licensing Director Julie Smartz Art Director Hanne Bo Picture Editors Allan Baggesø, Lisbeth Brünnich, Peter Eberhardt

Good news! Solar cells can also work at night, thanks to the cold of space.

CLIMATE & CO2

72

EDITORIAL Editor Jez Ford editor@scienceillustrated.com.au

76 PHOTODOC: MARS The continuing adventures of the Curiosity rover, now alone on Mars.

82 TEST YOURSELF! Mind bombs of assorted flavours to test your talents.

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NEXTMEDIA Managing Director Hamish Bayliss Science Illustrated is published 8 times a year by nextmedia Pty Ltd ACN: 128 805 970 Level 8, 205 Pacific Highway, St Leonards NSW 2065 Under license from Bonnier International Magazines. © 2019 Bonnier Corporation and nextmedia Pty Ltd. All Rights Reserved.

Reproduction in whole or part without written permission is prohibited.

Science Illustrated is a trademark of Bonnier Corporation and is used under limited license. The Australian edition contains material originally published in the US and UK editions reprinted with permission of Bonnier Corporation. Articles express the opinions of the authors and are not necessarily those of the Publisher, Editor or nextmedia Pty Ltd. ISSN 1836-5175.

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MEGAPIXEL

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SCIENCE ILLUSTRATED

ARMY ANT

Army bivouac: Nomadic ants build living castle

WILDLIFE PHOTOGRAPHER OF THE YEAR

Army ants switch between living in a colony and being nomads in search of a new home.

When in their travel mode, they need to protect their resting queen en route, so the colony’s soldiers stand on top of each other, interlocking their legs to form a structure that acts as a temporary nest.

When daylight comes, the army moves on to new battlefields, consuming up to 500,000 creatures per day on the way. The brave photographer here was nominated in the Wildlife Photographer of the Year competition for this image, taken in Costa Rica.

Photo // Daniel Kronauer

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MEGAPIXEL

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SCIENCE ILLUSTRATED

RED SPRITES

Plasma on parade: Vast red sprites haunt the sky They tower high in the sky, like huge jellyfish with extended tentacles. These red sprites appear above active thunderclouds and can grow up to 100km high. But they light up the sky for only a few milliseconds, so it has proven an almost impossible task to capture good photos of this mysterious phenomenon. The red sprites consist of ionised plasma, and they are triggered by powerful electric charges in the thunderclouds, from where the flashing light cascades downwards for those few milliseconds in an electrical avalanche.

Photo // Stephane Vetter

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MEGAPIXEL

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PLANTS ON MARS

SCIENCE ILLUSTRATED

EPA/RITZAU SCANPIX

Red spread: Scientists are learning to farm on Mars With water such a scarce resource on Mars, the surface offers nowhere near the nutrientrich environment that plants enjoy on Earth. Several research projects are developing crop-growing methods that could feed future Martians. Scientists from the Czech University of Agriculture have produced this system in which plants are sprayed with nitrogen-based nutrients, with all water reused.

The project could also benefit farmers who are facing increasing shortages of water here on Earth.

Photo // Martin Divisek

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THE LATEST FINDINGS AND DISCOVERIES

The face of Denisovan humans One single little finger bone has provided American scientists with the genetic information required to produce the first portrait of this extinct human species.

A jawbone, some teeth, and a little finger bone: those were the only fragments available to scientists from Stanford University in the US who were working to establish the likely physical appearance of Denisovans – the human species that co-existed with Neanderthals and Homo sapiens up until at least 40,000 years ago. Thanks to the successful extraction of DNA, they now have a theory which can compare the Denisovan skeleton and skull with the bone structure of Neanderthals and modern man.

Scientists examined DNA from the small finger bone, which came from a Denisovan girl who lived 40,000 years ago.

Molecules known as methyl groups on DNA strands can identify whether a gene is active or not, allowing the scientists to identify which genes were active in Denisovans and to compare EVOLUTION

these with active genes in our own species and those from known samples of Neanderthal DNA. The study uncovered 56 differences by which the Denisovans diverged from Neanderthals and modern man, 32 of which would result in anatomical differences relating to the development and strength of bones in different parts of the body. The Denisovans had wider pelvises and chests than modern man, but narrower, flatter faces than Neanderthals. The upper skull was broader in Denisovans than in either Neanderthals or humans, though generally a Denisovan skull was closer to that of a Neanderthal – flatter than ours with a low forehead and powerful brow ridges.

To test the method’s accuracy, the scientists made the same comparisons with chimp DNA, with the differences they found correctly predicting 85% of anatomical features.

Denisovans were more like Neanderthals New DNA studies have revealed that the Denisovans' skull structure was more like that of the Neanderthals than of modern man.

FLAT PATE The top of the skull was flatter than ours, but much like that of Neanderthals.

D E N I S O VA N

Homo sapiens

LOW FOREHEAD The forehead was lower than ours, but resembled that of the Neanderthals.

Neanderthal

LARGE SKULL BASE The base on which the brain rests was larger than ours, as in Neanderthals.

PROTRUDING JAW Like in Neanderthals, the jaw was longer than ours.

BROAD SKULL The upper part of the skull was broader than in Homo sapiens and Neanderthals.

D E N I S O VA N

Homo sapiens

DISTINCTIVE BROW RIDGE The ridge behind the eyebrows was powerful and distinctive, as in Neanderthals.

BROAD FACE The face was broader than ours, but slightly narrower than the Neanderthals'.

POWERFUL CHIN As in Neanderthals, the chin was both broader and higher than ours.

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SCIENCE ILLUSTRATED

Neanderthal

Editor: Jens E. Matthiesen

MARKUS SCHOLZ/MLU

A new method allows the creation of targeted vaccines against plant viruses. The vaccines are absorbed via spraying onto plant leaves, and can be quickly altered if the virus mutates.

DNA studies of this 40,000-year-old little finger bone revealed how the skull and skeleton of the extinct Denisovans would appear.

Plants to be vaccinated against viruses way; indeed only a handful among Just like animals and thousands of pieces achieve the desired humans, plants are often attacked by result. In the lab, scientists mimicked a viruses, and the results can severely virus attack on plant cells and identified damage agricultural crops. Scientists the RNA fragments that functioned the from the MLU university in Germany best. Subsequently, they used those to have invented a plant vaccination vaccinate tobacco plants, method that can improve A VACCINE is a method spraying them onto plant plants’ natural defences for improving the immune leaves. Later, when the against viruses. system, so it becomes better plants were subjected to an The plants’ normal at identifying and defeating attack by the same virus, defence uses enzymes that an attacking microbe.

90% of them could combat function like small scissors, the enemy effectively. cutting the RNA molecules The new result is particularly of the virus into pieces. The tiny promising because while current gene fragments of RNA are subsequently modification methods can make plants linked with special proteins that use immune to specific viruses, those them to identify the attacking virus, so methods lose effect when the viruses the plant can improve its counterattack. mutate. The new technique allows quick Unfortunately, the plant’s strategy is production and adjustment of targeted not always efficient, as not all RNA vaccines against different viruses. fragments are equally effective in this BIOLOGY

MAAYAN HAREL/EPA/RITZAU SCANPIX/E. ANDREW BENNETT ET AL./AAAS/DAVID GOKHMAN ET AL./CELL/SHUTTERSTOCK

This portrait of a Denisovan girl was made using DNA gene information from a little finger bone found in Siberia.

1.6 MILLION kilometres – that is the distance that could be driven using a new battery developed by Tesla, the electric car company. This achieves Tesla’s goal of a million mile battery, which the company says could be used in driverless taxis. scienceillustrated.com.au

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S C I E N C E U P DAT E

STSCI/NASA

Three supermassive black holes on a collision course For the first time ever, astronomers have discovered a system of three supermassive black holes orbiting each other.

The discovery was made after observations from several telescopes that operate in different parts of the light spectrum.

Scientists from George Mason University in the US were searching for pairs of black holes that orbit each other. But then they spotted this rare trio located around a billion light years away. The discovery was made by the SDSS optical telescope, and was subsequently confirmed by the infrared WISE telescope and the Chandra X-ray telescope.

Observations of the three black holes might solve a theoretical paradox involving black holes that merge. Two black holes will ASTRONOMY

rotate ever closer to each other without meeting, because each one loses energy to stars and other passing matter. As a star passes by, it is supplied with energy and ejected at a higher speed, with the black holes losing the same quantity of kinetic energy. The loss makes the two black holes approach each other slightly, but the effect subsides when the distance between the two black holes reaches a few light years, and so they should never merge. Yet gravity wave data has shown that this does, in fact, happen.

According to scientists, this might be explained by the presence of a third, heavy object. Calculations have shown that three black holes in orbit approach each other much faster than if there are only two.

The three black holes in visible light

X-radiation from the black holes

One billion light years away, three black holes are orbiting each other.

All three of them emit X-radiation, indicating that they suck up matter.

SHUTTERSTOCK

BY THE WAY One big whale is worth US$2m Economists from the International Monetary Fund have put a value on the world’s largest marine mammal.

Their complex calculations show that in its lifetime, a large whale generates a value of US$2 million.

The calculations are based on the whale’s value as a subject of ecotourism plus its worth in terms of carbon dioxide storage in the animal’s huge body.

A N D TA L K I N G O F W H A L E S . . .

ERIC BACCEGA/NATUREPL

STOCKTREK/IMAGESELECT

SHUTTERSTOCK

Ancestors lost genes in water

Dog-paddling to the Atlantic

Narwhal is genetically fragile

When the ancestors of whales evolved into marine animals, they lost at least 85 genes, according to DNA studies of killer whales and others made by German scientists. The genes regulating saliva production and lung function were either irrelevant or obstructive in their new environment.

Fossils show that the first whales originated in what is now India, and they swam in the same way that four-legged terrestrial animals do today. A new discovery of a 42-million-year-old skeleton in Senegal shows that dog-paddling brought early whales south of Africa to the Atlantic.

DNA analyses by Danish scientists show that there is very little genetic variation in the population of narwhal: three times more limited even than in pandas. Genetic variation is key to whether a species can survive crises, so scientists worry that narwhals will struggle in a warmer climate.

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SCIENCE ILLUSTRATED

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S C I E N C E U P DAT E

84% of California’s wildfires originate close to roads and other busy areas.

The Klebsiella pneumoniae bacterium can produce enough alcohol to make a human drunk and subject to liver damage.

EYE OF SCIENCE/SPL

Auto-brewery gut bacteria get you drunk

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SCIENCE ILLUSTRATED

A new liquid which can be sprayed in advance onto high-risk vegetation might prevent Californian wildfires from taking hold.

In this terrible fire season, Australians don’t need any more statistics to know the crucial importance of fire prevention. But scientists from Stanford University have a new idea after working with fire authorities to obtain and analyse data from 305,000 fires in California over the past 10 years. They found that 84% of these fires originated along roads and in other populated places, typically in dry grass and other low vegetation. If such high risk zones could be made significantly more fire-resistant, it is possible that a great many fires could be stopped before they really get started. The scientists have come up with a fire-resistant liquid that might be suitable for the task. The CHEMISTRY

familiar red fire-resistant liquids that we see dropped from planes typically contain phosphate fertiliser which helps cool down and slow the fire; the colouring marks the area that has been treated. The new liquid is thicker and more durable, almost like a sticky gel. When sprayed onto grass, etc., it spreads and settles as a film. In the event of fire, the heat makes the ingredients of the gel react together, resulting in a layer of insulating carbon that keeps both heat and oxygen away from the grass, so the fire can quickly die out. The gel protects against fire throughout the dry season, and it would be rinsed away only when the drought is broken by heavy rain.

Fire-resistant liquid sticks to grass Wildfires in the USA often originate in low vegetation such as grass. A new liquid can stick to the grass for months, making it impossible for fires to start there.

U N S P R AY E D G R A S S

LIQUID SETTLES AS FILM The fire-resistant liquid settles to produce 1 a film on the surface of the grass.

one minute after catching fire

Fire-resistant liquid

1m

Blade of grass

FILM FUNCTIONS AS INSULATION In a fire, the liquid changes into a barrier of 2 carbon that both insulates against heat and prevents fire from intensifying. The fire soon stops.

S P R AY E D G R A S S one minute after catching fire

Heat

Oxygen

Insulating carbon layer

1m

SHUTTERSTOCK/ANTHONY C. YU ET AL./PNAS

A special type of a well-known intestinal bacterium could be responsible for some cases of severe liver disease, according to new studies.

Scientists from the Capital Institute of Pediatrics in China discovered the harmful bacterium in a patient who was clearly becoming very drunk without him consuming any alcohol.

He suffered from the very rare condition of ABS (auto-brewery syndrome), which causes the intestines to produce alcohol.

Scientists had initially suspected that the condition was due to a yeast cell infection, but when they studied the patient’s intestinal flora they found no evidence of yeast.

Instead they found a special variant of the Klebsiella pneumoniae bacterium that could produce four to six times more alcohol than the variant which normally exists in the intestinal flora. Apart from becoming unpleasantly drunk, the patient also suffered from severe infection and a fatty liver.

Subsequently, the scientists identified other patients with the same symptoms and studied their bacterial strains. It turned out that 60% had variants of the more common bacterium, all of which produced more alcohol.

Experiments with mice produced identical secondary complications to those in the human patients.

Fatty liver is the world’s most common liver disease. In those cases where it is caused by the intestinal flora, it may now be treatable with targeted antibiotics.

MEDICINE

FIRESTOPPER: gel could fireproof high-risk areas

SAVE THE DATE FOR SYDNEY’S ALL-NEW HI-FI SHOW XXX IJà DPN

SCIENTISTS ANSWER QUESTIONS FROM OUR READERS

What are ‘brittle bones’?

“I often hear of people who have ‘brittle bones’, and I know this means osteoporosis.

But what causes the phenomenon, and why does it lead to bone fractures?”

Osteoporosis originates when the tissue of the body’s bones is broken down more quickly than the body can produce new bone tissue. The condition is also known as decalcification, because the bones of the body lack calcium. The condition means that the bones become less efficient at resisting stress such as a fall or a blow. The degree of brittleness is estimated based on bone density, which is measured in an DXA (Dual energy X-ray Absorption) scanner.

PHYSIOLOGY

Bone density typically reduces with age. From the age of 40 onwards, 0.5-1% of our bone mass disappears annually, and the process is faster in women past menopause. Everybody develops osteoporosis with age, but the speed of the breakdown of the bones is partly genetic.

Doctors have also identified other risk factors that accelerate the process such as smoking, alcohol, vitamin D deficiency, and lack of calcium in food. Osteoporosis in itself does not have to be a problem, but

because the bones are weak, the risk of fractures increases. Osteoporosis is often identified in connection with unexpected bone fractures such as in the forearm, or the spine collapsing gradually with the breakdown of vertebrae.

In Europe, doctors record a rising number of cases of osteoporosis.

Since 1990, the number of spinal fractures have quadrupled in both men and women, and hip fractures have tripled in men.

Porous bones make the body collapse The bones become ever more porous as the level of bone mineral is reduced. In extreme cases even slight stresses can cause fractures.

NORMAL BONE MASS Normal bone mass is defined based on the bone density in fairly young, healthy people.

LOW BONE MASS The bone density starts to decrease in the initial stage of osteoporosis.

The risk of fractures rises slightly.

OSTEOPOROSIS The bone density is critically low, and bone strength is markedly reduced.

The risk of fractures is more than doubled.

Why do lions have large muscles? most efficient way to meet their daily energy Even though lions relax for an requirement is to find and eat the largest impressive 18-20 hours a day, they still have prey available. Hunting large animals large strong muscles. This seems surprising, requires a highly energetic ‘workout’ – given that humans quickly weaken if we lie from identifying and chasing prey to the down 75% of the time. The explanation is sprint, struggle and kill. primarily that lions are naturally 20 km – is how far a lion Another of a male lion’s equipped with much stronger can patrol during a day in most important tasks is to fight muscles than humans, and order to mark his territory by other males and chase them off these are maintained by the roaring and making himself their territory. The fights also active portions of their lifestyle. seen by other predators. contribute to keeping the Lions are extremely active animals in good condition. for the short period of time In contrast our human bodies have during which they do not sleep and relax. become adjusted to a very different lifestyle Male lions regularly patrol up to 20km to than that of lions. Any human desiring the scare off other animals, and they roar to “strength of a lion” is likely to require a great mark their territory. Their strong bodies deal of non-lifestyle working out to achieve it. require large quantities of energy, and the WILDLIFE

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SCIENCE ILLUSTRATED

SHUTTERSTOCK

18

Although lions seem lazy, they have to work extremely hard in their few active hours.

Editor: Esben Schouboe

Osteoporosis weakens body bones and increases the risk of fractures.

Weak vertebrae crumble A vertebra fracture is one of the worst results of osteoporosis.

Vertebrae can also crumble slowly, causing the spine to collapse.

Forearm easily fractured Forearm fractures are often the first signs of osteoporosis and can occur even without falls nor blows, caused only by mild stresses or slight impacts.

Brittleness causes thigh bone fracture

STEVE GSCHMEISSNER/SPL & SHUTTERSTOCK

Femur neck fracture is the most common effect of osteoporosis.

