Gravitational waves

The equations describing gravitation as part of the theory of general relativity are nonlinear. This means the solutions cannot be superposed (added together). The implication is that gravitational waves interact with each other and with the electromagnetic waves (bending of light). This is unlike, say, the interaction of two wave pulses travelling down a string, which can be described very well using linear equations.

Unlike the Electromagnetic radiation that had different frequencies like light, where the energy is contained in packets of photons, There is less understanding of the particulate or quark that is part of the gravitational wave, or how it interacts with matter.