We traditionally consider Black Holes to be lonely entities in space somehow huddled in a galactic center but how realistic is this interpretation. Surely black holes could be clustered together? If not, why not?
We therefore have to accept the possibility of binary black hole pairs, or tertiary groups or more.
If we disclaim this possibility we need to postulate good evidence to the contrary.
Just a junk in space huddles together then so too should black holes huddle. Will binary, tertiary, quaternary etc clusters emit gravity waves that we could measure? Are we looking? Surely the idea of some lonely black hole infesting the center of a cosey galaxy is somewhat unlikely. Surely black holes would cluster.
Such a combination would be accelerating. Gravity waves would be emitted. Any emission of energy implies an energy loss. Where does this energy go?
Can we claim that energy just goes into orbital decay? Could some of this energy loss cause black hole mass transfer?
Perhaps there are a lot of black holes orbiting their siblings out there. Do we seek their signatures?
Could a modulated gravity force be measured? Would the warping of space-time get in the way of a measurement system? It seems that our moon is measurable in terms of our tides so surely tertiary black hole systems would exhibit some measurable effect back here at home?