The nature of interstellar dust as revealed by light scattering

We discuss the important roles played by interstellar dust in the evolution of the interstellar medium of the Milky Way and other galaxies. We show the mathematical techniques that enable the optical properties of spherical grains and clusters of spheres to be computed. We describe two current approaches to modelling the properties of interstellar dust. Finally, we consider some possible limitations of these approaches and suggest that revised models may be required to take account of these concerns.