Numerical Simulation, An Art of Prediction 1

4The Data World

With Three Days of the Condor, American filmmaker Sydney Pollack (1934–2008) proposed in 1975 a film very much rooted in his time: that of the contestation of powers based on mistrust – and a salutary counter-power embodied in the press. Joseph Turner, the character played by American actor Robert Redford, works in a CIA office in New York. What does he do for a living? He reads a quantity of information found in different media (books, newspapers, reports, etc.), in order to discover unexpected relationships – the strategic intentions of States, organizations, companies, etc. Without knowing it, he uncovered one relationship which precipitated him into a race for life. He gets out of difficult situations thanks to an imagination that takes his pursuers by surprise. One of them wonders how he does it. “He reads a lot”, replies another. This film anticipated by a few decades the importance of data* and the use that can be made of them for different purposes: understanding, learning, knowing, anticipating and acting.

Putting the world into equations in order to understand it, in the way we have approached it in the first chapter of this volume, is limited to physical phenomena that are sufficiently “regular”. The limits of equation-based models are reached for some processes encountered in physics, biology or chemistry that are too complex to allow for effective mathematical or numerical modeling. They are also rapidly reached in the human and social sciences, ...