Our knowledge of the universe

Has been sharpened, thanks to new data from the Sloan Digital Sky Survey (SDSS). Using observations of more than 200 000 galaxies, the SDSS team measured, with small and well-controlled systematic errors, the three-dimensional galaxy power spectrum of the universe. Those data alone provide strong new constraints—for example, on the matter spectrum—and independent confirmation of the basic theoretical framework of modern cosmology. When combined with data from the Wilkinson Microwave Anisotropy Probe (WMAP), the new Sloan observations help tamp down uncertainties in several pivotal cosmological numbers. The new best value for the Hubble constant is 0.70 with an uncertainty of about 0.04; the matter density is 0.30, also with an uncertainty of 0.04; the upper limit on neutrino mass is now 0.6 eV. Combining data from SDSS, WMAP, and type I supernova surveys, the age of the universe has now been found to be 13.5 billion years with an uncertainty of 0.2 billion years. In a separate project, astronomers from the SDSS have created a new 3D map of the universe that shows features ranging from Earth’s core, through the Solar System and the Milky Way galaxy, past the galaxies of the SDSS, and out to the cosmic microwave background. The cosmic cartographers say that the conformal map, which preserves local shapes and structures at every stage, is suitable as an educational tool. (M. Tegmark et al. , http://arXiv.org/abs/astro-ph/0310723 ; J.R. Gott III et al. , http://arXiv.org/abs/astro-ph/0310571 .)