QI: The Book of General Ignorance - the Noticeably Stouter Edition (10 page)

It’s a solid.

You may have heard it said that glass is a liquid which has cooled but not crystallised, and which just flows fantastically slowly. This is untrue – glass is a
bona fide
solid.

In support of the assertion that glass is a liquid, people often point to old church windows, where the glass is thicker at the bottom of the pane.

The reason for this is not that the glass has flowed over time, but that medieval glaziers sometimes couldn’t cast
perfectly uniform sheets of glass. When that happened, they preferred to stand the glass into the window with the thick edge at the bottom, for obvious reasons.

The confusion about whether glass is a liquid or solid stems from a misreading of the work of German physicist Gustav Tammann (1861–1938) who studied glass and described its behaviour as it solidifies.

He observed that the molecular structure of glass is irregular and disordered, unlike the neat arrangement of molecules in, say, metals.

Reaching for an analogy, he compared it to ‘a frozen supercooled liquid’. But saying glass is like a liquid doesn’t mean it is a liquid.

These days, solids are categorised as either crystalline or amorphous. Glass is an amorphous solid.

As well as mercury, gallium, caesium and francium can all be liquids at room temperature. As these liquids are very dense (being metals), bricks, horseshoes and cannon balls theoretically float in them.

Gallium (Ga) was discovered by French chemist Lecoq de Boisbaudran in 1875. Everyone assumed it was a patriotic name but
gallus
is Latin for ‘a Gaul’
and
‘rooster’ – as in ‘Lecoq’. It was the first new element to confirm Dmitri Mendeleev’s prediction of the periodic table. Gallium is used chiefly in microchips because of its strange electronic properties. Compact disc players also make use of it because when mixed with arsenic it transforms an electric current directly into laser light, which is used to ‘read’ the data from the discs.

Caesium (Cs) is most notably used in atomic clocks – it is used to define the atomic second (see page 220) It also explodes extremely violently when it comes into contact with water. Caesium’s name means ‘sky blue’ because of the bright blue lines it produces as part of its spectrum. It was discovered in 1860 by Robert Bunsen using the spectroscope he had invented with Gustav Kirchoff, the man who had earlier discovered that signals travel down telegraph wires at the speed of light.

Francium (Fr) is one of the rarest elements: it has been calculated there are only ever thirty grams of it present on Earth. This is because it is so radioactive it quickly decays into other, more stable elements. So it is a liquid metal, but not for very long – a few seconds at most. It was isolated in 1939 by Marguerite Perey at the Curie Institute in Paris. It was the last element to be found in nature.

These elements are liquid at unusually low temperatures for metals because the arrangement of electrons in their atoms makes it hard for them to get close enough to each other to form a crystalline lattice.

Each atom floats around freely, without being attracted to its neighbours, which is exactly what happens in other liquids.

Silver.

The best conductor of both heat and electricity is also the most reflective of all the elements. Its drawback is that it is expensive. The reason we use copper wire in our electrical equipment is because copper – the second most conductive element – is much cheaper.

As well as its decorative uses, silver is now mostly used in the photographic industry, for long-life batteries and for solar panels.

Silver has the curious property of sterilising water. Only tiny amounts are needed – just ten parts per billion. This remarkable fact has been known since the fifth century
BC
when Herodotus reported that the Persian king Cyrus the Great travelled with his own personal water supply taken from a special stream, boiled, and sealed in silver vessels.

Both the Romans and Greeks noticed that food and drink put in silver containers did not spoil so quickly. Silver’s strong antibacterial qualities were made use of for many centuries before bacteria were discovered. This may also explain why silver coins are often found at the bottom of ancient wells.

A word of caution before you start filling your silver tankard.

First, while silver will certainly kill bacteria in the lab, whether or not it will do so in the body is controversial. Many of the supposed advantages are unproven: the US Food and Drug Administration has forbidden companies from advertising health benefits.

Second, there is a disease called argyria which is linked to the intake of silver particles diluted in water, the most obvious symptom of which is a conspicuously blue skin.

On the other hand, silver salts in swimming pools are a safe
substitute for chlorine and, in the US, athletes’ socks are impregnated with silver to stop their feet smelling.

Water is an exceptionally poor conductor of electricity, especially pure water, which is actually used as an insulator. What conducts the electricity is not the H
₂
O molecules but the chemicals dissolved in it – salt, for example.

Sea water is a hundred times better at conducting electricity than fresh water, but it’s a
million
times worse at conducting electricity than silver.

It’s either osmium or iridium, depending on how you measure it.

The two metals are extremely close in density and have changed places several times over the years. The third-densest element is platinum, followed by rhenium, neptunium, plutonium and gold. Lead is way, way down the list – it’s only half as dense as either osmium or iridium.

Osmium (Os) is a very rare, very hard, silvery-blue metal discovered (along with iridium) in 1803 by the English chemist Smithson Tennant (1761–1815).

Tennant was a vicar’s son from Richmond who was also the first man to show that diamond is a form of pure carbon.

