The World's Greatest Idea

by Farndon, John

  #48 The Stirrup

  The stirrup is included in this book not because it is a great idea, though it may be that, but because of the power of a good story, and a bit of provocation.

  Just under half a century ago, Stanford medieval history professor Lynn Townsend White wrote a groundbreaking book entitled Medieval Technology and Social Change. In it, he contended that technology played a key role in medieval society, and ever since then, no one seriously seeking to understand the Middle Ages has been able to ignore its technology.

  The most attention-grabbing bit of White’s book, though, was the idea that it was the introduction of the stirrup that led to the development of the feudal system. Never one to understate his case, White asserted that: ‘Few inventions have been so simple as the stirrup, but few have had so catalytic an influence on history. The requirements of the new mode of warfare which it made possible found expression in a new form of western European society dominated by an aristocracy of warriors endowed with land so that they might fight in a new and highly specialized way.’

  About a century ago, historians such as Heinrich Brunner had asserted that the key to the success of Frankish and Gothic invaders over the fading power of Rome in the fourth and fifth centuries was its individualism. While the once legendary discipline and cohesion of the Roman infantry was breaking down, the individualism of the Franks and Goths spurred them on to become heroes, and what better way to become a hero than mounted on a horse? The hero horsemen of the Franks and Goths, the theory goes, developed into the famous knights of the Middle Ages. It was these horsemen that gave the Carolingian kingdom of the Franks in France – the kingdom of Charles Martel and Charlemagne – its strength and stability.

  The Franks, it seemed, weren’t able to put great ranks of disciplined infantry into the field like the Romans. But what they could do was send out elite cavalry. Cavalry had been used on the battlefield for thousands of years before the Carolingian knights. But their role was fairly minor; simply harrying and chasing, while the victory centred on the ranks of infantry. There was something so new and so frightening about the new breed of Carolingian horsemen that they had the power to turn battles. These powerful horsemen were so firmly mounted on their big steeds that they could wear heavy armour and ride full tilt at the enemy with lances and swords in shock assaults so overwhelming that ranks of infantry crumbled before them. Heavy cavalry became like the tanks of the world wars.

  White’s contention was that it was only the introduction of the stirrup that gave horsemen the firm platform to fight this way. Stirrups, he argued, gave horsemen the stability to fight from horseback with swords. They gave the support the rider needed to wear heavy armour. Above all, stirrups allowed the rider to channel the power of the horse into a lance thrust out in front like a deadly missile. Shock assault by heavy cavalry introduced a third phase for the horse in warfare, after chariots and then mounted horsemen.

  Training knights, equipping them with horses and armour, swords, lances and shields and giving them a proper support team must have been an expensive business, however. Each one was a costly, specialist unit. This is why, White contends, the Carolingians in the eighth century and subsequently other Western European countries adopted the feudal system. The kings seized land and gave it to overlords who would have serfs to work it. Only such a system, in which serfs were obliged to provide the support for their lord, would provide the financial support for such elite fighters. The deal was that while the peasants were obliged to labour, the knight was obliged to provide protection. So, White contends, we owe class society, the aristocracy and the working class, to the stirrup.

  It’s a fascinating thesis, and one so potent that it’s sunk into popular consciousness. Unfortunately, the evidence is not on White’s side, as many scholars have since pointed out. One of the problems is that White dates the arrival of the stirrup in France to about 700 AD. Yet there is plenty of evidence that heavy cavalry were in use without stirrups in other places long before this time. Indeed, heavy cavalry called cataphracts[1] were seen in battles against the Romans 1,000 years earlier. It’s the shape of the saddle that is the key to stability, it seems, and not the stirrup.

  Another problem is that there is no evidence that the Carolingian kings won any of their key battles with shock assaults by heavy cavalry. A third is that stirrups aren’t mentioned in any of the documents or military manuals of the time, nor do they turn up in any eighth-century warriors’ graves. Finally, it seems the evolution of the feudal system and the seizure of land was far more complex and gradual than White’s theory implies.

