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The results of the preceding sections on Omegam and OmegaLambda are summarized graphically in Figure 2. The diagonal dashed line denotes a flat (Omegam + OmegaLambda = 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 Omega ~ 0.2-0.3. In addition, the preliminary results from the Perlmutter et al. (1997) type Ia supernova search are plotted with quoted 1sigma error bars, along with the 95% limits (OmegaLambda < 0.66) on Omegam and OmegaLambda from gravitational lens statistics from Kochanek (1996), shown as an arrow along the diagonal.

Figure 2

Figure 2. Summary of Omega Determinations. The dashed line corresponds to the case for a flat Universe: (Omegam + OmegaLambda = 1). See text for details.

What can be concluded about the value of Omega? 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.

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