Hi all, I have a question that bothers me a little about this release from NASA: http://science.nasa.gov/headlines/y2003/09sep_blackholesounds.htm?list726251 The argument is that the structures seen by Chandra around a supermassive black hole in the Perseus Cluster are evidence of sound waves booming through the surrounding gas. The sound waves "sweep across hundreds of thousands of light years," the Chandra folks say at: http://chandra.harvard.edu/photo/2003/perseus/more.html. The problem I have is that surely, those hundreds of thousands of light years encompass mostly vacuum. What mechanism could allow an excited gas atom 300 miles away from the next atom to pass along sound? Doesn't it require physical contact? If not, I guess those old Flash Gordon movies were right after all, and we should hear the buzz as those sparkler-driven spaceships cruise the interstellar medium. Thanks, Joe Joe Bauman science & military reporter Deseret News bau@desnews.com (801) 237-2169