Black Holes Constitute All Dark Matter
  The dimensionless entropy, ${\cal S} \equiv S/k$, of the visible universe,
taken as a sphere of radius 50 billion light years with the Earth at its
"center", is discussed. An upper limit ($10^{112}$), and a lower limit
($10^{102}$), for ${\cal S}$ are introduced. It is suggested that
intermediate-mass black holes (IMBHs) constitute all dark matter, and that they
dominate ${\cal S}$.
