# How the rotation of gravitational field is a source for the field?

In lecture notes that I have about black holes and space-time metrics it says:

The Schwarzschild solution, which is appropriate outside a spherical, non-spinning mass distribution, was discovered in 1916. It was not until 1963 that a solution corresponding to spinning black holes was discovered by New Zealander Roy Kerr. This solution leads to the possible existence of a family of rotating, deformed black holes that are called Kerr black holes.

Angular momentum is complicated: In Newtonian gravity rotation produces centrifugal effects but does not influence the gravitational field directly. But angular momentum implies rotational energy, so in general relativity rotation of a gravitational field is itself a source for the field.

I understand that in Newtonian mechanics rotation invokes a centrifugal force, how to reconciliation this in the case of gravity is something I hope somebody could elaborate here. thank you!

• Is there maybe a translation issue here? Is the original in English? Is the lecturer a native English speaker? I can't make much sense of that sentence (and not just because of the minor error of a missing article after "of"). I'm guessing it means to say something more like a rotating gravitational field is a source for the field — which I suppose could be considered true in the sense that (for example) a black-hole binary stirs up gravitational waves as it rotates. Is there any more context?
– Mike
Jan 20, 2018 at 15:41
• Which lecture notes? Jan 20, 2018 at 16:24