> If, us, that distant observer, never see the black holes merge, then what does that mean for the gravity waves? The black holes don't need to merge to create

> If, us, that distant observer, never see the black holes merge, then what does that mean for the gravity waves? The black holes don't need to merge to create gravity waves, they only need to orbit each other. It turns out that all orbiting bodies create gravity waves, but in most cases the waves are too weak to detect. For black holes, because of their great mass and sometimes close separation, there is a good chance they will create detectable gravity waves. The idea is, if there are no gravity waves, then two black holes could orbit forever with the same separation (no loss of energy). But if gravity waves are real, then the black holes will eventually merge, due to the loss of energy the waves represent. There is already good indirect evidence for gravity waves: https://en.wikipedia.org/wiki/Gravitational_wave https://en.wikipedia.org/wiki/Gravitational_wave The idea here is that the period of orbiting pulsars will change due to the loss of energy represented by the gravity waves. In some cases we can see the change of orbital period, and it's consistent with the expected energy of the gravitational waves (which have not been directly observed).