QI: The Book of General Ignorance - the Noticeably Stouter Edition (12 page)

Nitrogen. As every twelve-year-old knows, it accounts for 78 per cent of the air.

Less than 21 per cent of air is oxygen. Only three hundredths of 1 per cent of the air is carbon dioxide.

The high percentage of nitrogen in the air is a result of volcanic eruptions during the formation of the Earth. Vast amounts of it were released into the atmosphere. Being heavier than hydrogen or helium it has stayed closer to the surface of the planet.

A person weighing 76 kg contains almost 1 kg of nitrogen.

Nitre is the old name for saltpetre, or potassium nitrate. A key ingredient in gunpowder, it is also used to cure meat, as a preservative in ice cream, and the anaesthetic in toothpaste for sensitive teeth.

For several hundred years, the richest source of saltpetre was the organic mulch that had seeped into the earth floor of human houses. In 1601, the unscrupulous activities of the ‘Saltpeetermen’ were raised in Parliament. They would break into houses and even churches, dig up the floors and sell the earth for gunpowder.

The word nitrogen means ‘soda-forming’ in Greek.

Beer cans with pressure-sensitive ‘widgets’ contain nitrogen, not carbon dioxide. The smaller nitrogen bubbles make a smoother, creamier head.

The only other significant gas in air is argon (1 per cent).

It was discovered by William John Strutt, Lord Rayleigh, who was also the first man to work out why the sky is blue.

Don’t bother going to the seaside.

The nineteenth-century cult of healthy sea air was based on a fundamental misunderstanding. The bracing, salty tang has nothing to do with ozone, an unstable and dangerous gas.

Ozone was discovered in 1840 by the German chemist Christian Schönbein. Investigating the peculiar odour that lingers around electrical equipment he traced it to a gas, O
₃
, which he named after the Greek for ‘to smell’ (
ozein
).

Ozone or ‘heavy air’ found favour with medical scientists still in the grip of the ‘miasma’ theory of disease, where ill health was thought to spring from bad smells. Ozone, they thought, was just the thing to clear the lungs of harmful ‘effluvia’ and the seaside was just the place to get it.

A whole industry grew up around ‘ozone cures’ and ‘ozone hotels’ (there are still some carrying the name in Australasia). As late as 1939, Blackpool was still boasting ‘the healthiest ozone in Britain’.

Nowadays, we know that the seaside doesn’t smell of ozone – it smells of rotting seaweed. There’s no evidence this smell does you good or harm (it’s mostly compounds of sulphur). It may simply trigger positive associations in your brain, linking back to happy childhood holidays.

As for ozone, the fumes from your car’s exhaust (when combined with sunlight) create far more ozone than anything on the beach. If you really want a lungful, the best thing would be to clamp your mouth round an exhaust pipe. This is emphatically not recommended. Apart from doing irreparable damage to your lungs, you could burn your lips.

Ozone is used to make bleach and to kill bacteria in drinking water as a less noxious alternative to chlorine. It is also generated by high-voltage electrical equipment such as televisions and photocopiers.

Some trees, such as oaks and willows, release ozone which can poison nearby vegetation.

The shrinking ozone layer, which protects the planet from dangerous ultra-violet radiation, would be fatal if inhaled. It is 24 km (15 miles) above the Earth’s surface and smells faintly of geraniums.

If you said ‘yellow’ or ’brown’ go to the bottom of the class. Nicotine is colourless.

Nicotine is found in all plants of the
Solanaceae
, or nightshade family, which includes tobacco, deadly nightshade, tomatoes, potatoes, aubergines and chilli peppers. In theory, cigarettes can be made out of potato or tomato leaves and some programmes designed to help people stop smoking also advise giving up potatoes and tomatoes in order to eliminate low-level nicotine intake completely.

Cauliflower and coca leaves, from which cocaine is made, also contain nicotine.

In small doses, the nicotine compound solanine that is present in all these plants produces feelings of pleasure by increasing levels of the hormone dopamine in the brain. It’s why tobacco is more addictive than either cocaine or heroin, but it’s also why we sometimes find ourselves craving chips or pizza. Solanine generates adrenaline, leading to higher blood pressure, a faster heart rate, and enhanced sugar levels in the blood, producing a combination of euphoria and alertness.

In large doses, however, solanine and nicotine are as deadly as the nightshade whose relative they are. Tomato leaves can be made into a potent insecticide. The nicotine in a single
cigarette, if taken direct into the bloodstream, would be fatal. Eating one cigarette could make you severely ill and swallowing a packet of ten would definitely kill you. In 1976, the Department of Health urged pregnant mothers to wear rubber gloves when peeling potatoes and more than a kilogram (2.2 lb) of potatoes eaten at a single sitting would be certain death.

Fortunately for smokers, most of the nicotine in a cigarette is burned before it ever gets to the lungs. The other good news is, it doesn’t stain your fingers or your teeth or the ceiling of the pub. It’s not only colourless but soluble in water, so it comes off when you wash your hands. The stain on a smoker’s fingers is caused by tar.

