Not only does your heart do amazing things, it does so tirelessly, every minute of every day from the moment you’re born (actually, even a bit before then) to the instant that you die. It weighs somewhere between 0.2 to 0.3 kg – slightly more if you’re male, less if you’re female. Its sole purpose is to push blood through your circulatory system, providing crucial oxygen and other nutrients to all your organs.

The heart is considered a double pump because the right half sends ‘used’ blood to your lungs. There, the blood drops off a load of carbon dioxide and picks up some fresh oxygen, which you have helpfully provided by breathing. Then the oxygenated blood returns to the left half of the heart. This ‘heart-to-lungs-to-heart-again’ trip is known as pulmonary circulation. The left side of the heart then pumps this oxygenated blood to every organ in your body other than your lungs. Your brain, your skin, the muscles in your thigh, your spleen – they all get blood (and therefore oxygen) by virtue of your beating heart.

Even the heart itself gets blood, via a special set of veins and arteries known as the coronary system. The myocardial muscle within the wall of the heart needs oxygen and other nutrients to keep beating. Unfortunately, the coronary arteries that do this job are very narrow, between 1.7 and 2.2 millimeters in diameter. If they become clogged with cholesterol or other fatty deposits, the heart stops working. This is bad for you.

Of course, the relatively simple concept of the double pump is fairly complex in practice. A series of valves control blood flow to the heart’s four chambers, allow for the build-up of enough blood pressure to get the job done, and direct the blood to the correct veins and arteries.
Science

How does the heart work?

We take a look inside the heart to find out how it keeps us ticking.
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One of the most numerous armoured vehicles during World War II, the Soviet Union’s T-34 medium tank is considered by military historians to be one of the most important and influential tanks ever to be built.

Evolving out of the BT series of fast tanks (Soviet cavalry tanks with thin armour and high mobility), the T-34 at its introduction was the first tank to sport a complete balance between firepower, mobility, protection and longevity – something that modern tanks now take for granted. Further, it was an especially refined and simple design that allowed for costs (135,000 rubles) and production time frames to be kept low, meaning that many tanks could be produced in very little time and allow Russia to mitigate its higher-than-average losses quickly and cheaply. Indeed, this became a very important factor towards the end of the war when the superior – but hard and expensive to manufacture – German Tiger and Panther tanks could not be replaced fast enough.

The T-34 was fitted with a good balance of weaponry, sporting a 76.2mm F-34 tank gun – ideal for taking down medium and light armoured enemy vehicles – and twin 7.62mm DT machine guns, perfect against unarmoured targets and to suppress advancing soldiers. Its armour also offered a great balance between protection and weight, with up to 63mm of armour plating standing between its crew and the shells and bullets of the enemy. This meant that only the largest of enemy cannons – such as the 88mm beast fitted to the German Tiger tank – could breach its hull or turret and, considering its high top speed of 33mph, this was only possible if it became entrenched or caught unawares. By keeping the armour thickness to a medium level though, the total weight of the T-34 was kept down to 26 tons, under half that of the German Tiger and allowing the T-34 unrivalled dynamism in the field.

Historically, the T-34 will be remembered as the vehicle that swept German forces from Russia, advancing from Stalingrad all the way to Berlin in 1945. However, its usage continued right up to 1958, when it was finally replaced by its successor the T-54. Despite its official retirement however, the T-34 has continued to be used in Third World militaries right up to the present day and has also found itself bought and operated by both private collectors and military museums.

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History

T-34 Tank Cutaway

How It Works breaks down a T-34 tank to see what made it one of the most popular armoured vehicles of World War II
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A star with a mass of less than 1.5 solar masses (the mass of the Sun) forms a white dwarf at the end of its lifetime, owing to its gravity being too weak to collapse it further. If the mass of a star is greater than five solar masses, the forces will be so intense that the star collapses past the point of a neutron star and becomes a black hole. However, between these two extremes a neutron star will form as the result of a supernova, although only approximately one in a thousand stars will become one.

As a star runs out of fuel it will eventually collapse in upon itself. In the formation of a neutron star, the protons and electrons within every atom are forced together, forming neutrons. Material that is falling to the centre of the star is then crushed by the intense gravitational forces in the star and forms this same neutron material. Like the Earth, magnetic fields surround neutron stars and are tipped at the axis of rotation, namely the north and south poles. However, the magnetic field of a neutron star is more than a trillion times stronger than that of Earth’s.

