### 35. The Hubble constant

We now discuss the impact of a Cepheid distance to the Fornax cluster
in estimating the general expansion rate of the Universe. Below we
present and discuss three independent estimates, where the analysis is
based both on the new Fornax distance and the distances to other Key
Project galaxies. At the end we intercompare the results for
convergence and consistency. The first estimate is based solely on
the Fornax cluster, its velocity and its Cepheid-based
distance. This
scrutinizes the flow sampled in one particular direction at a distance
of ~ 20 Mpc. We then examine the inner volume of space, leading
up to and including both the Virgo and Fornax clusters. This has the
added advantage of averaging over different samples and a variety of
directions, but it is still limited in volume (to an average distance
of ~ 10 Mpc), and it is subject to the usual caveats concerning
bulk flows and the adopted Virgocentric flow model (Table 4). The
third estimate comes from using the Cepheid distance to Fornax to lock
into secondary distance indicators, thereby allowing us to step out to
cosmologically significant velocities (10,000 km/sec and beyond)
corresponding to distances greater than 100 Mpc. Local flow
uncertainties then are replaced by largescale flow uncertainties;
while the systematically secure Cepheid distances are replaced by
currently more controversial secondary distance indicators. This is
done in order to increase volume and the sample. Averaging over the
sky, and working at large redshifts, alleviates the flow problems.
Examining consistency between independent the secondary distance
estimates, and then averaging over their far-field estimates should
provide a systematically secure value of *H*_{0} and, more
importantly,
a measure of its external error. Comparison of the three ``regional''
estimates (Fornax, local and far-field) then can be used to provide a
check on the systematics resulting from the various assumptions made
independently at each step.