Is it possible to make a call in a black hole?

Answer 1

In the canonical sense it would be highly difficult to make a call from inside a black hole. It would certainly be impossible to make a call from the inside to the outside, since no information can exit the event horizon once crossed; thus, the call would have to be placed entirely from within it. One would have to consider the means by which the person making the call and the person receiving it entered the black hole; both would have had to survive crossing the event horizon and thus have survived the intense gravitational field, tremendous tidal forces (for all but the largest black holes) and the radiation from the accretion disk and polar relativistic jets. Presuming this is possible, there would remain the functionality of the infrastructure to make a call, such as the presence of operational public switched telephone network equipment, whose existence inside a black hole would once again be highly unlikely, and whose entrance into the black hole subject to the same stresses. Further, presuming all these factors to be favorable, the conditions inside the black hole would have to be conducive to placement of a call; the physics of spacetime inside a black hole are counterintuitive and likely not yet fully understood.

Some theories posit that the black hole is a boundary to another universe, and/or that we are ourselves within a separate universe bounded by the event horizon of a black hole observable from a universe from which ours originated; although these theories are speculative, in this case it might be possible that all the calls we make are from within a black hole.