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luckyfrank
2010-May-30, 10:30 PM
I find this fascinating so if a nuclear bomb went off in the vacuum of space and i was 5 miles away from the blast also in space i wouldnt hear a thing ?

And if i were in a protective bubble lets say and were near a star going supernova and i was in space i wouldnt hear a thing ?

01101001
2010-May-30, 10:48 PM
I find this fascinating so if a nuclear bomb went off in the vacuum of space and i was 5 miles away from the blast also in space i wouldnt hear a thing ?

Or if you set an alarm clock to go off in 1 minute, put it under a bell jar, evacuate the air, you'll hear nothing when it vibrates its bell, if you got a good vacuum. That's a cheap and effective demo frequently done in schools.

Here's a video of a continuously ringing bell in air of declining density: YouTube: Bell in a Bell Jar (http://www.youtube.com/watch?v=ce7AMJdq0Gw)

DrRocket
2010-May-30, 10:54 PM
I find this fascinating so if a nuclear bomb went off in the vacuum of space and i was 5 miles away from the blast also in space i wouldnt hear a thing ?

And if i were in a protective bubble lets say and were near a star going supernova and i was in space i wouldnt hear a thing ?

At 5 miles from a nuclear blast you would not hear a thing. But the energy emitted across the spectrum would take care of you quite handily.

A supernova ejects rather a lot of matter. You would not near a thing until that matter reached you, and then you would not feel a thing -- no bubble is going to protect you from a nearby supernova.

astromark
2010-May-31, 07:01 AM
I have seen it argued that although it is said you are in space... If you are in a cloud of nebulocity with a density that allowed the transmission of a shock wave... yes you would hear it... But as that density of mater is very high. Earths atmosphere is at 14pounds per sq inch.. and please avoid the temptation to tell me thats pressure not density... I know. The general rule applies that NO. In the vacuum of space sound does not carry. . . and yes. To watch a nuclear explosion or a nova event... You must be a considerable distance from these things to avoid the radiation shock wave that is coming at you. If you hear the sound of subatomic particles ripping through the structure of your space craft. You are in trouble... In the Star Wars epic scene where Darth Vader's Death Star gets it's beans... The sound track should be silent.

JohnD
2010-May-31, 08:50 AM
Luckyfrank,
You have had the assurances of assembled gurus that you really, really can't hear a bomb in space, let alone a scream, and I'm sure you will believe them.

But belief isn't as useful as understanding. Do you understand what sound is, the transmission of energy between gas molecules, so close together that whne they move, they collide, and what space is, a vacuum, a lack of anything, so that nothing can be transmitted across it except electromagnetic energy, including light ? Leave here with that and you have far more to be fascinated with than just a belief!

John

cosmocrazy
2010-May-31, 09:08 AM
Luckyfrank,
You have had the assurances of assembled gurus that you really, really can't hear a bomb in space, let alone a scream, and I'm sure you will believe them.

But belief isn't as useful as understanding. Do you understand what sound is, the transmission of energy between gas molecules, so close together that when they move, they collide, and what space is, a vacuum, a lack of anything, so that nothing can be transmitted across it except electromagnetic energy, including light ? Leave here with that and you have far more to be fascinated with than just a belief!

John

Just to add to Johns post, sound is transmitted as waves through a medium i.e a body of matter that is dense (molecules close enough together) enough to transfer the energy from molecule to molecule. Most of the sound waves you experience are transmitted at around 750mph..ish through the air that surrounds you. In general space is too empty to allow for the transfer of sound waves.

pzkpfw
2010-May-31, 09:30 AM
There's no doubting the lack of sound in space, but ...

---

Driving home through a fairly industrial area, and living in a windy city, I'm used to the sound of wind-blown grit "pitter pattering" against my car.

I imagine it could be like that in a "space battle" (as mentioned in posts above). That is, you'd not hear your enemy blow up, but you'd perhaps hear the bits of him/her and their spaceship hitting your own ship/shields as you "flew" through their debris cloud. (That would change the sound-effects portion of a such a movie).

---

It also occurs that light does have some physical effect - see light sails as a means of transportation.

