SCIENCE
The Universe
The Sun
The Sun is an immense sphere of plasma; intensely hot, electrically charged gas, mostly hydrogen and helium. With a diameter of 1,391,000 kilometres, it dwarfs other members of our solar system. More than one million earths could fit into it.
As it formed from the gas and grit of the solar nebulae, the sun sucked in virtually all matter for billions of miles, ending up with more than 98.8% of the solar system’s mass.
Nuclear fusion in its core powers the sun. The enormous heat and pressure generated within the sun’s centre, fusing hydrogen into helium and releasing electromagnetic energy, can take hundreds of thousands of years to move from the core, where the temperature reaches 15 million degrees Celcius, to the sun’s visible surface which is 5600 degrees Celcius.
Magnetic fields twisting in its body pull streamers of gas far into space (solar flares). The flare ejects clouds of electrons, ions, and atoms through the corona of the sun into space. These clouds typically reach Earth a day or two after the event.
The Sun dominates the solar system not only through its gravitational influence, which extends up to 200,000 astronomical units away, but also through its solar wind of charged particles, which reach beyond 100 astronomical units (far past Pluto).
An astronomical unit (AU) is 149,597,871 kilometres, or roughly the same distance between Earth and the Sun.
The Planets
The planets where shaped by the nearby sun and ended up rocky, small and dense, with at least one, Earth, orbiting at just the right distance to hold on to watery oceans and host the chemical of life.
The planets can be divided up into two groups of four.
Closest to the sun are the four inner planets, Mercury, Venus, Earth and Mars. The inner planets are compact and rocky with just three moons between them. They are called terrestrial planets because they are more or less earth-like. All of them have secondary atmospheres (produced after their formation) and at least three of them planets may once have had oceans; Venus, whose seas may have been boiled off by the greenhouse effect; Mars, whose once liquid oceans might now be frozen under its surface and Earth, the Blue Planet, orbiting at just the right distance from the sun to maintain liquid water on its surface.
Far from the sun, beyond the asteroid belt, orbit the four gas giants - Jupiter, Saturn, Uranus and Neptune. These four outer planets are huge and vaporous, possessing rings and more than 160 natural satellites between them.
Mercury
Mercury is just 4878 kms in diameter, making it the smallest of the planets. Due to Mercury’s off-centre orbit of the sun, bringing it as close as 46 million kms to the sun at its closest point and as far as 69.82 million kms from the sun at its furthest point, the planet see great extremes in temperature, going from highs of 427 degrees celcius to lows of -173 degrees celcius. Mercury has no natural satellites.
Venus
In size, Venus is a near match to Earth, at 12,103 kms in diameter, only 653 kms smaller than earth. Its mass is only slightly less than that of Earth and its density and surface gravity are also close to our own planet. However, Venus is, in fact, a smoggy furnace beneath a crushing acidic atmosphere with an average surface temperature of 462 degrees Celcius, making it the hottest planet in the solar system. It has no natural satellites. Venus is the brightest object in the sky from Earth other than the sun and moon and is often referred to as the Morning or Evening star.
Earth
Earth is the largest of the four terrestrial planets, at 12,756 kms in diameter. Earth is not completely spherical but slightly wider at the centre because of its rotation. Earth is denser than other rocky planets and has a higher surface gravity. It is the only planet with liquid water on its surface. Its surface is varied and dynamic, consisting of crustal plates slowly shifting under a stable, shallow, moist atmosphere. Protecting Earth from radiation is the magnetosphere, a magnetic field thousands of miles long. Earth’s only moon circles the planet at a distance of 384,400 kms away.
Mars
Known as the red planet, Mars is the fourth planet from the sun and the outermost of the rocky planets, orbiting at an average distance of 227.9 million kms from the sun. It is roughly half the size of Earth and is now a dry, barren planet with a surface marked by large canyon systems and huge extinct volcanos, its most famous being Olympus Mons, the largest volcano in the solar system. Vast dust storms whip around the planet and clouds and falling snow have been seen by spacecraft sent to explore its surface. Like Earth, Mars has seasons and ice caps and evidence suggests that liquid water flowed across the Martian surface billions of years ago. Mars has two moons, Phobos and Deimos, both very small moons with the largest, Phobos, being only 27 kms long and 22 kms wide.
