In 1979 I read a book on black holes ( haven't been able to find the book since) and it was describing the various types of black holes; with/without charge, with/without magnetic fields, spinning and non-spinning and various combinations. And something just occurred to me. Yes my friends do call me a bit slow at times.
When star goes supernova and it is massive enough to form a neutron star, much of angular momentum is conserved and the neutron star that forms is spun up, often to incredible speeds. Yet does the same happen with black holes. Is angular momentum conserved and if it is what is it conserved to?
The "black" hole that is "observed' is only the event horizon, not the actual black hole, or more correctly the singularity. And this is my problem. How can a mathematical point, that has no size, retain the angular momentum that should be conserved as increase in rotational rate. I.e how can a point source 'spin'?
I can understand a gravity well due to the mass present at that point source, but how can momentum be conserved???
And if it is conserved in a point source couldn't that mathematical point's angular momentum be spun up to somewhere near to, or heaven forbid faster than the speed of light (angularly
. I mean look at a neutron star. Something the diameter of a moderate city spinning dozens if not hundreds of times a sec. What rotational rate a black hole/singularity.
Please keep this simple for a simple man. I'm sure there are lengthy mathematical dissertations out there on exactly this topic, but a laypersons explanation would be appreciated.