The ideal and the feasible: physical constraints on evolution

The laws of physics and the properties of the physical environment impose constraints on evolution. Structures and processes that may be imagined cannot in some cases be evolved, because they are physically impossible. This paper explores the consequences of the particulate nature of matter and of light; of the wave nature of light and sound; of the laws of diffusion and heat exchange; of the mechanical properties of materials; of limits to aerodynamic and hydrodynamic performance; and of the behaviour of electricity.