Wonders of the World

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Discover the secrets of the International Space Station; revolutionary nano-robots; the 13,171 mile long Great Wall of China; the mysterious story of Machu Picchu; the figures of Easter Island and much more.

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Human achievement

Find out why we're the most intelligent beings on the planet; how fire and language shaped our evolution; why the common antibiotic is the key to our modern world; why altruism is essential to human survival and much more.

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our planet

Uncover jaw-dropping freak weather events; the science behind tornadoes, lightning, the jet stream and the auroras; the amazing secrets hidden in the depths of every volcano; how the Grand Canyon was created and much more.

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natural world

Meet the deadliest animals and plants in the world; the creatures who use magnetism and quantum physics to navigate; the world's cleverest, fastest and biggest animals; the secrets behind evolution and much more.

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Page 8 1. Engineering International Space Station....8 Terracotta Army.........................12 Easter Island................................ 14 Channel Tunnel...........................16 Seven Wonders of the Ancient World.................18 Panama Canal.............................22 Acropolis........................................24 Nanobots.......................................26 Colosseum of Rome.................30 Stonehenge..................................32 Great Wall of China....................34 Machu Picchu..............................37

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Page 42 2. Natural World Animal intelligence....................42 Biggest lifeforms.......................46 Oldest living things....................48 Fastest animals.........................50 Deadliest living creatures......52 Animal eyesight..........................56 Sense of smell.............................58 Magnetic sensitivity.................60 Hibernation...................................64 Swarms..........................................66 Galรกpagos Islands.....................68 Evolution........................................70 Deep sea vents........................... 74 Serengeti migration.................76

3. Human Achievement Intelligence...................................82 Physical feats..............................86 Using fire.......................................88 Altruism.........................................90 Electricity......................................94 Antibiotics.....................................96 Language......................................98 Splitting the atom..................102 Time..............................................104 Money..........................................109

issue ONE OCTOBER 2013 Future Publishing Ltd, 30 Monmouth Street, Bath, BA1 2BW Email: scienceuncovered@futurenet.com Web: www.science-uncovered.com Find us on Facebook: www.facebook.com/sciuncovered Follow us on Twitter: @sciuncovered

Editorial Editor: Andrew Ridgway, andrew.ridgway@futurenet.com Art editor: Fraser McDermott, fraser.mcdermott@futurenet.com Managing editor: Catherine Ellis, catherine.ellis@futurenet.com Production assistant: Dom Reseigh-Lincoln, dom.reseigh-lincoln@futurenet.com Design: Paul Blachford, Mat Gartside, Matt Orton Images: ThinkStock.co.uk

Contributors Graham Barlow, Aaron Boardley, Matthew Bolton, Alex Cox, Catherine Ellis, Ian Evenden, Ben Everard, Sam Gibbs, Dan Grabham, Duncan Greere, Andrew Gregory, Christian Hall, Matthew Hanson, Tim Hardwick, Adam Hurrell, Ian Osborne, Christopher Phin, Steven Raynes, James Rivington, Luis Villazon

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4. Our Planet Freak weather.......................... 114 The jet stream..........................118 Lightning....................................120 Tornadoes..................................122 Tsunamis....................................124 Volcanoes...................................126 Glaciers........................................130 Deserts........................................132 The Grand Canyon..................134 The Great Barrier Reef.........136 Mount Everest..........................138 Rainforests.................................140 Auroras........................................ 144

Next ISSUE ON SALE: Thursday 5 December Printed in the UK by William Gibbons and Sons Ltd on behalf of Future Distributed in the UK by Seymour Distribution Ltd, 2 East Poultry Avenue, London EC1A 9PT Tel: 020 7429 4000 Overseas distribution by Future Publishing Ltd, Bath Tel: +44 (0)1225 442244

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Engineering The Colosseum is at the centre of Rome’s ancient landscape (and is now right next to a busy dual carriageway)

Are you not entertained?

The magnificent Colosseum is one of the most impressive remnants of the Roman Empire, and a constant reminder of its bloodthirsty legacy t’s one of Italy’s most famous landmarks, but if you were to travel back in time to ancient Rome and ask for directions to the Colosseum (in Latin, of course), you’d be met with blank looks. Its original name was the Flavian Amphitheatre, after the dynasty of emperors who had it constructed (Vespasian, Titus and Domitian).