Today, doctors can exchange the entire hip as a preventive measure or as a cure.

BIG NUMBERS ¡ Which has more objects – the Kuiper Belt or the Asteroid Belt?

Asteroid Belt

Kuiper Belt

This area between the orbits of Mars and Jupiter contains mostly rocks and rock lumps loaded with iron and nickel that are the remains of planetary formation.

As of 2019, scientists had identified 796,971 objects in the belt.

SHUTTERSTOCK

Their total mass equals 4% of the Moon.

125

more times ts are objec ted to a estim e Kuiper h lie in t han have Belt t dentified been ihin the wit d Belt. i Astero

SHUTTERSTOCK

796,971 objects exist in the belt.

This stretches from Neptune towards interstellar space and contains mainly ice lumps left from the formation of the Solar System's outer planets. Astronomers estimate that 100+ million objects exist in the Kuiper Belt.

100 million objects exist in the belt.

200 times the mass of the Asteroid Belt.

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ASK US

How do plants stretch towards the sunlight? roots and buds of plants. Auxin concentrates in the dark side of a plant, and since the hormone makes plant cells more flexible, the cells stretch to grow larger on the dark side. Hence plants will stretch in the direction of the brightest light, so that plants in window boxes will lean outwards if you don’t remember to rotate them occasionally.

SHUTTERSTOCK

As plants grow, they will very often turn towards the brightest light source they can find – which is almost always sunlight.

The Ancient Greeks named the phenomenon phototropism, which means ‘light turning’.

Scientists have discovered that phototropism is caused by auxin, a hormone that exists in the stem, BIOLOGY

TURN FROM THE DARK SIDE: Plants ‘stretch’ towards light aided by auxin, a hormone that makes cells on the dark side of the plant grow longer.

4 STEPS · Why does a shower curtain stick to us?

Answer: The shower curtain is sucked towards us for two reasons, the main one being that the water from the shower causes a whirl of air that sucks the bottom of the curtain inwards. In a warm shower, the air is heated, rises, and produces underpressure, which further affects the curtain.

Cold air pushes the curtain towards you Cold air flows under the shower curtain to replace the rising warm air. The pressure from the cold air intensifies the curtain’s motion towards the inside of the shower cabinet.

3

Water makes the air rotate The motion of the water makes the air rotate like a small air pump, so the curtain is sucked inwards. Known as the cyclone effect, the phenomenon exists in both cold and warm showers.

1

An open door extends the duration of the phenomenon If the door is open, cold air will constantly flow in to affect the curtain. If you close the door, all the air of the bathroom will become heated, so the air flow stops.

4

Warm air rises Warm water heats the air, which expands, rises, and settles on top of the cold air.

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SCIENCE ILLUSTRATED

CLAUS LUNAU

20

Paris

10 ,0 00 km

Dental floss consists of one or more thin threads of nylon – a strong, synthetic fibre.

The thread is covered in wax to ensure flexibility between the teeth.

Dental floss has a tensile strength of more than 200 megapascals (MPa), compared with a figure of just 16 MPa for a rubber band.

The first dental floss was made of silk, but after WW2, stronger and more flexible nylon took over.

One metre was defined as one 10-millionth of the distance between the North Pole and the Equator.

SHUTTERSTOCK & ALAMY/IMAGESELECT

WHAT IS DENTAL FLOSS MADE OF?

Equator

How did units of measurement originate?

Who decided the length of our units of measurement?

And how is a length of one metre actually defined?

The metric system – with the basic elements of metres, litres and kilograms – was developed by scientists in Paris in the late 1700s. Before then, length was measured by variable units, such as a foot, which corresponded to the length of an adult man’s foot, too variable as a standard.

The French scientists based the new system on the distance between the North Pole and the Equator measured along the degree of longitude that passes through Paris. The length of one metre was defined as being one UNITS

10-millionth of this distance.

The kilogram unit was linked directly with the metre, defined as the mass of water that – at four degrees – could be poured into a container of 1/1000m3 . A platinum-based 1kg ingot was created as a reference, ‘Le Grand K’, which was kept locked away in a safe in Paris. But variations in the reference and its successors led the world’s top measuring scientists to vote in 2018 to redefine the kilogram in relation to the unchanging Planck constant. The change took effect from 20 May 2019.

THE FRENCH DEFINED THE METRE The metric system was introduced by statute in France in 1799, when scientists made a prototype known as the ‘Archive metre’. Marble blocks engraved with metres were installed in Paris, so people could get used to the measure.

Dental floss consists of nylon: a strong and flexible synthetic fibre.

SHUTTERSTOCK & GETTY IMAGES

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ASK US

Does water’s boiling point change with altitude?

Water’s boiling point depends on pressure, so yes, it changes with altitude or depth. At sea level, where the pressure is 1013 hectopascals (hPA), the boiling point is 100°C. At the peak of PHYSICS

BOILING POINT OF WATER Mt. Everest, 8848m: 71°C Burj Khalifa, 828 m: 97°C Sea level: 100°C

Mariana Trench floor, -11,000m: 180°C

SHUTTERSTOCK

Ocean floor, -3800m: 112°C

Mount Everest, an altitude of 8848m, pressure is 335hPa and the boiling point 71°C. On the Mariana Trench floor, 11km below sea level, the boiling point rises to 180°C. As water is heated, more molecules evaporate, creating a rising vapour pressure, and when the vapour pressure reaches the pressure of the surroundings, the water boils.

Up a mountain, the water’s vapour pressure need only match the lower external pressure at altitude, so the water boils earlier, at a lower temperature. Far more energy is required to boil water under higher external pressures.

The higher your location, the faster you can make water boil, because the atmospheric pressure is reduced with altitude.

WHAT IS THIS? · Ice circle on American river A circular ice floe on the US Presumpscot river was formed by a rotating eddy of melted water.

The huge ice floe forms when small ice floes merge, with the circular shape due to rotation which continuously grinds the edges of the floe as it touches the river bed.

Rotating ice circles are rare, and the Presumpscot ice circle was one of the biggest on record, with a diameter of 90 metres, The circles are also known from Piteälven, Sweden.

Lab experiments have shown that small ice circles start to rotate by themselves due to an eddy of meltwater produced under the ice, sinking towards the bottom.

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SPECIAL EFFECTS · Forested and swamped Star Wars scenes on the Endor moon were shot in a Californian forest.

Can a planet be covered in forest or swamps?

The Star Wars universe includes planets entirely covered by forest (Endor) or swamps (Dagobah). But could such planets really exist?

An alien planet could not be covered in forest of trees that are biologically similar to the ones that we know from Earth. It would require a climate in which no areas are so cold or elevated that they are permanently covered in snow and ice, or so dry and warm that desert takes over. Such a climate could only exist by means of forceful ocean currents carrying energy from the equator to the poles throughout the year (atmospheric winds are not enough). So the planet could not be 100% forest, as major oceans would be needed for the required climate.

NATURE

Lots of forests and swamps

In Star Wars: Episode V, Luke Skywalker meets his mentor Yoda on Dagobah – a planet covered in swamps. It’s a highly unlikely planetary ecology.

470 million years ago: Algae were dominant

310 million years ago: Swamp produced coal

Humans conquered a forested planet

The first terrestrial plants were algae and mosses that extracted nutrients from the rocky ground, leaving chemical compounds which removed carbon dioxide from the air.

Swamps covered all terrestrial regions from the Equator to close to the modern Arctic Circle, where ferns grew. Most of Earth’s coal reserves formed during this period.

Farming and the first cities originated when much of Earth was covered in wood. Six billion trees covered the planet and were important for the technology of early civilisations.

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ALAMY/IMAGESELECT & AP PHOTO/LUCASFILM LTD/RITZAU SCANPIX

Earth was never entirely covered in swamps or forest, but for periods of time specific growths were more numerous than others. Algae were followed by swamps, then by the forest that was dominant when humans conquered the planet.

A planet covered in swamps makes even more demands on biology, climate and geography. A swamp is a wetland with large-growth vegetation – on Earth either trees or bushes. Very few species of Earth’s plants like having their roots in water, so it requires a targeted evolution of species.

Moreover, precipitation must be at a sufficiently high rate throughout the year to maintain such vast shallow areas, and the geography would need to be so flat that no islands of drier land occur. The existence of a swamped planet is therefore highly unlikely, but not impossible.

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New discoveries disclose the dinosaurs’ dying days:

DOOMSDAY MOMENT BY MOMENT Earthquakes, monster waves, and red-hot glass balls – a new discovery has revealed details of what happened to Earth’s animals in the first seconds, minutes and hours after the meteor strike that ultimately wiped out the dinosaurs.

THE FIRST SECONDS

THE FIRST MINUTES

THE FIRST HOURS

THE FIRST YEARS

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By Antje Gerd Poulsen

Tonnes of tiny hot glass balls rained down on the world after an asteroid struck 66 million years ago.

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PREHISTORY

DINOSAURS

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bright flash overloads the retina of an unsuspecting three-horned dinosaur as it stares down the river banks towards the inland sea. Triceratops blinks slowly, and raises its head as the earth starts to shake beneath its feet. A huge black cloud rises slowly above the horizon, and quake builds upon quake until trees start falling and the animals, whether tiny or titanic, scatter, run and fall in panic.

Then comes a moment of quiet. As the shaking subsides the dinosaur gets up cautiously, its widely set eyes still peering towards the sea. In the distance, the water

75% of the world's species suddenly ‘went extinct’ 66 million years ago.

has risen into a monster wave. The animal turns to retreat, but feels a sudden burning impact on its scaly back. Then another, followed by a third. Tiny red-hot balls of glass are raining down around the dinosaur, and the trees still standing are bursting into flames. Triceratops takes off at its top speed, but doesn't take notice of the lie of the land, the river banks rising higher on each side.

From the eerie silence of the sea comes the roar of approaching water, and the great beast is swept away.

Later, when the water retreats, the land is strewn with drowned and injured animals entangled in a morass of tree trunks and ocean algae. A few fish still struggle for their lives in pockets of dirty water. But then another wave floods the coast, burying these remains of disaster under a thick layer of mud.

There they remained, until 66 million years later when a team of American scientists removed that particular layer of ancient mud under what had become North Dakota, USA, revealing for the first time what happened during the first fateful minutes after the Earth was struck by a huge asteroid.

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the few small, feathered animals that would evolve into modern birds. The cause of this sudden extinction was uncertain for many years and debated over more than a century, with theories including shrinking brains, disease pandemics, and lack of sexual drive.

By the 1970s, scientists were starting to favour the theory that the disaster was caused by intense volcanic eruptions. But this theory was challenged in 1980 by a group of US scientists headed by father and son Luis and Walter Alvarez.

Walter was a geologist, and had gathered a collection of samples taken from a layer of red clay in Italy formed at the time of the dinosaurs’ disappearance. Back in the US, he was assisted in a close examination of the samples by his father – a physicist and Nobel Prize laureate for his invention of a hydrogen bubble chamber. Together they were trying to determine the age difference between the top and bottom layers of clay. But instead they discovered something much more interesting.

The clay layer included unusually high quantities of iridium, an element which is rare on Earth, but sometimes exists in large quantities in asteroids. The iridium levels were a clear clue to the cause of the yet-undetermined catastrophe of that era, but they knew they needed to confirm that the iridium was not merely local to Italy. So they travelled to Denmark, and to New Zealand, gathering more clay layers from the same crucial time period. Sure enough, the iridium levels were high all over.

It was a clincher. A massive asteroid had struck the Earth, and had left its evidence throughout the world. Such an impact could well have caused the observed extinction events. And as they came to their realisation and imagined the extent of the disaster, father Luis Alverez must have felt a shadow from his past. Decades earlier, on 6 August 1945, he had flown closely behind the plane that dropped the nuclear bomb on Hiroshima, his task being to observe what happened. Now here was another explosion 66 million years earlier, and the asteroid that had hit Earth was billions of times more forceful than that Hiroshima bomb.

The asteroid theory attracted attention – but also scepticism. And crucially, where was the crater for this supposed epoch-ending impact? It took another 10 years for scientists to find the answer. On the edge of the Yucatan peninsula in Mexico, they discovered a huge crater with a diameter of 180km, and its estimated formation date was a perfect match. Here, then, was the impact that destroyed the dinosaurs.

25 TRILLION TONNES OF ROCK EJECTED The asteroid collision makes more than 25 trillion tonnes of molten rock and gas from the Earth’s crust enter the atmosphere.

The material ends up across the world, influencing the climate for decades.

THE FIRST SECONDS

Asteroid showers Earth in molten rock A massive metal-containing rock larger than Mount Everest collides with Earth at a speed of 100,000km/h. The strike liquifies the ground beneath into a porridge, and Earth is showered in molten rock.

1500m-HIGH TSUNAMI SPREADS The asteroid strikes the Gulf of Mexico, causing a 1500m-high tsunami.

In the following days, the wave spreads across the world, with monster tsunamis flooding the shores of all continents.

AURION RAE/ECORD/IODP

Crater resulting from asteroid strike

VISITOR FROM JUPITER PULVERISED The asteroid has a diameter of around 12km and comes from the Asteroid Belt between Jupiter and Mars. It strikes Earth with the force of more than 21 billion Hiroshima bombs, pulverising itself.

MOUNTAIN OF MOLTEN ROCK EMERGES Drill samples from the crater reveal that the strike first causes a 25kmdeep hole. Subsequently, the underground ‘strikes back’, for several minutes forming a 15km-high mountain of molten rock.

Drill sample from the crater

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Volcanoes covered India in lava The debate about the dinosaurs’ extinction didn’t end there. Many scientists contended that even if the world had been hit by a major asteroid, dinosaurs were on their way out before the impact anyway. And they already had a candidate for the cause.

The Deccan Traps in India are one of the largest volcanic features on the planet, an igneous geological formation created by activity during the late dinosaur era. Scientists have discovered a two-kilometre-thick layer of ancient lava covering an area of about 500,000km2, formed when the volcanoes of the area began to erupt some 300,000 years before the asteroid hit. They undoubtedly influenced the fauna of the time, and global temperatures apparently fluctuated during the eruptions.

The question is exactly how much the eruptions influenced life on Earth. Some scientists believe the eruptions were responsible for the majority of the mass extinctions from this time; others believe that the erup-

tions only had a limited effect, or that the effects combined with those of the asteroid on the other side of the world.

One problem is the sequence of events.

The Deccan volcanoes started to erupt before the impact, but the biggest eruptions might have happened afterwards. Other analyses also differ in indicating that the dinosaurs had been severely weakened before the impact, while others consider the dinosaurs to have been in perfect shape until the impact.

The disagreements are partly due to a lack of widespread data. Scientists are familiar with finds from only a few places that correspond to this final era of the dinosaurs – and none of these have yielded fossils from the time close to the impact.

A new discovery has changed that. In a remote area of northern USA, scientists have uncovered a prehistoric version of Pompeii, with animals preserved as they died their violent deaths only a few minutes after the asteroid struck.

Something fishy in North Dakota Palaeontologist Robert DePalma from the Palm Beach Museum of Natural History in Florida was not overly enthusiastic when in 2012 a private collector told him about fossil fish near Bowman, North Dakota. The town is located close to the fossil-rich Hell Creek Formation that stretches through Montana, North Dakota, South Dakota, and Wyoming – a barren and deserted area known as the ‘Badlands’, with clay-rich soil and rocks which have been eroded by wind and water over millions of years so that in many areas their layers are exposed like sections of a sponge cake. And some of these layers are ripe with dinosaur fossils.

The fossil collector had given up extracting the fragile fish fossils, and offered to let Robert DePalma take over the site. DePalma agreed to take a look, and found some nice fish fossils in what he thought must be a prehistoric lake.

But there was

THE FIRST MINUTES

Earthquake causes monster waves The asteroid strike shakes the foundations of our planet and makes huge oceans ripple like in a bowl of water. In Tanis, North Dakota – 3000km from the impact zone – waves flood a river estuary, burying animals and plants in mud.

FISH

DEVELOPING G I A N T WAV E S

EARTHQUAKE

Asteroid makes Earth shake

Earthquake produces waves

The strike causes an earthquake some 1000 times more powerful than the worst earthquake in modern times. Three waves caused by the earthquake hit Tanis, North Dakota – 3000 km away – 6, 10 and 13 minutes after the strike.

The earthquake causes ‘ripples’ on limited water masses such as inlets and inland seas throughout the world, causing up to 100m-high waves. This occurs in the huge inland sea that stretches across the USA from Texas to North Dakota and Tanis.

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something odd about the fish he extracted.

Many had small, round stones in their gills.

The palaeontologist recognised the stones as tektites – gravel-sized glass pearls, the remains of molten rock balls falling to Earth from clouds of molten silicate droplets ejected under the pressure of an asteroid impact. And such tektites were already well-established as evidence of the Gulf of Mexico impact 66 million years ago.

He also found small pieces of quartz which demonstrated clear evidence of rocks having been subjected to extreme pressure.

DePalma realised that he might have uncovered a preserved ‘crime scene’ from the very doomsday of the dinosaurs. He set out to

WAVE CARRIES FISH ASHORE At Tanis, scientists have found lots of fish – such as ancient relatives of sturgeons and paddlefish – along with tree trunks, and other detritus. The fish all face the same way, indicating that they were carried ashore by a monster wave.

