Satellite observations of thought experiments close to a black hole

Since black holes are 'black', methods for their identification must necessarily be indirect. Due to the very special boundary conditions on the horizon, the advective flow behaves in a particular way, which includes the formation of a centrifugal-pressure-dominated boundary layer or CENBOL where much of the infall energy is released and outflows are generated. The observational aspects of black holes must depend on the steady and time-dependent properties of this boundary layer. Several observational results are written down in this review which seem to support the predictions of thought experiments based on this advective accretion/outfow model. In future, when gravitational waves are detected, some other predictions of this model could be tested as well.