Andrzej Radosz

Red shift in communication by means of exchange of electromagnetic signals is discussed for objects around the event horizon in the case of Schwarzschild space-time. Above horizon this redshift may be expressed in a simple form in terms of local speed. Nontrivial aspects of communication below horizon are pointed out. It is argued that the arrow of time below horizon cannot be inferred by observations carried out outside. Two scenarios are possible: one corresponding to Unruh's metaphor and the other one, that turns out to be even more exotic.