Question: Which member of the LIGO Scientific Collaboration is an expert on gravitational waves?
Context: The LIGO Scientific Collaboration (LSC) is a scientific collaboration of international physics institutes and research groups dedicated to the search for gravitational waves.  The LSC was established in 1997, under the leadership of Barry Barish.  Its mission is to ensure equal scientific opportunity for individual participants and institutions by organizing research, publications, and all other scientific activities, and it includes scientists from both LIGO Laboratory and collaborating institutions.  Barish appointed Rainer Weiss as the first spokesperson. Bernard F. Schutz (born August 11, 1946, in Paterson, New Jersey) is an American physicist.  His research is on Einstein's theory of general relativity, more concretely on the physics of gravitational waves.  He is one of the directors and head of the astrophysics group at the Max Planck Institute for Gravitational Physics in Potsdam, Germany.  He is principal investigator in charge of data analysis for the GEO600 collaboration (which, in turn, is part of the LIGO Scientific Collaboration, the largest concerted effort to directly detect gravitational waves).  Schutz is also a member of the science team coordinating the planning and development for the space-borne gravitational wave detector LISA (Laser Interferometer Space Antenna), and he was instrumental in the foundation of the electronic, open access review journal "Living Reviews in Relativity". Barry Clark Barish (born January 27, 1936) is an American experimental physicist.  He is a Linde Professor of Physics, emeritus at California Institute of Technology.  He is a leading expert on gravitational waves. Nergis Mavalvala, PhD is a Pakistani-American astrophysicist known for her role in the first observation of gravitational waves.  She is the Curtis and Kathleen Marble Professor of Astrophysics at the Massachusetts Institute of Technology (MIT), where she is also the Associate Head of the Department of Physics.  She was awarded a MacArthur Fellowship in 2010.  Mavalvala is best known for her work on the detection of gravitational waves in the Laser Interferometer Gravitational-Wave Observatory (LIGO) project, but she has also obtained prominent results on other physics problems that evolved out of LIGO: for example, she has performed pioneering experiments on laser cooling of macroscopic objects and in the generation of squeezed quantum states of light. The gravitational wave background (also GWB and stochastic background) is a possible target of gravitational wave detection experiments.  The detection of such a background would have a profound impact on early-universe cosmology and on high-energy physics.  The emission of gravitational waves from astrophysical sources can create a stochastic background of gravitational waves.  For instance, a sufficiently massive star at the final stage of its evolution will collapse to form either a black hole or a neutron star – in the rapid collapse during the final moments of an explosive supernova event, which can lead to such formations, gravitational waves may theoretically be liberated.  Also, in rapidly rotating neutron stars there is a whole class of instabilities driven by the emission of gravitational waves. A gravitational-wave observatory (or gravitational-wave detector) is any device designed to measure gravitational waves, tiny distortions of spacetime that were first predicted by Einstein in 1916.  Gravitational waves are perturbations in the theoretical curvature of spacetime caused by accelerated masses.  The existence of gravitational radiation is a specific prediction of general relativity, but is a feature of all theories of gravity that obey special relativity.  Since the 1960s, gravitational-wave detectors have been built and constantly improved.  The present-day generation of resonant mass antennas and laser interferometers has reached the necessary sensitivity to detect gravitational waves from sources in the Milky Way.  Gravitational-wave observatories are the primary tool of gravitational-wave astronomy. The first observation of gravitational waves was made on 14 September 2015 and was announced by the LIGO and Virgo collaborations on 11 February 2016.  Previously gravitational waves had only been inferred indirectly, via their effect on the timing of pulsars in binary star systems. The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool.  Two large observatories were built in the United States with the aim of detecting gravitational waves by laser interferometry.  These can detect a change in the 4 km mirror spacing of less than a ten-thousandth the charge diameter of a proton, equivalent to measuring the distance to Proxima Centauri with an accuracy smaller than the width of a human hair. The Advanced LIGO Documentary Project is a collaboration formed in the summer of 2015 among Caltech, the Massachusetts Institute of Technology and Director Les Guthman to document the Advanced LIGO search for gravitational waves, both to videotape a longitudinal record of the project for history and to make a documentary of the LIGO project's then-expected detection of the first gravitational waves. Gravitational waves are ripples in the curvature of spacetime that are generated in certain gravitational interactions and propagate as waves outward from their source at the speed of light.  The possibility of gravitational waves was discussed in 1893 by Oliver Heaviside using the analogy between the inverse-square law in gravitation and electricity.  In 1905 Henri Poincaré first proposed gravitational waves ("ondes gravifiques") emanating from a body and propagating at the speed of light as being required by the Lorentz transformations.  Predicted in 1916 by Albert Einstein on the basis of his theory of general relativity, gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation.  Gravitational waves cannot exist under Newton's law of universal gravitation since that law is predicated on the assumption that physical interactions propagate at infinite speed.
Answer: Barry Barish