Jupiter
Within the solar system, Jupiter is second only to the Sun is size and mass. The gas giant, at 142,984 kms in diameter, and could hold 1300 Earths. It is almost two and a half times the combined mass of the other 7 planets put together. Jupiter takes almost 12 years to circle the Sun but rotates once every 9.9 hours, so fast that it is more egg shaped than sphere. Composed mainly of hydrogen and helium, like the sun, it has no real surface but a deep and windy atmosphere over a liquid hydrogen ocean. Jupiter is not just a planet, but a planet-moon system with 63 natural satellites, one of which, Ganymede, is the largest moon in the solar system. Jupiter’s atmosphere is affected by colossal, oval shaped storms whipped up by the planets internal heat and very fast rotation. The largest of these storms is the Great Red Spot which is about twice the size of Earth and has been raging for more than 350 years.
Saturn
Saturn, seen as one of the most beautiful planets with its rings, made from billions of ice particles sculpted into multiple bands by the gravity of some of Saturn’s moons. It has 61 natural satellites, the largest of which is Titan, the only satellite in the solar system to possess a thick atmosphere and, apparently, liquid lakes (of methane and ethane) on its surface, possible havens for life. Saturn is 1.4 billion kms from the sun and is the second largest planet in the solar system after Jupiter. It consists almost entirely of the lightest elements, hydrogen and helium and as a result is the least dense planet in the solar system.
Uranus
One of the two ice giants, Uranus is the third largest planet in the Solar System and lies twice as far from the sun as Saturn (2.9 billion kms). Neptune is pale blue in colour, which comes from the methane in its atmosphere. It is featureless with a sparse ring system and 27 moons. As a result of what is thought to have been a collision with a planet-sized body not long after it formed, Uranus’s spin axis is tipped over by 98%, giving it the appearance of moving along on its orbital path on its side, with its moon encircling it from top to bottom. Its spin is retrograde – meaning it rotates in the opposite direction to that of most other planets.
Neptune
The second of the two ice giants, Neptune is the coldest planet in the Solar System. Neptune is 4.5 billion kms from the Sun and takes 163.7 Earth years to orbit the Sun, so has only completed one circuit since its discovery in 1846. Neptune has a core of rock and metal, surrounded by a liquid layer of water, ammonia and methane. Above this is a hydrogen dominated atmosphere affect by huge wind speeds of up to 2000 kms per hour – the highest wind speed found on any planet. It has 13 moons, the largest of which is Triton.
SCIENCE
Inventions
An A – Z of some inventions that changed the world
Abacus, AD190
Use of the abacus, with its beads in a rack, was first documented in China in about AD190, but the word dates to much earlier calculating devices. ‘Abacus’ derives from the Hebrew ibeq, meaning to ‘wipe the dust’ or from the Greek abax, meaning ‘board covered with dust’, which describes the first devices used by the Babylonians. The Chinese version was the fastest way to do sums and in the right hands, can still outpace electronic calculators.
Archimedes Screw, c.700BC
Purportedly devised by the Greek physicist Archimedes in the 3rd century BC to expel bilge water from creaking ships, the screw that bears his name in fact predates Archimedes by about 400 years. Recent digs have established that earlier screws, which are capable of shifting water uphill, were used in the Hanging Gardens of Babylon in the 7th century BC. So effective is the device, it is still used today in several sewage plants and irrigation ditches.
Aspirin, 1899
Little tablets of acetylsalicylic acid have probably cured more minor ills than any other medicine. Hippocrates was the first to realise the healing power of the substance – his related ancient Greek treatment was a tea made from willow bark, and was effective against fevers and gout. Much later, in turn-of-the-century Germany, chemist Felix Hoffman perfected the remedy on his arthritic father, marketing it under the trade name Aspirin.
