Reva Kay Williams is a theoretical astrophysicist. She is the first person to successfully work out the Penrose process using Einstein's Theory of Relativity to extract energy from black holes. Also, she is the first Black American woman to earn a PhD in theoretical astrophysics. Her work focuses on general relativistic astrophysics.

Gravitoelectromagnetism, abbreviated GEM, refers to a set of formal analogies between the equations for electromagnetism and relativistic gravitation; specifically: between Maxwell's field equations and an approximation, valid under certain conditions, to the Einstein field equations for general relativity. Gravitomagnetism is a widely used term referring specifically to the kinetic effects of gravity, in analogy to the magnetic effects of moving electric charge. The most common version of GEM is valid only far from isolated sources, and for slowly moving test particles.