Gravitational wave spectrum

Whereas astrophysical electromagnetic waves are typically much smaller than their sources, ranging from a few kilometres down to sub-nuclear wavelengths, gravitational waves are larger than their sources, with wavelengths starting at a few kilometres and ranging up to the size of the Universe. A gravitational perturbation larger than the Universe would not be called a wave because it would not have any detectable oscillation; in fact, it would not be detectable at all.

The following diagram illustrates some typical amplitudes and wavelengths of gravitational waves across this entire spectrum, and the sensitivities of several detection methods. Some of these sources are quite speculative, or have highly uncertain amplitudes. There are also many more speculative sources that have not been included here.

The h axis is not the raw, instantaneous strain of the source. (In particular some sources are stochastic in nature and have no well-defined "instantaneous" strain.) Instead, it is the "characteristic" strain that one obtains by accumulating the signal over some timescale. For rotating sources the strain is also averaged over possible inclination angles. Specifically:



Future detectors:

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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