QI: The Second Book of General Ignorance
Page 7
Airline statisticians like to say that you are ten times more likely to be hit by a comet than to die in a plane crash. This is because, once every million years or so, an extraterrestrial body collides with Earth. The next time this happens it will probably wipe out half the world’s population but, as far as we know, the last time anyone was hit by a comet was 12,900 years ago.
It is the case, however, that you are many times more likely to die in the taxi on the way to and from the airport than you are on the flight itself.
DAVID MITCHELL I imagine your survival swings on the whistle that you get on the life jacket.
JIMMY CARR It does rather rely on someone having quite selective hearing, and going, ‘I didn’t hear that plane go down,’ but …
What’s the word for the fear of heights?
It’s not vertigo.
The fear of heights is called acrophobia (from the Greek akros, ‘highest’).
Reactions include clinging, crouching, or crawling on all fours as well as the usual symptoms associated with other phobias such as sweating, shaking and palpitations. Acrophobia is unusual among phobias in that it can actually cause what the person is frightened of. A panic attack at height may lead them to lose control and fall.
Vertigo (Latin for ‘whirling’) is a recognised medical condition. It’s a type of dizziness where sufferers feel they are moving when they are in fact stationary. Women are two to three times more likely to suffer from it than men and it gets more common with age. Up to 10 per cent of people experience some form of vertigo in their lives. Vertigo doesn’t necessarily take place high above the ground and it’s not the same thing as acrophobia.
The confusion wasn’t helped by Alfred Hitchcock’s film Vertigo (1958). In the movie, an ex-police detective (Jimmy Stewart) suffers from acrophobia as a result of witnessing a fellow officer fall to his death in a rooftop chase. His condition haunts him and the film comes to a climax when he apparently fails to prevent the woman he loves falling from a bell tower. He is unable to climb the stairs due to his crippling fear of heights and an attack of vertigo.
In real life, people with acrophobia may never suffer from vertigo – and vice versa.
A sensible caution towards high places seems to be built into all of us. In 1960, psychologists E. J.Gibson and R. D. Walk created the ‘visual cliff experiment’ in which infants from different species (including human babies) had to cross a transparent glass panel with an apparently sharp drop-off point beneath it. They found that all the species in the experiment saw and avoided the cliff as soon as they were old enough to manage independent movement – six months for a human or one day in chicks.
While not everyone is frightened of heights, acrophobia appears to be the second most common human phobia of all.
The first is fear of public speaking.
What’s the world’s second-highest peak?
Actually, it’s also Everest.
Mount Everest’s main summit is the highest point on the Earth’s surface measured from sea level. It rises 8,850 metres (29,035.4 feet) into the sky. The second-highest separate mountain is K2, but the unremarkable bump of Everest’s south summit is in fact higher, at 8,750 metres (28,707 feet). This beats K2 – 8,611 metres (28,250 feet)– by almost 140 metres (460 feet).
K2 is not in the Himalayas. It’s in a range called the Karakorum – the initial K of which gives K2 its rather functional name.
K2 was a temporary label given to it by Lieutenant Thomas Montgomerie (1830–78) a young officer in the Great Trigonometric Survey of India, which lasted through most of the nineteenth century. He named the biggest peaks he saw in the Karakorum range K1, K2, K3, etc., in the order that he came across them.
K1, which he first saw in 1856, is only the twenty-second highest mountain in the world, but it already had (and has) a local name: Masherbrum. And so, as it eventually turned out, did all the others in Montgomerie’s list – except K2.
K2 hadn’t been given a local name (and still hasn’t) by either the Pakistanis in the south or the Chinese in the north. The reason for this is the mountain’s remoteness. Despite its majestic height, it cannot be seen from any of the villages in the area – and it’s possible that no one even knew of its existence until the Great Trigonometric Survey. An early attempt to name it Mount Godwin-Austen – after another surveyor, Henry Godwin-Austen (1834–1926) – was rejected by the Royal Geographical Society. But K2 is informally known as ‘The Savage Mountain’ – one in four people who attempt to get to the summit die, and it has never been conquered in winter.
The south summit of Everest may be a long way up, but it is only a cone of snow and ice about the size of an ordinary dinner table. For most climbers it is just another stop on the way to the highest point on Earth, a time to change oxygen bottles and admire the view of the final slopes of the main summit.
The south summit is inside what mountaineers call the ‘Dead Zone’ (above 8,000 metres or 26,246 feet). Although Everest kills fewer people proportionately than K2, many more people climb it. As a result, the Dead Zone is full of rubbish and frozen corpses. In 2010 a team of twenty Sherpas began a concerted effort to tidy it all up. As well as removing several bodies, they expect to clear 3,000 kilograms (about 3 tons) of old tents, ropes, oxygen cylinders, food packaging and camping stoves from the mountain.
Pedants should be aware that the English name for the world’s highest mountain should be spoken aloud as EEV-uh-rest, not EV-uh-rest.
This is how Sir George Everest (1799–1866), the Welsh-born Surveyor General of India, after whom it is named, pronounced his surname.
