Differences between gravitational and electromagnetic radiation

So far we have been emphasizing how, at a fundamental level, the generation and propagation of gravitational and electromagnetic radiation are basically quite similar. This is a major point in demystifying gravitational waves. But, on a more practical level, gravitational and electromagnetic waves are quite different: we see and use electromagnetic waves every day, while we have yet to make a confirmed direct detection of gravitational waves (which is why they seemed so mysterious in the first place).

There are two principal differences between gravity and electromagnetism, each with its own set of consequences for the nature and information content of its radiation, as described below.

  1. Gravity is a weak force, but has only one sign of charge.
    Electromagnetism is much stronger, but comes in two opposing signs of charge.

    This is the most significant difference between gravity and electromagnetism, and is the main reason why we perceive these two phenomena so differently. It has several immediate consequences:

  2. Gravitational charge is equivalent to inertia.
    Electromagnetic charge is unrelated to inertia.

    This is the more fundamental difference between electromagnetism and gravity, and influences many of the details of gravitational radiation, but in itself is not responsible for the dramatic differences in how we perceive these two types of radiation. Most of the consequences of the principle of equivalence in gravity have already be discussed, such as:

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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