The scientific name for tobacco is
Nicotiana tabacum
. The name of the plant and the word nicotine derive from Jean Nicot (1530–1604), French ambassador to Lisbon, and the man who first introduced tobacco to France in 1560. He originally promoted it as a medicine, believing it healed wounds and cured cancers, and sent some, in the form of snuff, to Catherine de Medici, Queen of France. She was so impressed when it stopped her migraine that she decreed it should be called
herba regina
, the ‘queen’s herb’.

Pure nicotine is one the most powerful poisons known: one and a half times as toxic as strychnine and three times as toxic as arsenic. Arsenic is also present in tobacco, along with 4,000 other chemicals, 200 of which are carcinogenic, including formaldehyde (used to preserve dead bodies), acetone (the main ingredient of nail-polish remover), cadmium (used in batteries) and hydrogen cyanide (the gas in Nazi death camps).

That depends.

It’s often said that the speed of light is constant, but it isn’t. Only in a vacuum does light reach its maximum speed of nearly 300,000 km per second (186,282 miles per second).

In any other medium, the speed of light varies considerably, always being slower than the figure everyone knows. Through diamonds, for example, it goes less than half as fast: about 130,000 km per second, or 80,000 miles per second.

Until recently, the slowest recorded speed of light (through sodium at –272 °C) was just over 60 kph (38 mph): slower than a bicycle.

In 2000, the same team (at Harvard University) managed to bring light to a complete standstill by shining it into a bec (Bose-Einstein condensate) of the element rubidium.

Rubidium was discovered by Robert Bunsen (1811–99) who didn’t invent the Bunsen burner which is named after him.

Astoundingly, light is invisible.

You can’t see the light itself, you can only see what it bumps into. A beam of light in a vacuum, shining at right angles to the observer, cannot be seen.

Although this is very odd, it’s quite logical. If light itself was visible, it would form a kind of fog between your eyes and everything in front of you.

Darkness is equally strange. It’s not there but you can’t see through it.

They’re not attracted to them. They are disorientated by them.

Apart from the odd forest fire, artificial light sources have been in existence for an extremely short time in comparison with the age of the relationship between moths and the Sun and Moon. Many insects use these light sources to navigate by day and night.

Because the Moon and Sun are a long way away, the insects have evolved to expect the light from them to strike their eyes in the same place at different times of day or night, enabling them to calculate how to fly in a straight line.

When people come along with their portable miniature suns and moons and a moth flies past, the light confuses it. It assumes it must somehow be moving in a curved path, because its position in relation to the stationary ‘sun’ or ‘moon’, has unexpectedly changed.

The moth then adjusts its course until it sees the light as stationary again. With a light source so close, the only way this is possible for an object which is so close is to fly round and round it in circles.

Moths do not eat clothes. (It’s their caterpillars that do it.) 

Not a hundred.

The word centipede is from the Latin for ‘a hundred feet’, and though centipedes have been extensively studied for over a hundred years, not one has ever been found that has exactly a hundred legs.

Some have more, some less. The one with the number of legs closest to one hundred was discovered in 1999. It has ninety-six legs, and is unique among centipedes in that it is the only known species with a even number of pairs of legs: forty-eight.

All other centipedes have odd numbered pairs of legs ranging from fifteen to 191 pairs.

It’s either six or eight.

For reasons known only to taxonomists the sloths in question are called ‘two-toed’ rather than ‘two-fingered’. Both two-toed and three-toed sloths have three ‘toes’ on each foot. Two-‘toed’ sloths are distinguished from three-‘toed’ sloths by the fact that they have two ‘fingers’ on each ‘hand’, whereas three-toed sloths have three.

Despite their obvious similarities, three-toed sloths and two-toed sloths are not related to one another. Two-toed sloths are slightly faster. Three-toed sloths have nine bones in their necks; two-toed have six.  

Three-toed sloths make good pets, but two-toed sloths are vicious. Three-toed sloths produce shrill whistles through their nostrils. Two-toed sloths will hiss if disturbed.

Sloths, generally, are the world’s slowest mammals. Their top speed is slightly over 1.6 km (1 mile) an hour but they mostly inch along at less than 2 metres (about 6 feet) a minute.

They sleep for fourteen to nineteen hours a day and spend their entire lives hanging upside down in trees. They eat, sleep, mate, give birth and die upside-down. Some move so little that two species of algae take root on them, giving them a greenish tinge, which also acts as useful camouflage. Several species of moth and beetle also make their home in sloth fur.

Their metabolism is slow, too. It takes then more than a month to digest their food and they pass urine and faeces only once a week. They do this at the base of the trees they live in, these unsavoury piles being romantically known as ‘trysting places’.

Like reptiles, they practise thermoregulation – basking in the sun to warm up, creeping into the shade to cool down.

This slows down their complex and lethargic digestive rate. During the rainy season when they stay put under leaves to stay dry, some sloths perform the astonishing feat of starving to death on a full stomach.