Abstract
Matter and light are intimately linked in our modelling of the physical world. From the development of quantum theory to the invention of the laser, the interaction between atoms and radiation has played a central role in the development of today's science and technology. Mastery of this interaction now makes it possible to reach the lowest temperatures ever measured. The cooling of atomic gases by laser light produces "quantum matter" with properties radically different from those of ordinary fluids. These cold atoms form the basis of a new metrology of time and space, with applications in fields as diverse as navigation, telecommunications and geophysics.
