Diffusion

Abstract

The concept of diffusion describes regularities in the temporal propagation of people, objects, practices, or information in geographical space. The Swedish geographer Torsten Hägerstrand attached his name as early as the 1950s to the first formulation of the theory of the spatial diffusion of innovations. The spatial constraint on movement is expressed both in terms of proximity and in terms of connectivity. The theory establishes a generic link between behaviors observed at the microscale (those of individuals) and the resulting configurations at the meso‐ or macroscale (regional, continental, and global). Indeed, spatial diffusion theory, with associated concepts and simulation models, has found applications for analyzing and predicting a large variety of spatiotemporal processes. The main ones concern migrations, innovation diffusion, and the spread of epidemics. Recent research focuses on the transmission of epidemics, information, and opinions, particularly via digital networks.