Black Holes As Bottomless Pits of Questions?
The black hole mystery represents the boundary of known physics, a window into the thorniest problems of known physics – the marriage of quantum mechanics (QM)and general relativity (GR).
Singularities tell us that they are a point of infinite density. This cannot be but we do not yet have a theory of quantum gravity that tells us what is happening at the center of a black hole. Similarly the event horizon is the boundary of a black hole the region where if you cross it you can’t return. Hawking radiation whereby BH emits a little bit of radiation shows us that the event horizon is a quantum surface that interacts with gravity, like a singularity but a surface which we can theoretically touch. Hence the interest in firewalls, information paradoxes that may give us insights into quantum gravity.
Nor are black holes just windows into quantum gravity, the intersection of GR and QM. They also play an important role in the wider universe, emitting radiation that regulates star formation, galactic evolution and our analysis shows giant black holes in the early universe when they should be smaller.
So many questions! With our new telescopes and new minds looking at the data maybe we can answer some.
Black Holes The Key To Understanding the Universe Professor Brian Cox
Paul Sutter (Ask A Spaceman) summaries the issues well in AAS#200 What are the Top 5 Mysteries in Astronomy? About 15 min from the end