Astrophysics (index)

Birkhoff's Theorem

(shows GR qualities of a spherically-symmetric mass)

Birkhoff's Theorem proves qualities about General Relativity (GR) that demonstrate its relation to Newtonian Gravity, i.e., conditions under which the two converge.

One consequence is that under GR, isolated, non-rotating, spherically-symmetric masses are equivalent to gravity from a point mass, analogous to what Isaac Newton proved about Newtonian Gravity to make it practical to apply it to the dynamics of the solar system. A corollary to this is that a spherically symmetric pulsation (e.g., a star's pulsating that happens to retain perfect spherical symmetry of its mass) creates no Gravitational Waves (GW).