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Friday, January 14, 2005



First Sound Waves Left Imprint on the Universe



The early universe rang with the sound of countless cosmic bells, which filled the primordial darkness with ripples like the surface of a pond pounded by stones. The wave fronts later served as spawning grounds for galaxies, astronomers announced Tuesday.

The effect had been predicted by theory. Researchers found its imprint on the sky in two independent, comprehensive galaxy surveys presented here at a meeting of the American Astronomical Society.

The findings give scientists greater confidence that their limited understand of the universe's structure, contents and evolution are on track.

Sound waves in space may sound unlikely. Here's what astronomers back in the 1960s theorized:

The universe was initially a thick, hot soup that trapped light. About 350,000 years after the Big Bang -- the theoretical beginning of it all some 13.7 billion years ago -- things cleared and an imprint of the earlier conditions was left on the entire cosmos. Scientists previously detected this imprint as the Cosmic Microwave Background. It is everywhere in the sky and packs important clues about the structure of the nascent universe.

Something similar should have happened with sound, explained Daniel Eisenstein of the University of Arizona and leader of one of the studies, based on the Sloan Digital Sky Survey.

In the dark era, if you pushed on a pocket of hot gas, it would resist being compressed and bounce back.

"The whole thing sits there and rings like a bell," Eisenstein said. The thick hot soup would transmit sound waves in the same manner that air or water do. When the fog cleared, the sound waves would have remained as countless ripples of material. (cont.)





posted by DW  # 1:00 PM


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