FISH

TREE TRUNK

50CM

excavate the layers with greater enthusiasm, renting the excavation site from the local land owner, a cattle breeder. It became clear from the deposits that this had not been a lake, but rather a river area that had been flooded.

Layer by layer he uncovered a chaotic death scene with wreckage from ocean, fresh water, and land. Using a chisel and a paint brush, he liberated fragments of ammonites, shelled octopuses and algae side by side with incinerated tree trunks, branches and roots tangled up with freshwater fish and the bones of terrestrial animals, including the Triceratops dinosaur from the beginning of our story. This was a mass grave of plants and animals from terrestrial, fresh water and sea environments, all buried on the same day 66 million years ago. Like a detective, DePalma began to piece together what had happened.

He named the place Tanis after an ancient Egyptian royal city, and in 2019 finally shared his discoveries with the world. His studies provide a rare insight into the last fateful minutes of the dinosaurs.

CLAUS LUNAU & SHUTTERSTOCK

Monster waves ravage river banks

TRICERATOPS

Tanis is located on a river a few kilometres from the American inland sea, but it is still hit by two 10+-metre-high waves within two hours of the impact.

The waves carry shellfish and fish from both sea and river ashore, burying dinosaurs and other terrestrial animals in a thick layer of sand and mud.

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ROBERT DEPALMA & ROBERT DEPALMA/THE UNIVERSITY OF KANSAS/AFP/RITZAU SCANPIX & RICHARD BARNES

PREHISTORY

DINOSAURS

Scientists unearth asteroid victims

Scientists wrap up fossils Fossils are fragile, so the scientists wrap them in plaster before moving them. In the lab, plaster and rock is removed, so the fossils can be studied in greater detail.

Scientists have been excavating in Tanis, USA, where dinosaurs and fish were bombarded with tiny rocks flung thousands of kilometres by a huge asteroid.

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Fossils kept their shapes

Impact crushed minerals

Palaeontologist Robert DePalma unearths fossils of tree trunks and other detritus near Tanis. The fossils have kept their original shapes in the mud.

The impact sent pieces of quartz 3000km to Tanis – and across the rest of the world. The impact pressure caused wrinkles and cracks in the mineral.

SCALES

FIN

SKULL

Fish still have their fins At Tanis, scientists found fossils of extinct relatives of sturgeons and paddlefish. Bones, scales, fins, and gills were all extremely well-preserved.

Fossils in the wilderness Tanis is located in a deserted part of North Dakota, USA. The rocks were formed in the late Cretaceous and the early Paleogene.

Famous geologist visits Tanis Geologist Walter Alzarez, who in 1980 contributed to documenting the impact, studies a piece of rock that the asteroid had flung all the way to Tanis.

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THE FIRST HOURS

Red-hot glass balls rain down 40,000 cubic kilometres of molten rock is flung into the atmosphere, much of it in the shape of glass droplets, which harden into balls. Ejected at speeds up to 36,000km/h, they rain down on the planet’s animals and plants.

GLASS BALLS

GLOWING GLASS DROPS

FISH

DINOSAUR

CRATER

Gill arch

CLAUS LUNAU & ROBERT DEPALMA & SHUTTERSTOCK

ASTEROID SENDS GLASS DROPS TOWARDS THE SKY The asteroid collision makes the rock of the ocean floor melt, and some 40,000 cubic kilometres of molten rock are flung into the atmosphere in the shape of glass droplets. The glass drops are carried throughout the world, and some of them even end up in space, where they travel probably as far as Jupiter.

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‘GLASS RAIN’ FALLS TO THE GROUND The glass drops harden into balls high up in the atmosphere. The first balls hit Tanis 13-25 minutes after the impact, and the glass rain continues to fall for two hours.

On their way through the atmosphere, the balls heat the air around them, probably setting the vegetation of the area on fire.

Glass ball

GLASS BALLS KILL FISH The glass balls are only 1mm diameter, but they hit animals and plants at speeds up to 36,000km/h. The first glass balls hit Tanis before two monster waves wash the fish of the area onto the shore. Fossils show that the balls ended up in the fish’s gills, possibly making them suffocate.

Back then, 66 million years ago, DePalma’s Tanis was a subtropical river delta with swamps, cypresses and ginkgo trees. A few kilometres to the east, the river was linked with a large inland sea that cut the US in two, stretching from the Gulf of Mexico to the northernmost part of the modern US, with Tanis located at the northern end, 3000km from the asteroid strike.

The site includes several layers of rock.

The layer that includes the newly-discovered fossils is around 1.3m-thick, while underneath are sloping rocks that once made up the banks of the river. Above the fossil layer a few centimetres of reddish clay is rich with the iridium that landed during the days, weeks, perhaps years after the impact.

The fossil layer consists of hardened mud or fine sand, and is divided in two. The bottom section was washed onto the river bank in one single violent event. This part shows no signs of drying out, indicating that the top part ‘landed’ to cover it more quickly than would occur under natural processes.

The fossils of the layer include many marine animals, so DePalma concluded that the layer must have been produced by two monster waves from the sea that flowed several kilometres up-river, leaving their contents on the river banks. The sloping river banks rose at least 10 metres above the river’s normal level – and are completely covered in wave contents. So the waves must have been at least 10 metres high.

The glass tektites from the strike have been discovered throughout the layer.

ROBERT DEPALMA

Monster waves bury river bank

The glass balls were tiny, but deadly.

Scientists calculate that the first of these balls would have reached the sky above Tanis 13-25 minutes after the strike, and that they would subsequently have rained down for about two hours. The entire layer must have been deposited during this limited time span.

A seiche, not a tsunami The Tanis death scene reminds us of the entangled wreckage we see in news reports following modern tsunamis. But DePalma is confident that Tanis did not experience a tsunami. The Mexico asteroid certainly did cause monster tsunamis; they spread across the world, but not to Tanis. First of all, the inland sea to which the Tanis river linked

was shallow, so that a tsunami would have lost its power en route. Secondly, a tsunami from Mexico would have taken 18 hours to reach Tanis, yet the tektites indicate that the location was hit no more than two hours after the impact.

DePalma and his colleagues believe instead that Tanis was hit by another type of wave, a seiche, which originates in an enclosed water mass, with the motion more like the waves created if you push a bowl of water. A seiche can be triggered by an earthquake thousands of kilometres away. In 2011, for example, a Norwegian fjord-side community experienced waves almost two metres high only 30 minutes after an earthquake 8000km away in Japan, a category 9.2 on the moment magnitude scale (the modern version of the Richter scale). The asteroid strike 66 million years ago triggered earthquakes of 10-11.5 on the same scale, which is 2800 times more forceful than the 2011 earthquake. Such intense earthquakes could have caused seiches of up to 100 metres throughout the world.

DePalma and his colleagues have been able to establish the first accurate picture of the earliest minutes and hours following the strike. But much work remains to be done.

Only a few of the site’s fossils have yet been studied, yet according to DePalma, Tanis includes a treasure trove of extraordinary finds, including the bones of a catalogue of dinosaurs, pterosaurs and mammals, plus large, well-preserved feathers, and eggs with embryos. If that is true, it indicates that the dinosaurs – at least in North America – were doing well up until the impact, supporting the idea that it was the asteroid, not the Indian volcanic eruptions, that ended dinosaur dominance in this region.

PREHISTORY

DINOSAURS

struck a few hours earlier or later, it would have hit a relatively harmless spot in the Atlantic or the Pacific, and the planet would not have suffered the devastation of losing some 75% of its species – including pterosaurs, large marine reptiles, and most dinosaurs. On the other hand, of course, mammals might never have become the dominant animal group, so for humans, the luck might be considered to be on our side.

Saved by the beak

The primitive Waimanu penguin existed only five million years after the impact.

ROMAN UCHYTEL

From the core of the crater Tanis is not the only 66-million-year-old crime scene that scientists are now studying in detail. In 2016, an international team of scientists collected drill samples from the collision crater itself in the Gulf of Mexico.

The samples from 506m to 1335m under the ocean floor allowed scientists to recreate the impact moment by moment. One surprising find was several layers of carbon in the crater, probably from burnt trees and plants – yet the asteroid hit far away from the coast. The scientists believe that the impact set forests on fire up to 1500km away, and that the monster tsunamis which flooded Mexico and other land areas carried the carbon back to the crater within the hours that followed.

There is another carbon layer on top of the first, but this one seems to have formed during the following months or years, from still more widespread forest fires which sent carbon particles into the atmosphere over a longer period — descending into the crater over time. The forest fires were probably lit by the glass tektites and other debris from the impact falling across the world.

tonnes of sulphur, 425 billion tonnes of carbon dioxide, and at least 1.8 billion tonnes of soot were released.

Carbon dioxide traps the Earth’s heat, and so can heat the world. But sulphur and soot block out the sunlight, with the opposite effect. The quantities of sulphur and soot in the atmosphere remained for years, probably lowering Earth’s temperature by more than 15 degrees for several years. The lack of

billion tonnes was the estimated weight of the asteroid that hit Earth 66 million years ago, which is 1700 times the weight of the visible portion of Uluru.

Sulphur and soot Yet the most severe consequence of the impact came not from fire and flood waters.

The drill samples reveal something still more disastrous. The asteroid struck rock that included 30-50% sulphurous minerals, and the impact liberated the sulphur as gas.

The rock also included large quantities of carbon-based minerals and organic matter, much of which was converted into carbon dioxide and soot in the impact. The scientists believe that a total of some 325 billion 34

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sunlight also meant that that plants could not photosynthesise. Entire ecosystems collapsed. The sulphur also combined with water vapour to produce acid rain in vast quantities, acidifying the oceans and killing marine animals.

Some estimates indicate that only 13% of the world’s rock contains sufficient quantities of these elements to have such an effect, so the dinosaurs might be considered to have been rather unlucky. If the asteroid had

The disaster 66 million years ago was so severe that scientists have sometimes wondered how any animal managed to survive. Fossils from the period offer part of the explanation. First of all, it was primarily smaller animals which survived – thanks to their more limited food requirements.

Secondly, animals in lakes and rivers did better than animals on dry land or in the oceans. Ecosystems in lakes and rivers depend less on plants and algae than those on dry land and in the sea, and the food chain is based more on dead organic material. After the strike, plants and algae were a limited resource, whereas dead organic material was plentiful.

One single group of dinosaurs survived the disaster – the ancestors of modern birds.

Scientists have tried to establish why the birds made it, whereas their closest relatives disappeared. The explanation probably has nothing to do with their feathers and wings – many other dinosaurs had developed in that

direction. Rather it may have been their toothless beaks which gave them the edge. The beak was ideal for eating plant seeds, and large quantities of seeds would have been available in the ground, even long after the plants had disappeared.

While only this one branch of the dinosaur family tree survived, new research shows that it quickly thrived. Fossils and genetic analyses of modern birds show that the evolution of birds exploded in the period right after the impact. Over a few million years, all the bird groups that we know today had originated.

The dinosaurs were undoubtedly hit hard by the asteroid, but with 10,000 modern species – twice as many as mammals – their bird descendants remain one of the most species-rich groups of vertebrates in the world.

SHUTTERSTOCK

Soot and sulphur cause ice age Earth is showered with 40 billion tonnes of sulphuric acid. The first days following the impact are catastrophic for Earth's animals, but it gets even worse. Soot and sulphur black out the sky, causing an extreme ice age.

TIMELINE

D AY S Acid rain destroys oceans

WEEKS

The impact sends large quantities of sulphur gas into the atmosphere, where it reacts with water vapour to form sulphuric acid. Over the next three days, 40+ billion tonnes of acid falls on the planet, killing marine animals.

Fires consume forests Glass balls flung into the air during the impact fall down, heating the air around them. For a short period, the atmosphere is like a 260-degree-hot oven. The heat causes forest fires throughout the world that last for weeks.

MONTHS Black cloud puts out light Soot and sulphur block out the sunlight, and the quantity of solar energy that hits Earth is reduced by more than 98% for months or years. Plants and algae cannot photosynthesise, and when they die, the rest of the food chain also collapses.

YEARS Darkness lowers temperatures The average world surface temperature before the impact is about 20 degrees, but the darkness of the planet causes a reduction of 15-30 degrees in the years that follow. Not until three decades later does the world return to its previous temperature range.

The last large dinosaurs succumbed to an ice age.

TECHNOLOGY

INVERTED SOLAR CELL

Cold from space

The cold of space ‘sucks up’ heat The temperature of space is minus 270.43°C, i.e. close to absolute zero.

Heat always flows towards cold, so Earth’s heat flows towards space.

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Power from solar cell

Heat flow generates power Heat passes through an inverted solar cell, in which the heat flow sets electrons in motion, generating an electric current.

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SHUTTERSTOCK & KEN IKEDA/ILLUSTRERET VIDENSKAB

Heat radiation rises from Earth Earth is heated by sunlight during the day, but at night the heat leaves Earth again in the shape of invisible, infrared radiation.

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High temperature

A new, inverted solar cell generates power as heat flows towards the cold of space at night.

By Henrik Bendix

Power in the darkness from inverted solar cells It seems counter-intuitive, but the utter coldness of outer space could offer a new source of energy. Scientists have invented a technology that converts heat that naturally flows towards the cold of space into useful power that could light houses at night, and even help us to live on Mars.

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arkness falls on Palo Alto in California, and a starry sky can be observed over Stanford University. All is quiet on the campus, but not everyone has finished their day’s work. On the roof of one of the university’s buildings, a small group of physicists and electrical engineers is carrying out a ground-breaking experiment.

In the cool air of the night, they have erected a device which aims to turn on its head everything that we usually think about solar energy. The scientists check their measuring equipment, and confirm their results. It is a breakthrough: the invention successfully generates power – and not in spite of the dark, cold night sky, but because of it.

The scientists have invented an inverted solar cell. Ordinary solar cells generate electricity when they are exposed to sunlight, but this new technology generates power at night, when it harnesses solar heat radiation

into space. The ground-breaking technology is known as negative lighting, and it could provide the world with a new and unique type of renewable energy.

The technology could lead to solar cells that operate 24/7, because they can generate power both during the day and at night.

Inverted solar cells could also generate electricity from warm smoke that leaves factory chimneys. The cells might even provide the energy source we will need in order to be able to live for long periods on Mars.

Heat cools houses The precursor of the inverted solar cell is cooling technology. Huge amounts of power is consumed to cool houses – in the US, 15% of all the energy consumed in buildings is related to air conditioning. That energy consumption could be reduced if the heat could flow into space instead of being removed by air-conditioning equipment. In

Inverted solar cell is based on steam engine theory

Old theory revived The idea of harvesting energy from heat that flows towards cold dates back to 1824, when French physicist Sadi Carnot had an ‘aha’ moment after wondering why steam

Heat will always flow towards cold, and the heat causes motion en route.

Piston

Warm container

Cold container

SHUTTERSTOCK & KEN IKEDA MADSEN/ILLUSTRERET VIDENSKAB

In 1824, physicist Sadi Carnot concluded that a steam engine works because heat always flows towards cold, and that heat flow is converted into motion. In a steam engine the heat makes vapour expand, causing a piston to move, with the steam giving off heat again in the process.

The principle can be transferred to any machine that works due to temperature differences. In an petrol engine, motion is produced when air heated in petrol combustion expands to push a piston. The heat can also make electrons move, and that is the process scientists are using in the newly-developed inverted solar cell.

2014, that idea led the Stanford scientists behind the inverted solar cell to build a radiator that cools the air around it instead of heating it. The inverted radiator absorbs heat from the air below it and directs it upwards towards the cold of space. Importantly the scientists designed the radiator to emit heat – infrared radiation – at specific wavelengths that can pass through the atmosphere’s gases, which would otherwise curb or reflect the radiation.

The radiator successfully cooled the building below it. But then the scientists wondered whether the cold of space could be used not only for cooling, but also as a source of energy.

Piston

Steam

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TECHNOLOGY

INVERTED SOLAR CELL

In 2018, scientists Shanhui Fan and Wei Li developed a solar cell that cools the building underneath it.

engines work the way they do. He realised that temperature differences can be converted into motion because heat always flows from hot towards cold, and the heat flow can set things in motion en route. He also found a formula for calculating the maximum mechanical energy that any given temperature difference can generate.

The Stanford scientists have taken up this almost 200-year-old idea again. The Earth itself is warm compared to the cold of outer space, because it is constantly absorbing energy from sunlight. If a temperature difference can set things in motion, and electricity consists of electrically charged particles – typically electrons – that move, then it should be possible, the scientists thought, to develop an electronic device that can harvest electrical energy from the termperature difference compared with the cold of space, where the temperature is minus 270.42°C, only 2.73 degrees above absolute zero.

the circuit in the opposite direction. The heat radiation towards colder surroundings ‘steals’ its energy from the electrons of the photo diode, and they begin to move more slowly at the coldest end of the diode. This causes a difference in charge between the warm and the cold ends. If the two ends are linked via an electric circuit, electrons will flow though the circuit to reestablish the balance — and power is generated. That was

1.1 billion people are not on any electricity grid.

