Your October 2016 article on black holes describes a singularity with infinite density. It has been my understanding that anything with infinite density also has infinite mass and infinite gravitational attraction. Wouldn’t anything with infinite attraction collapse the universe?

A simple description is that the infinite density of the singularity corresponds to the finite mass of a star collapsed to a point. The density is infinite but the volume infinitesimal, so the mass is still finite. The true description is a bit more complex due to the distortion of space-time that the concentration of mass produces.

However, we believe that the general theory of relativity of Einstein stops being valid before the star shrinks to a point and has to be replaced by a more general theory that takes quantum effects into account. There is no general agreement yet on what such a theory looks like. There are some preliminary indications that such theories would replace the singularity with a region of large density and large quantum fluctuations.