Changing The Reference Frame
Every isolated unstable black hole decays rapidly to a stable black hole; and (modulo quantum fluctuations) stable black holes can be completely described (in a Cartesian coordinate system) at any moment in time by these eleven numbers:
- mass-energy M,
- linear momentum P (three components),
- angular momentum J (three components),
- position X (three components),
- electric charge Q.
These numbers represent the conserved attributes of an object which can be determined from a distance by examining its gravitational and electromagnetic fields. All other variations in the black hole will either escape to infinity or be swallowed up by the black hole.
By changing the reference frame one can set the linear momentum and position to zero and orient the spin angular momentum along the positive z axis. This eliminates eight of the eleven numbers, leaving three which are independent of the reference frame. Thus any black hole which has been isolated for a significant period of time can be described by the Kerr–Newman metric in an appropriately chosen reference frame.
Read more about this topic: No-hair Theorem
Famous quotes containing the words changing, reference and/or frame:
“The distempers of the soul have their relapses, as many and as dangerous as those of the body; and what we take for a perfect cure is generally either an abatement of the same disease or the changing of that for another.”
—François, Duc De La Rochefoucauld (1613–1680)
“If we define a sign as an exact reference, it must include symbol because a symbol is an exact reference too. The difference seems to be that a sign is an exact reference to something definite and a symbol an exact reference to something indefinite.”
—William York Tindall (1903–1981)
“Writing a novel is not merely going on a shopping expedition across the border to an unreal land: it is hours and years spent in the factories, the streets, the cathedrals of the imagination.”
—Janet Frame (b. 1924)