Cold can light a bulb The scientists’ theory for an inverted solar cell is based on an infrared photo diode, such as those normally employed in infrared detectors such as night vision equipment. An infrared photo diode converts the heat radiation from humans and animals into electrical impulses, which become visible light on a display. But the scientists realised that an infrared photo diode generates electricity not only when it is influenced by exterior heat radiation, but also when it is itself warmer than its surroundings – although in these circumstances the electricity flows around 38

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how the Stanford scientists generated electricity with their photo diode on the roof in Palo Alto in 2019.

In that roof experiment, a thermometer measured a temperature of 20°C, and the wattage was measured at a modest 64 billionth of a watt per square metre. However, the scientists calculate that the method can be optimised to generate 4 watts/m2 – and consequently, an inverted solar cell of 1m2 can power an LED light bulb that shines with the same intensity as an old-fashioned incandescent bulb of 40 watts.

Lighting up Mars Since the new technology can generate environmentally-friendly energy at night, it might illuminate the darkness for the 1.1 billion people of the world who are still not on any electricity grid. Most of these people live in warm countries, and the higher the temperature the more efficiently the inverted solar cells will function.

The inverted solar cell can also be used to generate environmentally-friendly electricity from surplus heat, such as from warm smoke rising from factory chimneys, power stations or incineration plants. With the major temperature rises in these environments the solar cell’s performance is able to rise still further: when the scientists heated their photo diode to 96°C, it generated about 80 times more power than it did at 20°C. Inverted solar cells could even become key to our exploration of the Solar System. A related technology is already used for the Curiosity rover on Mars (see p76). Curiosity is powered by a generator in which the heat from radioactive plutonium is converted into power. The new technology can generate more power per degree of heat than existing methods. And if humans are to survive on other planets such as Mars, we will need renewable energy 24/7. Mars is further away from the Sun than Earth, so solar cells are not quite as efficient in their operation. On the other hand, the new inverted solar cells could provide energy all through the night on Mars, which has a relatively thin and almost cloudless atmosphere that would do little to curb heat emission.

The cold of the universe generates power When Earth’s heat rises towards the freezing cold of space, it brings energy.

Electrons lose energy as infrared radiation from the top of the inverted solar cell, causing a voltage difference that causes electricity to flow through a circuit.

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At room temperature, electrons speed about in random directions in a material consisting of mercury, cadmium and tellurium. This material was chosen because it can convert infrared radiation into energy no matter whether it receives or emits radiation. As all electrons move at the same speed, the charge is the same throughout the material.

When the warm material of the solar cell is subjected to the cold of space at night, the material emits heat radiation in the form of infrared photons. Each photon carries energy away from the material, and as the energy is removed from the electrons, these slow down in the upper part of the solar cell that faces space.

The difference between the number of fast electrons at the top and bottom causes a voltage difference, as more electrons move about freely at the bottom. The voltage difference forces power around a circuit, because the electrons flow from the negatively-charged end to the positivelycharged end to offset the imbalance.

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HUMANS

BODY

YOUR BODY IS

UNKNOWN TERRITORY Your body includes thousands of cell types that scientists know hardly anything about. New technology has revealed a yawning gap in our knowledge about the body, but a global research project is aiming to close it, with more than 1000 scientists working to map our organs. Their discoveries might lead to new treatments against cancer, cystic fibrosis and more.

NEWLY DISCOVERED CELL PLAYS AN IMPORTANT ROLE IN YOUR BRAIN. SCIENCE PHOTO LIBRARY

By Jonas Grosen Meldal

UNKNOWN STEM CELL COULD SAVE SICK LIVERS.

GENE THERAPY TARGETS NEW LUNG CELL TYPE IN AN ATTEMPT TO CURE CYSTIC FIBROSIS.

SCIENCE PHOTO LIBRARY

PHOTO RESEARCHERS/RITZAU SCANPIX

A new research project has identified a series of previously unknown cells in the human body.

SHUTTERSTOCK & CLAUS LUNAU

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New accurate maps of body tissue are revealing new cell types in the brain and elsewhere in the body.

SCIENCE PHOTO LIBRARY

Scientists apply bar codes to cells A new ground-breaking technology known as single-cell RNA sequencing allows scientists to read active genes from hundreds of thousands of cells, all at once. And special DNA ‘bar codes’ make it possible to trace every single active gene back to a cell.

Water drop including cell and bead Bead

Bar code from a single bead

RNA from the cell binds to DNA on the bead

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Cell Oil

Cells get a bead each Scientists dissolve a tissue sample and direct the cells of the tissue through a tube in which they are mixed with small beads.

Subsequently, oil is added. The oil causes the formation of water droplets that each include a cell and a bead.

CLAUS LUNAU

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The cell liberates its RNA

DNA captures active genes

2 The cell liberates its RNA

molecules, which reflect the active genes. The RNA binds to tiny pieces of DNA that scientists have placed on the bead. All the pieces include a specific DNA ‘bar code’ that exists only on one particular bead.

RNA is translated into DNA

Bar code from another bead

Scientists trace bar codes

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into DNA sequences that include the bar code. Scientists sequence the DNA from all water drops simultaneously, but can trace each sequence back to one single bead and cell thanks to the bar codes.

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rain researcher Ed Lein is surprised at the results of an analysis of brain cells taken from the exterior layer of a cerebral cortex. Together with his colleagues from the Allen Institute in Seattle, USA, he has just examined the brains of two dead people. The analysis identified all the familiar types of brain cells, but also a cell type that they had never seen before. Eager to observe the unknown cell with their own eyes, the scientists get behind their microcope to see a round cell body from which a wealth of thin ramifications protrude. The shape reminds them of a rosehip, so the cell is named a rosehip cell.

The new discovery was made in cooperation with scientists from the US and Europe, and is one of the first to be made in connection with a new global project known as the Human Cell Atlas. The project aims to map out all cells of the human body, aiming to thereby revolutionise our surprisingly sparse knowledge about cellular activity.

Some 1500 scientists from 62 nations are participating in the project, and they have already identified a series of previously unknown cell types, and have drawn up detailed maps for several of our organs.

The new breakthroughs have revealed the cells behind the incurable disease of cystic fibrosis, and how cancer cells attack otherwise promising immune therapy. The project now paves the way for new types of treatment which leverage these diseases’ hidden weaknesses.

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determine both its unique shape and its particular range of functions.

Over the past 150 years, scientists have identified some 200 different cell types based on their shapes and their locations in the body. But in recent decades, new methods have allowed us to see exactly which genes the cells express, and there is every indication that the body’s cells can be divided into many more types – perhaps thousands of them.

Until recently, however, even sophisticated genetic methods have not allowed scientists to unravel this confusion of cells in our bodies. They could either study a few cells at a time, or they could identify the genes that were active in a particular organ, without learning which cells expressed what. But new technology has changed that.

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trillion is the number of cells in the human body, according to a study from 2016.

Each cell has its own pattern

TAMAS LAB/UNIVERSITY OF SZEGED

The human body includes a huge variety of cell types, each looking different, each carrying out its series of tasks. Red blood cells are full of the protein haemoglobin, which they need to carry oxygen about the blood. Nerve cells have long threads and many links with their neighbours, ensuring quick and efficient communication. Fat cells can be more than 200 times larger than red blood cells, as they store fat as energy reserves.

The variation of cell types in the body is all the more remarkable when you consider that they all have exactly the same DNA. However, the cells express the DNA in different ways, bringing different proteins into play. A brain cell expresses genes that are responsible for the formation of neuro-transmitters such as dopamine and serotonin. Those genes, on the other hand, are of no use to immune cells, which require genes for the production of substances which assist in defense against infection. So, every cell type has its own pattern of active and inactive genes that

SHUTTERSTOCK

Today, scientists can analyse a sample consisting of hundreds of thousands of cells, and still identify the gene activity in every single one of them.

Algorithm reveals new cell types One of the cornerstones of the Human Cell Atlas project is a method known as singlecell RNA sequencing, or scRNA-seq. Within the past 10 years this technique has become so sophisticated that scientists can simultaneously measure the gene activity in all cells of a tissue sample, and this technique is now helping to map the human body. The method analyses the RNA molecule contents of all cells. When a cell expresses a gene, it will scienceillustrated.com.au

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first translate it into an RNA sequence, and that is subsequently translated into a protein. The RNA hence reflects the active genes of the cell.

If the cells included only two or three genes, it would have been relatively easy to categorise them according to gene activity. But with 20,000+ genes, there are so many possible combinations that scientists needed newly-developed algorithms to handle the large quantities of data. The algorithms use the data to place each cell in a kind of coordinate system with 20,000+ dimensions – one dimension for every gene – and then depending on the genes’ activity level, the cell gets allocated its place in the coordinate system. Cells that are close together in the system have similar patterns of gene activity, and so can

84% of all cells in the body are red blood cells, yet these make up only 4% of the body's weight.

However, the rosehip cell is not the only new cell type revealed by the Human Cell Atlas – and probably not the most important either. Ionocytes in the lungs might prove to be an even more vital discovery.

Ionocytes express higher levels of a gene known as CFTR than any other cells in the body. CFTR plays the main role in cystic fibrosis – a genetic disease suffered by more than 70,000 people worldwide. The gene codes for a protein that carries water and chloride ions in and out of cells, and it is involved in the secretion of slime in the lungs. People with a mutation of the gene produce an overly thick layer of slime in the lungs, and suffer from potentially lethal breathing problems.

Years of intensive research into the disease have not produced a cure, but the discovery of ionocytes bodes well for the future. Scientists have long believed that the production of the CFTR protein was carried out by a series of well-known airway cells. However, the new discovery shows that by far the most CFTR is expressed in the ionocytes, and these make up only about 1% of the airway cells.

This knowledge makes possible brand new cystic fibrosis treatments in which scientists can aim directly for the ionocytes in an effort to achieve normal CFTR activity levels in people born with the disease.

Biologist Aviv Regev from MIT in the US is one of the driving forces behind the Human Cell Atlas.

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be placed wthin the same cell type. The algorithm identifies related groups of cells in the coordinate system, giving scientists a general impression of the cell types present in the tissue.

And this is the manner of presentation which has now led to the discovery of several new cell types, and of subgroups within familiar cell types.

New cells can suggest treatment Ed Lein’s rosehip cell was one of the first discoveries from the Human Cell Atlas. It is a nerve cell, but unlike many other nerve cells, it slows down electric signals instead of passing them on. It contributes to the control of which messages reach their destination – an important role to ensure that the brain does not drown in unnecessary signals.

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The Human Cell Atlas goes beyond the identification of new cell types. One of the project’s most important aims is to draw up detailed maps of the cells within the individual organs and tissues, to find out how the different cells cooperate.

In one of the project’s studies, scientists looked at the tissue that links mother and embryo during the first weeks of pregnancy.

At this time, the embryo’s placenta is attached to the womb via a slimy layer produced in the womb: decidua. So far, our knowledge about this layer has been very limited. Scientists knew that cells from the embryo communicate and mix with the mother’s cells in the decidua and that the layer is extremely important in the early stages of pregnancy. But exactly where the interaction between the mother’s cells and the embryo took place was a mystery.

Normally, the immune system attacks unfamiliar cells, but during pregnancy the mother’s immune system is kept in check despite another human occupying her body.

After the Human Cell Atlas’ mapping out of some 70,000 decidua cells, analyses revealed new types of cells and information regarding their interactions. Three types of

CASEY ATKINS PHOTOGRAPHY, COURTESY OF BROAD INSTITUTE

Map solves a pregnancy mystery

Map of liver reveals new stem cells

Area enlarged

Scientists have drawn up the most detailed map of the liver so far. The process has revealed previously unknown stem cells and genes responsible for the development of liver cancer.

Three types of hepatocytes

SCIENCE PHOTO LIBRARY & CLAUS LUNAU

Bile duct

Blood vessel Blood vessel Kupffer cell

Cancer tumour

Stem cell

SCIENTISTS DIVIDE CELL TYPE IN THREE > Just about all known liver cell types can now be divided into subgroups. Hepatocytes exist in three versions, of which one is good at removing ammonia, and another at breaking down substances by means of oxygen.

THE LIVER REVEALS NEW IMMUNE CELLS > The mapping out of the liver has revealed three new subgroups of Kupffer immune cells. They differ from each other by curbing or improving the immune system’s reactions in the liver.

GENES REVEAL CANCER ORIGIN > Comparison of healthy and cancerous livers has identified the genes that trigger cancer development.

Scientists observed increased activity of genes that are normally expressed by liver stem cells.

scienceillustrated.com.au

SCIENCE PHOTO LIBRARY & SHUTTERSTOCK & CLAUS LUNAU

STEM CELLS CAN SAVE SICK TISSUE > Scientists have revealed an unknown cell type in the bile ducts of the liver.

It functions as a stem cell and can develop into different types of liver cells. The cell might be used to treat sick tissue.

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immune cells differed from corresponding immune cells in the blood, and one of the new cell types seems to have a particularly close relationship with the embryo. It produces proteins that recognise the embryo’s cells, while it also releases substances that calm other immune cells.

All in all, the decidua map revealed an environment optimised to curb the immune system’s reactions to the embryonic cell invasion. This new insight might help discover ways to treat women who find it hard to get pregnant because their immune cells tend to reject the embryo.

Project reveals cancer genes Scientists are also busy exploring the liver, one of the body’s most important organs,

38 trillion bacteria exist in our bodies, but the tiny microbes only weigh a total of 200g.

SHUTTERSTOCK

disarming toxins, purifying the blood and adjusting the metabolism. The liver is also the only organ that can regenerate – even after having been reduced by 75%. Although the liver has been thoroughly explored for more than 100 years, some of its cells have remained hidden from scientists – until the scientists from the Human Cell Atlas project recently mapped out the cells of the liver tissue of nine donors.

The scientists analysed 10,000+ cells.

They primarily found familiar cell types, but they also revealed subgroups of liver cells that scientists had never before come across. They discovered a new type of cell in the liver’s bile ducts – a network of passages that direct bile from the liver to the gall bladder. The cell functions like a stem cell and can develop into ordinary liver cells and bile duct cells.

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Apart from healthy livers, the project’s scientists also explored cancerous livers – and by comparing the two, they managed to identify a number of genes involved in the conversion of healthy liver cells into cancer cells. This should make it possible to develop extremely targeted treatments that can curb the early stages of liver cancer.

G NEW LUN CELL IS I N V O LV E

Atlas guides new treatments Most diseases can be traced back to undesirable changes at the cellular level. A complete atlas of all cells in the body will provide scientists with the optimum information to make accurate diagnoses and develop new treatments.

The scientists from the Human Cell Atlas project are already on the track of more efficient treatments for cystic fibrosis, inflammatory diseases, and cancer.

Armed with their new knowledge about the ionocytes of the lungs and their role in cystic fibrosis, scientists can now work on the development of gene therapies that are specifically aimed at the ionocytes and at correcting their mutated CFTR gene.

Unlike cystic fibrosis, inflammatory diseases can involve hundreds of genes, all contributing to the disease, with many of these genes and their effects still unknown to scientists, even the cells in which they are most active. The Atlas is now changing that. In one example, scientists have compared the maps of cells in the gut tissue of healthy people with those from people with inflammatory gut diseases. They discovered a handful of cells in the sick tissue that did not exist in the healthy tissue, and could also see how more familiar cells changed their activity in the sick tissue. The scientists now have the tools to develop treatments that would remove the sick cells or correct their gene activity.

New knowledge about cancer cells’ gene activity has provided scientists with another new approach. Immune therapy, which helps the immune system combat cancer, has proved promising but is not equally efficient in all patients – and in many cases, is efficient only for a limited time before the cancer cells become resistant. A mapping out of cancerous tissue has shown that cancer cells which develop resistance against immune therapy activate a specific genetic program that protects them against the therapy.

Scientists have now discovered a way to deceive the cancer by combining immune therapy with a drug which deactivates this protection program.

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Nanoparticles

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NANOPARTICLES TRACK DOWN LUNG CELLS Gene therapy against cystic 1 fibrosis could include the CRISPR gene tool inserted into nanoparticles that the patient inhales. The particles end up in lung slime, where they have access to the new ionocyte cell type. The particles can be equipped with antibodies that ensure close contact with the ionocytes.

PARTICLES RELEASE GENE TOOL When the antibodies on the 2 nanoparticle bind to the ionocyte’s surface, the particle merges with the cell, so the particle’s contents end up in the cell. The contents are made up of CRISPR and a healthy version of the cell’s sick CFTR gene.

GENE TOOL REMOVES SICK GENE includes an RNA 3 CRISPR strand that tracks down the sick CFTR gene in the cell nucleus, and an enzyme that cuts up the gene. The cell tries to glue the ends together, but instead it mistakenly inserts the healthy version of the gene in the hole. So the cell now has only a healthy CFTR gene.

Cystic fibrosis causes slime to accumulate in the lungs, potentially impeding breathing.

Gene therapy to target new lung cells PHOTO RESEARCHERS/RITZAU SCANPIX

A map of the cells in the lungs has revealed a new cell type, the ionocyte, that plays an apparently central role in the incurable disease of cystic fibrosis. Scientists now hope that gene therapy aimed at ionocytes might revolutionise treatment of the disease.

