This book deals with all aspects of gravitational-wave physics, both theoretical and experimental. This first volume deals with gravitational wave (GW) theory and experiments. Part I discusses the theory of GWs, re-deriving afresh and in a coherent way all the results presented. Both the geometrical and the field-theoretical approach to general relativity are discussed. The generation of GWs is discussed first in linearized theory (including the general multipole expansion) and then within the post-Newtonian formalism. Many important calculations (inspiral of compact binaries, GW emission by rotating or precessing bodies, infall into black holes, etc.) are presented. The observation of GWs emission from the change in the orbital period of binary pulsar, such as the Hulse-Taylor pulsar and the double pulsar, is also explained, and the pulsar timing formula is derived. Part II discusses the principles of GW experiments, going into the detail of the functioning of both interferometers and resonant-mass detectors. One chapter is devoted to the data analysis techniques relevant for GW experiments.