I have two questions regarding Kerr black holes, which I am hoping some of you might be able to shed some light on for me. 1. What is the physical significance / meaning of the inner ergosurface, the one beyond the inner horizon ? If considered as a boundary surface, what would it separate from what ? 2. With regards to the hypothetical closed time-like curves beyond the Cauchy horizon, how would a test particle need to free-fall in order to describe such a geodesic ? Would it have to fall through the Cauchy horizon in a specific manner to "enter" a CTC, or does it always happen when you cross this boundary ? I am aware of the instability issue in the Kerr geometry; the above questions are meant only to help me better understand the geometric structure of this metric.