  The Great Stirrup Controversy as it became known has now been laid to rest by most scholars. So what is the history of stirrups? It seems that horsemen in India may have had a leather loop for the big toe of the barefoot rider as long ago as 500 BC. And Buddhist carvings from the first or second centuries BC show riders with their feet tucked into the saddle girth. Recognisable pairs of stirrups, though, seem to have first appeared in China as late as the fourth century AD. From there they spread east into Japan by the fifth century and west to Europe by the seventh century, particularly with horse-riding invaders from Central Asia such as the Avars. Over a hundred seventh-century cast-iron Avar stirrups have been found at various sites in Hungary.

  There is no doubt that stirrups greatly aid a rider’s stability, and they have been almost universally adopted for leisure riding long after the days of the knights. They make riding much, much easier, not only helping the rider stay in the saddle, but increasing control. Indeed, they make riding so much easier that most people can learn to ride in a fairly short time. Without them, the balance required is beyond all but the most agile and dedicated.

  So the greatness of the stirrup as an idea lies not in something as grand and world-changing as the creation of the knight and feudal society, but something far more down-to-earth. It was the stirrup, perhaps, that turned the horse from the mount of the soldier or specialist to everyday personal transport for millions of ordinary (well-enough off) people down through the ages until the coming of the automobile.

  The impact of the horse as personal transport was huge, and is the reason why the horse looms so large in personal and social histories. It not only gave countless people the kind of personal freedom that we often associate with the coming of the car – but it did so many, many centuries earlier. It also gave many a personal relationship with an animal that is quite unique, special and thrilling. Listen to the Dauphin in Shakespeare’s Henry V:

  When I sit astride him, I soar, I am a hawk. He trots on air. The earth sings when he touches it. The lowest part of his hoof is more musical than Pan’s pipe.

  And many riders through the ages, most of who would never have ridden without the stirrup, would echo his words. Even today, it gives to many people a magical, transcendental experience. ‘A man on a horse,’ wrote John Steinbeck, ‘is spiritually as well as physically bigger than a man on foot.’ That’s, of course, a tribute to the horse but maybe, without the stirrup, very few would ever have got to know.

  [1] The cataphracts of Eurasia predate the medieval knights by a thousand years, yet they too were heavily armoured warriors on horseback. Like the knights, they rode big horses, with both horse and rider draped from head to foot in heavy scale and chain armour. Like the knights too, they rode into battle bearing a lance. Indeed, when the Roman general and historian Ammianus Marcellinus describes cataphracts riding against them in the fourth century, he could have been describing knights: ‘But no sooner had the first light of day appeared, than the glittering coats of mail, girt with bands of steel, and the gleaming cuirasses, seen from afar, showed that the king’s forces were at hand.’ Their origins lie in Persia, in the time of the Medes, perhaps 2,500 years ago, but they reached their apogee with the Parthians in the third century BC and the Sassanid Persians in the third and fourth centuries AD. They managed entirely without stirrups, though.

  #47 The Aerofoil

  There is perha
ps no simpler nor more elegant idea in our list than the aerofoil. And what an idea! Just a little gentle curvature, a curvature that makes a wing – and on those wings we can soar into the sky far above the ground, we can glide over high mountains, we can cross the world’s widest oceans in hours. Even for those used to flying, the moment when your accelerating plane finally gains the speed to lift off with a kick beneath you is still exhilarating. How can such a vast weight, something so heavy that it would take a crane to lift, suddenly become so feather-light, so fantastically defiant of gravity that it can bear not only its own weight but yours and your fellow passengers’ rapidly up into the air? It seems like magic.

  The magic, of course, is in the physical interaction between the wings and the air. If the shape of the wing – the aerofoil – is right and the plane is moving fast enough, the wing is pushed into the air as it slices through it. It seems like magic because our all-too-literal brains tell us that because air is invisible it must be insubstantial too. But air is not nothing; air is a substance, chock-full of gas. Think of a wing slicing through water rather than air and you can begin to imagine how air might provide the upward push that aeronautical scientists call ‘lift’.

