m AND 
MEASUREMENTS
The results of the preceding sections on m and
are summarized graphically
in Figure 2. The
diagonal dashed line denotes a flat (m + =
1) Universe. Plotted are the results from dynamical measurements
(rotation curves, Local Group dynamics, galaxy velocity dispersions,
X-ray clusters) that tend to give low values of
~ 0.2-0.3. In addition, the preliminary results from the
Perlmutter et
al. (1997)
type Ia supernova search are plotted
with quoted 1
error bars, along
with the 95% limits
( < 0.66) on m and
from gravitational lens statistics from
Kochanek (1996),
shown as an arrow along the diagonal.
|
Figure 2. Summary of Omega
Determinations. The dashed line corresponds to
the case for a flat Universe: ( |
What can be concluded about the value of ? Given the available
evidence and the remaining uncertainties, plus underlying assumptions
at the present time, in my own view the data are still consistent with
both an open and a flat Universe. This undesirable situation is very
likely to be resolved in the near future with more accurate mapping of
the anisotropies in the cosmic microwave background radiation (see
Section 9). At this point in time, however,
I believe that it is
premature either to sound the death knell for (``standard'')
inflationary theories or to conclude contrarily that an open Universe
is not a viable option.