"The singularity is the most mysterious and problematic part of a black hole. It's where our concepts of space and time ...

Einstein's special relativity, established in 1905, unified space and time into a four-dimensional continuum. It relies on two core principles: Galileo's relativity and the constancy of light's speed.

Even the drastic simplification of reducing the space-time dimension to two or less seemed hard, but work done in 1987-89, including that by Vladimir Kazakov and Alexander Migdal (Landau Institute, ...