Gravitational radiation, or gravitational waves, are often described as "ripples in the fabric of spacetime", and depicted using rubber-membrane images like the one shown here. This description is certainly poetic, and fits well with the geometric gravity-as-curvature interpretation of Einstein's General Theory of Relativity (GR). However, this imagery is not necessarily the best approach to a deeper understanding of the mechanics and properties of gravitational waves.

In fact, gravitational radiation is not unique to GR, but is a necessary consequence of nearly any theory of gravity that is consistent with the more basic rules of Special Relativity. It arises from the simple fact that a change in the gravitational field of an object takes time to be felt at large distances: the effect cannot propagate instantaneously or at any speed greater than the speed of light.

This fact is true for other fields besides gravity, and
gravitational radiation can be viewed as analogous to
*electromagnetic radiation:* a more familiar phenomenon that
covers everything from radio waves, through visible light, to x-rays
and gamma rays. The following pages will therefore begin with a
discussion of how electromagnetic radiation occurs, and how a similar
underlying mechanism leads to gravitational radiation. I will then go
on to explain how gravity *differs* from electromagnetism, and
how this affects the generation and detection of gravitational waves.

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Sections marked with provide optional
additional mathematical detail.

Start: Gravitational waves demystified

Analogy: Electromagnetic fields

Electromagnetic field of an accelerated charge

Derivation of the radiative electromagnetic field

Electromagnetic waves

Gravitational tidal field

Equivalence between dipole and tidal field

Gravitaional waves

Formulae and details

Differences between gravitational and electromagnetic radiation

Gravitational wave spectrum