by John Lloyd
Dislike of speed cameras is nothing new. The Automobile Association was established in 1905 to help motorists avoid police speed traps which (then as now) many felt were more to do with extorting money than road safety. All drivers speed at some point: 75 per cent admit to doing it regularly. But for all the grumbling, according to the Department for Transport, 82 per cent of us think speed cameras are a good thing.
Gatsonides certainly thought so. ‘I am often caught by my own speed cameras and find hefty fines on my doormat,’ he once confessed. ‘I love speeding.’
JEREMY CLARKSON There’s a marvellous new club in Holland called the Tuf Tuf Club that goes around destroying speed cameras.
STEPHEN Oh, really?
JEREMY You get prizes if you can think of the most imaginative way. My favourite one was to put some of that builders’ foam in. It just bursts and then sets in a rather ugly, Dr Who-y special effect. Which is quite good.
What’s the word for a staircase that goes round and round?
It’s not ‘spiral’, it’s helical.
A spiral is a two-dimensional curve which radiates out from a fixed, central point. The longer it gets, the less curved it becomes, like a snail shell. A helix is a three-dimensional curve, like a spring or a Slinky, which doesn’t change its angle of curve no matter how long it gets.
In the Scottish Borders there’s a legend that the Kerr family built their castle towers with helical staircases that went round in the opposite direction to everybody else’s. Because most of the male Kerrs were left-handed, this gave them an advantage in defending the stairs against a right-handed swordsman.
Sadly, it isn’t true: Kerrs are no more left-handed than any other family. A 1972 study in the British Medical Journal reported a 30 per cent incidence of left-handedness among Kerrs against a 10 per cent incidence in the British population generally, but the research turned out to be flawed. It had been based on a self-selecting sample, i.e. left-handed people with the surname Kerr were encouraged to come forward, and so the results were badly skewed. A later and more careful study in 1993 found no such tendency.
What’s more, the staircase trick wouldn’t work: if a defender was left-handed then an anticlockwise staircase would indeed allow him to use his sword more effectively, but it would also give a right-handed attacker the same advantage. So, a staircase that twisted the other way would only be useful when defending against another Kerr (not impossible given their bloodthirsty reputation).
The Chateau de Chambord in the Loire Valley has a double-helix staircase: two staircases which wind around each other so that people going up don’t bump into people coming down – and the cliff-top fortifications at Dover have a triple-helix staircase (known as the ‘Grand Shaft’) designed to get three columns of troops down to harbour level simultaneously.
The most famous of all double helixes is the molecule called deoxyribonucleic acid, better known as DNA. Francis Crick and James Watson first described its structure in 1953, although they were inspired by an X-ray photograph of DNA taken by Rosalind Franklin (1920–58), who almost beat them to it.
If you unravelled all the DNA strands in your body they’d stretch for 1,000 billion kilometres (620 billion miles), which is nearly 7,000 times further than the distance to the sun, and further away in the other direction than the edge of the Solar System.
To put that in perspective, to count to 620 billion you would have to have started 20,000 years ago, in the middle of the last ice age.
What’s so great about the golden ratio?
Every Dan Brown fan has heard of this mysterious figure that crops up everywhere – in the human body, in ancient architecture, in the natural world – and whose appeal nobody can explain. The truth is that it doesn’t appear in most of the places it’s supposed to, and many of the claims about it are false.
The golden ratio (also known as ‘the golden mean’ or the ‘divine proportion’) is a way of relating any two quantities – such as the height (a) of a building to the length (b) – in the following simple way.
In the nineteenth century, this ratio was given the name phi – φ – after the great Greek sculptor Phidias (490–430 BC), who supposedly used it in the proportions of his human figures. The reason that such a simple formula produces such a complicated, unharmonious looking number is that phi (φ), like pi (π), cannot be written as a neat fraction, or ‘ratio’, so it is called an irrational number. Irrational numbers can only be expressed as an infinite string of decimal places that never repeat themselves. A prettier way of expressing phi in maths is: (√ 5+1) divided by 2.
A ‘golden spiral’ is one that gets further from its central point by a factor of φ for every quarter turn it makes. A frequently quoted example of this is the beautiful shell of Nautilus pompilius, a member of the octopus family. But in fact this is a ‘logarithmic spiral’, not a golden one. In 1999 the American mathematician Clement Falbo measured several hundred shells and showed quite clearly that the average ratio was 1 to 1.33: a long way from 1.618. (If you did want to use a shell to demonstrate the golden mean, the abalone would do well, but they’re not nearly as photogenic as the nautilus.)
The Greeks knew about the golden ratio, and the Parthenon is the usual example given of its use in architecture. But any diagrams showing how its side or front elevations demonstrate a ‘golden rectangle’ always either include some empty air at the top or leave out some steps at the bottom.
The golden ratio was forgotten for hundreds of years after the fall of Rome, until Luca Pacioli (1446–1517), a Franciscan monk and Leonardo da Vinci’s tutor, wrote about it in De Divina Proportione (1509). Leonardo did the illustrations for the book but, despite what it says in The Da Vinci Code, he did not use the golden ratio to compose either the Mona Lisa or his famous 1487 drawing of a man in a circle with his limbs extended.
