NASA Gravitational waves: Ripples in space-time

Gravitational waves are invisible ripples in the fabric of space-time. They are caused by some of the most violent and energetic events in the universe

These include colliding black hole collapsing stellar cores, merging neutron stars or white dwarf stars the wobble of neutron stars that are not perfect speheres and possibly even the remnants of gravitational radiation created by the birth of the universe
In this video Dr.Padi Boyd explains gravitational waves nad how important Hubble is to exploring the mysteries of the universe.