The Second Book of General Ignorance (3 page)

It’s not the Cape of Good Hope.

The residents of nearby Cape Town often have to explain this to visitors. The southernmost point of the continent is the altogether less famous Cape Agulhas, 150 kilometres (93 miles) south-east of the Cape of Good Hope.

The usual reason given for the Cape of Good Hope’s fame (and its name) is that it was the psychologically important point where sailors, on the long haul down the west coast of Africa on their way to the Far East, at last began to sail in an easterly, rather than a southerly, direction.

On the other hand, it might have been an early example of marketing spin.

Bartolomeu Dias (1451–1500), the Portuguese navigator who discovered the Cape of Good Hope and became the first European to make the hair-raising trip around the foot of Africa, named it Cabo das Tormentas (‘Cape of Storms’). His employer, King John II of Portugal (1455–95), keen to encourage others to adopt the new trade route, overruled him and tactfully rechristened it Cabo da Boa Esperança (‘Cape of Good Hope’).

The King died childless, aged only forty. Five years later Bartolomeu Dias also died. He was wrecked in a terrible storm – along with four ships and the loss of all hands – off the very cape he had so presciently named.

Cape Agulhas is equally treacherous. It is Portuguese for ‘Cape of Needles’, after the sharp rocks and reefs that infest its roaring waters. The local town is home to a shipwreck museum that commemorates ‘a graveyard of ships’.

Because of its isolation and rocky, inaccessible beach, the area is rich in wildlife. On land, it is home to the critically endangered micro-frog (
Microbatrachella capensis
) and the Agulhas clapper (
Mirafra (apiata) majoriae
), a lark whose mating display involves much noisy wing-flapping.

In the waters offshore, between May and August, the sea boils with billions of migrating South African pilchards (
Sardinops sagax
). These shoals form one of the largest congregations of wildlife on the planet, equivalent to the great wildebeest migrations on land, and can stretch to be 6 kilometres (3.7 miles) long and 2 kilometres (1.2 miles) wide. Hundreds of thousands of sharks, dolphins, seals and seabirds travel in the fishes’ wake, snacking on them at will but making little impact on the overall numbers.

Cape Agulhas is at 34° 49' 58" south and 20° 00' 12" east and it is the official dividing point between the Atlantic and Indian oceans. If you sailed past it, along the relatively unimpressive, gradually curving coastline, you probably wouldn’t even notice it but for the cairn that marks the tip’s exact location.

It’s not diamonds any more.

In 2005 scientists at Bayreuth University in Germany created a new material by compressing pure carbon under extreme heat. It’s called hyperdiamond or aggregated diamond
nanorods (ADNR) and, although it’s incredibly hard, it looks rather like asphalt or a glittery black pudding.

It’s long been known that one form of pure carbon (graphite) can be turned into another (diamond) by heat and pressure. But the Bayreuth team used neither. They used a third form of pure carbon, fullerite, also known as buckminsterfullerene or ‘buckyballs’. Its sixty carbon atoms form a molecule shaped like a soccer ball, or like one of the geodesic domes invented by the American architect Richard Buckminster Fuller (1895–1983).

The carbon atoms in diamond are arranged in cubes stacked in pyramids; the new substance is made of tiny, interlocking rods. These are called ‘nanorods’ because they are so small –
nanos
is Greek for ‘dwarf’. Each is 1 micron (one millionth of a metre) long and 20 nanometres (20 billionths of a metre) wide – about 1/50,000th of the width of a human hair.

Subjecting fullerite to extremes of heat (2,220 °C) and compression (200,000 times normal atmospheric pressure) created not only the
hardest
, but also the
stiffest
and
densest
substance known to science.

Density
is how tightly packed a material’s molecules are and is measured using X-rays. ADNR is 0.3 per cent denser than diamond.

Stiffness
is a measure of compressibility: the amount of force that must be applied equally on all sides to make the material shrink in volume. Its basic unit is the pascal, after Blaise Pascal (1623–62), the French mathematician who helped develop the barometer, which measures air pressure. ADNR’s stiffness rating is 491 gigapascals (GPa): diamond’s is 442 GPa and iron’s is 180 GPa. This means that ADNR is almost three times harder to compress than iron.

Hardness
is simpler to determine: if one material can make a scratch mark on another, it’s harder. The German mineralogist Friedrich Mohs (1773–1839) devised the Mohs Hardness
scale in 1812. It starts at the softest end with talc (MH1). Lead is fairly soft at MH1½; fingernails are graded MH2½ (as hard as gold); in the middle are glass and knife blades at MH5½. Ordinary sandpaper (which is made of corundum) is MH9, and right at the top end is diamond at MH10. Since ADNR can scratch diamond, it is literally off the scale.

And there’s more disappointing news for diamond fans: they aren’t ‘forever’. Graphite (which, oddly enough, is one of the
softest
known substances, as soft as talc) is much more chemically stable than diamond. In fact all diamonds are very slowly turning
into
graphite. But the process is imperceptible. There’s no danger of anybody suddenly finding their earrings have become pencils.

