  Multiple scattering is a process in which a particle is repeatedly deflected
by other particles. In an overwhelming majority of cases, the ensuing random
walk can successfully be described through Gaussian, or normal, statistics.
However, like a (growing) number of other apparently inofensive systems,
diffusion of light in dilute atomic vapours eludes this familiar
interpretation, exhibiting a superdiffusive behavior. As opposed to normal
diffusion, whereby the particle executes steps in random directions but with
lengths slightly varying around an average value (like a drunkard whose next
move is unpredictable but certain to within a few tens of centimeters),
superdiffusion is characterized by sudden abnormally long steps (L\'{e}vy
flights) interrupting sequences of apparently regular jumps which, although
very rare, determine the whole dynamics of the system. The formal statistics
tools to describe superdiffusion already exist and rely on stable, well
understood distributions. As scientists become aware of, and more familiar
with, this non-orthodox possibility of interpretation of random phenomena, new
systems are discovered or re-interpreted as following L\'{e}vy statistics.
Propagation of light in resonant atomic vapours is one of these systems that
have been studied for decades and have only recently been shown to be the scene
of L\'{e}vy flights.