Barcode, 1973
Barcodes were conceived as a kind of visual Morse code by a Philadelphia student in 1952, but retailers were slow to take up the technology, which could be unreliable. That changed in the early 1970s when the same student, Norman Woodland, then employed by IBM, devised the Universal Product Code. Since then, black stripes have appeared on almost everything we buy.
Battery, 1800
For the battery we must thank the frog. In the 1780s, the Italian physicist Luigi Galvani discovered that a dead frog's leg would twitch when he touched it with two pieces of metal. Galvani had created a crude circuit and the phenomenon was taken up by his friend, the aristocratic Professor Alessandro Volta, whose voltaic cells stacked in a Voltaic pile amazed Napoleon. The pile was also the first battery, whose successors power more than a third of the gadgets on this list.
Biro, 1938
Had the Hungarian journalist Laszlo José Biró kept the patent for the world's first ballpoint pen, his estate (he died in 1985) would be worth billions. As it happened, Biró sold the patent to one Baron Bich of France in 1950. Biró's breakthrough had been to devise a ball-bearing nib capable of delivering to paper the smudge-resistant ink. Today around 14 million Bic "Biros" are sold every day, perhaps making the pen the world's most successful gadget.
Camera, 1826
British William Talbot, inventor of one of the earliest cameras (Joseph Nicéphore Niépce had produced the earliest surviving photograph on a pewter plate in 1826), was inspired by his inability to draw. He described one of his sketches as "melancholy to behold", wishing for a way to fix on paper the fleeting photographic images that had been observed for centuries using camera obscura. His early developing techniques in the late 1830s set the standard for decades – he invented the negative/positive process – and photography began to take off, helped in large part, in 1888, by George Eastman's Kodak, the first camera to take film.
CD, 1965
For the US inventor James Russell, the crackly sound of vinyl ruined music, so he patented a disc that could be read with a laser. Philips and Sony picked up the trail in the early 1970s, when they perfected the Compact Audio Disc or CAD, later shortened to CD. The first discs appeared in the early 1980s and could play 74 minutes, on the insistence of Sony chief Akio Morita, who stipulated one disc could carry Beethoven's Ninth Symphony.
Clockwork radio, 1991
With the wind-up radio, not only did deprived areas of the developing world get access to public information, but we were gifted a true legend of invention. British Trevor Bayliss, a former professional swimmer, stuntman and pool salesman, devised the contraption after being horrified by reports from Africa that important information wasn't getting through to people outside the cities.
Compass, 1190
Forced to rely on natural cues such as cliffs or spits of land, as well as crude maps and the heavens, early mariners would get hopelessly lost. Desperate for something more reliable, sailors in China and Europe independently discovered in the 12th century lodestone a magnetic mineral that aligned with the North Pole. By 1190, Italian navigators were using lodestone to magnetise needles floating in bowls of water. The device set humanity on the course to chart the globe.
Digital camera, 1975
There could be no digital camera without the charge-coupled device (CCD), the "digital film" that captures images electronically. Developed in 1969, the widget allowed the Kodak engineer Steven Sasson to build the first digital camera, which resembled a toaster. The first, horribly blurry snap (of a female lab assistant) he took boasted just 0.01 megapixels and took almost a minute to record and display, but in those 60 seconds, Sasson had transformed photography – today digital cameras have all but killed off film and made photographers of us all.
Dynamite, 1867
Few inventions, save perhaps the atomic bomb, can claim to have shaken the world in quite the same way as nitroglycerine. And few inventions can have claimed so many lives. The first to succumb to the explosive force of Dynamite was the inventor's brother; Alfred Nobel's youngest sibling perished when an early experiment to stabilise nitroglycerine by adding a chalky material called kieselguhr, went horribly wrong. In 1896, Nobel used his Dynamite fortune to endow the Nobel Prizes.