The earliest record we have of it being called the Colosseum comes from Bede, an Anglo-Saxon scholar writing in the Middle Ages. The new name might have come about because of a neighbouring 30m-high statue of the Emperor Nero, which stood near the site. This statue - or colossus - has long since been scavenged by the city’s inhabitants for scrap.

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The Colosseum is linked in most people’s minds with gladiators, but gladiatorial combat was used to entertain the Roman crowds long before the amphitheatre was built. Despite their modern reputation as tyrants, Caligula and Nero were both loved by the common people, largely because they held great gladiatorial contests in wooden theatres, which were destroyed by the fire in 64AD (the same fire in which Nero is said to have fiddled while Rome burned).

“Gladiatorial combat was used to entertain crowds long before the Colosseum was built”

In the unrest that engulfed Rome after Nero’s suicide, the emperor Vespasian took the politically brilliant step of building a permanent stone amphitheatre, with a capacity of around 50,000. The games held there kept the restless population of Rome amused, and provided cheap entertainment for every level of Roman society - from the sacred Vestal Virgins (priestesses of the goddess Vesta) to lowly household slaves.

A stage without actors The seating was strictly segregated, with women other than the priestesses confined to the uppermost tier. Senators, knights and ambassadors enjoyed the privilege of sitting lower down, closer to the action, with the general public seated behind them. Only

Engineering

Building the Colosseum

Make your own amphitheatre

Thousands of tourists now visit the Colosseum every day, and there is a museum to Eros on the top floor

The Colosseum has survives earthquakes, a lightning strike and invasion by fearsome barbarian tribes from the north when the Roman Empire eventually fell - but its greatest enemy has always been the people of Rome.

Here’s why it’s lasted so long.

3. Stone pillars

The structure is supported by pillars made out of squared-off blocks of tufa, a form of limestone formed by mineral deposits in lakes and rivers, which is abundant in Italy and Turkey.

4. Facade

1. Foundations

The building’s facade was made of 100,000 cubic metres of travertine, a similar material to tufa, but less porous. This gives it a smoother finish, like a lighter, cheaper version of marble.

The whole massive structure sits on a ring of concrete 51 metres wide and 12m deep. The site of the Colosseum used to be a lake, so the Romans had to drain the site and provide this heavy base to support the building.

5. Fight in the shade 2. Seats

The steeply banked seating areas, as in a modern-day stadium, meant that all spectators had a good view.

In contrast to today, however, the better seats in the amphitheatre were originally made of marble, which has long since been reused elsewhere.

Missing from the present-day Colosseum (but accurately represented in the film Gladiator) is the velarium - a retractable covering, which provided shelter from the sun and rain and also created a cooling breeze for the spectators.

6. The arena

Plants thrive in the masonry. In the 19th century, attempts to protect the stone by removing the plantlife failed

The fighting ground itself was a wooden platform, like a theatre stage, covered with sand to soak up the blood. Originally the arena may have been able to hold water to host mock sea battles, but this facility would have been lost when the hypogeum was built.

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7. Underground

The hypogeum (literally ‘underground’) was a warren of cells and corridors. Animals, prisoners and gladiators would have spent their last moments here before surfacing into the arena.

The use of arches and vaults made it possible to create a structure that was both enormous and incredibly strong

actors (disreputable), gravediggers (unlucky) and former gladiators were barred from the Colosseum; for the rest of Roman society, it provided a centrepiece.

Prisoners from conquered areas were forced to fight, condemned men were executed in combat with gladiators, and it is said that Christian martyrs were put to death (although there is debate about whether this actually took place within the Colosseum itself) - all to entertain the people of Rome. It’s a great irony then that, after centuries of neglect after the fall of the Roman Empire, the amphitheatre was only saved from having its stone stolen and reused by Pope Benedict IV, who declared it a church dedicated to the Christian martyrs.

Andrew Gregory

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Natural world

All-seeing eyes The evolution of eyesight in nature has taken many a turn, yet rarely met a blind alley. See for yourself just how varied and awesome animal vision can be… ision is a crucial sense for the survival of most animals. In fact your eyes are the most complex and refined organs this side of your brain.