The gravitational forces in a neutron star are also incredibly strong. The matter is so densely packed together into a radius of 20 kilometres (12 miles) that one teaspoon of mass would weigh up to a billion tons, about the same as Mount Everest. They also spin up to 600 times per second, gradually slowing down as they age.

Oddly enough, as a neutron star becomes heavier it also becomes smaller. This is because a greater mass means a greater force of gravitational attraction, and therefore the neutrons are squeezed more densely together. In fact, if you were able to drop an object from a height of one metre on the surface of a neutron star, it would hit the ground at about 2,000 kilometres (1,200 miles) per second.

Space

Peer inside a neutron star

We take a look into the heart of one of the most massive objects in the universe.
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Hurricanes are massive heat engines. They form over tropical waters with a minimum temperature of 27˚C (80.6˚F). Hot water evaporates very quickly, rising up through the atmosphere until it condenses into clouds and water droplets. The incredible thing is that condensation itself creates even more heat. The recharged air soars even higher, building a cluster of towering, fat thunderstorms called a tropical disturbance.

Once the heat engine has been jump-started, rapid condensation within the storm continues to force air upward while more hot air rushes in from below to fill the void. This suction of hot air from the ocean surface creates lower and lower air pressure. When air rushes from high pressure to low pressure, it creates powerful winds. When wind velocity reaches 38mph (60 kph), the storm is called a tropical depression.

Satellite images of hurricanes show a swirling vortex of storm clouds. The spin is caused by two main forces: the Coriolis force and the pressure gradient. In the northern hemisphere, the Earth’s rotation pulls winds to the right (Coriolis force), but the extreme low pressure at the storm’s centre pulls them back to the left, creating a net counter- clockwise spin. The opposite is true south of the equator. As the heat engine chugs on, more water condenses, more heat rises, the pressure drops further and spin increases until winds reach 38 to 75mph (60 to 120 kph), enough to qualify as a tropical storm. Seven out of ten tropical storms spin even faster than 75 mph (120 kph), officially becoming a hurricane.

Environment

Inside a hurricane

What’s going on inside this deadly force of nature?
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Cells are the building blocks of all living organisms. Individual cells are classified as living things, and there are millions of organisms that are unicellular across the planet.

As they are living units, cells consequently need energy, and therefore respire to survive. Parts of the cell, called organelles, work like organs of a body. Energy for the cell to process can be provided by the cell, such as through photosynthesis in plants, or absorbed into the cell through cell membranes and then processed within it by the mitochondrion. Single cells operate like this, and there are billions of unicellular organisms that survive independently or within multicellular organisms. These single cell organisms are generally prokaryotic cells, which are much smaller and have fewer organelles, most importantly lacking a nucleus. Multicellular organisms are primarily made up of eukaryotic cells which are more complex and can therefore specialise so the organism can become more complex. They do this by grouping together to form tissues, which then group to form organs within the organism.

Cells reproduce to replace old, damaged cells in an organism, to allow growth or growth of a new individual. In unicellular organisms, cell reproduction is obviously the only way a population will grow. Prokaryotes favour binary fission, where all genetic information is doubled and then the cell divides into two new, identical cells. Eukaryote cells use either mitosis, which results in two identical organisms or cells, or meiosis, which results in each new cell having half the number of chromosomes of the original cell.

Science

What’s inside a cell?

The building blocks of life are explained as we take a look inside an animal cell.
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At the centre of every atom is a nucleus containing protons and neutrons. Together, protons and neutrons are known as nucleons. Around this core of the atom, a certain number of electrons orbit in shells. The nucleus and electrons are referred to as subatomic particles. The electrons orbit around the centre of the atom due to the charges present; protons have a positive charge, neutrons are neutral and electrons have a negative charge. It is the electromagnetic force that keeps the electrons in orbit due to these charges, one of the four fundamental forces of nature. It acts between charged objects – such as inside a battery – by the interaction of photons, which are the basic units of light.

An atom is about one tenth of a nanometre in diameter. 43 million iron atoms lined up side by side would produce a line only one millimetre in length. However, most of an atom is empty space. The nucleus of the atom accounts for only a 10,000th of the overall size of the atom, despite containing almost all of the atom’s mass. Protons and neutrons have about 2,000 times more mass than an electron, which results in the electrons orbit the nucleus at a large distance as they in turn have an extremely low mass.

An atom represents the smallest part of an element that can exist by itself. Each element’s atoms have a different structure. The number of protons inside a specific element is unique. For example, carbon has six protons whereas gold has 79. However, some elements have more than one form. The other forms – known as isotopes – will have the same number of protons but a different number of neutrons. For example, hydrogen has three forms which all have one proton; tritium has two neutrons, deuterium has one neutron and hydrogen itself has none.

