Sorry for asking such a stupid question, but this one has been nagging me for some time now:

Sound as we know it exists because of air movements, right? When sound is created, it disturbs the air that exists around us. When that disturbance reaches our ears it's decoded by our brains and that's how we hear sound, right? Assuming that sound happens the way I just said ( and I'm not sure it happens that way... ) there shouldn't be any sound in space, since there's no air out there. But assuming that there is an explosion on board a space station or something equivalent that has air inside it. If the explosion breaks the hull of the craft, the air escapes, right? Is it possible that when that air escapes some sound of the explosion can be heard? Assuming we're in a position where the air can reach us, of course...

Thanks in advance

I'd expect (meaning SWAG) that the air would disperse so quickly, from such a small volume inside the station into the ultimate void, that, were you floating a few meters away from the hull listening (and not getting pushed by the wind) you'd get a very faint sound of rushing wind.
The explosion wouldn't be audible, because the air wouldn't be in space when the explosion happened.

Yes, sound is simply waves of low and high pressure in the air travelling out from something vibrating. Your ear has a drum, which, in turn, is vibrated by the sound waves. Your inner ear then converts these vibrations into nerve signals sent to the brain.

If a volume of air, such as the interior of a space ship, suddenly exploded, the air would decompress very rapidly once in the vacuum of space. By the time the air got to the hearer it would be so thin that it wouldn't be able to support sound waves, i.e. the air molecules would be too far apart.

If the volume of air was big enough and the hearer close enough, I suppose the air could carry the sound of the explosion to the hearer.

Although it would probably be the last thing he heard.

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Not really, no. And it isn't a stupid question at all. When you go somewhere where there isn't air, there are a lot of things that behave rather differently (heating and cooling for instance, but that's a different story altogether).

It isn't so much the air as some "medium" which transmits sound. Go stand next to a really loud speaker at a concert sometime and you can feel the floor vibrating. That is a sound wave travelling through the floor. This is also why astronauts will touch their helmets together if they want to talk directly to each-other: the helmet glass transmits the sound between them.

In space, there is no medium to transmit the sound. So your exploding ship wouldn't be heard by anyone. The gas that escapes would spread out far to quickly to actually allow you to hear anything. So all those wonderfully loud explosions in Star Trek, Babylon 5 and all the movies in space wouldn't actually sound like anything at all.

I couldn't actually find an article about this on the main BA website. HEY PHIL! Think you've got time in that schedule to do a short thing about sounds in space? You could even touch on the Galileo/EOS plasma noises, pulsar blips and various spacecraft vibrations (those aren't all sounds, but can be readily converted into sound, and some are quite strange when you do that).

[note: dang... looks like I wasn't fast enough on this one... oh-well. the more explanations, the better, right?]

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Thanks for the answers, gang. That sure cleared up a couple of ideas I had in my head. By the way, what does SWAG mean?

Someone's Wild-A** Guess.

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Hmmm...

It's important to remember that sound is not really due to the movement of air, but to the movement of pressure waves with air as the medium. Yes, individual air molecules may move back and forth a bit, but the bulk air doesn't move as sound waves move through it.

Now, take a parcel of air (or the hot gases created by an explosion) and turn them loose in the vacuum. Now we have a situation in which the medium itself is moving... rapidly! Every particle of that medium is doing its best to get away from all the others. At the outside edge of the expanding ball of gas, the particles will have little interaction with each other. Deeper in the fireball they will bounce off one another more often, but as time proceeds they will get ever further apart until they, too, no longer interact.

So it seems to me that in this expanding gas cloud, any "sound" (pressure waves) will quickly damp out - the gas molecules simply don't interact enough to sustain sound propagation. Any sound that does get started will only drive the fireball to expand faster, making it even more rarefied and less able to transmit sound. And a really big explosion will expand faster than the speed of sound! By definition, you can't propagate sound under those conditions.

At most, if you're close enough, you might feel (more than hear) a "thump" or shock as the leading edge of the fireball passes you. If it's energetic enough (or you're extremely close) it may put you in motion -- "blow you away", as it were. Other than those effects, I believe it would be pretty much silent. (Of course, other mechanisms could cause you harm -- IR or microwave radiation could cook you, for example.)

SWAG - Scientific Wild A-- Guess

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Sound and Space. Doesn't that come on right after Hearts of Space on the alternative music station?

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