That’s because nature has been busy honing your visual perception since Pre-Cambrian times – for some 600 million years.

According to scientists, tiny oceanic creatures called hydras were the first to evolve light-receptive cells – not in specialised visual organs, but in their mouths to help search out their prey (apparently some animals really did eat with their eyes). Mutations in a gene called opsin allowed these cellular receptors to interact with different proteins in new ways

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– interactions that underlie the genetic machinery of modern-day human vision.

Hawk vision The human eye is like a camera, using a single lens to focus images onto a lightsensitive membrane lining the inside of the eyeball called the retina. Around 147,000 cone cells per square millimetre in the retina can distinguish about 10 million colours – but that pales in comparison to the eyesight of a hawk.

A hawk’s eyes boast 300,000 cones per square millimetre, and unlike humans, each cone has an individual nerve fibre connecting it to the bird’s brain, allowing it

to see up to eight times as much detail. Not only that, in addition to the ‘trichromatic’ red, green and blue light spectrum that we can see, many bird species can also detect ultraviolet and fluorescent light, allowing them to better discern mating plumage and detect the trails left by prey.

Bug eyes Birds aren’t the only creatures that put our eyesight to shame. Bees are able to see a whole world of ultraviolet patterns in the petals of flowers, and can use these as maps to direct them to their favourite plant’s cache of nectar. It doesn’t stop there, either.

Honeybees can perceive movements that are

Images © ThinkStock

A hawk’s eyes are eight times more sensitive than a human’s

Natural world

Through the eyes of a dragon Dragonflies aren’t just aerial acrobats. These fast-flying insects boast outrageously honed vision, optimised for seeking out mosquitoes, wasps and other airborne creatures in low-light conditions with devilish precision. Behold the most complicated insectoid eye structure in the world.

1 Look around The two semi-spherical compound eyes of the dragonfly are so large that they occupy half of its head. Processing a 360-degree visual field is no easy task, which is why over 80 per cent of a dragonfly’s brain is dedicated to doing precisely that.

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Each eye is made up of 30,000 individual lenses called ‘ommatidia’ – in contrast to your own eyes, each of which contains just the one. Every single lens boasts a series of light sensitive cells, making for exceptionally good eyesight, whatever the weather conditions.

separated by 1/300th of a second (compared to the human eye’s 1/10th of a second), which means that if they sat down to enjoy A Bug’s Life at the cinema, they would be able to differentiate each frame projected on the screen. With five eyes working together – three that distinguish light intensity and two movement-detecting eyes, each containing around 7,000 lenses – bees also have a greater field of vision than humans.

That’s some feat for an unassuming insect, but nothing compared to the strength of vision of the tropical ogre-faced spider; its eyes are so sensitive to light that the membrane covering them is destroyed at dawn and renewed each night, giving it powerful nocturnal vision that puts cats, sharks and even owls in the shade.

Tim Hardwick

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These non-reflective black spots at the front and top of the dragonfly’s eyes are known as ‘pseudo-pupils’.

These concentrated areas of ommatidia are amazingly sensitive, and are perfect for spotting tiny mosquitoes in the air and avoiding predators such as birds.

4 Technicolour

Human eyes have three proteins, covering the trichromatic range of red, green, and blue light. Dragonflies have five proteins, allowing them to see polaised and ultra-violet light too, which humans are blind to without the help of special sunglasses.

5 Greedy vision

Dragonflies also have three smaller eyes called ‘ocelli’, located centrally on the top of the head in a trianglular shape. These are highly sensitive to light intensity, and provide information on the position of the horizon that helps the insect orient its acrobatic flight paths and hunt down prey.

Subtropical super-optics Nothing comes close to the spectral sensitivity of the mantis shrimp

Along the equator, in the tropical and subtropical waters off Africa and South America, lives the predatory mantis shrimp. Noted for its aggressive nature and powerful claws, the colourful crustacean is also known for its killer vision. Its rarified eyes are compound like that of a dragonfly, but rather than settle for the insect’s five colour-receptive rods, the mantis shrimp boasts an astounding 16. Just think: this The mantis shrimp can detect 16 colours of light, little creature can resolve red, green, blue, plus and is strong enough to break aquarium glass 13 other colours your eyes can’t even process.

