H2O by Philip Ball, Weidenfeld & Nicolson, 拢17.99, ISBN
0297643142
IMAGINE that a giant bucket holds all the water on the planet. Dip in a
finger. That single drop is all that鈥檚 fit to drink, a hundredth of a per cent.
For even that drop to reach your lips, the Earth has to function efficiently as
a gigantic water processor.
It鈥檚 a slow process鈥攅very three thousand
years, a volume of water equivalent to all the oceans of the world passes
through the atmosphere. Carried up by evaporation, it eventually falls as rain,
snow or hail. Every day, 30 trillion gallons鈥攇o metric for an impressive
136 trillion litres鈥攃ycles from the sea to the land. Of this, it鈥檚
possible to reach only a third. When there isn鈥檛 enough to go round, we panic:
growing shortages for crop irrigation have led to predictions that it鈥檒l be the
cause of a third global conflict, the World Water War.
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Water is the most familiar chemical on Earth. Yet it remains one of the least
understood, as Philip Ball points out in his marvellous H2O.
It鈥檚 easy to assume that everything about water has been discovered. Everyone
knows how oddly water behaves when it freezes, perversely expanding rather than
contracting鈥攁nd that it becomes less dense. If it behaved like most
liquids, there would be no annoying burst pipes in spring, no icebergs鈥攕o
no Leonardo DiCaprio dying in Titanic.
To explain why water behaves as it does requires some understanding of one of
this century鈥檚 most intriguing but least sexy branches of science, the physics
of liquids. It is a tribute to Ball鈥檚 skill that he has turned this potentially
soporific material into a compelling read. The secrets of many of water鈥檚
idiosyncrasies lie in the chemical bonding that keeps two hydrogen atoms
attached to one oxygen in water鈥檚 banana-shaped molecules. 鈥淥xygen hogs the
electrons like a selfish lover stealing most of the duvet,鈥� he points out. The
result is a highly directional electrical attraction between neighbouring
molecules. The American chemist Gilbert Lewis named this effect 鈥渉ydrogen
bonding鈥� in 1923, following a suggestion by one of his undergraduate
students.
Hydrogen bonding makes water much more ordered and more highly structured
than most liquids. This allows it to be what the biology Nobel laureate Albert
von Szent-Gy枚rgyi aptly called 鈥渢he matrix of life鈥�. Ball complains at the
impression some biologists give, that their subject is just about genes and
proteins. 鈥淏iological structures and processes can only be understood in terms
of the physical and chemical processes of water,鈥� he says. The directional bonds
of water niftily facilitate the interactions of all its companion molecules
within cellular walls.
Throughout H2O, Ball reminds us that water remains a hot
research topic, not least in the planetary sciences. The popular myth that only
Earth held copious quantities of water has been shattered. In 1995, astronomers
used spectroscopic data to prove that even the Sun is wet, surprising many
experts. There was much more fuss in January 1998 when NASA鈥檚 Lunar Prospector
missions showed conclusively that there is ice on the Moon. It鈥檚 clear that
water鈥攁lbeit not in liquid form鈥攊s all over the Solar System. Is
this a hint that there is life beyond the blue planet?
The breadth of Ball鈥檚 coverage is deeply impressive. But I would quarrel with
the space he gives to three off-the-wall topics: polywater, cold fusion and the
idea that water can remember molecules dissolved within it. But it shouldn鈥檛
have taken up a sixth of the book.
Nonetheless, this is one of the best science books of the year. By dint of a
lot of flair and eclectic learning, Ball makes us look afresh at the most
commonplace subject imaginable. Somehow, he has made water exciting. Buy a few
copies and spread the news this Christmas.