> I know, infalling matter sees a black hole - but we don't Sure we do; a black hole is defined by the presence of a horizon, and we will certainly see infalle

> I know, infalling matter sees a black hole - but we don't Sure we do; a black hole is defined by the presence of a horizon, and we will certainly see infallers suffering one-way dimming and redshifting into undetectability. Nobody outside will see what has become of any of the original collapsed matter, either, barring failure of the censorship conjectures and ignoring evaporation. (Infalling matter, however, will collide with whatever state matter inside takes, whether that's classical GR's gravitational singularity or some degenerate form of matter that avoids ultimate collapse.) > "frozen stars" ... "collapsed stars" Right: collapsed to the point where all the material has become too dim and redshifted to observe; frozen to the point where outside observers cannot track the evolution of the material inside the horizon. > quark stars (similar to neutron stars) Similar in that the critical radius is inside the object, rather than the reverse, and that the critical density is not reached within that radius because of terms offsetting internal pressure. Earth is similar to neutron stars in that way too. An ultrarelativistic fermion gas of quarks inside a horizon is still a black hole to any outside observer; the observables from abolishing the gravitational singularity using such a gas (or anything similar; cf. preon stars etc.) are only revealed, if at all, during evaporation.