How do I smell?

Miles from the blast site of Hiroshima, people saw a blinding flash of light and smelled burning rubber in the air. The smell was impossible to explain, defying all known laws of science. For while light travels instantly, smell consists of molecules that do not. How then could this be?

Luca Turin, the so-called Emperor of Scent, thinks he knows, because he believes he has unravelled one of the last great puzzles of science - how our noses work.

Compared with our sense of taste, our ability to smell is incredibly complex. Our tongues react to only six stimuli, but our noses can identify an infinite number of smells.

To the scientist who cracks the secret of smell, not only are monumental scientific acclaim and a Nobel Prize promised, but also untold riches.

The global perfume industry is worth $20billion a year. Manufactured smells permeate our lives in a multitude of products ranging from chic designer perfumes to mundane household products such as soap powder, polish, shampoo, toothpaste and candles.

Imagine then a means of predicting smell from its molecules. There would be no need for the giant perfume-making companies to conduct their expensive research, or to maintain laboratories that employ hundreds of chemists.

They would know before they began mixing their potions that a certain concoction would smell of damp grass mixed with wet dog, a little mint and a splash of tuber rose.

A precocious and inquisitive child, Turin was born to Italian-Argentine parents. He became fascinated by smell from an early age. As a young man, he trained as a biologist and began collecting perfumes. Between research jobs for a few months, he compiled a guide to perfume, describing each scent in opulently eloquent yet precise prose.

'Mortals can at last know the scent of goddess Diana's bath soap. The more time passes, the stronger its grace becomes, as if fading allowed its inner light to radiate more easily,' he wrote of the classic Seventies perfume Rive Gauche.

When his book was published in 1992, it became a bestseller. But the guide was merely a sideline to what became Turin's overriding objective - his craving to explain how smell worked.

Received wisdom holds that when we smell, receptors in our nose are identifying scent molecules by their shape. Turin's idea flies in the face of this theory.

When we sniff frying bacon or lily-of-the-valley or mouldy bread, Turin says, our nose is working like a spectroscope. Receptors in the nose identify the smells not by their shape but by the vibrations of the molecules they contain.