The latter is called Vitruvian Man after the Roman architect Vitruvius, who lived in the first century BC and is sometimes called ‘the world’s first engineer’. He based his buildings on the proportions of the ideal human body, where the height is equal to the span of the arms and eight times the size of the head. He didn’t use φ at all, whether or not Phidias once used it for a similar purpose.
What kind of stripes make you look slimmer?
Vertical ones, surely?
Nope.
According to research carried out in 2008 at the University of York, it is stripes running across the body that make the wearer appear more trim.
The experiment asked people to compare over 200 pairs of pictures of women wearing dresses with either horizontal or vertical stripes and say which of them looked fatter.
The results showed conclusively that, with two women of the same size, the one wearing the horizontal stripes appeared to be the thinner of the two. In fact, to make the women appear to be the same size, the one in the horizontal stripes had to be 6 per cent wider.
Led by psychologist Dr Peter Thompson, the York team had been puzzled that the conventional view that vertical stripes are ‘slimming’ went against a famous optical illusion, the Helmholtz square, in which a square filled with horizontal lines appears taller than one filled with vertical ones.
Hermann von Helmholtz (1821–94) was a German polymath. Not only was he a qualified physician and a theoretical physicist, he also helped found the discipline of experimental psychology and transformed the science of optics, writing the standard textbook on the subject and, in 1851, inventing the ophthalmoscope, an instrument which enabled people to see the inside of the eye for the first time.
On the matter of striped dresses, von Helmholtz was absolutely categorical: ‘Frocks with cross stripes on them make the figure look taller.’
For some reason, everyone has steadily ignored him for well over a century. When Sheriff Joe Arpaio of Maricopa County, Arizona, reintroduced striped prison uniforms in 1997, female inmates begged him to make the bars vertical so they wouldn’t look fat. He said: ‘I told them I am an equal-opportunity incarcerator – t
he men have horizontal stripes, and so will the women.’
Striped prison uniforms, first introduced in the early nineteenth century, made it easier to spot escapees in a crowd. But they were also intended as a psychological punishment. In the Middle Ages, striped clothes were the pattern of choice for prostitutes, clowns and other social outcasts – whether or not they were overweight.
One piece of received fashion wisdom the York team did confirm was that black really does make you look slimmer. This research was provoked by another famous optical illusion, in which a black circle on a white background appears smaller than a white circle on a black background.
ROB BRYDON I have a friend who’s quite short and he likes to wear vertical stripes because they make him look taller.
DAVID MITCHELL Only when he’s not standing next to anyone. It’s not going to make him look taller than a taller man. It’s all relative. You won’t just say: ‘Oh, there’s a normal size man next to an enormous man’ and then go: ‘Oh thank God, he’s taken his striped shirt off, it’s actually a tiny man next to a normal man.’
How many eyes do you need to estimate depth and distance?
One.
You’d think that we need both eyes, but we don’t.
It is true that most depth perception is created by the different angles of vision produced by each eye. It’s the way that 3-D film works, combining the output of two different cameras. When we look at something we create a single ‘field of view’, with the visual information split between the right and the left eye. The right-hand field from both eyes is sent to the right side of the brain; the left half of the field is sent to the left side. The brain merges them into a single solid-looking image.
However, our brains can still judge distance with a single eye. If you lose sight in one eye, the brain processes information from the remaining eye and plots it against the motion of your body. It then combines these visual and non-visual clues to create a sense of depth.
In fact, it turns out that you don’t need eyes to ‘see’ at all.
Over thirty years, US neuroscientist Paul Bach-y-Rita (1934–2006) experimented with ‘sensory substitution’. He had noticed that, although different parts of the body collect different types of sensory information, the way they’re transmitted – electrical nerve impulses – is always the same. In theory, this meant the nervous system could be rewired, swapping one sense for another.
In 2003 he began to test a device called the BrainPort. This uses a camera attached to the head to record visual images, which are translated into electrical signals that are sent to electrodes attached to the tongue. (The tongue has more nerve endings than anywhere on the human body except the lips.) What the tongue feels is a sequence of pulses of different length, frequency and intensity, which corresponds to the visual data. Gradually the brain learns to ‘see’ the image being sent to the tongue. The results are remarkable: after a while, people wearing the device can recognise shapes, letters – even faces – and catch balls that are thrown to them. Brain scans show that even blind people using it are having their visual cortex stimulated.
Darting movements of the eyes are called saccades (from the French saquer ‘to twitch’, and pronounced ‘suck-hards’). They are the fastest movements produced by the human body.
Our eyes are also continually vibrating. These tiny, imperceptible movements, each covering 20 arcseconds (or 1/5,000th of a degree) are called microsaccades. They are an essential component of vision: without them we’d be blind. In order to send nerve impulses to the brain, the rod and cone cells need to be continually stimulated by light. Microsaccades ensure that light keeps striking the retina, but the brain edits them out as unnecessary.
