system
Given the following post, respond as if you're commenting on Reddit:
human
If stars conserve angular momentum when they collapse into a black hole, shouldn't the rate at which the black hole spins that tell us that whatever is in the center of a black hole has a measurable diameter rather than being an infinitely dense point?

After all, if there were an infinitely dense point with no diameter at the center of a black hole, wouldn't the black hole have to spin infinitely fast?
gpt
A rotating or "Kerr" black hole, as descibed by general relativity, has a ring singularity, with a non-zero major radius (across the ring) but zero minor radius (thickness of the ring 'material'). The singularity being a ring resolves the angular momentum issue.