Gravitational waves are ripples in the fabric of space-time according to Einstein's Theory of Relativity. They are theorized to originate from a source, then flow outward from the source in the form of ripples. As waves, they are capable of transmitting energy in the form of radiation. Sources of this type of wave are binary systems, black holes, and neutron stars. The mass contained in these types of objects are much more massive than objects here on earth. According to Einstein's general theory of relativity, the generation of gravitational waves is an occurrence upon which the curving of space-time is dependent. This curving effect is dependent upon the amount of mass in an object. The more massive the object, the greater the curving of space-time. This directly affects the amount of gravity generated by the object. As these massive objects move around within the structure of the universe, they generate accelerations in the curvature of space-time. These generations of accelerations occur at the speed of light and are known as gravitational waves.
Gravitational waves from the beginning of time in the news:
"Gravity Waves from Big Bang Detected," March 2014
"Has giant LIGO experiment seen gravitational waves?" September 2015
"Scientists struggle to stay grounded after possible gravitational
wave signal," January 2016