CLAUS LUNAU

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ANIMALS

OFFSPRING

Instant Expert: parental care

Giving it all up FOR QUEEN AND COLONY Some of the animal kingdom’s most closed and hierarchical communities exist among honey bees, ants, and naked mole-rats.

They all live in colonies where only the queen is allowed to reproduce.

The other members of the colony are assistants allowed only to defend the home, gather food and, not least, raise the queen’s offspring. related individuals with parental care, the individual that does not reproduce makes sure that some of its own genes are passed on. This happens because closely-related individuals are genetically closer than non-related individuals. Known as ‘kin selection’, this behaviour is observed only in cases where the loss for the individual without offspring is more than compensated by the advantage of helping a closely-related individual.

A less extreme type of kin selection is observed in species that are willing to risk their lives to save closely-related individuals. One example is the chipmunk, which uses loud screams to warn peers of predators. By screaming loudly, the chipmunk subjects itself to danger. The degree of self-sacrifice depends on how closely related the chipmunk is to the other individuals nearby. Scientists have observed that females which breed near to closelyrelated individuals are the most likely to use the characteristic warning screams.

Bee queen sends messages by pheromone

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he purpose of life for most individuals is to grow large and reproduce. But some species have developed a special type of social structure in which only a few individuals have offspring, while others are never allowed to breed.

All such species live in colonies, and the individuals that do not breed have other important functions in the colony. They expand, maintain or defend the home, or they carry out parental care. This special type of social structure – with a queen that is responsible for all reproduction – has been adopted by only two mammals: the naked mole-rat and the Damaraland mole-rat. But we know it best from insects that live in colonies, such as bees, ants and termites. Among those species, some individuals are even born sterile. From an evolutionary point of view, it may not seem sensible to develop a reproduction strategy by which only a few individuals can reproduce. But by providing closely-

Workers feed the larvae with royal jelly. Later, they are supplied with honey and pollen.

The queen of a beehive lays some 1000 eggs a day. Workers are responsible for the subsequent parental care, and the care is determined by the queen’s release of pheromones – neurotransmitters which act as commands to the workers.

One mound, one queen, one king

SHUTTERSTOCK

Termites have specific roles in the colony. Some are sterile, and all individuals are very closely related.

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Termites are known for their social structure that includes several castes with different tasks, and all individuals are somehow involved in parental care. Some are born sterile, having lost the ability to reproduce so that they can concentrate on raising the queen’s offspring.

Termites live in mounds that they construct in wood or soil.

These often very large colonies are built and maintained by workers, and are defended by soldiers. The workers and soldiers can be females or males, and all are wing-less and sterile. Only fertile males and the queen have wings.

The queen mates continuously, but has only one partner, the king, which always remains in the colony with the queen.

BERT VAN DEN BRINK

A few larvae are fed royal jelly as they grow up. Consequently, these few develop into new queens.

A beehive is made of characteristic hexagonal wax cells that are made by the workers, and in which the larvae develop.

BEEHIVE HIERARCHY

Bee colonies consist almost entirely of females.

At the top of the hierarchy is the queen, who is waited on by sterile female workers. By mating with a few males, known as drones, the queen stores sperm cells which will be used for fertilising eggs for the rest of her life.

The queen uses neurotransmitters to control whether eggs develop into males or females.

Workers are females developed from fertilised eggs that the queen lays in her youth.

FRANK GREENAWAY/GETTY/SHUTTERSTOCK

A larva passes through several stages before building a pupa inside its cell, which it eventually leaves as a fully developed individual.

Drones are males developed from unfertilised eggs. They ensure the continuation of colony genes.

ZSSD/SUPERSTOCK

Everyone works for the rat queen

The almost blind naked mole-rat is 8-10 cm long. It lives in the ground in Africa in colonies, where everybody works for the queen and her offspring.

With greyish pink hairless skin, a few bristly hairs and protruding front teeth, the naked mole-rat is an unusual creature not only for its looks, but for a social structure that is very rare among mammals.

The naked mole-rat lives almost its entire life in dark tunnels that it digs in Africa’s dry soil while searching for food.

There the naked mole-rats build large colonies with a queen that is the only one that reproduces. And for this purpose, she has a harem of males to mate with, and all

from the same colony, making ongoing generations highly inbred and almost genetically identical. The queen gives birth to 4-5 litters a year. A typical litter consists of 12 babies, but litters of 27 babies have been recorded. The offspring get care from workers at the bottom of the hierarchy, who also feed the queen.

Above the workers, but below the queen and her harem, are the soldiers which protect the colony against enemies; these are identified by their different smells.

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THE UNIVERSE

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HOW BIG IS THE UNIVERSE? Some questions are so complex that they remain unanswered for centuries. Yet the search for a solution often yields information and wisdom even while the final answer remains out of reach.

Receding horizons in space and time Over the past century, the universe has exploded in size – according to our conception of it. Modern cosmology has redefined its dimensions from a few hundred thousand light years to a size that is a million times greater. And that’s just the part of the universe that we can see. The invisible universe is hundreds of times larger still – and might even be infinite. scienceillustrated.com.au

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et us take a stroll around the universe! That was the invitation to an audience at the Smithsonian National Museum of Natural History in Washington, D.C. on 26 April 1920, where two astronomers were to give a lecture. From the advertised programme, few would have anticipated that the event would develop into a vigorous confrontation. But this encounter at the museum became known as ‘The Great Debate’, and it remains a legendary example of how easy it is for scientists to deliver flawed calculations when they are exploring the limits of what science can measure and observe.

The astronomers were Harlow Shapley and Heber Curtis, and the general topic of their discussion was the size of the universe.

According to Shapley, the Milky Way made up the entire universe, and the ‘spiral clouds’ that could be observed in the sky were just new solar systems under development. To Shapley, therefore, it was clear that the universe had a diameter of about 300,000 light years.

Curtis, on the other hand, considered the spiral clouds to be independent galaxies which were located far beyond the stars of the Milky Way, so that he believed the universe to stretch much further than our own galaxy, which he considered far smaller, with a diameter of some 30,000 light years.

Shapley was slightly closer with his estimate of the Milky Way’s size – the diameter is now estimated to be 100,000-150,000 light years. But he was wrong regarding the spiral clouds.

Curtis, on the other hand, had underestimated the size of the Milky Way, but he was right ASTRONOMER HEBER CURTIS (1872-1942) about the big picture, and the in the early 1900s, when it was unclear whether the Milky Way constituted the entire universe. existence of far more distant independent galaxies.

The idea that the Milky Way might be only one of many galaxies was both controversial and bold, as Curtis himself admitted, saying: “It is certainly a wonderful, a brain-staggering conception, that our own stellar universe may be but one of hundreds of thousands of similar universes.”

If it seems surprising today that such a fundamental fact about the universe was still under discussion a mere 100 years ago, it demonstrates the leaps made in cosmology since then. Besides, the two astronomers were facing a challenge with which modern cosmologists are still struggling. It is simply very difficult to measure distances in the universe.

It is a wonderful, a brain-staggering conception that our own stellar universe may be but one of hundreds of thousands.

UNIVERSITY OF PITTSBURGH

Too big to comprehend The universe has been growing in our conception of it throughout the history of astronomy. The estimation of distances to remote objects has been particularly marked by gross underestimation. Roman-Egyptian mathematician and astronomer Ptolemy (100-170 AD) 52

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had a surprisingly good idea of nearer dimensions in comparative terms, such as stating the Moon’s distance compared to Earth’s size. He calculated that the distance to the Moon was 29.5 times Earth’s diameter – very close to the modern figure of 30.2 times Earth’s diameter.

The Sun's distance was more difficult. Ptolemy came up with a value around a twentieth of the correct one.

And for the stars, he was simply unable to fathom the possibilities. He estimated them to be about 10,000 Earth diameters away. The real distance to the closest star, Alpha Centauri, is 6,455,555,555 Earth diameters. It didn't help that Ptolemy also underestimated Earth’s diameter. His entire universe could have fitted inside a region corresponding to Earth’s orbit around the Sun. More accurate measurements had to wait for astronomers such as Tycho Brahe and Johannes Kepler in the 1500s and 1600s. But their view was still limited by an increasing inaccuracy in their methods for calculating longer distances. The only method available to them was the parallel axis theorem, drawing sight lines towards a star at six-month intervals, and subsequently calculating the distance to the star based on the angle between the sight lines and the diameter of Earth’s orbit around the Sun. The method is good, but it requires more accurate instruments than were available to Brahe and Kepler, who couldn’t reliably calculate distances to even the closest stars. And the astronomers of their day did not conceive anything more remote than the stars in the night sky.

Isaac Newton didn't either, when he published his major work Philosophiae Naturalis Principia Mathematica in 1687. But inspired by his falling apple, Newton did change his view of the universe, by defining gravity as its controlling power. The same rules apply to the motions of all heavenly bodies, he proclaimed, and they all exist in a uniform space. This founded what is known as ‘the cosmological principle’ in modern cosmology, that when viewed on a sufficiently large scale, the properties of the universe are the same for all observers.

The cosmological principle Imagine that you are standing on the surface of a huge inflated spherical balloon. Look in any direction along its surface, and it looks the same.

That is the essence of the cosmological principle, and it usefully deals with any idea that there is something special about our location in the universe.

The principle involves two assumptions. One is that on a grand scale, the universe is homogenous, roughly the same and with the same qualities no matter where we might be located. The other is that it is isotropic, meaning that things look the same in any direction.

The cosmological principle also implies that the universe has no specific centre – or that all places are an equivalent centre, as is the case when we’re standing on the surface of that spherical balloon.

Like Newton, Albert Einstein supported the cosmological principle, but his general relativity theory from 1915 also provided cosmologists with a new way of viewing the universe. Einstein united time with the three spatial dimensions to produce his 4D space-time, and he could use his equations to calculate models for how the

Two telescopes allowed us to see deeper into space Edwin Hubble’s observations in the 1920s with his ground-breaking Hooker telescope proved that the universe continues millions of light years beyond the Milky Way. Since then, the space telescope that bears his name has improved our vision still further.

100 YEARS AGO: One galaxy!

universe must look on a grander scale. But he soon encountered a problem. When he used his equations on the entire universe, he didn't get the expected result – either the equations showed that gravity would quickly make the universe collapse, which clearly hadn't happened, or the equations showed that the universe was growing, which contradicted thinking at the time that the universe was static, and of constant size.

Einstein solved the problem in 1917 by introducing a constant into the equations, which later became known as ‘the cosmological constant’. It was a step that he would later bitterly regret, reportedly describing it as “the biggest blunder of my life”.

The universe develops growing pains

ANDROMEDA

EDWIN HUBBLE uses the Hooker telescope in California.

Hubble defined the Milky Way 100 years ago, spiral nebulas such as Andromeda were considered phenomena inside the Milky Way. Edwin Hubble measured the distance to them and established that they were located much further away and so were independent galaxies.

! es xi la ga of s on lli bi of s ed dr un H : W O N

NASA & ESA/NASA & EMILIO SEGRÈ VISUAL ARCHIVES/AMERICAN INSTITUTE OF PHYSICS/SPL & SHUTTERSTOCK

REMOTE GALAXY

CLOSE GALAXY

The Hubble telescope made us tiny The Hubble space telescope has shown us that there are at least 100 billion galaxies in the universe – and perhaps even twice as many.

The remote galaxies appear in this image as small red dots. The light that we receive from them was emitted some 13 billion years ago.

Einstein’s biggest blunder was unmasked by a very large telescope which was put into service in that same year of 1917. With its 2.5-metre mirror, the Hooker telescope at California's Mount Wilson Observatory had the sharpest vision of its day. Together with astronomer Edwin Hubble, it was about to revolutionise our understanding of the universe.

Hubble began to work for the observatory in 1919, and his access to the telescope allowed him to study the spiral clouds about which Shapley and Curtis had their ‘great debate’ in 1920. Hubble was searching for a very specific type of star in the clouds – cepheids, which exhibit brightness that varies according to a specific rhythm, with a close connection between a star’s rhythm and its light intensity. By observing a star’s rhythm, astronomers can calculate how much light it emits, and then can subsequently estimate how far away it is by applying what they know about how light intensity is reduced across a distance. Hubble discovered cepheids in several spiral clouds, including Andromeda, and in 1924 he could assert with confidence that there were such things as ‘foreign galaxies’ far beyond the other stars of the night sky.

In spite of his epoch-making realisation that our own galaxy is only one among countless others in an incredibly vast universe, Hubble humbly considered his discovery to be just another step within the story of mankind’s reaching for the stars, writing that: “The history of astronomy is a history of receding horizons.”

Hubble continued to look deeper into space, using the large telescope to zoom in on even remoter galaxies and then analysing their light. This led to another breakthrough in 1929, when Hubble discovered the ‘red shift’, where the further away a galaxy is, the redder is its light, a phenomenon caused by the light waves of an object being stretched if it is moving away from us.

Again Hubble underestimated the importance of his discovery. He was a practical astronomer more than a theoretical cosmologist, and he did not consider the consequences if red shift were to be a quality of the entire universe. The red shift of light from remote galaxies could only mean that they are moving away from us and, because the cosmological principle implies we are not in a special central position, that

According to cosmologists, the universe is homogenous, and it looks the same in all directions, no matter where we are.

The idea is known as “the cosmological principle”, and it dictates that there is no centre: the universe is like the surface of a balloon.

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they are also all moving away from each other. Einstein quickly realised the implication that the universe was not static, but expanding. So there had been no need for the cosmological constant he had introduced into his equations 12 years previously. His ‘blunder’ was revealed.

The implications of red shift went further. The breakthrough supported the ideas of Belgian priest and astronomer Georges Lemaître who, two years previously in 1927, had introduced the conception of a universe that had expanded – and hence had not always existed.

Hubble’s observations were perfectly consistent with Lemaître's idea, where the galaxies were moving away from each other as if painted on the surface of a balloon that is gradually inflated. And if this were true, it would also be possible to calculate backwards to a time when the entire universe was united at one point. Lemaître imagined that the universe was born in the explosion of a “primaeval atom”, and had been expanding ever since.

In the following years, Lemaître's ideas were adopted by several other astronomers, developing into what is now know as the ‘Big Bang’ model. But this was far from being widely accepted. The very name ‘Big Bang’ was invented by one of the theory’s main opponents, British astronomer Fred Hoyle. He used the term rather scornfully during a 1949 radio programme in which he argued in favour of his own alternative, the Steady State theory. Together with other proponents of that theory, Hoyle believed that the universe was expanding, but not changing, since matter would be constantly produced in step with the expansion, so that the universe’s density would remain the same. This addition of new matter has never been observed, but according to the theory’s proponents, it probably wouldn’t ASTRONOMER EDWIN HUBBLE (1889-1953) be, because very little would be modestly places his revolutionary discovery of an expanding required to maintain the universe within the context of historical astronomy. density. Calculations show that it could be sufficiently achieved through the generation of a quantity of matter corresponding to a single hydrogen atom per cubic metre per billion years – hence it is not strange that we might not observe this happening. And furthermore, the Steady State theory not only satisfies the cosmological principle, it achieves “the perfect cosmological principle” by being homogenous over time as well as space, with the continuous formation of matter ensuring that the universe remains homogenous in all spatial directions and throughout its development. According to the Steady State theory, the universe is infinite as regards both time and space, and unlike the Big Bang model, it does not require that the universe had a ‘beginning’.

Over the next decade and a half these two opposing theories were strongly contested one against the other, until an accidental discovery in 1964 provided a major evidential boost for one of them.

The history of astronomy is a history of receding horizons.

Knowledge has spread in successive waves.

SPL

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What’s that noise?

Two radio astronomers, Arno Penzias and Robert Wilson, were struggling with a 15-metre-long horn antenna in New Jersey. They had received permission to re-use the antenna, originally designed to communicate with a huge metallic balloon satellite called Echo, to conduct a survey of radio signals from space. But no matter what they did, their measurements were interrupted by a continuous and irritating background noise. Penzias and Wilson aimed the antenna away from New York to eliminate man-made radio sources. The noise continued.

They discovered that the antenna’s horn was full of pigeon and bat excrement. They scraped it all out, along with a few pigeon nests, cleaning and polishing every component. They resumed work with a clean antenna.

The noise remained. After a full year they concluded that a microwave background was present for which they could not account.

Then in 1964 at an astronomy conference, Penzias learned that Robert Dicke and James Peebles from Princeton University were predicting that light from the ‘Big Bang’, if that theory were correct, might today be detectable as microwaves, an idea which had been presented even earlier by another American, Ralph Alpher, that there should be very weak, uniform radiation from all directions, which dated back from the birth of the universe.

Penzias and Wilson contacted Dicke, and together they concluded that their irritating noise was indeed exactly this predicted cosmic background radiation. In 1965, the two radio astronomers and Dicke published their results and interpretations of the data.

Einstein shapes the universe The cosmic background radiation confirmed both the Big Bang model and the cosmological principle stating that on the grand scale, the universe is homogenous and isotropic. The radiation is almost uniform no matter in which direction it is measured, and it would remain so even if Earth had been located in a different place.