Not only that, the reef-dweller also perceives ultraviolet, infrared and polarised light, making it runaway victor in the evolutionary arms race for most complex eyesight on the planet. No wonder biologists call them “shrimps from Mars”..

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Humans

Power to the people

An electric circuit is formed when electrons move between atoms of a conductive material, carrying a negative charge along with them

ome 2,600 years ago, the Ancient Greeks discovered that when amber was rubbed against animal fur, it could be used to attract small objects such as dust particles. This was one of the first times humans harnessed the amazing power of electricity, but it was a long time until it became a part of our everyday lives.

Electricity is a transfer of energy from one place to another, but it only moves through certain materials. To understand why, we need to know the structure of the atoms that make up those substances.

Each atom consists of a nucleus, which is a cluster of positively charged particles

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called protons, and neutral particles called neutrons. This nucleus is surrounded by a shell of negatively charged particles called neutrons. In materials that conduct electricity well, such as copper, not all of these electrons are strongly bound to the nucleus, and some can move from one atom to another. These are called ‘free electrons’.

Current affairs If an atom loses some of its free electrons, it has an positive charge. Free electrons will attempt to move there to neutralise it. When they move, they carry a negative charge along with them. This is an electric current.

Other materials, like glass and rubber, don’t conduct electricity well because their electrons aren’t free to move around. These are called insulators. The phenomenon noticed by the Greeks was the result of a static electric charge, which is created when insulating objects are rubbed together.

When this happens, some atoms gain electrons, becoming negatively charged, whereas others lose electrons, becoming positively charged. An object’s static charge is neutralised when it’s brought close to a conductive material, or a material with an opposite charge, enabling electrons to move.

Catherine Emma Ellis

Images © ThinkStock

The ability to understand, create and control electric currents put technological innovation into overdrive

Humans

Putting the spark in daily life The ability to manipulate electricity had an incredible effect on the speed of technological progress. Modern devices would seem magical to early innovators, but there’s still an key collection of principles behind all electrical technology

Generators

When you place a magnetic field near a wire, the magnetism pushes electrons through the wire.

Likewise, passing a current through a wire will generate an electric field. This relationship is used in a generator, which uses a mechanism to move a magnet near a wire to induce an electric current in it.

AC/DC

Batteries use direct current (DC) to move electrons through a circuit, and they always travel in the same direction. Electricity is sent to your home using alternating current (AC). The current in an AC circuit reverses 50 times per second (60 times in the US).

Volts and amps

The number of electrons moving in a circuit is measured in amps, while the pressure that forces them through the circuit is measured in volts. By upping the voltage, you can transmit electricity long distances through a thin wire. At the other end, a power transformer reduces the voltage to a level that’s safe for household use.

Motors

An electric motor uses an electromagnet – usually created by wrapping a copper wire many times around an iron bar – to make kinetic energy out of electrical energy. When magnets are placed in the right place, you can use AC to very quickly flip the magnet back and forth, creating motion.

Batteries

Batteries consist of two terminals, with an electrolyte solution in between. One of these terminals, the cathode, is full of negatively charged ions, created by an electrochemical reaction within the electrolyte.

The other, the anode, is full of discharged ions. If you connect the terminals with a conductor, such as a copper wire, a current will flow through it.

Shocking discoveries

How the Victorians empowered the human race

Michael Faraday’s discoveries led to the creation of the world’s first incandescent lightbulb

In the early 19th century, Michael Faraday – perhaps the first celebrity scientist – famously gave jaw-dropping displays of static electricity in London. Until then, people had observed the amazing power of lightning storms in cloudy skies, but been unable to understand why they happened. Ancient civilisations believed that enraged omnipotent beings were responsible for lightning forks – in Norse mythology, it was believed that thunderstorms were the result of the god Thor riding his chariot through the skies, with lightning bolts appearing when he threw his mighty hammer, Mjölnir. It wasn’t until Faraday’s discovery that we learned the true nature of electricity, and how to harness it for ourselves.

