  The cause of the extended rotation curves of galaxies is investigated. It is
shown that conventional sources and most exotic sources for the needed
gravitational fields are implausible. We suggest spatial fluctuations in a
scalar field, similar to the inflation field, are responsible for the
gravitational fields. These fluctuations play the role of `dark' halos around
galaxies. They take $\sim 10^5$ yrs to develop and could not have been
important in the early days of the universe. When galaxies are clustered, a
$\Lambda-$term appears naturally in this theory. The universe's present energy
density associated with these scalar field ariations is $\Omega \sim 1/2-2/3$.
A possible scenario is uggested in which the cosmic scale factor ${\cal R}(t)$
would have experienced a recent acceleration. A discussion of further
observations and theoretical work needed to resolve some ambiguities in the
theory is given.
