Today's question has as once again plumbing the depths of space. It comes from Keg who asks:
Why can't anyone hear you scream in space?Well, for one, it wouldn't be a very effective marketing campaign if the slogan was "In space, you can scream all you like and we'll be along shortly." Not that it would have mattered for our friends on the Nostromo as some of those people were bound and determined to end up as Alien food.
But I digress. On Earth, or any other planet with an atmosphere, your screaming causes a soundwave to propagate through the atmosphere. Basically the vibrations of your vocal cords cause the surrounding molecules to be disturbed. They in turn slam into other molecules which slam into other molecules and so on and so forth until said wave hits someone's ears. Their ears then collect the waves and translates them into something their brain recognizes as your plaintive wailings. They then tell you to keep it the hell down as they're trying to watch "Dharma and Greg". That Jenna Elfman is a hoot.
Air isn't the only thing that sound can proprogate through, however it gives us the best chance of being understood as anyone who has ever tried to speak underwater, or hear an argument through a wall can attest to. To be honest, I'm not sure if there's anything specific to our atmosphere that facilitates the transmission of sound waves, so it's possible that people could hear you scream on other planets in our solar system with an atmosphere, they just may be choking/burning/freezing to death while doing so.
Space, on the other hand, has no atmosphere, so when that Alien decides to use your fingers as toothpicks, the vibrations of your vocal cords vibrate the air molecules in your throat which then slam into...nothing. No slamming means no soundwaves. No soundwaves meand no sound and sooner than you can say "lickety split", or I guess mouth the words "lickety split", you're course numero uno for our slime dripping friend.
Now, that doesn't mean that sound doesn't exist in space, just not on any level that we can hear it. There is a gaseous ether that fills the void of space to the tune of about 10 atoms per cubic centimeter of space. Large scale galactic events like solar flares and explosions of planets as a result of fully operational Death Stars, cause vibrations in this galactic ether which then propagate through space. The wavelengths of these disturbances are so huge, that our ears can't collect the waves, and subsequently we can't hear the results of these disturbances. We can detect them through electronic means though, and then compress them into something we puny humans can understand. I guess the Alien poster should have had a disclaimer stating "Note: Does not apply to solar storms."
Ask the Astronomer - Is there really sound in space?
Google Answers - Sound in space?
Wikipedia - Sound Waves