3 ms·

> But they will take infinite time to actually merge though. Yes, from the perspective of a distant observer. From the perspective of an observer falling into

by lutusp 11y ago

> But they will take infinite time to actually merge though. Yes, from the perspective of a distant observer. From the perspective of an observer falling into the BH, time will pass in the usual way, indeed it must. > The closer they get to that event horizon the slower time goes, so they will take longer and longer to orbit. Only from the perspective of a distant observer. This might explain why black holes last as long as they do, from the perspective of a distant observer. For all we know, they all blow up in short order from the perspective of an observer falling into one.

ars 11y ago
I am speaking about the distant observer though. I am speaking the search for gravity waves. If, us, that distant observer, never see the black holes merge, then what does that mean for the gravity waves?
- lutusp 11y ago
  > 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).

by lutusp 11y ago

ars 11y ago

I am speaking about the distant observer though. I am speaking the search for gravity waves. If, us, that distant observer, never see the black holes merge, then what does that mean for the gravity waves?

lutusp 11y ago
> 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).