One spooky way of demonstrating how much the brain edits our sight is to stand facing a mirror and look at one eye and then the other. You won’t be able to see your eyes moving (although it’s quite obvious to anyone else).
What’s the natural reaction to a bright light?
Squinting or shading the eyes is instinctive for most people, but at least a quarter of us respond to bright lights by sneezing.
This is called the photic sneeze reflex (from photos, Greek for ‘light’) or, with rather heavy-handed humour, the ACHOO syndrome (Autosomal-dominant Compelling Helio-Ophthalmic Outburst).
It was first medically described in 1978, but people have been known to sneeze after looking at the sun since Aristotle; he blamed the effect of heat on the nose. Francis Bacon (1561–1626) disproved Aristotle’s theory in the seventeenth century by going out into the sun with his eyes closed; he suffered from photic sneeze reflex, but with his eyes shut nothing happened. Since the heat was still there, he decided that the sneezing must be caused by light; he guessed that the sun made the eyes water and this water irritated the nose.
In fact, the disorder is caused by confused signalling from the trigeminal nerve, the one responsible for sensation in the face. (Trigeminal means ‘triple-origin’ because the nerve has three main branches.) Somewhere along its passage to the brain the nerve impulses from around the eye and inside the nose become scrambled, and the brain is tricked into thinking that a visual stimulus is a nasal one. The result is that the body tries to ‘expel’ the light by sneezing.
Photic sneeze reflex affects between 18 per cent and 35 per cent of people. It most often occurs when someone leaves a dark place such as a tunnel or a forest and emerges into bright sunlight. The usual number of sneezes is two or three, but it can be as many as forty. This surprisingly common trait is inherited. Both men and women can get it, and they have a fifty–fifty chance of passing it on to their children. Because it’s genetic, it isn’t equally distributed but occurs in geographical clusters.
‘Honeymoon rhinitis’ is another genetic condition where people are attacked by uncontrollable sneezing during sex. One theory is that the nose is the only part of the body other than the reproductive system (and, strangely, the ears) to contain erectile tissue. It may be that the ‘arousal’ impulse, in some people, triggers both the nose and the genitals simultaneously.
An interesting side effect of this is that, like Pinocchio, our noses really do get bigger when we lie. Guilt causes blood to flow to the erectile tissue in the nose. This is an automatic reflex, and explains why people who are not very good liars often give themselves away by touching or scratching their noses or ears.
How do you know when the sun has set?
‘When it has disappeared below the horizon’ is the wrong answer.
The sun has already set when its lower edge touches the horizon.
As the setting sun falls in the sky, its light passes through the atmosphere at an increasingly shallow angle and is bent more and more as the amount of air it has to pass through increases. At the end of the process, the light is bent so much that we can still apparently see the sun even though it’s physically below the horizon. By coincidence, the degree of bending is almost equal to the width of the sun – so when we see the lower rim of the sun kiss the horizon, the whole of it has in fact completely disappeared.
What we’re looking at is a mirage. The bending of the light also has the effect of reducing the apparent distance between the top and bottom of the sun. This can cause the sun to appear oval.
When sunlight travels through the atmosphere, green light is bent very slightly more than red light – as when passing through a prism. This means that the top of the setting sun has a very thin green rim – too thin to be seen by the naked eye. Very occasionally, when atmospheric conditions are right, this green rim can be artificially magnified and it shines for a second or so just as the sun disappears from view. This phenomenon is known as the ‘green flash’ and is considered a good omen by sailors.
Another common mirage is the one you see on a road in summer. Hot tarmac heats the air above it, producing a sharp shift in its density, which causes light to bend. You think you see water; what you’re actually seeing is a reflection of the sky. The brain tells you it’s water, because water als
o reflects the sky.
Desert mirages are the same: the thirsty adventurer only ever ‘sees’ water.
Any other images of the type associated with mirages in cartoons and films (palm trees, ice-cream vans, dancing girls, etc.) are just figments of a heat-addled imagination.
STEPHEN Light from the setting sun passes through our atmosphere at a shallow angle; it is gradually bent as the air density, i.e. the pressure, increases. Not dissimilar to the image of your legs when you sit in a swimming pool. Our brains cannot accept that light is bent. The effect is to artificially raise the sun in the last few minutes of its decline, through the thickness of the atmosphere at that shallow angle there. And by coincidence, the amount of bending is pretty much equal to the diameter of the sun, so it’s exactly, exactly as it is there, that it’s actually disappeared.
PHILL JUPITUS I hate this show.
What are the highest clouds called?
‘Everyone knows’ that the wispy cirrus clouds are the highest – but they aren’t.
Clear midsummer evenings can occasionally reveal one of the loveliest and least understood phenomena of the night sky. Noctilucent (‘night-shining’) clouds are silvery blue streaks that form so high up in the atmosphere they catch the sun’s light, even at night. At over 80 kilometres (50 miles) in altitude, they are seven times higher than the highest cirrus clouds.