As different atoms have different numbers of protons and neutrons, they also have different masses, which determine the properties of an element. The larger the mass of an atom the smaller its size, as the electrons orbit more closely to the nucleus due to a stronger electromagnetic force. For example an atom of sulphur, which has 16 protons and 16 neutrons, has the same mass as 32 hydrogen atoms, which each have one proton and no neutrons.

(Image credit: Science Photo Library)
Science

Inside an atom

We take a look inside the particles that make up all matter in the known universe.
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Unlike rocky planets such as Earth, the sun does not have a definitive outer boundary. However, the different layers beneath the Sun’s surface are defined by their temperatures and density. Although the core is on average the hottest part of the Sun, the complex relationship between rising heated gases and falling cooled gases create temperature fluctuations within the layers of the Sun itself.

(Image courtesy of NASA)
Space

What is the Sun made of?

We take a look inside the heart and soul of our Solar System.
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The dawn of the digital format has revolutionised the imaging industry and in turn the way we work our cameras. Furthermore the internal DNA of the camera body has been entirely restructured to make way for the new electrical system; or has it?

In fact film and digital cameras operate in a similar manner. Varying the size of the lens’s diaphragm (aperture) in tandem with the amount of time the shutter is open, focusing light on to the image detection material, the only difference being that this is now received in an electrical rather than chemical form.

A DSLR (digital single-lens refl ex) camera employs a mechanical mirror system that directs the light travelling through the attached lens upwards at a 90 degree angle allowing the photographer to compose the shot through the viewfinder. As the shutter button is pressed the exposure takes place: the mirror swings out of the way and the shutter opens allowing the lens to project the light on to the image sensor. In low light scenarios the shutter will need to stay open for a longer period of time for the image to be recorded, this is why photographers support their cameras with tripods as the smallest degree of camera shake will disturb the quality.

The sensor is formed of millions of pixels laid out in thousands of rows and columns: the more pixels or dots of light, the higher the megapixel count and in theory the higher the resolution. The light travels through a colour filter above the individual sensors and is converted from light waves into an analogue signal which is then processed through a digital convertor. Next the conversion is fine tuned through a series of filters that adjust aspects such as white balance and colour. The resulting image can be made into a JPEG by compressing the file size and discarding unnecessary pixels. The final image is shown on the LCD.
Technology

Inside a DSLR camera

We go under the hood to find out how all the magic happens.
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The biology of the eye is extremely complex, especially when you consider the human eye only has the rough diameter of 2.54 cm and weighs approximately 7.5 grams. It is made up of around 15 distinct parts, all with different roles to play in receiving light into the eye and transmitting the electrical impulses, which ultimately relay image information to our brains so that we can perceive the world we live in.

The eye is often compared to a basic camera, and indeed the very first camera was designed with the concept of the eye in mind. We can reduce the complex process that occurs to process light into vision within the eye to a relatively basic sequence of events. First, light passes through the cornea, which refracts the light so that it enters the eye in the right direction, and aqueous humour, into the main body of the eye through the pupil. The iris contracts to control pupil size and this limits the amount of light that is let through into the eye so that light-sensitive parts of the eye are not damaged.

The pupil can vary in size between 2 mm and 8 mm, increasing to allow up to 30 times more light in than the minimum. The light is then passed through the lens, which further refracts the light, which then travels through the vitreous humour to the back of the eye and is reflected onto the retina, the centre point of which is the macula.

The retina is where the rods and cones are situated, rods being responsible for vision when low levels of light are present and cones being responsible for colour vision and specific detail. Rods are far more numerous as more cells are needed to react in low levels of light and are situated around the focal point of cones. This focal gathering of cones is collectively called the fovea, which is situated within the macula. All the light information that has been received by the eye is then converted into electrical impulses by a chemical in the retina called rhodopsin, also known as purple visual, and the impulses are then transmitted through the optic nerve to the brain where they are perceived as ‘vision’. The eye moves to allow a range of vision of approximately 180 degrees and to do this it has four primary muscles which control the movement of the eyeball. These allow the eye to move up and down and across, while restricting movement so that the eye does not rotate back into the socket.

Science

Look inside the human eye

An eye-opening look into how vision and sight works.
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Octopuses are the superheroes of the animal kingdom, with so many amazing abilities and adaptations that it begins to look greedy. They can solve mazes, open screw-top jars and use tools. They can walk, they can swim and they can even jet propel themselves at high speed. They can change colour, imitate other animals, squirt ink, inject poison and jettison their own legs. When you can do all that, who cares if you can predict football results or not?

