General relativity has entered a new phase of its development as technical advances have led to the direct detection of gravitational radiation from the merging of single pairs of stellar-sized black holes.

The exquisite sensitivity of pulsar signal timing measurements has also been exploited to reveal the presence of a background of gravitational waves, most likely arising from the mergers of supermassive black holes thought to be present at the center of most galaxies.

This book demonstrates how general relativity is central to understanding these and other observations.