Gravitational Waves

According to Einstein's general theory of relativity, gravity is not a force acting between objects and transmitted through space; gravity is instead the result of the space-time curvature caused by the presence of mass or energy. 

If a massive object, such as a black hole (BH), would change its position in space due to an acceleration, as in the case of two BHs orbiting each other in a binary system, it would create continuous changes to the curvature of the space-time; these changes propagate at the speed of light and are what we call gravitational waves (GWs). 

When a GW passes through a GW detector, typically a laser interferometer, it will stretch and contract its arms, and as a consequence, the (laser) light travelling along its arms will create an interference pattern, which in turn produces a detectable signal. By studying this signal, one can infer the properties of the system that has generated the GW.

Video resources on this page are taken from the official LIGO educational resources webpage.