فربین ِ بیرکهوف farbin-e Birkhoff
*Fr.: théorème de Birkhoff*
For a four dimensional → *space-time*, the
→ *Schwarzschild metric*
is the only solution of → *Einstein's field equations*
which describes the gravitational field created by a spherically
symmetrical distribution of mass. The theorem implies that
the gravitational field outside a sphere is necessarily static, and that the
metric inside a spherical shell of matter is necessarily flat. The theorem was first demonstrated in 1923 by George David Birkhoff (1884-1944),
an American mathematician; → *theorem* |