  Spacetime foam manifests itself in a variety of ways. It has some attributes
of a turbulent fluid. It is the source of the holographic principle.
Cosmologically it may play a role in explaining why the energy density has the
critical value, why dark energy/matter exists, and why the effective dynamical
cosmological constant has the value as observed. Astrophysically the physics of
spacetime foam helps to elucidate why the critical acceleration in modified
Newtonian dynamics has the observed value; and it provides a possible
connection between global physics and local galactic dynamics involving the
phenomenon of flat rotation curves of galaxies and the observed Tully-Fisher
relation. Spacetime foam physics also sheds light on nonlocal gravitational
dynamics.
