Cosmology The SDSS’s map of the Universe. Each dot is a galaxy; the color bar shows the local density. Measurements of large-scale structure in SDSS maps of galaxies, quasars, and intergalactic gas have become a central pillar of the standard cosmological model that describes our understanding of the history and future of the Universe. SDSS data have helped to demonstrate that the Universe is dominated by unseen dark matter and pervasive dark energy, and seeded with structure by quantum fluctuations in the infant cosmos. Those fluctuations have grown into the large-scale structure we see today. The SDSS’s high-precision maps of cosmic expansion history using baryon acoustic oscillations (BAOs) have been especially influential in quantifying these results, yielding exquisite constraints on the geometry and energy content of the universe. BAOs were first detected in galaxy clustering by the SDSS-I and in the contemporaneous 2dF Galaxy Redshift Survey, and have since also been detected in intergalactic hydrogen gas using Lyman-alpha forest techniques. These BAO measurements are beautifully complemented by the results of the SDSS-II Supernova Survey, which has provided the most precise measurements yet of cosmic expansion rates over the last four billion years. In addition, statistical measurements of galaxy motions and weak gravitational lensing provide some of the strongest evidence to date that Einstein’s General Relativity is an accurate description of gravity on cosmological scales.
Posted on: Sat, 19 Jul 2014 08:22:15 +0000
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