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?

by Jonny O'Callaghan
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

by Jonny O'Callaghan
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

by Jonny O'Callaghan
An eye-opening look into how vision and sight works.
218

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

by Jonny O'Callaghan
The incredible abilities of this eight-legged wonder of the natural world are exposed in this illustration.
137

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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

by Jonny O'Callaghan
Take a virtual stroll around the Red Planet.
99

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

by Jonny O'Callaghan
How do these incredible machines traverse both land and sea?
85
Apollo_15_flag,_rover,_LM,_Irwin Space

Top 10: Videos from the Moon landings

by Jonny O'Callaghan
We’ve picked our ten favourite videos from the six manned missions to visit the Moon. Did Neil Armstrong’s first steps make it to number 1? Find out after the jump.
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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

by How It Works
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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