View Full Version : Question (Sound in a Nebula)!

Solid Bismuth
2008-Oct-29, 12:42 PM
Can sound travel through a nebula?

2008-Oct-29, 12:45 PM
Can sound travel through a nebula?


But not the sort of sound waves that would allow you to hear someone shouting 30 feet away. Sorry.

2008-Oct-29, 12:48 PM
Hi Solid Bismuth,

Would you please make sure your thread title gives a clue what the thread is about in the future? I've updated this one.

2008-Oct-29, 12:56 PM
:) As Calvin says above. Depends on the density, and how loud your sound is I should imagine.

p.s. you giving up on your story?

Solid Bismuth
2008-Oct-29, 01:08 PM
Well, if I was outside my ship in the middle of a dense nebula. Would I hear a gunshot 40 ft. away?

P.S. No, I am just basically scrapping that condensed intro and will work on turning it into an actual novel.

Jeff Root
2008-Oct-29, 01:18 PM
Most places in most nebulae have a density far, far lower than that of
Earth's atmosphere near the surface. Nebulae are visible because you
are looking through clouds that are light-days to light-years thick.
Sound can still travel through such thin gases, because the molecules
will still bump into each other, but as far as humans are concerned, it
might as well be a perfect vacuum. You might feel the expanding gases
from a gunshot 4 feet away, but you couldn't really hear anything.
At 40 feet, the gases might cause a light sheet of paper to flutter.

-- Jeff, in Minneapolis

Solid Bismuth
2008-Oct-29, 02:56 PM
Alright, thanks.

2008-Oct-29, 06:15 PM
As you will have noted. Jeff's answer is all you need to know. I will just add (un-necessarily), That audible sound is nothing more than reverberating shock waves that have moved your ear drum. The frequency of such dictates volume and tone.
Only in a dense enough strata could sound be transmitted. It works nicely here on Earth thanks to a 14psi atmospheric pressure.

2008-Oct-29, 06:18 PM
Well, if I was outside my ship in the middle of a dense nebula. Would I hear a gunshot 40 ft. away?

Not unless/until the bullet struck your helmut...

2008-Oct-29, 09:18 PM
Even louder if it hit you in the helmet

2008-Oct-30, 12:37 AM
Then again, you may still not hear anything if it hit you in the helmet;)

2008-Oct-30, 03:11 PM
I wear the good helmets when I'm gun fighting during an EVA.

2008-Oct-30, 06:29 PM
I wear the good helmets when I'm gun fighting during an EVA.

BigDon...Ya, but the bad guys use armor penetrating bullets, depleted uranium slugs, titanium skins, and a teflon coating...ouch.:shifty:pete

2008-Oct-31, 07:47 PM
Good thing I'm faster.

man on the moon
2008-Nov-02, 05:11 AM
If you had a gun that could fire in a nebula, I think the bullet would be moving faster than it would if fired on Earth. The idea of a gun is to explode the charge and disrupt the otherwise balanced "~14 lbs/sq inch" so that the round has the sudden urge to allow the now rapidly changing pressure behind it to equalize with the pressure ahead of it.

With 14/i pushing down the barrel at it, it reaches whatever speed it is supposed to and continues out into the atmosphere where air drag (slightly) affects its cruising speed.

In a vacuum (or close enough in this case w/the nebula) there would NOT be 14 lbs/inch to start with, so the pressure differential would be that much greater when the charge goes off. Second, the drag created on the round would be much less (and no gravity to pull it down either) so...

Hope you down a Monster or two before you go into a shooting match Big Don!

man on the moon
2008-Nov-02, 05:12 AM
*At least I think I got it right...

Solid Bismuth--I think "sound" in the sense of disruption of molecules in a gas perpetuating itself through that medium COULD occur. It would have to be a rather "big/energetic" sound, and would be transmitted somewhat more slowly than one is used to sound traveling through the atmosphere here on Earth. By energetic, I mean it would have to be able to give the gas molecules the necessary momentum to traverse the distance between themselves and their neighbors. If the sound were to go any great distance, it would have to be more energetic than...example: A nebula gnat, comparable in size to our own gnats on Earth, flaps its wings and contacts two gas molecules due to decreased density. The rocket you are outside of fires up and moves a few million. The two the gnat moves would not be particularly detectable by you unless it were inside your helmet (which it is not in this scenario). The few million WOULD, but at a far lower pressure than you would experience were you standing on a launchpad on Earth when the rocket fired up.

The exact speed of the "sound" would depend on the density of the gas, but probably not quickly enough to warn you of a shot coming from 40 feet away. Even on Earth it is rather hard to dodge a bullet from 40 feet, even if you skip the sound and go straight to watching for the smoke/ejected shell.

*Still pretty sure I got this (close to) right...