  The key to the aerofoil’s lift is the flow of air around it. Of course, still air is neither moving nor flowing; air flows around an aerofoil because the aerofoil is moving, just as the bow of a boat creates a flow in still water. What matters is the way the curved shape of the aerofoil diverts the flow around it. To really see why, it’s worth playing about with knives and spoons under a running tap.

  Hold a knife flat under the stream and the water flows straight and undisturbed past the blade. Twist the blade slightly at an angle to the stream and you can see how it begins to block and split the flow, breaking it into turbulent eddies – and you may see the turbulence increase as you increase the angle of the knife. Hold a spoon under the stream instead, however, and something different happens. Unlike the flat knife, the spoon diverts the water, but does not disrupt it. You have to twist the spoon at a much steeper angle before it disrupts the flow. Like the curvature of the spoon, the curvature of the aerofoil ensures the flow of the air around it is diverted but not broken up.

  It is the way that the flow is made to curve like the aerofoil that is crucial. Far above or below the aerofoil, the airflow is undisturbed, but the closer it is to the aerofoil the more its flow is bent to follow the aerofoil’s shape. As the flow changes direction it begins to push in a different direction too, and the more it bends the greater the change. Right on top and underneath the aerofoil the pressure of the airflow turns effectively at right angles, pushing the aerofoil upwards and creating lift.

  Since it is the way that the airflow is distorted that creates lift, it is clear that the pattern of the airflow distortion is important. This depends on the angle that the aerofoil moves through the air – its ‘angle of attack’. The steeper the angle of attack, the greater the lift, up to the ‘stall’ point where the angle is so steep that the airflow is broken up altogether and all lift is lost.

  The shape of the aerofoil is also crucial. A gentle, thin, flat curve provides the best lift, and this is the shape of bird wings and the shape that the flexible wings of hang-gliders and microlights bow into. But it is hard to make a large wing strong enough in this shape. So the wings of most large aircraft are a narrow teardrop shape in profile. This doesn’t give us much lift, which is why the wings have to be huge, but is easier to make strong, and the hollow inside the wing provides room for fuel storage. Elevator flaps on the rear of the wings swing up or down to alter the aerofoil curvature and its effective angle of attack and so allow the pilot to vary the lift to climb or descend.

  Of course, the wings of birds were the original inspiration for the aerofoil. Countless thinkers in the distant past must have marvelled at birds gliding through the sky and guessed that they were held aloft by their outstretched wings. And maybe some even guessed it was the shape of the wings that mattered, such as the fifth-century Greek philosopher Archytas who is said to have built a mechanical bird that flew. Brave pioneers like the ninth-century Cordoban, Abbas ibn-Firnas, were bold (or foolish) enough to strap artificial wings to their arms and leap from high places. Ibn-Firnas was successful (or lucky) enough to glide through the air for ten minutes before crash-landing and almost breaking his neck.

  Yet the first person who really began to explore the shape of wings methodically was the British engineer Sir George Cayley (1773–1857), and it is to Cayley that we owe the idea of the curved aerofoil. Yorkshire-born Cayley was an extraordinary and inventive man, and he is credited with developing self-righting lifeboats, wire-spoked wheels, seatbelts and even an internal combustion engine. But it is mostly as the ‘father of aviation’ that he is remembered, and it is he who pioneered much of the theory of flight. He carried out many experiments with wings on whirling arms to discover the forces acting on them, and what shapes and angles produced the greatest lift. In his analyses, he developed the names for the four key forces involved in flight – weight, lift, drag and thrust – still used by scientists today. Flight itself involves a balance between these four forces.

  Cayley wasn’t just a theorist, though. In the early 1800s, he began to build model gliders to try out his ideas. Then in 1849, he built a miniature biplane in which a ten-year-old boy is said to have flown a short distance, using ‘flappers’ to propel himself along. Most famously, however, in 1853 the by then 80-year-old Cayley built a full-size glider in which his terrified coachman or butler is said to have been launched out across Brompton Dale near Scarborough on Cayley’s estate. The butler survived and thus made the world’s first aeroplane flight. Cayley had clearly mastered lift, but for a successful aeroplane you need both power and control, which is why it took another half-century before the Wright brothers made their historic flight at Kittyhawk on 17 December 1903.

