This volume contains a number of essays by experts in areas of theoretical physics and astrophysics including cosmology, classical and quantum gravity, string theory and relativistic astrophysics. It will provide the reader with excellent reviews of current research in these frontier areas. Several of the essays emphasise alternative views of the Universe by leading astronomers and physicists who are known for their pioneering contributions. The volume is dedicated to Professor Jayant Narlikar, who has concerned himself with fundamental issues in cosmology and gravitation theory over a long and distinguished research career.