In the largest galaxy survey ever, the Sloan Digital Sky Survey (SDSS) confirmed the role of gravity in growing structures in the universe, using the result to precisely measure the geometry of the universe.
The SDSS researchers from the University of Arizona, New York University, the University of Portsmouth (UK), the University of Pittsburgh and the Massachusetts Institute of Technology, detected ripples in the galaxy distribution made by sound waves generated soon after the Big Bang. "These sound waves left their imprint in the Cosmic Microwave Background, remnant radiation from the Big Bang seen when the universe was 400,000 years old," lead investigator Daniel Eisenstein of the University of Arizona said. "We are now seeing the corresponding cosmic ripples in the SDSS galaxy maps. Seeing the same ripples in the early universe and the relatively nearby galaxies is smoking-gun evidence that the distribution of galaxies today grew via gravity."
Eisenstein made the announcement today during a press conference at the winter meeting of the American Astronomical Society in San Diego. The paper, "Detection of the Baryon Acoustic Peak in the Large-Scale Correlation Function of SDSS Luminous Red Galaxies" was submitted for publication to the Astrophysical Journal on December 31, 2004. Ripples as yardsticks The early Universe was smooth and homogenous, quite a contrast from the clumpy array of galaxies and clusters of galaxies observed today. One of the major goals of cosmology is to understand how these structures grew out of the initially smooth universe.
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