The Properties of Spherical Geodesics in the Kerr Metric
This small methodological chapter is devoted to considering the motion of particles along spherical geodesical trajectories around rotating black holes. The study of this motion is necessary for understanding the inner structure of the disc tilted to the equatorial plane of the rotating black hole. Moreover, this chapter uses a special approach to find out how the values that are measured in a local Lorentz frame of observers falling freely in an axially symmetric gravitational field are related to each other. This approach allows us to understand better the basic principles of measuring physical values in general relativity. These basic principles, which are systematically presented in the next chapter, are required for a more comprehensive understanding the structure of relativistic tilted accretion discs.