Although they are molluscs, octopuses don’t have a shell or bones and the only hard part of their body is a small beak, made of keratin. This allows them to squeeze through extremely small gaps – an octopus a metre across can pass through a tube the size of a 50 pence coin. Octopuses mainly eat crabs and small fi sh that they winkle out of crevices in rocks and coral reefs, but they can also tackle small sharks by enveloping the shark’s gill openings and suffocating them.

Octopus blood uses a greenish-blue copper pigment called haemocyanin, instead of the iron-based haemoglobin in our own blood. Haemocyanin can’t carry as much oxygen as haemoglobin, but it is actually more efficient at low oxygen concentrations and in cold water. Despite this, octopuses have poor circulation and quickly run out of energy. This may be one of the reasons for their intelligence – theydon’t have the stamina for a prolonged chase and must rely on their cunning. Male octopuses die almost immediately after mating. The females are even bigger martyrs. They guard their 20,000 eggs for a month and rather than leave the nest to hunt, they will eat some of their own legs. After that, the female dies and the eggs hatch into babies approximately the size of a walnut.

Environment

See inside an octopus

The incredible abilities of this eight-legged wonder of the natural world are exposed in this illustration.
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To date there have been 42 missions to Mars, with exactly half of them complete failures. Other than the Earth it is the most studied planet in the solar system, and for centuries it has been at the heart of wild speculation and groundbreaking scientific discoveries. Observations of Mars have not only revealed otherwise unknown secrets but also posed new and exciting questions, and it is for these reasons that it has become the most intriguing planetary body of our time. Take a look at the map above to see key geological points of interest as well as the landing and crash sites for several spacecraft.

This image of the surface of Mars was created by reconstructing data from NASA’s Mars Global Surveyor, the Mars Orbiter Laser Altimeter and observations by NASA’s Viking spacecraft.
Space

The surface of Mars

Take a virtual stroll around the Red Planet.
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The ability of hovercraft to cross dry land as well as water has seen them employed in the military and tourism sectors for many years. Although once billed as the next generation of transportation, they have somewhat decreased in popularity over the last decade. Despite this, their usefulness is still readily apparent.

The core principle of a hovercraft is that the hull of the vehicle is suspended on top of a giant cushion of air, held in place by flexible rubber that allows it to traverse difficult terrain or choppy waves without being torn apart. At the centre of a hovercraft is a huge fan that fi res air downwards, pushing the hull off the ground as high as two metres (6.5 feet). Smaller fans on top of the hull push air backwards, giving the hovercraft forward momentum. Rudders direct this fl ow of horizontal air to allow a hovercraft to change its direction.

Traditional hovercraft have an entirely rubber base that allows for travel on land or sea, but others have rigid sides that, while suited only to water, can have propellers or water-jet engines attached for a quieter craft.

Transport

Inside a hovercraft

How do these incredible machines traverse both land and sea?
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Rockets like Saturn V, the one used to launch NASA’s Apollo and Skylab programs, are multi-stage liquid-fuelled boosters. The Saturn V is considered to be the biggest, most powerful and most successful rocket ever built.

The Saturn V was 110.6m tall, 10.1m in diameter and had a payload of 119,000kgs to low-Earth orbit.

There were three stages, followed by an instrument unit and the payload (spacecraft). The total mission time for this rocket was about 20 mins. The centre engine was ignited first, then engines on either side ignited. The first stage lifted the rocket to about 70m and burned for 2.5 mins.

When sensors in the tanks sensed that the propellant was low, motors detached the first stage. The second stage continued the trajectory to 176km and burned for six mins. About halfway through this stage’s ignition, the instrument unit took control of calculating the trajectory.

Second stage complete, solid-fuel rockets fired it away from the third stage. The third stage burned for 2.5 mins and stayed attached to the spacecraft while it orbited the Earth, at an altitude of 191.2km.

It continued to thrust and vent hydrogen before ramping up and burning for six more minutes, so the spacecraft could reach a high enough velocity to escape Earth’s gravity.
Space

See inside the Saturn V rocket

This illustrated cutaway of the Saturn V shows the 110m high rocket and its 3 stages in amazing detail with full notes
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Widely considered by academics to be one of the most influential inventions of the past 1,000 years, the printing press set in motion both the democratisation of knowledge and the establishment of our modern, knowledge-based economies.

For the first time, valued texts could be produced in their thousands and – thanks to the co-evolution of nationwide and international trade routes – allowed texts to be accessed widely by the majority, not just the wealthy aristocracy and intellectual elite.

