Which way do comets tails face? Does dark matter exist? Where did the universe come from and what is it made of? What's at the end of the universe? Dr Paul Francis discusses some of the 'greatest unsolved mysteries of the universe' at The Australian National University on 31 March 2010.This talk will explore the greatest unsolved problems of modern astrophysics, describe why they are hard, and discuss the efforts being made to solve them.Paul Francis is an astronomer at The Australian National University. He conducts research on comets, quasars, high redshift galaxies, and novel interactive teaching techniques. He grew up in London, studied at Cambridge and has worked with the Steward Observatory in Tucson, Arizona, with the University of Melbourne, and has been based at ANU since 1997.