 Taking relativistic considerations into account, however, we find that black holes are far more exotic entities. Given the usual understanding that relativity theory rules out any physical process propagating faster than light, we conclude that not only is light unable to escape from such a body: nothing would be able to escape this gravitational force. That includes the powerful rocket that could escape a Newtonian black hole. Further, once the body has collapsed down to the point where its escape velocity is the speed of light, no physical force whatsoever could prevent the body from continuing to collapse further, for that would be equivalent to accelerating something to speeds beyond that of light. Thus once this critical point of collapse is reached, the body will get ever smaller, more and more dense, without limit. It has formed a relativistic black hole. Here is where the intimate connection between black holes and singularities appears, for general relativity predicts that, under physically reasonable and generic conditions, a spacetime singularity will form from the collapsing matter once the critical point of black-hole formation is reached (Penrose 1965; Schoen and Yau 1983; Wald 1984). 