Out of my league here for sure but trying to understand, great input from everyone, thanks!
So is it true that black holes never merge, two "merging" black holes continue to merge until one of the two (the smaller) black holes totally dissipate in gravity waves? If a black hole is dissipating then something has to cross the event horizon right?
No, they *do* merge. The result is a BH larger than either of the original two. But the total mass in the BHs has gone down because of a decrease in energy of the system with consequent emission of gravitational waves.
My confusion is that the event horizon is caused by a singularity of a lot of mass, that mass can not merge with another singularity because if the event horizon, stuff spiraling in to the black hole is probably burnt off as gravity waves... But what happens to the singularity itself? Doesn't it have to remain unique to itself?
Thanks!
Once the event horizons merge into one continuous boundary, the singularities inside quickly also merge. It is the event horizon that identifies something as a BH.
It is, however, a mistake to say the singularity has a lot of mass. The mass is a global characteristic, not a local one (for BHs).