Thanks! So it appears that the "dissipative" mechanism of GR is gravitational radiation. Some dissipation mechanism is required in order to differentiate "forwards" movies from "backwards" movies -- e.g., "heat" is the dissipation mechanism in the Second Law. Theoretically, magical gravitational radiation could come from infinity to enable black holes to move away from one another, but the probability of such radiation appearing in exactly the right time & phase is vanishingly small. Is there anything like a mirror for gravitational waves? I presume that gravitational waves are "lensed" like light waves around a black hole, so perhaps an appropriate configuration of black holes might be able to focus gravitational waves back towards a point in space?? At 05:20 PM 7/26/2009, Eugene Salamin wrote:
I assume that you mean that _any_ configuration of exactly 2 black holes -- regardless of size ratio, energy & angular momentum -- will eventually merge into one black hole, with the emission of gravitational radiation.
[Yes, that is correct. The radiated energy is supplied by increased gravitational binding.]
Even dumber question: what eventually happens to the resulting black hole & its gravitational radiation? In the classical GR case, is this an infinite universe?
[Assuming the initial conditions to be asymptotically flat space, the same will be true after the merger. The resulting black hole is an ordinary black hole with mass and angular momentum, while the radiation propagates off to infinity.