Physicists are now looking a bit deeper into Luca Turin's controversial theory that claims our sense of smell is based on recognizing molecular vibrations rather than molecular shapes.

"Most strikingly, some molecules can smell different — to animals, if not necessarily to humans — simply because they contain different isotopes (atoms that are chemically identical but have a different mass).

Turin's explanation for these smelly facts invokes the idea that the smell signal in olfactory receptor proteins is triggered not by an odour molecule's shape, but by its vibrations, which can encourage an electron to jump between two parts of the receptor in a quantum-mechanical process called tunnelling. This electron movement could initiate the smell signal being sent to the brain

This would explain why isotopes can smell different: their vibration frequencies are changed if the atoms are heavier. Turin's mechanism, says Marshall Stoneham of the UCL team, is more like swipe-card identification than a key fitting a lock.

Vibration-assisted electron tunnelling can undoubtedly occur — it is used in an experimental technique for measuring molecular vibrations. "The question is whether this is possible in the nose," says Stoneham's colleague, Andrew Horsfield."

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My brain can't stop speculating what could be the impact of proving this theory. Would it explain why natural aromatics smell better than synthetic aromachemicals? Would it provide a new scientific (rather than psychological) explanation for the the time-travelling experience of smelling something from the past? And what about the practical and commercial implications: besides the outcome (and income...) of companies such as Flexitral, would there be anything new and exciting to be offered - how about a quantum-leaping olfactory time-traveling machines?

Your comments, as always, are welcome.

Thanks to Mark for the tip!