So I do wonder if a sudden intense burst of light (from an A-bomb or whatever) could produce audible effects - either from the light itself, or through sudden heating of the lit-up panels of ones' craft. (Though I'd guess such effects - if they exist at all - would be too small to notice...)

---

A third thought comes from crews of space craft and stations reporting seeing "flashes" in closed eyes - as cosmic rays hit their retinas.

Could some form of radiation have a noticible effect on a persons auditory nerves and/or sound processing parts of their brain?

Van Rijn
2010-May-31, 09:37 AM
Could some form of radiation have a noticible effect on a persons auditory nerves and/or sound processing parts of their brain?

Perhaps not directly, but there is the matter of "hearing" meteors. From:

http://science.nasa.gov/science-news/science-at-nasa/2001/ast26nov_1/



Colin Keay, a physicist at the University of Newcastle in Australia, not only believes in electrophonic meteors, he's also figured out what causes them. According to Keay, glowing meteor trails give off not only visible light, but also very low frequency (VLF) radio signals. Such radio waves, which oscillate at audio frequencies between a few kHz and 30 kHz, travel to the ground at the speed of light -- solving the vexing problem of simultaneity.

Of course, human ears can't directly sense radio signals. If Keay is right, something on the ground -- a "transducer" -- must be converting radio waves into sound waves. In laboratory tests, Keay finds that suitable transducers are surprisingly common. Simple materials like aluminum foil, thin wires, pine needles -- even dry or frizzy hair -- can intercept and respond to a VLF field.

Here's how it works: Radio waves induce currents in electrical conductors. "Strong, low-frequency currents can literally shake ordinary objects," explains Dennis Gallagher, a space physicist at the NASA Marshall Space Flight Center. "When things shake, they launch vibrations into the air, which is what we hear."

undidly
2010-May-31, 10:46 AM
Just to add to Johns post, sound is transmitted as waves through a medium i.e a body of matter that is dense (molecules close enough together) enough to transfer the energy from molecule to molecule. Most of the sound waves you experience are transmitted at around 750mph..ish through the air that surrounds you. In general space is too empty to allow for the transfer of sound waves.

Do the molecules have to bump together?.
I think not.
A single shell of molecules,each traveling along a radius from an explosion in space, would certainly make a sound if it was to
hit a space ship hull.
This can be tested by noting if the flash of the explosion is seen before the sound is heard.
In space ,as on Earth,molecules are slower than light.

Jeff Root
2010-May-31, 11:22 AM
Just to add to Johns post, sound is transmitted as waves
through a medium i.e a body of matter that is dense
(molecules close enough together) enough to transfer the
energy from molecule to molecule. Most of the sound waves
you experience are transmitted at around 750mph..ish
through the air that surrounds you. In general space is too
empty to allow for the transfer of sound waves.
Do the molecules have to bump together?.
I think not.
A single shell of molecules,each traveling along a radius
from and explosion in space, would certainly make a sound
if it was to hit a space ship hull.
The molecules have to bump together to transmit sound.
What you describe is an impact, and sound resulting from
that impact. A shotgun fired at your spaceship in space
generates a loud bang in the material of the gun itself, but
the sound does not go anywhere. When the pellets hit the
hull of your ship, they will create a bit of a racket inside,
although your Whipple shield and thermal insulation should
limit it to sounding like a very brief torrent of raindrops on
a Quanset hut.

-- Jeff, in Minneapolis

Shaula
2010-May-31, 11:25 AM
Do the molecules have to bump together?.
I think not.
I think so. What you are describing is a shell of molecules striking a skin of metal which recoils or somehow reacts to the impact. The vibrations/energy from this is then passed into the air inside the ship where it can propagate as a sound wave as the medium is dense enough. Sound is defined as a longitudinal pressure wave propagating through a medium - it is not about motion of the molecules as you have envisaged it. When I talk to you the air that leaves my mouth doesn't actually travel from my lips to your ear in order to be heard - it induces a pressure wave which is modulated to carry information to you. The ISM is so tenuous that is cannot support this kind of propagation.

rebel
2010-May-31, 06:05 PM
luckyfrank,
As you can see by these posts, and the bell in a vacuum test, there is a difference between radiation(energy) and acoustic radiation(sound). I hope that if you were confused, that these guys helped you. Good Luck in the future.

