  What is the average density of a black hole, assuming its spin can prevent it
from collapsing into a singularity? For stellar black holes, the average
density is incredibly dense and has over a trillion G force and tidal force
that will rip almost anything apart at the black hole boundary.
  Surprisingly, the average density decreases dramatically for massive black
holes. A black hole of 387 million solar masses would have the average density
of water and would be comparable to a giant water balloon extending from the
sun almost to Jupiter. A black hole of 11 billion solar masses would have the
average density of air and would be analogous to a giant air filled party
balloon extending 2.5 times farther out than Pluto. The average mass density in
space itself, however small, eventually can become a low density black hole. If
the average density of the universe matches the critical density of just 5.67
hydrogen atoms per cubic meter, it would form a Schwarzschild low density black
hole of approximately 13.8 billion light years, matching the big bang model of
the universe.
  A black hole can use rotation and/or charge to keep from collapsing. The G
and tidal forces become negligible for large low density black holes. Thus one
can be living in a large low density black hole and not know it. Further
analysis about the critical density rules out an expanding universe and
disproves the big bang theory. Higher densities could produce a much smaller
reflecting universe.
