  The 1974 discovery, by Russell A. Hulse and Joseph H. Taylor, of the first
binary pulsar PSR B1913+16, opened up new possibilities for the study of
relativistic gravity. PSR B1913+16, as well as several other binary pulsars,
provided {\it direct} observational proofs that gravity propagates at the
velocity of light and has a quadrupolar structure. Binary pulsars also provided
accurate tests of the strong-field regime of relativistic gravity. General
Relativity has passed all the binary pulsar tests with flying colors. The
discovery of binary pulsars had also very important consequences for
astrophysics: accurate measurement of neutron star masses, improved
understanding of the possible evolution scenarios for the co-evolution of
binary stars, proof of the existence of binary neutron stars emitting
gravitational waves for hundreds of millions of years, before coalescing in
catastrophic events radiating intense gravitational-wave signals, and probably
leading also to important emissions of electromagnetic radiation and neutrinos.
This article reviews the history of the discovery of the first binary pulsar,
and describes both its immediate impact, and its longer-term effect on
theoretical and experimental studies of relativistic gravity.
