Cathie Clarke is Reader in Theoretical Astrophysics at the University of Cambridge and Director of Studies in Astrophysics at Clare College. She developed the original course in Astrophysical Fluid Dynamics as part of Part II Astrophysics in 1996 and delivered the course 1996–9. Her research is based on accretion disc theory and star formation (both of which are strongly based on fluid dynamics) and she is the author of around 70 articles in refereed journals, plus a further 50 reviews, proceedings etc. She has taught extensively within the University of Cambridge, having also delivered lecture courses in Statistical Physics, Mathematical Methods and Galactic Dynamics, and has supervised for a variety of courses within the Physics and Mathematics Triposes. Bob Carswell is Professor of Astronomy at the University of Cambridge. He lectured the Part II Astrophysics course on Astrophysical Fluid Dynamics 2000–3, and developed the course notes to reflect a revised syllabus to include accretion disks and some MHD concepts. He has also given courses in Relativity to both third-year and fourth-year undergraduates, as well as specialist courses on Gaseous Nebulae at the postgraduate level. His research relates to quasars, the intergalactic medium and large-scale structure.