Stuart Clark obtained both his first degree and his Ph.D. at the University of Hertfordshire, where he continues to teach and to develop numerical models for the scattering of light by dust particles in space. He has published six popular books on astronomy and has more on the way. Address: Department of Physical Sciences, University of Herfortdshire, College Lane, Hatfield AL10 9AB, UK. Internet: sclark@star.herts.ac.uk.