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We thus end up with a picture of the distribution of the density of energy density in a flat universe represented by Figure 1 [99]. One of the most striking things about the present era in cosmology is the remarkable agreement between the values of the cosmological densities and the other cosmological parameters obtained by different methods - except possibly for the quasar lensing data which favors a higher Omegam and lower OmegaLambda, and the arc lensing data which favors lower values of both parameters. If the results from the new CMB measurements end up agreeing with those from the other methods discussed above, the cosmological parameters will have been determined to perhaps 10%, and cosmologists can focus their attention on the other subjects that I mentioned at the beginning: origin of the initial fluctuations, the nature of the dark matter and dark energy, and the formation of galaxies and large-scale structure. Cosmologists can also speculate on the reasons why the cosmological parameters have the values that they do, but this appears to be the sort of question whose answer may require a deeper understanding of fundamental physics - perhaps from a superstring theory of everything.

Figure 1

Figure 1. The Great Seal of the United States, found on the back of the American dollar bill, includes a pyramid representing strength and duration, capped by the eye of Providence. Here we use this to represent the visible matter in the universe (Omegavis approx 0.005), with the upper triangle containing the eye representing the metals (elements heavier than hydrogen and helium, with Omegametals approx 10-4) since most of the mass of our bodies is made up of these elements. The three-dimensional nature of the pyramid, which here continues below the part shown on the Great Seal, makes it useful for showing graphically the relative proportions of the dark baryons, cold dark matter, and cosmological constant (or dark energy).

This work was supported in part by NSF and NASA grants and a faculty grant at UCSC. I am grateful to Leo Stodolsky for hospitality at the Max Planck Institute for Physics in Munich, and to the Alexander von Humboldt Foundation for a Humboldt Award.

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