The cosmic background radiation was released when the universe was only 380,000 years old. The universe had sufficiently expanded and cooled for electrons and protons to unite into atoms. This meant that radiation in the shape of photons, which was previously halted by free electrons, could now travel freely through the universe – astronomers talk about the universe becoming ‘transparent’; indeed this is thought to be the limit determining how far back in time it is possible to see.

The discovery of background radiation thereby gave the universe a history of development, with the ‘Big Bang’ model defining when the universe was born and how it has subsequently changed. And it can even reveal the shape of the universe.

When Einstein published his general relativity theory, several astronomers began to use his equations to calculate the geometry of the universe as a whole.

One of them was Alexander Friedmann of Russia. In 1922, he introduced models for how the universe might appear if it were to satisfy both Einstein’s equations and the cosmological principle.

With these constraints, the universe must bend in the same way, no matter where we are. And this can only happen in three different ways.

First option: the universe could be closed, like the surface of the balloon we imagined earlier. A closed The cosmic background radiation, which was discovered in 1964, was important proof of the universe has a limited extent. If we send two parallel Big Bang theory. Suddenly it was clear that the light beams out into a closed universe, they will meet at universe is neither static nor has an infinite past, some point, as do longitude lines on Earth at the poles. rather it has a beginning and a history.

Second option: the universe bends in the opposite way, resulting in an open universe with a saddle-like shape. Here the two light beams will never meet, moving ever further away from each other. Such an open universe has no limits: infinite in all directions.

The third option is a flat universe, in which the two light beams remain parallel. Like the open universe, the flat universe is infinite.

THE RADIO ANTENNA Since the discovery of that discovered cosmic background radiation, it has background radiation. been mapped out several times, with the COBE, MAP OF THE COSMIC BACKGROUND RADIATION WMAP, and Planck satellites providing ever more detailed recordings of the radiation, And analyses indicate that the universe is flat – or at least close to being flat.

To astronomers, the shape of the universe was quite important, as it was closely linked with the likely future of the THE PLANCK SATELLITE universe. A closed shape would mean that which mapped out the gravity would at some point overcome the radiation in 2013.

Radiation is a relic expansion of the universe, which would have to from the young universe contract and end up in a collapse, a ‘Big Crunch’.

The cosmic background radiation is consistent with But that scenario was revised radically around 2000, the Big Bang model's account of a hot newborn and once again it was due to astronomers using a new universe which later cooled as it expanded. The radiation method that could reach deeper into the universe. is very uniform from all directions, and the minor differences can be explained by the universe expanding extremely fast immediately after the Big Bang.

Bigger and faster

Background radiation gave the universe a history

Stable expansion (7 billion years)

Accelerating expansion (7 billion years)

The universe grew irregularly Since the Big Bang, the universe has grown in three limited epochs: an ultrashort period of explosive growth (inflation), a long period of stable growth, and an equally long period in which the expansion accelerated.

WMAP SCIENCE TEAM/NASA & PLANK COLL./ESA & ESA & NASA

BIG BANG

Inflation (a split second)

Astronomers love a supernova, and one special type in particular, known as ‘Ia’. This type of supernova originates in a special way, so that its light can be used to measure distances.

An Ia supernova forms from a double star system, in which one of the stars is a white dwarf. If the two stars orbit each other closely, the white dwarf will gradually absorb matter from its mate, until it reaches a specific critical mass. Then it explodes into a supernova, producing light so intense that it outshines the light of all other stars in its galaxy. As astronomers know the critical mass, they also know the supernova’s absolute brightness, and so they can calculate the distance to it in the same way as Hubble could with the cepheids. But supernovas are very much brighter than cepheids, and so they can be observed over much longer distances.

In 1998, American astrophysicist Saul Perlmutter and his colleagues from the Supernova Cosmology Project began to look for Ia supernovas in very remote galaxies.

They measured the light from them and subsequently calculated their distances. And also, just like Hubble, they studied how much the light had been red-shifted, to establish how fast the galaxies are moving away from us.

The expansion of the universe means that, generally, the galaxies move ever further apart. No matter which galaxy we are in, all the others are moving away from us and from each other – as if painted on the surface of a balloon which is inflated.

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The light from such very remote galaxies has not only travelled further than the light from galaxies that are closer, it has taken longer to do so. We are looking back into time, so the light can tell us how fast the universe was expanding billions of years ago. And surprisingly, it turned out that the speed of the more remote galaxies was apparently much lower than it should be, according to the logic discovered by Hubble.

There could be only one explanation: the galaxies of the universe were moving more slowly away from each other billions of years ago than they do now. In other words, the expansion of the universe is accelerating.

“What we were seeing was a little bit like throwing the apple up in the air and seeing it blast off into space,” Saul Perlmutter later said about the realisation, referring to the the apple that made Newton realise the nature of gravity. At the same time as Saul Perlmutter’s breakthrough, a rival team of scientists headed by Adam Riess arrived at the same results, and both Perlmutter and Riess were awarded the 2011 Nobel Prize for their contributions.

Yet their result indicated the opposite of what was expected. If nothing but gravity were at play, then the expansion of the universe would not accelerate, but rather slow down with the age of the universe.

An accelerating expansion of the universe indicates that there is a force that has the opposite effect of gravity, and is significant enough to overcome it. But what is this force, and where might it be coming from?

The answer is made particularly hard to find because in our own galaxy and even in the galaxies close to ours, we do not observe the effect of the opposASTROPHYSICIST SAUL PERLMUTTER, ing force, because gravity is after he and his colleagues made the amazing discovery that the universe's expansion is accelerating. much stronger at such distances.

But on a grand cosmological scale, the unknown force plays a vital role – indeed it implies we are unaware of some 70% of the total of matter and energy existing throughout the universe.

In 1998, the unknown force was named “dark energy”

by American cosmologist Michael Turner, as it does not interact with electromagnetic radiation such as light.

The name is doubly appropriate, because scientists are completely in the dark when it comes to understanding what makes up this mysterious force.

What we were seeing was throwing the apple up in the air and seeing it blast off into space.

ROY KALTSCHMIDT/ BERKELEY LAB

Space fills up with dark energy There are clues, yet these can seem equally baffling in themselves. One of the oddest characteristics of dark energy is that there seems to be ever more of it. The dark energy makes the universe expand, so the average density of the matter in the universe would, logically, become ever lower. But the density of dark energy is constant, so in a growing universe, the quantity of it must grow proportionally. This reinforces the acceleration – dark energy produces expansion, allowing room for new dark energy, which causes more expansion... et cetera.

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Although scientists do not know the nature of dark energy, they can calculate its effect, and it turns out that mathematically it is very much in keeping with the cosmological constant that Einstein introduced in his equations in 1917. It turns out that the idea he himself considered to be a blunder was not all that stupid after all.

The cosmological constant can be understood as a measure of vacuum energy. It is the minimum energy – also known as zero-point energy – that is present in a perfect vacuum in space. The problem here is a huge difference between the value that scientists calculate from theory and the value that is consistent with observations. This is currently considered one of the major unsolved mysteries of science.

However, this does not make astronomers doubt the Big Bang theory. All sorts of other observations are so consistent with the Big Bang that it is now widely accepted as the model of our universe’s history. It also provides us with an idea of the universe’s size.

The light from the most remote galaxies that we can see in the universe is red-shifted so much that astronomers calculate it to be about 13.8 billion years old. This means that the ‘transparent’ universe is about the same age. But that doesn’t mean that these galaxies are located 13.8 billion light years away from us. If the universe has expanded while the light from the galaxies travelled towards us, then they are now much further away than when they emitted the light. Indeed, the remotest galaxies from which light reaches us are now located 46.1 billion light years away. And if this is true in any direction, then what astronomers call “the visible universe” has a diameter of 92.2 billion light years.

But what about “the invisible universe” – the part of the universe that is even further away and which we cannot see? Here, cosmologists become more careful – but a few of them have already tried to come up with a theory.

Invisible, infinite, and faster than light?

In 2016, scientists from the University of Oxford set out to calculate the dimensions of the invisible universe.

They collected all the distance measurements that they could get concerning all object types and fed them into a complex computer model, programming the computer to calculate all possible scenarios in which the measurements could make sense, including the likelihood of the distance measurements being consistent with different universe curvatures, and what these would mean to the general geometry of the universe.

The computer’s most probable answers were consistent with a universe that is almost flat. A completely flat universe would mean that its extent is infinite, if the cosmological principle holds, since this says that the universe is the same in any direction, and in a flat universe this can only be so if it is infinite. But we could also imagine an invisible universe that is so big that our visible universe makes up only a very small part of it – as if we drew a small circle on the surface of a huge balloon.

If so, we might experience a visible universe that was almost flat, although it was really bending slightly.

Astronomers’ cautious interpretation of the Oxford results is that the invisible universe is at least 251 times as big as the visible universe. That gives it a diameter of

23,343 billion light years. But the scientists emphasise that it might easily be even larger. and perhaps even infinite.

No matter how big the universe, we can be sure of one thing: it is growing even bigger. For the past seven billion years, dark energy has outcompeted gravity in the universe, and the expansion has accelerated. This will continue; indeed dark energy will dominate the universe ever more, so that the speed of expansion will gradually grow, becoming much higher than it is today, the galaxies of the universe moving ever faster away from each other.

They can even move away from each other faster than the speed of light, which is otherwise the absolute and impassable speed limit of the universe. This apparent anomaly is possible because the distance to the galaxy increases not only because the galaxy moves away from us, but because the space itself also expands.

The remotest places of the visible universe, located 46.1 billion light years away, are now moving away from us at 10 times the speed of light, due to the expansion of the universe. Any light that might come from these regions in the future will never reach us.

That is also how it will go with galaxies which are now closer to us. Eventually they will be travelling so fast away from us that we will no longer see their light, and in the far future it will not be possible to observe galaxies other our own (assuming we are still around to observe such things).

So, we are fortunate to live in an era during which we have such an exciting and expansive view of foreign spiral galaxies, elliptical galaxies, quasars and other exotic astronomical phenomena. If we were living in a later era, everything that we observed would be contained within our own galaxy, and we would be likely to conclude that our own Milky Way constitutes the entire universe – just as astronomers thought 100 years ago.

Our horizons in the universe are limited by the speed of light What we can see is determined by a combination of the speed of light and the speed at which the universe is expanding.

The general relativity theory allows for three different ways in which the universe could bend.

The three ways allow it different characteristics and determine whether it is finite. So far, observations indicate that the universe is flat.

A closed universe

1 has a positive

curvature. Two light beams that are sent off in parallel will meet at some point, and the angles of a triangle will total more than 180 degrees combined.

EXTENT: FINITE

A flat universe

2 has no curvature.

The two parallel light beams will never meet, and the total of the angles of a triangle add up to 180 degrees, as we know from 2D geometry.

EXTENT: INFINITE

An open universe

3 has a negative

curvature. Over long distances, the two light beams will remove themselves from each other, and the combined angles of a triangle will be less than 180 degrees.

EXTENT: INFINITE

THE VISIBLE UNIVERSE Our visible universe extends 46.1 billion light years in any direction.

Light from the most remote objects in this area was emitted almost 13.8 billion years ago. We will never see the light that the objects emit now.

THE HUBBLE HORIZON 14.5 billion light years away, the Hubble Horizon defines the boundary between galaxies that are moving away from us faster than the speed of light and the ones that are moving more slowly.

The light emitted by the latter now will eventually be visible to us.

FRÉDÉRIC MICHEL/ESO

THE INVISIBLE UNIVERSE The light from objects which are now more than 46.1+ billion light years away from us has not reached us yet.

And the light that is now emitted from this area will never reach us.

Astronomers are getting the size right

Observations and measurements of the cosmic background radiation indicate that our visible universe is flat and so a part of an infinite universe. However, it cannot be ruled out that it bends slightly and hence could be part of a huge, closed – and consequently finite – universe.

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TECHNOLOGY

BRAIN CHIP

Neuralink's chip might one day allow us to eliminate anxiety attacks due to PTSD and other disorders before they develop.

NEURALINK & CLAUS LUNAU

By Gorm Palmgren

READING MINDS TO FIX MINDS By implanting thousands of electrodes in the brain of rats, scientists have analysed and decoded the signals which represent the creatures' thought patterns.

The mind-reading experiment could be a key to curbing neurological diseases.

W

ith short swift motions, a robot is sewing. But it is not stitching fabric, nor is it using cotton sewing thread. Instead it is using an ultrathin flexible cable that is lined with thousands of electrodes, and it is very accurately sewing up to 192 electrodes per minute into the top millimetre of the brain of a rat.

The task takes around 45 minutes, embedding a total of 3072 electrodes and then linking them with a microchip that is attached to the rat’s head. Scientists can now literally read the mind of the rat.

The man behind the experiment is Elon Musk, the man also responsible for the Tesla electric car, the SpaceX space programme and Adelaide’s giant Tesla battery. For two

Normally, the ‘globus pallidus’ brain area initiates body motions and makes them fluid, but in Parkinson’s patients, the area is impaired, causing tremors and non-fluid motions. Neuralink can improve the impaired brain area by providing a connection to the motor centre of the brain. The connection is a small chip located behind the ear, which captures the nerve signals from the motor centre that cause the tremor instructions.

Subsequently, the chip stimulates the globus pallidus to make the motions from the motor centre more fluid.

The detail of the mind The idea behind the new chip is that the microscopic electrodes each settle beside separate brain cells, recording all nerve signals sent by them. This data can then be used to identify how the brain cells communicate, mapping out the brain’s activity in greater detail than has been previously attempted. The robot sewing machine has increased the density of electrodes in an

area by more than 20 times compared to similar previous experiments. This means that the procedure can be less wide-ranging in terms of the area of brain affected, with the required electrodes implemented in a smaller space. And the electrodes can do more than read out the data. With electrodes sewn into several area of the brain, their separate microchips can be linked, able to communicate and cooperate with each other. This could remedy diseases that are triggered across different areas of the brain.

Many neurological conditions are caused by damaged brain circuits, or by undesirable communications between brain areas.

Doctors hope that the brain chip might help people with post-traumatic stress disorder (PTSD) to curb the stress reactions that

CLAUS LUNAU

Electrodes reduce tremor in Parkinson’s patients

years, his company Neuralink has been developing a brain chip that is hoped to pave the way to combatting a long list of neurological conditions including post-traumatic stress disorder (PTSD), and which might in the longer term enable control of machines by the power of thought.

MOTOR CENTRE

1

ELECTRODE

GLOBUS PALLIDUS

2

3

CHIP

Nerve signals from a tremor in a Parkinson’s patient are registered in the motor centre (1), and information is sent to a microchip behind the ear (2). The chip analyses the signals and stimulates the globus pallidus (3), which reduces the tremor.

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TECHNOLOGY

BRAIN CHIP

Sewing machine

Cable

Cerebral cortex

0.05 MM

The sewing machine sews 96 cables with 32 electrodes each into the cerebral cortex.

NEURALINK

occur when the mind travels back to a moment of trauma. The traumatic memory can be sufficient to activate the fear centre of the amygdala, so triggering an experience of the same intense feelings of horror and fear as had been created by the original trauma. But if the new technology were able to recognise the patterns produced by a traumatic memory as it materialised in the hippocampus, the brain chip might send electric impulses via tiny cables to the amygdala to make the centre of fear calm down before the main stress reaction is triggered. With the implanted electrodes sensing the arrival of the attack’s cause, the stress reaction and the PTSD attack could be moderated or prevented.

Tremor can be moderated Even with only a limited resolution of electrodes, the microchip can in some cases pick up sufficient nerve signals to get a good idea of what is happening in the brain. Already in 2012, engineer Roman Genov from the University of Toronto in Canada showed that 64 electrodes in a rat brain were enough to predict an epileptic attack. The microchip could also react quickly enough to trigger stimulation of the part of the brain in which the attack was developing, and hence curb it. The engineer managed to prevent 80% of the rats from suffering epileptic attacks.

Scientists are now developing similar systems which could help patients with Parkinson’s disease. When the electrodes detect tremors in the motor centres of 60

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80% of epilepsy attacks in lab rats were curbed by the microchip’s responses.

patients, the brain chip reacts by stimulating other brain centres in order to smooth out the tremor and make the motions more fluid.

The second half of this system, in which brain centres are stimulated to curb tremors, is already being successfully used by doctors to treat Parkinson’s. The method is known as deep brain stimulation, but currently the brain centres are over-treated, as they need to be stimulated all the time, whether the patient is trembling or not.

To avoid this, scientists need to be able to detect the tremor in the motor centre as it occurs, a sensitivity which requires an electrode density which has not been possible to achieve until Neuralink’s new, more refined technology.

Mind-control of robots A brain chip could go beyond the correction of problems that manifest as diseases. The technology could also be used to allow

patients and others to control robots by the power of thought.

In 2018, robotic engineer Christian Peñaloza from the Advanced Telecommunications Research Institute International in Japan showed that a test subject could control a robotic arm at the same time as using his own two arms. That experiment used a kind of bathing cap lined with electrodes that picked up brain waves through the skull. Such an apparatus is far less sensitive than a brain chip paired with the 3000+ electrodes of Neuralink’s technology, each of which records individual nerve signals to provide far more detailed knowledge about what is going on in the human brain. More specific and detailed analysis of our minds’ thoughts could pave the way for more accurate and complex control of external systems. Success in mind-reading is the gateway to mind control.

