In most attempts to describe the uncertainty principle, formulated by Werner Heisenberg in 1927, it is customary to say that “observing a phenomenon disturbs it”. But this account needs to be taken with a grain of salt. It essentially means one cannot know many things about an elementary particle both precisely and simultaneously. One needs to choose what to know: the particle’s position in space, its speed, its energy, or the exact moment in which it is found in a certain place? The uncertainty principle doesn’t say that these characteristics cannot be observed in absolute terms, only that they cannot be known at the same time. Heisenberg’s formula is a set of few symbols associated with a great revolution in quantum physics, the validity of which is no longer in doubt and the achievements of which (including transistors and lasers) surround us in our daily lives. This book provides readers with an opportunity to explore the central nexus of one of the most exciting discoveries in human history.

Edoardo Boncinelli formerly taught at the Vita-Salute San Raffaele University in Milan and has directed research centres specializing in molecular development biology.