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The current best measurements for the cosmological parameters yield:

Omegam ~ (0.2 - 0.4) ± 0.1 (1-sigma)
H0 ~ (67 - 73) ± 7 km/sec/Mpc (1-sigma)
t0 ~ (14 - 15) ± 2 Gyr (1-sigma)
OmegaLambda < 0.7 (2-sigma)

The low value for Omegam and relatively high value for H0t0 do not favor the standard Einstein-de Sitter ( Omegam = 1, OmegaLambda = 0) Universe; however, this model cannot be ruled out at high statistical significance. Moreover, systematic errors are still a source of serious concern. If the new HIPPARCHOS calibrations are confirmed, the ages of globular clusters may be as low as 10-12 Gyr. Rapid progress is expected in addressing these systematic effects; in particular new data from HST, HIPPARCHOS, and MAP/PLANCK offer the enticing possibility that all of the cosmological parameters may soon be measured to unprecedented accuracies of ±1-5% within a decade. Let us hope that unexpected systematic errors will not continue to lurk (as they have done historically so many times before) in these future efforts to define the basic cosmological parameters.


It is a pleasure to thank the organizing committee for an extremely enjoyable and interesting conference, and for the opportunity to speak. The work presented on the Cepheid-based extragalactic distance scale (Section 5.4) has been done in collaboration with the Hubble Space Telescope Key Project team on the Extragalactic Distance Scale and I would like to acknowledge the contributions of R. Kennicutt, J.R. Mould (co-PI's), S. Faber, L. Ferrarese, H. Ford, B. Gibson, J. Graham, J. Gunn, M. Han, J. Hoessel, J. Huchra, S. Hughes, G. Illingworth, B.F. Madore, R. Phelps, A. Saha, S. Sakai, N. Silbermann, and P. Stetson, and graduate students F. Bresolin, P. Harding, D. Kelson, L. Macri, D. Rawson, and A. Turner. This work is based on observations with the NASA / ESA Hubble Space Telescope, obtained by the Space Telescope Science Institute, which is operated by AURA, Inc. under NASA contract No. 5-26555. Support for this work was provided by NASA through grant GO-2227-87A from STScI.

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