How can you tell how high up a mountain you are?
Make some tea.
The traditional method of estimating the height of a mountain while you’re on one is by taking the temperature of a pot of boiling water.
Water boils when the pressure of the steam trying to escape from it exceeds the pressure of the air above it.
Air pressure decreases with altitude in a rather neat (if non-metric) way. For every 300 metres (1,000 feet) gained in height, the boiling point of water reduces by 1°C.
So, at 4,500 metres (15,000 feet, the summit of Mont Blanc) water boils at 84.4°C. At the top of Everest it boils at 70°C and at nearly 23,000 metres (75,000 feet) it would boil at room temperature (not that any room would be at room temperature at that altitude).
This form of measurement is called hypsometry (from the Greek hypsos, ‘height’ and metria, ‘measure’).
In his travelogue A Tramp Abroad (1880), Mark Twain (1835–1910) tells how, on an expedition to the Swiss Alps, he tried to calculate the altitude by boiling his barometer in bean soup. This gave ‘a strong barometer taste to the soup’ which was so unexpectedly popular he had the expedition cook make it every day. The cook used two barometers, one in working order, the other not – the soup from the former went to the Officers’ Mess, the latter to the Other Ranks.
The Challenger Deep in the Marianas Trench in the Pacific is the deepest known part of the world’s oceans.
The pressure there is 1,100 times that at sea level, so if you wanted to make a cup of tea you’d have to wait awhile.
The kettle would start to boil at 530°C.
How can you tell which way is north in a forest?
It’s old woodsman’s lore that moss always grows on the north side of the trees, but it doesn’t.
Mosses prefer shady places but they can grow on the south, west and east of trees (as well as the north), if there’s enough moisture to sustain them. The presence of moisture depends as much on the direction of the prevailing wind as on being out of the sun. And, although a tree in isolation tends to have more shade on its northern side, trees in wooded areas throw shade on one another, making it perfectly possible for the south side to be the mossy one.
Can you tell which way is north from the sun? If you face the sunrise in the east, north is 90° to your left, isn’t it?
This isn’t foolproof either. The sun only rises
exactly in the east on two days a year, at the spring and autumn equinoxes, when night and day are of equal length. (Equinox is Latin for ‘equal night’.) In Britain, as a general rule, the sun rises in the south-east and sets in the south-west in winter; and rises in the north-east and sets in the north-west in the summer.
A more reliable method is to wait for nightfall and use the stars. Find the constellation of Ursa Major (Latin for ‘Great Bear’), better known as the Plough or Big Dipper. It looks a like a pan with a handle. Make a line between the two stars on the side of the pan opposite the handle and follow it upwards. Polaris – the North Star – is the next bright star you find along that line. It’s not exactly north; but it’s good enough for someone hopelessly lost in a forest.
Unfortunately, this doesn’t work so well in the southern hemisphere. The nearest star to the celestial South Pole, sometimes called Polaris Australis, or the ‘Southern Pole star’, is Sigma Octantis in the constellation Octans, but it’s barely visible without a telescope.
The North Star isn’t always due north, either. This is because Earth wobbles as it spins. Think of the Earth as a ball, spinning round an imaginary stick that passes through each pole. Because of the gravitational pull of the Sun and Moon, the stick moves slightly over time, slowly tracing a circle in the sky. This means that the end of the stick isn’t always pointing directly at Polaris: it’s either moving slowly towards or away from it.
You don’t need to worry about that for a while yet, though. The movement is very slow: each rotation of that circle takes 25,765 years to complete. For our Bronze Age ancestors in 3000 BC, the star Thuban in the constellation of Draco was closer to north. In 12,000 years time it will be Vega in the constellation Lyra. Polaris will be back in pole position again by AD 27800.
Meanwhile, a neat trick is to use your watch. Point the hour hand at the sun. Taking the middle of the angle formed between that and the number twelve gives a fairly good approximation to south.
STEPHEN You can float a razor blade on water and, if it’s magnetised, it would act as a compass.
ROB BRYDON But if you were lost in the forest and you were getting pretty despondent, and you thought, ‘I’ll float a razor blade on the water’, you would be tempted, wouldn’t you, as you looked at that razor blade, to end it all?
Do people really go round and round in circles when they’re lost?
Yes, they do. In situations where there are no navigational clues – such as in a snowstorm or thick fog – human beings who are convinced they’re walking in a straight line always end up going round in circles.
Until very recently this peculiar effect was explained away by the not very convincing theory that one of our legs is stronger than the other, so that over a period of time we tend to veer in the direction of the weaker leg. But research carried out in 2009 by the Max Planck Institute for Biological Cybernetics in Tübingen has shown that it’s not our legs, but our brains, that are at fault.
Volunteers were set down in a particularly empty bit of the Sahara in southern Tunisia or the dense, flat Bienwald Forest in south-west Germany and tracked as they walked, using GPS (the Global Positioning Satellite). When the sun or moon was out, they were perfectly capable of walking in a straight line. As soon as these were absent, the volunteers started to walk in circles, crossing their own path several times without noticing it. When another group of volunteers was blindfolded, the effect was even more obvious and immediate: the average diameter of the circle they walked was only 20 metres (66 feet).