H
₂
O.

Water, or hydrogen oxide, is the strangest substance known to science. With the possible exception of air, it’s also the most familiar. It covers 70 per cent of the earth and accounts for 70 per cent of our own brains.

Water is oxygen linked to hydrogen (the simplest and most common element in the universe) in the simplest way possible. Any other gas combined with hydrogen just produces another gas: only oxygen and hydrogen make a liquid.

And it’s a liquid that behaves so differently from any other that theoretically it shouldn’t exist. There are sixty-six known ways in which water is abnormal, the most peculiar being that nothing else in nature is found simultaneously as liquid, solid and gas. A sea full of icebergs under a cloudy sky may appear
natural, but in chemical terms it is anything but. Most substances shrink as they cool, but when water falls below 4 °C it starts to expand and become lighter. That’s why ice floats, and why wine bottles burst if left in the freezer.

Each water molecule can attach itself to four other water molecules. Because water is so strongly bonded, a lot of energy is needed to change it from one state to another. It takes ten times more energy to heat water than iron.

Because water can absorb a lot of heat without getting hot, it helps keep the planet’s climate steady. Temperatures in the oceans are three times more stable than on land and water’s transparency allows light to penetrate its depths, enabling life in the sea. Without water there would be no life at all. And, though you can put your hand right through it, it’s three times harder to compress than diamonds and water hit at speed is as hard as concrete.

Although the bonds between water molecules are strong, they aren’t stable. They are constantly being broken and remade: each molecule of water collides with other water molecules 10,000,000,000,000,000 times a second.

So many things can be dissolved in water that it’s known as the ‘universal solvent’. If you dissolve metal in acid, it’s gone forever. If you dissolve plaster in water, when all the water has evaporated, the plaster is still there. This ability to dissolve stuff without eradicating it also paradoxically makes water the most destructive substance on the planet. Sooner or later, it eats away everything – from an iron drainpipe to the Grand Canyon.

And it gets everywhere. There are substantial deposits of ice on the moon and on Mars: traces of water vapour have even been detected on the cooler patches of the sun’s surface. On Earth only a tiny fraction of all the water is in the atmosphere. If it fell evenly throughout the world, it would produce no more than 25 millimetres or an inch of rain. Most of Earth’s
water is inaccessible, locked deep inside the planet, carried down when tectonic plates overlap, or held inside the mineral structure of the rocks themselves.

If this hidden water were released it would refill the oceans thirty times over.

Pure water doesn’t freeze at 0 °C, nor does seawater.

For water to freeze, it needs something for its molecules to latch on to. Ice crystals form around ‘nuclei’, such as small particles of dust. If there are none of these, you can get the temperature of water down to –42 °C before it freezes.

Cooling water without freezing it is known as ‘supercooling’. It has to be done slowly. You can put a bottle of very pure water in your freezer and supercool it. When you take the bottle out and tap it, the water will instantly turn to ice.

Cooling water extremely fast has a completely different effect. It bypasses the ice stage (which has a regular crystalline lattice structure) and transforms into a chaotic amorphous solid known as ‘glassy water’ (so called because the random arrangement of molecules is similar to that found in glass). To form ‘glassy water’ you need to get the water temperature down to –137 °C in a few milliseconds. You won’t find glassy water outside the lab on Earth, but it’s the most common form of water in the universe – it’s what comets are made of.

Because of its high salt content, seawater regularly falls below 0 °C without freezing. The blood of fishes normally freezes at about –0.5 °C, so marine biologists used to be puzzled by how fish survived in polar oceans. It turns out that species like Antarctic icefish and herring produce proteins in
the pancreas that are absorbed into their blood. These prevent the formation of ice nuclei (much like antifreeze in a car radiator).

Given the peculiarities of water at low temperatures, it won’t surprise you to learn that the boiling point of water, even at normal pressure, isn’t necessarily 100 °C either. It can be much more. Again, the liquid needs to be warmed slowly and in a container that has no scratches. It is these that contain the small pockets of air around which the first bubbles form.

Boiling happens when bubbles of water vapour expand and break the surface. For this to happen, the temperature must be high enough for the pressure created by the vapour bubble to exceed the atmospheric pressure. Under normal conditions this is 100 °C, but if the water is free of places where bubbles could form, more heat is needed to overcome the surface tension of the bubbles as they struggle into life. (It’s the same reason that blowing up a balloon is always harder at the beginning.)

This explains why a boiling hot cup of coffee in the microwave can explode all over you once removed or stirred. The movement sets off a chain reaction, so that all the water in the coffee vaporises at high speed.

One last watery oddity: hot water freezes faster than cold water. Aristotle first noted this in the fourth century
BC
, but it was only accepted by modern science in 1963. This resulted from the persistence of a Tanzanian schoolboy called Erasto Mpemba, who proved it by repeatedly demonstrating that a hot ice cream mixture set more quickly than cold. We still don’t know why it does.