Faraday’s major contribution was the law of induction, which shows the connection between electricity and magnetism. He found that

changes in a magnetic field can be used to create a current in a wire. This is the basic principle behind both electric motors and generators, and led to a whole new branch of engineering.

The transformation of electricity from a curiosity into a powerful new technology laid the foundations for the electrical revolution that followed. Nikola Tesla and Thomas Edison soon produced the first incandescent lightbulbs, which used electricity to heat a metal filament, making it glow. Another early application of electricity was the electric telegraph, which enabled messages to be sent over great distances.

Electricity had been played with, demonstrated and investigated for thousands of years prior, but Faraday put it in the hands of the people for the first time, providing the key to unlocking the electric age.

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Our planet

Volcanoes: Earth’s inner source of power Volcanoes are one of the Earth’s most destructive forces, but what’s the secret of this most violent geological phenomenon, and could they have a beneficial side, too?

Let’s take a look at volcanoes throughout history

olcanoes are an awesome demonstration of the heat and energy trapped within the Earth.

Our planet was extremely geologically violent when it was formed 4.5 billion years ago, but as it cooled, a solid crust formed on the Earth’s surface. This crust is less than 100 miles thick, and is made up of tectonic plates that move around over time. Areas of high volcanic activity are usually where the Earth’s tectonic plates rub against each other. Friction caused by their movement melts the rock beneath the Earth’s crust, causing chambers of magma, or molten rock, to build up. This magma becomes a volcano when it’s forced through rifts in the plates, erupting onto the surface as lava.

Such eruptions also emit gas, rocks and (most notably) ash clouds, all of which can cause terrible devastation on the surface of the planet.

Around the world, there are about 1,500 volcanoes classified as currently active, almost 90 per cent of which are located in the so-called ‘ring of fire’ , which circles the Pacific Ocean – this region is sometimes referred to as the ‘circum-Pacific belt’.

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Types of volcanic eruption vary according to the composition of the magma forcing its way through the Earth’s crust. Magma with a high silica content and a relatively low temperature is very slow moving, and doesn’t travel far. Because the slow-moving, viscous lava solidifies quickly, the volcano grows into a tall, conical structure called a stratovolcano or composite volcano. They’re the most common type, and famous examples include Krakatoa and Vesuvius.

Explosive eruptions Because a stratovolcano’s lava is so thick, gas build-ups often find it difficult to escape.

As a result, when gas content is high, an explosive eruption can occur, throwing rocks, ash and lava great distances at speeds of up to 200mph. These eruptions can be so violent they destroy part of the volcano itself. For example, when Mount St Helens erupted in 1980, it lost 13 per cent of its volume, and its height was reduced by around 1,300 feet.

If the lava has less silica, it’s less viscous too. This type of lava flows further before solidifying, forming a wide, squat volcano..

“The Hawaiian islands are still being formed by a chain of under-sea volcanoes. The largest of these, Mauna Loa, is also the largest volcano on Earth, standing 13,680 feet above sea level” 125

Our planet

Myths and legends Geological phenomenon or ancient gods? Many civilisations had their own unique take on the power of volcanoes In Greek mythology, Hephaestus (Vulcan to the Romans) was the god of fire, metalworking, the underworld and volcanoes. He served as a blacksmith to the gods, making all their weapons.

Hephaestus’ smithy lay beneath the crater of the volcano of Aetna in Italy. It was said that when he got angry, he turned up the fires of his furnace, causing an eruption.

To the Hawaiians, Pele was the goddess of fire, lightning, wind, and volcanoes. She was deemed responsible for all volcanic activity on the islands of Hawaii, which she controlled from her home in the Halema’uma’u crater atop Kīlauea, the world’s most active volcano. Eruptions were said to be the result of her yearning for her true love, the chieftain Lohiau.

To the Māoris of New Zealand, Rūaumoko is the god of earthquakes, volcanoes and seasons. He is the youngest son of Rangi, the sky father, and Papa, the earth mother. He was accidentally thrown into the world below while still a baby, from where his moving around causes earthquakes and volcanoes.

Apollo in the Forge of Vulcan by Spanish Baroque artist Diego Velázquez, which was painted in 1630

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