Robotic arm moves by the power of thought In the future, it will be easier to control devices only by the power of thought, because Neuralink’s thousands of electrodes allow us to better identify specific thought commands and translate them into highly accurate actions such as controlling a robotic arm.

Electrodes are sewn into motor centre The customised sewing machine sews up to 96 threads that are 10 times thinner than a human hair into the motor centre, where the nerve signals are decoded. Each thread is a bundle of cables with a total of 32 electrodes with only 0.05mm between them, a total of 3072 electrodes.

1

Motor centre Thread with electrodes

Skull

Electrodes register what the brain wants The brain’s motor centre is sending nerve signals even before the motion begins, as the patient starts to think about moving his/her arm.

The electrodes in the motor centre pick up the specific combination of nerve signals that identify the wish to move the arm.

2

Motor centre with nerve signals

Brain’s wish is converted into instructions The thin cables lead to a computer chip located on the skull under the skin.

The electronic circuits convert the nerve signals into electric impulses that are forwarded to a robotic arm.

When the patient thinks about moving his/her arm, the brain chip instructs the robotic arm to do so.

Nerve signals are read.

Computer chip

The robotic arm moves

3

Skull

Cables CLAUS LUNAU /SHUTTERSTOCK

C L I M AT E

CARBON DIOXIDE

The truth about the climate Climatologists take up arms in a

ONGOING SERIES: Eden or Armageddon?

Plain answers and plans from the world of science.

WAR ON CARBON Global warming can only be slowed if we declare all-out war on carbon dioxide and other greenhouse gases. The climate army is developing new weapons for air, land and water, turning beaches green, using carboneliminating liquid, and developing huge ‘carbon vacuum cleaners’.

FROM THE AIR FROM THE OCEANS ON THE LAND

An army of scientists are developing new weapons for the war against climate change.

CLAUS LUNAU

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By Niels Halfdan Hansen

MISSION TO ENSURE A TEMPERATUR E RISE OF NO MO RE THAN 1.5°C .

Aim: Remove greenh ouse gas from the atmosp here.

Priority: Of the utmost im portance.

Location: Air, sea and land .

Status: Awaiting orders to attack.

C L I M AT E

CARBON DIOXIDE

Y

ou could once see the ocean inlet from here, looking east out of the apartment window.

Now you look directly out at a rising harbour wall, watching workers in yellow suits make it taller still.

The wall is the city’s latest defence against storm surges and ocean levels that are rising 5cm a year. You open the window to catch a breeze; the summers are increasingly warm and moist, and even at night, temperatures are rarely below 30 degrees. Air-conditioning has been banned to reduce energy consumption, and the window’s finemeshed fly-screen prevents fresh air from entering. Welcome to Australia in 2100 – and a world that is six degrees warmer.

The risk is, in fact, minimal that global warming will get so far out of hand as to make temperatures rise by six degrees during this century. But it could happen.

Meanwhile in 2015, the political leaders of the world agreed to try to limit the temperature rise to approximately 1.5 degrees

GREENHOUSE GASES CO2: Atmospheric levels have risen by 45% since 1850.

METHANE: Increased by 150% in the last 250 years.

OZONE: Exhaust and factory smoke has made this unhealthy gas settle near Earth's surface.

above levels at the start of the industrial revolution, when greenhouse gas emissions gained their rising momentum.

This target of temperature rise below 1.5 degrees can probably only be met by limiting the emissions of greenhouse gases such as carbon dioxide (CO2). But the transition is proceeding too slowly from fossil fuels such as coal, oil and gas to green ones that take

Many natural processes remove carbon dioxide directly from the atmosphere, binding it so the greenhouse gas can no longer influence the climate. Now, scientists are trying to imitate nature – and might even help feed the world’s growing population in the process.

LISBET JÆRE ALAMY/IMAGESELECT

GROUND ATTACK: Minerals and biochar remove CO2

SHUTTERSTOCK

ON THE GROUND

advantage of wind, sunlight, and water. So instead, scientists are now working to develop new weapons to be used against greenhouse gases. They aim to combat carbon dioxide levels with hungry minerals, biochar, and photosynthesis – and these new climate warriors are poised to take action.

Mineral absorbs carbon dioxide Scientists are fighting on two fronts in their war against CO2. The first step is to remove large quantities of the problematic greenhouse gas that have already entered the atmosphere. Using sophisticated chemistry and huge CO2 capturers, or by accelerating natural processes, they aim to extract the greenhouse gases from the atmosphere.

In this connection, the greenish olivine mineral is proving to be a true CO2 killer.

When the mineral comes into contact with water it absorbs carbon dioxide, converting the gas into harmless substances such as orthosilicic acid, which helps ocean algae to build their shells. Calculations show that

the world’s existing CO2 emissions can be counteracted if 1000 large cargo ships were to spread olivine on beaches throughout the world.

Another approach is to capture carbon dioxide from chimney filters and other emission points, but the harder step may be storing it once captured, so the greenhouse gas no longer contributes to global warming.

One solution is to bind the carbon dioxide in warm rock. In Iceland, a group of scientists has managed to convert CO2 from the air into minerals embedded in basalt.

Emissions are still on the rise The sooner these different CO2 weapons are ready to be used, the better. In spite of the international agreements on limiting the climate effect, carbon dioxide is still rising from the world’s chimneys, exhaust pipes and farmland.

The most recent data from the International Energy Agency (the IEA, an intergovernmental

The olivine mineral could be spread on beaches, where the moisture helps capture carbon dioxide from the air.

PROJECT VESTA

HARMLESS SUBSTANCES Moist mineral sucks up CO2

Olivine

Carbon dioxide

Water

Olivine is a mineral that exists in magma. The mineral reacts with CO2 in the air, producing harmless substances that make up a natural part of the carbon cycle, including building algae shells. Water is vital for the chemical reaction, so beaches would be the ideal place to spread the pulverised olivine, so that the mineral is kept moist by the water.

Mg 2 SiO 4

4 CO 2

4 H 2O

Magnesium bicarbonate Orthosilicic acid

1

Biochar could remove 12% of the atmosphere’s carbon dioxide

Carbon dioxide

Biochar includes calcium, and originates when organic material is heated without oxygen; a series of reactions on the surface allow 1g of biochar to bind 18-34mg of CO2, which remains in the ground for thousands of years, also improving the soil and hence crop yields. Globally, 12% of the world’s CO2 could be absorbed by biochar.

2 Mg(HCO 3 ) 2

H 4 SiO 4

Water

Calcium

Calcium hydrogen carbonate

H 2O

CaCO 3

Ca(HCO 3 ) 2

IMPROVES FARMING

2

Forests feast on CO2 Trees are an efficient way of removing CO2 from the atmosphere, as photosynthesis binds the greenhouse gas. A first step would be to stop ongoing deforestation. Together with drainage of wetlands (which releases CO2), de-forestation is responsible for 13% of the world’s total carbon dioxide emissions. The potential of curbing such loss is therefore huge.

CO 2

Carbon dioxide

Water

Glucose

6 CO 2

6 H 2O

C 6 H 12 O 6

Oxygen

OXYGEN PRODUCTION

3

6 O2

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CARBON DIOXIDE

1KM

THIRD LAGOON

SECOND LAGOON

FIRST LAGOON

On One Tree Island, scientists have successfully combated acid ocean water.

ONE TREE ISLAND RESEARCH STATION/UNI. OF SYDNEY/CARNEGIE SCIENCE

organisation that aims to ensure clean energy supply) reveals that the world’s total energy consumption rose by 2.3% in 2017/18.

The data also shows that the burning of coal, oil and gas was responsible for the majority of the increase. The total emissions of greenhouse gases rose by 1.7% in 2017/18, showing how things are still developing in the wrong direction – as they have been for more than 150 years.

Since the industrial revolution gained ground in the mid-1800s, mankind has contributed some 2000 billion tonnes of CO2 to the atmosphere. Back then, the concentration was some 280 carbon dioxide molecules per one million air molecules. That figure is now more than 410 CO2 molecules per one million air molecules. It may not seem a high proportion in itself, but the increase of 46% in just 150 years is significantly rapid. With CO2 acting as a greenhouse gas, these higher concentrations have seen global temperatures increase by approximately 1°C already in this time.

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1.7% increase in greenhouse gas emissions took place in 2017/18 alone.

In other words, we have only an increase of some 0.5 degree left before we hit the 1.5°C ceiling on which world leaders agreed in 2015. And as the temperature rise is a delayed effect compared to the rises in greenhouse gas emitted, scientists believe that we can emit only another 770 billion tonnes of carbon dioxide into the atmosphere if the temperature rise is to have a 50% chance of remaining below 1.5°C.

If we wish to improve those odds to 67%, then we can emit only another 570 billion tonnes of CO2. With the nations of the world currently pumping 40-50 billion tonnes of carbon dioxide into the atmosphere annually, the sums become simple: we can afford only 10-12 years of current emission levels before the 1.5°C limit is reached. And doing so only by preventing more greenhouse gas emissions now seems unrealistic.

More weapons to win the war It is both expensive and time-consuming to prevent carbon emissions by making wholesale changes to the world’s transport systems, the way we produce food and consumer goods, and the introduction of climate-friendly alternatives such as electric cars, solar cells, and wind turbines. These may be valuable and necessary changes, but they simply won’t be enough. Power stations based on fossil fuels such as coal, oil and gas are still being built for future use, and their estimated emissions will consume half of

FROM THE OCEANS

OCEAN OFFENSIVE: Coral chemistry The oceans are good at capturing CO2, but the greenhouse gas makes the water acid, impeding coral growth. Scientists will now employ chemical weapons against this acidification. They have successfully used an Australian island as their test site.

FIRST LAGOON

NaOH

Corals in neutral water

Corals influenced by acidification

CLAUS LUNAU

THIRD LAGOON

Shallow threshold Shallow threshold

Corals influenced by acid 35 M

One Tree Island is a coral island with three lagoons separated by shallow thresholds lined with corals.

On one of the thresholds, the water from the biggest lagoon flows into a smaller lagoon.

1

2

The sodium hydroxide reestablished the original acidity of the ocean, and the scientists observed that the corals that lived in neutral water grew 6-8% more rapidly.

3

DAVID LIITTSCHWAGER/NATIONAL GEOGRAPHIC IMAGE COLL.

that tight ‘budget’ of 570 billion tonnes of CO2 in advance – unless these plants are closed down before their expected lifetime or are converted to reduce emissions.

This is where the concept of CO2 elimination enters the scene. Scientists from England, the US, Scotland and Austria have analysed available knowledge and ideas on how to fight CO2, and they delivered several central conclusions. The most important is that the removal of carbon dioxide and other greenhouse gases from the atmosphere is “a biological necessity” to meet the international requirement of a maximum global temperature rise of 1.5 degrees. If the aim were two degrees, we might still make it by restructuring the energy sector to focus on renewable energy sources and choosing green solutions whenever possible.

The scientists also concluded that one weapon against CO2 will not be enough, so they recommend a carefully selected range of technologies, at the same time pointing out that a much swifter pace is required in

At one end of the 35m-wide threshold, the scientists slowly released 15,000 litres of very alkaline sodium hydroxide, NaOH, which neutralised extra CO2 in the ocean water.

CO2 lowers the pH value of the oceans. Acidification makes it harder for corals and shellfish to crystallise calcium from the water to produce their calcium shells. scienceillustrated.com.au

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GAETAN BALLY/CLIMEWORKS

the emitted carbon dioxide. But there are other ways to use these technologies.

Instead of preventing greenhouse gases at the point of emission, they might reduce the CO2 concentration of the wider atmosphere.

Increasing pressure

financing, research and development, as the weapons must be employed within 10 years, when the need to combat CO 2 is expected to be critical. Indeed the scientists highlight a handful of methods that are already highly efficient and so simple that we could be using them already.

First wave: wood and chemistry All studies agree that new forest is one of the cheapest ways to combat CO 2 in the atmosphere at a price of less than A$72 per tonne captured, with those costs covering purchasing land, planting small trees, plus continuous control and care. One of the challenges for this method is that large areas of farmland will need to be covered to make a difference, and such spare land is increasingly unavailable, with agricultural production rising to feed the world’s growing population. The planet already includes 7.7 billion people, with the number likely to rise to 9.8 billion by 2050. So scientists have set an upper estimate of 3.5 billion tonnes of removed CO2 per year that could come from new and reestablished forest – about 10% of the present annual emissions.

The longterm destiny of the trees from such forests is also important. Unless the trees are treated correctly when they get old and die, the greenhouse gas will escape again as the trunks rot on the forest floor. So the trees must be felled when they are ready, and either burned in power plants with chimney filters collecting and storing the carbon dioxide, or used as timber in high-quality furniture or houses that will have lifespans lasting decades.

The potential of chemically removing CO2 from chimney smoke is obvious, but at present the methods remain expensive because of the high energy expended in the process. If a plant powered by coal or natural gas is to be carbon neutral, 10-25% of its electricity production must be used to capture 68

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CLAUS LUNAU

Climeworks' huge CO2 capturer is tested outside Zurich, Switzerland.

The first such experiments are already taking place, and in FILTER PURIFIES ATMOSPHERE several places. One company at Scientists are constantly developing an advanced development new ways to capture CO2. The filters stage is Climeworks of Switzercan be used either on chimney smoke land. The company has test or on ordinary air; Switzerland’s Climeworks is set-ups with huge CO2 capturexperimenting with the latter. All materials can ers in several locations includgive off the captured CO2 and be used again. ing Hinwil, south-east of Zurich.

The technology is mature and ready to be employed.

Smoke or Climeworks’ method is, 1 atmospheric air however, expensive. To remove is forced through a the greenhouse gas from the catalyst that includes atmosphere requires even more a porous material which can bind CO2 – energy than from chimney such as zeolite smoke, because atmospheric minerals. concentrations are lower. The company estimates that the price per tonne of captured CO2 is currently as much as A$1000, The minerals 2 capture CO although cofounder Christoph 2 and bind it in the Gebald estimates that the price porous material. will fall rapidly to less than The rest of the gases A$150 with rising demand and in the air or smoke increased scale. Yet if the energy are forced out at the to power the CO2 capturer is top of the catalyst under high pressure. supplied by a coal-powered plant, the plant produces more CO2 than Climeworks captures.

The pressure of Today, the test set-ups are 3 the catalyst is powered by green energy, but if reduced, and the the system were to be upscaled concentrated CO2 to tens of thousands of plants can now be collected throughout the world, it could at the bottom.

The catalyst is put pressure on available solar, subsequently ready wind, and hydro energy. Furtherto purify new smoke more the process itself does not or air. store the captured carbon, so the efficiency of further use or of carbon storage also impacts upon the positive effects.

In spite of the challenges, these new climate warriors hope to have a wellequipped arsenal and a detailed action plan DEEP GROUND WAT E R against CO2 within 5-10 years. This does, however, not mean that it is the best solution to the climate crisis. Many scientists point out that the possibility of removing carbon dioxide emissions from the atmosphere can be used as an excuse for doing less in the way When the system has captured CO2, it must be stored in ways that of the necessary transition to greener techprevent its return to the atmosphere. nologies and practices. As in other conflicts, CLAUS LUNAU a solution reached around the negotiating table is always preferable to all-out war.

FROM THE AIR

AIR ATTACK: Sucking in CO2 Huge ‘vacuum cleaners’ with chemical filters are ready to purify the air. But the captured CO2 will also need to be stored in a safe place.

Engineers have in mind several suitable storage locations deep in the ground...

Captured CO 2

PRESSURE FORCES OUT THE LAST DROPS OF OIL Half-empty oil wells can be used for CO2 storage. When the greenhouse gas is pumped down under high pressure, the gas can help force 30-60% more oil out of the ground.

B A S A LT

GROUND WATER DISSOLVES GAS Deep ground water can dissolve CO2 and store it for thousands of years. Calculations show that US deep water reservoirs could absorb all the CO2 from American energy production for at least 100 years.

WARM ROCK CONVERTS CO2 INTO ROCK When CO2 is pumped down to warm basalt, the latter produces carbonaceous carbonate rock together with CO2.

Experiments in Iceland have shown that the process takes a few weeks, and no CO2 escapes.

KEVIN KRAJICK/LAMONT-DOHERTY EARTH OBSERVATORY/AFP/RITZAU SCANPIX

HALF-EMPTY OIL WELL

HUMANS

CELLS

Instant Expert: Cell death

Cell suicide is painless A healthy body not only depends on cells’ ability to grow and divide, but also on their ability to destroy themselves once they are no longer needed. This happens during the embryonic stage, or when cells are damaged, old or infected by a virus. The phenomenon is known as apoptosis, or programmed cell death.

A

poptosis is the human body’s natural mechanism for removing damaged or worn-out cells.

The programmed cell death of such cells prevents unintentional body growth, and contributes to maintaining a fairly constant number of cells in the body.

Cells can die in two ways: either they are killed by damage through infection, or they are persuaded to commit suicide.

Apoptosis happens when old cells need to be renewed, when damaged cells can’t be repaired so must be removed, when virus-infected cells must be destroyed, or when cells are subjected to stress and hunger.