He named osmium from
osme
, Greek for smell. It gives off highly toxic osmium tetroxide, which has a pungent, irritating odour and can damage the lungs, skin and eyes and cause intense headaches. Osmium tetroxide has been used in fingerprinting because its vapour reacts with minute traces of oil left by the fingers to form black deposits.

Its extreme hardness and resistance to corrosion made
osmium useful in the manufacture of long-life gramophone styluses, compass needles and the nibs of quality fountainpens – hence the trade name Osmiroid.

Osmium also has an unusually high melting point of 3,054 °C. In 1897, this inspired Karl Auer to create an osmium electric light-bulb filament to improve on the bamboo one used by Edison. Osmium was eventually replaced by tungsten, which melts at 3,407 °C. The name Osram was registered by Auer in 1906. It derives from OSmium and WolfRAM, the German for tungsten.

Less than 100 kg (220 lb) of osmium are produced worldwide every year.

Iridium (Ir) is a yellowish white metal which, like osmium, is closely related to platinum. The name comes from
iris
, Greek for rainbow, because of the many beautiful colours its compounds produce.

Iridium also has an extremely high melting point (2,446 °C) and is mainly used to make crucibles for metal foundries and to harden platinum. Iridium is one of the rarest elements on earth (eighty-fourth out of ninety-two) but improbably large amounts of it are found in the thin geological layer known as the KT boundary laid down about 65 million years ago.

Geologists have confirmed this can only have come from space, and it adds support to the theory that an asteroid impact caused the extinction of the dinosaurs.

Volcanoes. All diamonds are formed under immense heat and pressure beneath
the earth and are brought to the surface in volcanic eruptions.

They are formed between 160 km to 480 km (about 100 to 300 miles) underground. Most are found inside a volcanic rock called Kimberlite, and mined in areas where volcanic activity is still common. Any other diamonds are found loose, having been washed out of their original Kimberlite.

Twenty countries in the world produce diamonds. South Africa is now the fifth largest after Australia, the Democratic Republic of the Congo, Botswana and Russia.

Diamonds are made of pure carbon. So is graphite, the stuff that the ‘lead’ in pencils is made from, but with the carbon atoms arranged differently. Diamond is one of the hardest naturally occurring substances on earth with a score of ten on the Mohs Hardness scale, but graphite is one of the softest with a score of one and a half, only just harder than talcum powder.

The largest known diamond is 4,000 km (2,500 miles) across and measures ten billion trillion trillion carats. Found directly above Australia (eight light years away) the diamond sits inside the star ‘Lucy’ in the constellation Centaurus.

‘Lucy’ got its nickname from the Beatles classic ‘Lucy in the Sky with Diamonds’, but its technical name is white dwarf BPM 37093. The Beatles song was named after a picture drawn by John Lennon’s son Julian of his four-year-old friend Lucy Richardson.

Diamonds were once the world’s hardest known material. However, in August 2005, scientists in Germany managed to create a harder one in a laboratory. Called aggregated carbon nanorods (ACNR), it was made by compressing and heating super-strong carbon molecules to 2,226 °C.

Each of these molecules comprises sixty atoms that interweave in pentagonal or hexagonal shapes; they’re said to resemble tiny footballs. ACNR is so tough it scratches diamonds effortlessly.

The MMS Scale.

In the last decade, the Richter scale has been superseded in seismological circles by the Moment Magnitude Scale or MMS.

The MMS was devised in 1979 by seismologists Hiroo Kanamori and Tom Hanks (no relation) of the California Institute of Technology, who found the Richter scale unsatisfactory because it only measures the strength of the shock waves, which do not fully describe an earthquake’s impact. On the Richter scale, large earthquakes may have the same score but cause wildly different degrees of devastation.

The Richter scale measures the seismic waves or vibration as experienced 600 km (373 miles) away. It was devised in 1935 by Charles Richter, who was also, like Kanamori and Hanks, a Caltech seismologist. He developed it with Beno Gutenberg, the first man to measure accurately the radius of the Earth’s core. Gutenberg died of flu in 1960 without living to measure the Great Chilean Earthquake (the largest ever recorded, which took place four months later).

The MMS, by contrast, is an expression of the energy released by an earthquake. It multiplies the distance of the slip between the two parts of the fault by the total area affected. It was designed to give values that make sense when compared to their Richter equivalent.

Both scales are logarithmic: a two-point increase means 100 times more power. A hand grenade scores 0.5 on the Richter scale, the Nagasaki atom bomb 5.0. The MMS is only used for large earthquakes, above 3.5 on the Richter scale.

According to the US Geological Survey, on the basis of the area of damage (600,000 square km or 231,660 square miles) and the area it was felt in (5,000,000 square km or 1,930,502 square miles) the largest known earthquakes in
North America were the little-known Mississippi River valley earthquakes of 1811–12. They created new lakes and changed the whole course of the Mississippi. The area of strong shaking was ten times larger than that in San Francisco in 1906. Church bells rang spontaneously as far away as Massachusetts.

It is impossible to predict when an earthquake will happen. One expert claims that the best way is to count the number of missing cats and dogs in the local newspaper.

Britain has up to 300 earthquakes a year but they are so small that the public notices only about 10 per cent of them.