DrRocket
2010-May-31, 06:44 PM
---

It also occurs that light does have some physical effect - see light sails as a means of transportation.

So I do wonder if a sudden intense burst of light (from an A-bomb or whatever) could produce audible effects - either from the light itself, or through sudden heating of the lit-up panels of ones' craft. (Though I'd guess such effects - if they exist at all - would be too small to notice...)

The x-rays from a nuclear blast can have a physical effect. The x-ray flux, sufficiently close to the blast, can spall material from the back side of a material. This is a serious consideration in the nuclear hardening of ICBMs that are designed to fly near the fireball of incoming weapons.

Those effects would produce sound inside the vessel being so bombarded.

If you are close enough to experience that effect, you are in serious trouble, and not just from loud noises.

utenzil
2010-Jun-02, 03:40 PM
A more interesting thought experiment than it seems. As mentioned, sound requires vibration to be mechanically transmitted through a medium, and also "typical hearing" requires your eardrums to be mechanically coupled with that medium. Your protective bubble is presumably filled with air: in that scenario any condition that causes the bubble to vibrate can be heard, which isn't so much hearing in space but hearing things bounce off your spaceship.

It maybe leads to thinking about a device that is an "eardrum in space", some kind of a huge membrane with a giant horn-like ear/ear canal?

What sort of energy would be strong enough to push the sparse molecules of gas close enough together to bonk into each other and propagate a vibration? Seems like it would also cause a lot of other things to come a-hurtling shortly thereafter.

danscope
2010-Jun-02, 06:46 PM
You can not have sound wave propagation without a medium.... ie water or air or metal , some continuous matter.
Think: two round backyard pools, two feet appart. Throw a rock into one pool. Waves emminate from the initial spalsh to the edge of the pool and reflect back toward the splash. BUT..... they do not and can not continue in the adjacent pool. And if you throw a rock into a pool without water, you get no splash, no waves.
Well, sound is a wave. A complex wave with little waves running on top. But in a vaccuum , there will be nothing but an object passing through a vaccuum .
Now, if you used an hydrogen bomb to somehow turn an ice comet into steam all at once, and were close enough to it, there would be
something like sound comming from that event. And it will disperse quickly.

So.... no medium; no sound .

eburacum45
2010-Jun-02, 07:10 PM
What sort of energy would be strong enough to push the sparse molecules of gas close enough together to bonk into each other and propagate a vibration? Something like the nebula around a black hole, for instance. Here's a black hole which 'sings' a 'B-flat' note ; but you'd need huge ears to hear it.
http://www.nasa.gov/centers/goddard/universe/black_hole_sound.html

Luckmeister
2010-Jun-03, 01:52 AM
Here's (http://www-pw.physics.uiowa.edu/space-audio/cassini/bow-shock/) one of my favorite "sounds" from space. On June 27, 2004, the Cassini spacecraft recorded the Bow Shock approaching Saturn. Mission scientists converted the electric field noise to the audio spectrum and compressed the timeframe, and the resulting sound is one of the eeriest things I've ever heard. Of course nothing would have been heard within the spacecraft, had it been occupied. Click on the Java Animation link to hear it and see a color representation.

Mike

JohnD
2010-Jun-03, 08:46 AM
Luckmeister,
Think of that as a backing loop.
Now add a bass riff; Dah-dedah, dah-dedah, dah-dedah, dee-dee-dee, da-dedah, etc.

Dr.Who!

Van Rijn
2010-Jun-03, 09:03 AM
Here's (http://www-pw.physics.uiowa.edu/space-audio/cassini/bow-shock/) one of my favorite "sounds" from space. On June 27, 2004, the Cassini spacecraft recorded the Bow Shock approaching Saturn. Mission scientists converted the electric field noise to the audio spectrum and compressed the timeframe, and the resulting sound is one of the eeriest things I've ever heard. Of course nothing would have been heard within the spacecraft, had it been occupied. Click on the Java Animation link to hear it and see a color representation.