Apoptosis is also important in the embryonic stage. Apoptosis removes tissue and cells when the embryo’s fingers and toes are formed, and it removes surplus cells when synapses are developed between brain neurons. The process takes place in billions of cells every day, as surface cells of mucosa, the stomach, intestines and skin are replaced regularly by new ones.

Apoptosis is a necessary tool for destroying cells that make up a threat to the body’s condition.

Cells infected by viruses are killed via the immune system’s T cells, which induce the cells into a programmed death.

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A cell commits suicide Different types of external influence can activate a cell’s suicide program, also known as apoptosis.

It could be DNA damage that might originate due to radiation or subjection to chemicals. The damage activates a protein that triggers the process.

SCIENCE SOURCE/GETTY + ALLAN HØJEN

A six-week-old embryo has formed arms and legs, and fingers and toes are on their way. This is due to apoptosis.

RALPH HUTCHINGS/GETTY IMAGES

own body. This is because after a case of infection, the millions of immune cells that were produced to fight it must also be eliminated to avoid the scenario where they attack healthy body cells.

Finally, cells with DNA that has been damaged by radiation or toxic chemicals will stimulate their own apoptosis and kill themselves in order not to develop into cancer cells.

Apoptosis happens as a result of a highly controlled internal suicide program in all cells. The mechanism involves a series of biochemical reactions that cause changes in the cell’s appearance: the cell surface becomes full of holes and it shrinks; cell fragments unite in membranes; the nucleus crumbles, the chromosomes condense, and the DNA goes to pieces. The process is closely regulated and aims to leave neither toxic cell remnants nor the chance of re-infection.

CANCER

STIMULI

DNA damage

2 activates the p53

The cell’s suicide 1 program can be triggered by stress, ageing, immune cells, infections, hunger, or DNA damage.

protein, which immediately ends the cell’s life cycle.

DNA

ENZYMES P53 PROTEIN

Special cell-killing enzymes called

4 caspases are activated by the

proteins. From here, the apoptosis becomes self-reinforcing and cannot be stopped.

A cancer cell undergoes apoptosis.

If no mass suicide occurs, the cell will go on dividing unrestrained.

MITOCHONDRIUM

PROTEINS

The mitochondria

3 (the cell’s energy

factories) are affected by p53 to give off specific proteins in the cell.

The cell’s skeleton is

5 broken down, the cell shrinks, DNA condenses, and the cell's components are embraced by membranes.

Finally, the cell breaks into small pieces.

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Cancer cells only do what cells normally do: grow and divide.

But cells that divide out of control are very hazardous.

Apoptosis, or cell suicide is one of the most important processes regulating the quantity of cells, and preventing cancer. Cancer cells only develop when the apoptosis mechanisms do not function, or don’t take place in the way they are supposed to.

A cell might avoid committing suicide because of a mutation or biochemical blockage in the signals that instruct it to undergo programmed cell death, so that the cell continues to divide, and might develop into a cancer tumour.

In cancer tumours, there are often mutations of the p53 gene, the one responsible for halting cell division. Cervical cancer is due to a virus that disturbs the function of p53.

This could result in uncontrolled growth of cells in the cervix and subsequently the development of cancer tumours. When cancer cells develop, the cell itself or the immune system’s T cells try to activate apoptosis.

But often, the cancer cell's apoptosis program has been damaged in several places of the signalling process, making it almost impossible to stop the unrestrained cell growth.

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T R A N S P O R TAT I O N

E FROM TH IC SCIENTIFES ARCHIV P R E S E N T S TAT U S

AUTONOMOUS SMART CONTAINERS Today, shipping containers carry more than 90% of the world’s commodities to their destinations.

The steel boxes are equipped with GPS and SIM cards, so the receivers can check the state and location of their goods en route.

Fully automatic ships and trucks will soon be carrying cargo, and in Hamburg, Germany, engineers are developing a system that uses drones to move empty containers.

RUM BARRELS

CAN

HOUSEHOLD BARREL ROLLS-ROYCE

18 million litres of rum on its way to the British army in 1919. The alcohol industry is still one of the major buyers of wooden barrels today.

Car-maker Rolls-Royce is testing autonomous container vessels.

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By Jonas Bechgaard

A short history of the barrel Even the Romans gave up their beloved amphorae in favour of barrels.

For centuries, barrels were the preferred containers for the transportation and storage of anything from wine to salted herring... even for dead people.

I

n the late 1800s, 30,000 coopers were rolling out the 18 million barrels a year required by the English beer industry. South of the English Channel, the French poured wine into another 10 million barrels, and on the other side of the Atlantic Ocean, 7.5 million barrels were filled annually with American crude oil.

Denmark exported 1.6 million casks of butter to the UK. Global trade was already huge back then, and the barrel was king, with demand for the universal packaging of the time almost insatiable. Throughout the world, hundreds of thousands of coopers did nothing but make barrels, and still struggled to keep up with demand. Barrel making was an indispen-

sable craft, and it paid well; coopers could become relatively wealthy from the demand for their trade.

Rum in barrels The first historic account of barrels appears in 2700-year-old wall paintings from Ancient Egypt. But the bulging wooden container that we know today originated in ancient Gaul.

“In the vicinity of the Alps, they place their wines in wooden vessels to protect it against frost in the winter,” wrote Roman geographer and natural philosopher Pliny the Elder in the first century AD. The barrels were rough compared with the elegant clay amphoras used by the Romans for wine, oil, and many other things. But if the burly Gallic wooden

barrels lacked beauty, they were very durable and functional.

If a barrel took a fall, it didn’t break.

With its rounded shape, it could be rolled, whereas an amphora had to be carried.

Violent blows might make a barrel leak, but the damage was easy to repair. So once it was established that wine actually improved after storage for some time in a container made of oak, the Romans adopted the Gallic barrel. Ever more products were switched to wood when they were to be carried to remote destinations in the growing empire.

Barrels were subsequently divided into four main groups, with different purposes. Dry barrels were for the transportation of anything from salted fish to iron rivets. They were made of cheap

CONTAINERS AND BUCKETS KEEP COOPERS BUSY & WEALTHY Before plastic buckets and cheap tin made their work redundant, coopers were kept busy making the countless containers that every household needed for daily life.

Barrel-making was the central business, but coopers also produced many other wooden household containers for moving, storing and cooking

food and drink. The milk from cows ended up in buckets; beer and dairy products were made in tubs; wooden ‘cans’ were a practical way of bringing drinks on journeys.

Farmers and workshops were other big customers for the cooper, ensuring a healthy and potentially wealthy all-year trade in cooper-made products.

BUCKET

TUB

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TOOLS A cooper uses many special tools. The staves are rounded on the inside with the in-shave. By adjusting the rotator, the hoops can be forced together before they are merged or riveted in place. The compass measures the head’s diameter so it can be made completely circular to exactly the correct dimensions.

wood such as pine and fir, and often only used once, the equivalent of modern cardboard boxes.

Dry, sealed barrels were used for goods that did not tolerate moisture – such as flour, sugar or gunpowder.

‘White’ barrels were open containers such as tubs, buckets, and butter churns.

They were often made of ash wood, and were indispensable in households, used especially in connection with the making of dairy products.

‘Wet’ barrels were the most expensive. They were made of old oak wood and had to be able to hold liquid without leaking. The oak casks boasted long durability; if treated well, such barrels could be used and re-used over 50-100 years.

Thousands of herring barrels From the Roman Empire, barrel making spread across all of Europe. The Vikings used barrels, which are estimated to have reached Scandinavia in 200-400 AD. In the early days of their use, much of the population would have had barrel-making skills, but during the Middle Ages, the demand for barrels grew so big that they became a commodity, and their manufacture became a specialised profession.

In Scandinavia, it was the increasing trade in salted herring that particularly nourished the demand. Before the major herring market in late summer, hundreds

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COMPASS

R O TAT O R

I N - S H AV E

of coopers were busy making the thousands of barrels required for the salting and packaging of the fish before they were carried to Southern Europe to be consumed instead of meat during the Lent of the following year.

The role of the cooper extended to the market place, where they were kept busy sealing the full barrels. This work had to be done carefully, as poor packaging could ruin a shipment, and became punishable by death. But the profit was worth the risk. Before and during the main market season, a hard-working barrel-maker could earn a year’s salary in one month.

Historians estimate that in good years, some 300,000 barrels of salted herring were shipped south, corresponding to 35,000 tonnes of fish. The carriage of such quantities of herring would have been impossible without the robust wooden barrels.

Coopers unionise That particular market was declining by the 1400s, but the consumption of barrels kept on growing. There were plenty of other goods besides herring for which barrels provided the best packaging.

Trade was thriving throughout Europe, and ever larger fleets of merchant ships carried thousands of barrels between ports along the coasts of the continents and on the major rivers.

Barrel-makers were sufficently numerous in cities that they began to unionise.

Cooper associations were founded in many market towns, and they were given royal privileges, assisted in recognition by their value in being able to lay down common standards for barrel sizes.

“We must be masters of calculation and measuring, as how would we otherwise be able to determine the correct dimensions of the cask? Lord, my heart is leaping with joy when I see such a fine cask,” wrote the proud German master cooper Martin of Nuremberg in 1580.

Working as a barrel-maker was physically hard, not least for apprentices, as they were often beaten. One boy was so used to being beaten for small mistakes that after a day without a beating, he thought “that something was missing”.

But there were great prospects for those who completed the apprenticeship.

Unemployment was almost non-existent in the industry, and a cooper earned about three times as much as an ordinary worker. With hard work and good health, a barrel-maker could hope to end his days as a wealthy man.

Coopers set sail Up until the 1400s, sea voyages were usually short and limited to coastal areas.

But longer sea voyages of discovery soon made it necessary to bring larger quanti-

ties of supplies, and the many barrels in a hold required constant watching and maintenance, so that their vital contents were not lost. Domingo Vizcaino was the cooper on the Santa Maria when Columbus crossed the ocean to the New World in 1492. About 300 years later, James Cook took two coopers and an apprentice on the HMS Endeavour during his first expedition to the Pacific, along with 250 barrels of beer, 44 barrels of brandy, 17 barrels of rum, and other for pork, beef, flour, salt, sauerkraut and more.

Sailors quickly discovered that alcohol could last longer than water, so wine and beer became the preferred drink of European explorers on their long journeys across the Atlantic and south of Africa. On Spanish and Portuguese ships, every sailor was entitled to 1.5 litres of wine a day, and in the English Navy the daily ration was a remarkable gallon of beer, or a lesser amount of spirits on longer journeys where beer might spoil – the origin of the

famous Navy ‘rum ration’. In the 1600s, beer barrels took up one third of the space for supplies on the navy’s ships. In France, historian Jean Michel Deveau wrote that: “All major slave ships employ coopers.

Their pay of 35-40 livres earns them an average position among navy officers.”

Conquerors and colonisers followed in the wake of the explorers. European empires spread across the world; shipping traffic grew, and global trade alongside it. The coopers were kept busy.

Barrels came in all sizes. The world’s biggest brewing vat was made in England in 1806. With a height of 10 metres, it could hold a million litres of beer.

Barrels roll off With the discovery of oil in the US in the late 1800s, the demand for oil barrels initially exploded, but the rise of machines and new materials soon began to erode many of the traditional practices. Coopers themselves began to use machines to

increase their output; between 1844 and 1883 more than 400 barrel-making machine patents were granted in the US alone. The first machines were unreliable, and in some cases lethal to their operators, but gradually the technology improved, and ever more manual tasks were replaced by more efficient mechanical solutions. By the late 1800s their production had become mechanised to such an extent that the cost of a barrel had fallen to a sixth of its mid-century price. Then demand plummeted as barrels were challenged by cardboard boxes and metal drums. Coopering had all but disappeared by the mid-1920s.

Today, traditional drum barrels are made primarily for the alcohol industry, with much of the production taking place in France, where 500,000 oak crates are produced annually. This employs only 400 people. As with so many crafts, industrialisation has made an artisan niche out of a once great global profession.

FROM LOG TO BARREL The master cooper bought entire logs and cut them into staves, which the apprentices adjusted. Chips and surplus wood were sold as firewood, providing useful extra income.

The compass is

4 used to measure the bottom and head diameter.

Hoops made of willow

5 or iron are hammered down around the barrel’s ends. It is ready for use.

The barrel is erected

The rotator forces hoops

3 together, bending the

staves to provide the barrel with its characteristic shape.

The cooper uses a

1 special plane to make the staves narrower at the ends than at the centre.

2 by means of a hoop.

The hoop is fitted with a clamp that holds the staves in place at one side.

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CURIOSITY

w o n s i y t i s o i r Cu alone on Mars rover Opportunity In 2019, the rm. ajor sandsto m a to d e b succum nd the r Curiosity a e v ro w o ll fe e Its ite are now th Orbiter satell ft to only ones le . explore Mars

SOLO SELFIES Curiosity transmits regular self-portraits during its journey across Mars.

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JPL-CALTECH/MSSS/NASA

Curiosity has been exploring Mars for 2500+ days. Its primary mission was completed after 687 days, but the rover has proven much sturdier than anticipated, and continues its journey across the Red Planet.

By Henrik Vinther Nielsen

JPL-CALTECH/MSSS/NASA

Though water does not ow in torrents on Mars, the landscape clearly indicates that this was once the case: the layers in the foreground slope towards a basin, indicating that the plain was shaped by liquid water.

LANDSCAPE FORMATION Water shaped this now-barren Martian plain.

UNIVERSITY OF ARIZONA/JPL-CALTECH/NASA

While Curiosity takes samples of Mars’ surface, the Mars Reconnaissance Orbiter transmits aerial photos back to scientists on Earth. The probe has discovered a bedrock layer which displays evidence of acidiferous water.

AERIAL SUPPORT

Orbiter shoots and transmits photos from space.

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X-RAY VISION Spectrometer spots minerals under the surface.

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Curiosity is equipped with several instruments for scanning Mars.

The Alpha Particle X-Ray Spectrometer analyses the chemical make-up below ground, identifying minerals without having to extract them.

Cu ri os it y’ s

ty re -m ar ks

PhotoDoc IS THE CURIOSITY ING R O LAST W K ROVER ON MARS.

UNIV. OF ARIZONA/JPL-CALTECH/NASA

JPL-CALTECH/MSSS/NASA

Over seven years, Curiosity has only covered about 21km, corresponding to 8 metres a day, because scientists must steer the rover carefully across the uneven terrain in order not to cause permanent damage.

ROVER ON THE MOVE Orbiter takes a photo of Curiosity.

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Winds are rarely high on Mars, but they include very fine dust particles which can enter the machinery of Curiosity. Dust devils such as this one are not uncommon and can have diameters of up to hundreds of metres.

JPL/NASA

THE DEVIL IN THE DUST Fine dust presents a huge challenge for Mars missions.

JPL-CALTECH/NASA

This picture was taken shortly after the landing in 2012.

The mountain in the background is Mount Sharp, which the rover has circled for almost seven years to find out whether erosion by water shaped the mountain.

LIVE TRANSMISSION! One of Curiosity’s first images showed Mount Sharp.

The red area in the photo is really black, but Curiosity is equipped with a ChemCam, which reveals chemical compounds in the ground. In this case, the camera has spotted a small deposit that could be iron ore.

JPL-CALTECH/MSSS/NASA

IRON UNDERGROUND Curiosity’s ChemCam colours the world in search of compounds.

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BROWN UNIVERSITY/JPL/JHUAPL/MSSS/NASA

PhotoDoc IS THE CURIOSITY ING K R O W LAST ROVER ON MARS.

Soon, Curiosity will no longer be alone. This year NASA launches the next rover, Mars 2020.

It is scheduled to land in February 2021 in an area called the Jezero Crater, where X-rays have revealed large quantities of minerals in the ground.

MARS 2020’S LANDING SITE X-rays disclose a mineral-rich touchdown site.

scienceillustrated.com.au

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Editor: Jeppe Wojcik

ANSWERS ON PAGE 4

BREAK THE CODE

NUMERACYACY

CODE QUESTION 1

s ree problem Solve the th ed in b m co ďŹ nd a on the left to urn to page 4 .T code phrase ers and the sw an e th r fo the phrase. meaning of

1

What word is written in code here?

4

Which number belongs in the empty space?

5

Place numbers in the 6 empty spaces, so the total of each piece of pie is the same. The totals of the 3 circles must also be the same, but different from that of the pieces.

CODE QUESTION 2

LOGIC

2

Prometheus is not standing beside Perses or Atlas. Helios is shorter than Perses. Who is far right?

SHUTTERSTOCK

CODE QUESTION 3

6

3

Place the numbers 1-12 so that the total for each of the 3 large ovals and the central circle is 39. Which number belongs in the yellow circle?

ANSWERS Each answer makes up part of a code phrase.

If 5 pumpkins and 2 bunches of bananas cost $16, and 2 pumpkins and 3 banana bunches cost $13, what is the price of 1 pumpkin and 1 bunch of bananas?

Write the code words here:

1 2 3 Do you know what it means? Turn to page 4 to find out (no peeking!).

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7

Toss these three coins up in the air. What is the chance of at least two of them landing with the 5 facing upwards?

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