The man credited with the invention of the printing press is inventor Johannes Gutenberg, who lived and invented the press in Mainz, Germany. Here, around the year 1440 – an exact date is not known – Gutenberg designed a device based on screw presses that, when partnered with inked movable type heads, allowed paper to be quickly and efficiently pressed with letters.

The type heads were made by pouring a lead-tin alloy into a hand mould, and were then affixed to the top of movable, rectangular stalks. The stalks could then be arranged in order to create words and sentences within a rectangular container, before being fed under a screw press. The screw press then clamped a paper sheet on top of the type heads, pressing their ink onto the sheet.

While sounding crude by modern standards, in the 15th Century this was a groundbreaking invention. Before the Gutenberg press, texts were largely hand copied by monks and select few learned individuals. As such, the availability and cost of these texts was immense and they could only be accessed by a minuscule percentage of people.

Consequently, by the mid 16th Century and on to the Renaissance, printing presses had exploded all over Western Europe, producing millions of mass-produced texts on a diverse array of topics from politics to botany. Indeed, famous English philosopher Francis Bacon said that the emergence of typographical printing had “changed the whole face and state of things throughout the world.”
History

See inside the Gutenberg printing press

This exploded diagram of the Gutenberg printing press gives you a glimpse inside one of the most influential inventions of the past 1,000 years
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Designed in the aftermath of the evacuation of Dunkirk by the British Expeditionary Force, the Churchill tank was Britain’s attempt to readdress the technology gap between their ageing Matilda II battalion and the German Panzer tanks that had them out- gunned.

The result was the Mark I, a heavily armoured battle tank equipped with a two- pounder main gun, three-inch howitzer in the rear and the most advanced and robust suspension system yet conceived. It was a defensive juggernaut, designed with one goal: to dominate the European theatre of war.

From its introduction in June 1941, the tank proved a reliable and versatile weapon platform capable of engaging targets quickly and efficiently. Key to this was its high speed of 26km/h (16mph) and excellent turning ability, characteristics made possible by its multiple-bogie suspension system. The suspension was fitted to the hull under two large pannier enclosures on either side, with the tracks running over the top.

Initially, the Churchill was fitted with a two- pounder main gun and three-inch howitzer (artillery piece); however, the former was soon upgraded to a six-pounder cannon and the latter replaced with a high-calibre machine gun.

These cannons gave the Churchill decent stopping power against medium armour, yet still left them short in firepower when compared with their German contemporaries. The Churchill’s main cannon continued to be improved throughout its lifespan, with 75mm guns fitted to Mk IIIs.

Despite its average firepower, however, the Churchill’s high manoeuvrability and excellent armour made it one of the foremost tanks of WWII, being extensively deployed in Europe and North Africa.
History

See inside a Churchill Mk VII tank

Check out our illustrated guide to one of the most successful Churchill variants of World War II to discover what made it so ruthless, reliable and iconic
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Pianos work by transmitting the vibrational energy of taught wire strings into a soundboard, which in turn converts the vibrational energy into sound.

The piano achieves this through both its construction materials and action mechanisms. Pianos consist of five main parts: the frame, soundboard, strings, hammers and keys. The frame is constructed from metal and serves as a stable, immobile platform from which its strings (metal wires) and soundboard (vibration to sound conversion mechanism) can vibrate efficiently.

Steel is used as it helps mitigate unwanted vibrational energy being transmitted to the rest of the piano and surrounding area, a problem that leads to distortion of produced sounds. The hammers act as a striking mechanism, and when the piano’s keys are pressed by the player, they rise to strike their corresponding strings in order to produce vibrational energy.

The physics of the piano work in a chain-reaction. When a key on the keyboard is pressed, a complex system of jacks, pivots and levers raise a suspended hammer upwards to strike an overhung string, as well as a string damper (a felt block) that, once the string is stuck, comes into contact with the string and ceases its vibration.

In the short time between the hammer striking the wire and damper ceasing its motion, the vibrational energy is carried down the string and over a ‘bridge’, a raised bridge-shaped structure over which the string is tightly stretched.

The bridge receives this vibrational energy and transfers it into the piano’s soundboard, a wooden board chosen for its resonant properties that through the principle of forced vibration vibrate at exactly the same frequency of the struck string. Consequently, due to the large, expansive size of the board, the quiet tone created by the string is increased, and produces a loud note.
Technology

See inside a grand piano

This annotated cutaway diagram shows what goes on inside the piano when it plays
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