Yes, the size & the spin is explained by them merging before (an explanation so obvious that ofc it didn’t take an eureka moment from the scientists), there is no other explanation really (except them theoretically being like from the ultra young space just after the big gang bang - but the location pretty much affirms this isn’t the case even if those existed).
The spin isn’t an additional mystery, it’s the same one, just two different measurements the system is designed to estimate.
I don’t think this is entirely correct. If the spin of the two black holes aren’t in the same direction, I imagine that they will have less spin as a percentage of the maximum after the merger. It does seem odd to me - a layman with 30 years of interest in physics.
Yes, the size & the spin is explained by them merging before (an explanation so obvious that ofc it didn’t take an eureka moment from the scientists), there is no other explanation really (except them theoretically being like from the ultra young space just after the big gang bang - but the location pretty much affirms this isn’t the case even if those existed).
The spin isn’t an additional mystery, it’s the same one, just two different measurements the system is designed to estimate.
I don’t think this is entirely correct. If the spin of the two black holes aren’t in the same direction, I imagine that they will have less spin as a percentage of the maximum after the merger. It does seem odd to me - a layman with 30 years of interest in physics.