  The development of air travel since that pioneering day has been astonishing. According to the travel organisation IATA, 2.3 billion people flew on 35 million flights in 2009 alone. It is a remarkably safe way to travel. Of those 35 million flights, only nineteen came to grief in accidents, and fewer than 700 of those 2.3 billion passengers were killed in air accidents – in other words 1 in 30 million.

  Flight has transformed the way we experience the world. It seems a smaller, more connected place and many of us now frequently visit on brief holidays and business trips places that before air travel we may have travelled to only once in a lifetime. Millions of Britons, for instance, hop on a plane for weekend breaks in European cities, or travel right the way around the world for a short holiday in Thailand. Many ordinary people know about many foreign places and cultures not just because they have looked them up on the internet or watched a TV documentary, but because they have actually travelled there by plane.

  Air travel is not essential. Indeed, there are plenty of critics who argue that it is a wasteful luxury, and the global warming debate has focused attention on just how much we should be flying. The high energy cost of getting a plane into the air means that air travel is a major contributor to the greenhouse gases that are triggering global warming. Aeroplanes are very noisy, too, as anyone who lives under the flight-path near an airport will no doubt testify.

  Yet whatever level of flying ultimately proves sustainable, there is no doubt that the simple shape of the aerofoil has introduced something remarkable into our lives. It has given us all the chance of a magical experience. According to Plato, writing long before the aerofoil became a reality: ‘The natural function of the wing is to soar upwards and carry that which is heavy up to the place where dwells the race of gods. More than any other thing that pertains to the body it partakes of the nature of the divine.’

  For the pioneering aviator Charles Lindbergh, that divine quality was perhaps even too much: ‘Sometimes, flying feels too godlike to be attained by man. Sometimes, the world from above seems too beautiful, too wonderful, too distant for human eyes to see.’
(Spirit of St Louis, 1953)

  #46 Monotheism

  Back in 2005, conservative American Supreme Court Justice Antonio Scalia ruffled quite a few feathers when he said that monotheistic religions were the only ones the US government could endorse under the Constitution. The remarks certainly stirred up debate, but whatever the American legal position, Scalia certainly had numbers on his side.

  Well over 3.5 billion people around the world belong to the three great Abrahamic religions that are essentially monotheistic – Christianity (about 2 billion), Islam (1.5 billion) and Judaism (14 million) – and a further billion belong to the Hindu (950 million) and Sikh (23.8 million) faiths, which some people consider to be monotheistic at heart. So in purely democratic terms, monotheism gets the world’s vote as the best way to look at the world, with pretty much 75 per cent of the vote.

  It wasn’t always this way. Up until 2,000–3,000 years ago, the world’s religious beliefs were hugely varied and, as far as anyone can tell with such scant evidence, every small group of people had its own spirits or family of gods. Some worshipped tree spirits, some sky gods and moon gods. Some believed in the Great Goddess. Others followed the Bull. Many paid homage to stones. There wasn’t so much of a moral or social dimension or any personal insights in this cornucopia of beliefs; it was more a matter of keeping the gods happy to make sure that they were on your side, whether it was in the hunt or in the harvest, or in the field of battle. And then, it seems, it all changed.

  All across Eurasia, people began to look at the world in a different way. Sixty years ago, German philosopher Karl Jaspers talked of an Axial Age, a remarkable time when in just four centuries from 750–350 BC, ‘we meet with the most deep dividing line in history. Man, as we know him today, came into being.’ And he points out how, almost simultaneously, thinkers such as Confucius and Laozi in China, Prince Siddhartha (Buddha) in India, and Socrates in Greece all began to question the meaning of life in an extraordinarily new and profound way. ‘What is new about this age,’ Jaspers wrote, ‘… is that man becomes conscious of Being as a whole, of himself and his limitations.’