Page "General relativity" Paragraph 44

One of several analogies between weak-field gravity and electromagnetism is that, analogous to electromagnetic waves, there are gravitational waves: ripples in the metric of spacetime that propagate at the speed of light.

The simplest type of such a wave can be visualized by its action on a ring of freely floating particles.

A sine wave propagating through such a ring towards the reader distorts the ring in a characteristic, rhythmic fashion ( animated image to the right ).

Since Einstein's equations are non-linear, arbitrarily strong gravitational waves do not obey linear superposition, making their description difficult.

However, for weak fields, a linear approximation can be made.

Such linearized gravitational waves are sufficiently accurate to describe the exceedingly weak waves that are expected to arrive here on Earth from far-off cosmic events, which typically result in relative distances increasing and decreasing by or less.

Data-analysis methods routinely make use of the fact that these linearized waves can be Fourier decomposed.