This is far too rapid a change of course for the ‘stronger leg’ theory to explain. What the research proved is that, deprived of any visual points of reference, people have no instinctive sense of direction.
Vision is by far the most important of all human senses. Processing visual information uses 30 per cent of the brain’s activity, whereas smell, the directional aid used by most mammals, accounts for just 1 per cent. Only birds are as visually dependent as we are, but they navigate using ‘magnetoception’, the ability to plug into the Earth’s magnetic field. Embedded in their brains are crystals of an iron-based mineral called magnetite.
The bones of human noses also contain traces of magnetite, which suggests we may once also have had ‘magnetoception’ but have forgotten how to use it.
In 2004 Peter König, a cognitive scientist at the University of Osnabrück in Germany, made a belt that he wore round his waist constantly, even in bed. It had thirteen pads linked to a sensor that detected Earth’s magnetic field: whichever pad was pointing north vibrated gently like a cellphone. Over time, König’s spatial awareness radically improved. Wherever he was in the city, he found he knew intuitively the direction of his home or office. Once, on a trip to Hamburg, over 160 kilometres (100 miles) away, he correctly pointed towards Osnabrück.
When he finally removed the belt, he had a powerful sensation that the world had shrunk and that he had become ‘smaller and more chaotic’. The belt had reactivated – or perhaps re-educated – a sense he didn’t realise he had. It may be that our bodies have been faithfully sending out magnetoception signals all the time, but that our brains have lost the ability to interpret them.
STEPHEN Why do we walk in circles if we’re lost?
ALAN Homing pigeons: we’re descended from homing pigeons.
What’s the best way to weigh your own head?
Self-decapitation? Are you sure?
A severed head has left than five seconds of consciousness left, so you wouldn’t have much time to enjoy the results of your experiment.
Resting your head on the bathroom scales is another idea but it’s very inaccurate: your neck would still be supporting some of the weight.
The simplest way is to stick your head in a bucket.
The density of most people’s heads is very close to that of water. Put a bucket in a large tray, fill it to the brim with water and then dunk your head in it. Weighing the water that spills over into the tray will give you a fairly good approximation of the weight of your head.
For an encore, you can repeat the experiment with your whole body, using larger containers. You can then compare the amount of water displaced by your head to the amount displaced by your whole body, and work out what fraction of your total body weight your head is.
To ensure 100 per cent accuracy, though, what you really need is a CT scan.
Computed Tomography (CT) scanners use X-rays to produce an extensive series of images of objects in cross-section. (Tomography is Greek for ‘writing in slices’.) The information can be used to analyse any part of the human body and determine the exact density at each point within it. From this, a SAM – or Specific Anthropomorphic Mannequin – can be generated: a 3-D computer model that, among other things, will tell you the exact weight of your head.
If you’re not particularly bothered about accuracy and only want to know roughly what your head weighs, according to the anatomy department at Sydney University the weight of an adult human head (with hair removed), cut off at the third vertebra down, is between 4.5 and 5 kilograms (9.9 and 11 pounds).
If you like to be accurate to the point of extreme pedantry, you might be able to use this. It was the Greek mathematician Archimedes (about 287–212 BC) who discovered you could measure the volume of irregular objects by seeing how much water they displaced. He supposedly found this out while he was sitting in his bath and was so excited that he jumped out and ran naked through the streets of Syracuse yelling ‘Eureka!’ (Greek for ‘I’ve found it!’)
How do snakes swallow things bigger than their heads?
They don’t, as you may have heard, ‘dislocate their jaws’: they stretch them.
Most of the bones in a snake’s head – including the two halves of the jaw – are not locked in position, as in mammals, but are attached by a flexible ligament.
One of these bones links the snake’s lower jaw to its upper jaw in a double-jointed hinge. It’s called the quadrate bone because it is connected at four points.
The three-bone arrangement amplifies sound and is capable of much more acute hearing than the reptile system, where the eardrum is connected directly to the inner ear by just the single ‘stirrup’ bone. So, while we can’t swallow a goat whole, we can at least hear much better than snakes can.
Despite their big mouths, snakes sometimes bite off more than they can chew.
In 2005 the remains of a 1.8-metre (6-foot) alligator were found in the Florida Everglades National Park, protruding from the stomach of a 4-metre (13-foot) Burmese python. The python had tried to swallow the alligator whole and had then exploded. The alligator is thought to have clawed at the python’s stomach from the inside, leading it to burst.
Burmese pythons come from South-East Asia and are one of the six largest snakes in the world. In their natural habitat, they can grow to more than 6 metres (20 feet) long. They now infest the Everglades: all of them are pets that have been abandoned by, or escaped from, their owners.
In 1999 a study at Cornell University estimated that the control of invasive species cost the US a staggering $137 billion a year. In the following five years 144,000 more Burmese pythons were blithely imported into the United States.