Tuesday, February 9, 2010
The Sound of Space
"In Space, no one can hear you scream."
That was the tag line for Ridley Scott's film Alien, and it's generally assumed to be an absolute truth, since we've all been taught that space is a vacuum in which sound does not travel.
However, the actual truth is more interesting. While it may well be that humans cannot hear another human screaming in space (assuming they didn't die instantly from exposure to space anyway), sound waves do travel through space. Space is actually not the total vacuum it's made out to be, and atoms of gas that pervade the entire universe give it what might be defined as an atmosphere of sorts - albeit a very, very thin one.
Even if a human could live unprotected in space long enough to listen for that scream, they still wouldn't hear it, though. Not enough atoms would strike that person's eardrums to perceive the sound. But that doesn't mean the sound waves aren't there.
In 2003, the Chandra X-Ray Observatory announced their discovery that the Perseus galaxy cluster, some 250 million light-years away, was emitting a constant B-flat tone. That note has been sounding, the researchers said, for about 2.5 billion years. It's extremely low and bassy - 57 octaves below below a piano's middle C, to be precise.