File:Binary-wave.jpg

http://lisa.jpl.nasa.gov/gallery/binary-wave.html

Image Credit: K. Thorne (Caltech) , T. Carnahan (NASA GSFC)

Gravitational wave are propagating gravitational fields, "ripples" in the curvature of space-time, generated by the motion of massive particles, such as two stars or two black holes orbiting each other. Gravitational waves cause a variable strain of space-time, which result in changes in the distance between points, with the size of the changes proportional to the distance between the points. Gravitational waves can be detected by devices which measure the induced length changes. Waves of different frequencies are caused by different motions of mass, and difference in the phases of the waves allow us to perceive the direction to the source and the shape of the matter that generated them.