Mike

Have you watched Forbidden Planet (http://www.imdb.com/title/tt0049223/)? It would fit right in to the sound effects in that movie.

Hungry4info
2010-Jun-03, 12:12 PM
Driving home through a fairly industrial area, and living in a windy city, I'm used to the sound of wind-blown grit "pitter pattering" against my car.

I imagine it could be like that in a "space battle" (as mentioned in posts above). That is, you'd not hear your enemy blow up, but you'd perhaps hear the bits of him/her and their spaceship hitting your own ship/shields as you "flew" through their debris cloud. (That would change the sound-effects portion of a such a movie).

Agreed. The shuttle crew have reported before that the thrusters make a bit of a 'twang' sound when fired. Clearly the sound can propagate through the structure of the vehicle, and into the air of the cabin.

George
2010-Jun-03, 12:24 PM
Sounds in space? Yep....

Sound wave (http://science.nasa.gov/science-news/science-at-nasa/2003/09sep_blackholesounds/) propgating at 57 octaves below Bb.

[corn] All life forms engaged in metal excavation that were close to the supernova, of course, became A flat miners. [/]

Shaula
2010-Jun-03, 10:41 PM
Sounds in space? Yep....
Worth noting that that is through a nebula, not interstellar space. The nebula is pretty dense compared to the ISM.

George
2010-Jun-03, 11:46 PM
Worth noting that that is through a nebula, not interstellar space. The nebula is pretty dense compared to the ISM.
Why do you say that? Note that the propogation has traveled hundreds of thousands of light years, which is not this size of nebulae.


These ripples are evidence for sound waves that have traveled hundreds of thousands of light years away from the cluster's central black hole.

Shaula
2010-Jun-03, 11:56 PM
In the case of the Perseus cluster, the gas throughout it serves as the medium through which the sound waves coming from the central black hole travel.
The nebula surrounds the cluster. They can only see the sound waves where they are propagating through gas. Ergo the nebula must be at least as big as the range over which they have seen the effects. Sound is a transverse wave, it requires a medium. Sorry but that is the basic fact here. There are some areas where there is enough gas to get sound moving through it but generally the ISM is so tenuous that sound will no propagate. The OP's question referred to the vacuum of space, not the centre of a massive gas cloud.

Edit: D'oh, it was a galaxy cluster. I was tired. Ignore me. Although I would now add that it is worth reading how much power was being put out by that system to generate these density fluctuations. I'm still not happy calling them sound waves but I guess that is just my blind prejudice. After all I don't think of density waves in spiral galaxies as sound waves either.

rebel
2010-Jun-04, 02:29 AM
Just as a reminder, "space" is not completely empty. It's not a perfect vacuum. So....... technically, sound would travel in space. Just not with any significant "strength". To our human ears it would appear not to be traveling at all.

joema
2010-Jun-04, 03:08 AM
Just as a reminder, "space" is not completely empty. It's not a perfect vacuum. So....... technically, sound would travel in space. Just not with any significant "strength". To our human ears it would appear not to be traveling at all.
You can't extrapolate downward that far and assume there's non-audible sound. The best experimental laboratory vacuum is 3 trillion times better than a high school "bell jar" vacuum experiment. Yet that laboratory vacuum is 10,000 times to 100,000 times less perfect than the interstellar medium, at 10E-16 to 10E-17 Torr.

It's obvious from this that although we might call it "interstellar medium" (ISM), there's insufficient medium to carry sound waves, even if pumped by a nuclear warhead.

A typical ISM density is one atom per cubic centimeter. At the pressure of interstellar vacuum each hydrogen atom is on average 100 million atomic diameters from the adjacent atom.

If each atom in the interstellar vacuum was the size of earth, the next atom would farther away than Pluto. What's the chance of earth and Pluto colliding? That's why there's no sound propagation or shock waves in vacuum of deep space. It's not just weak sound that an instrument could hear -- there is none.

Jeff Root
2010-Jun-04, 06:11 AM
Yet George's link shows that sound waves *have* been found
in the interstellar medium of the Perseus cluster of galaxies.
Or, rather than "interstellar", maybe I should say "intergalactic".
That is not a nebula. It is the extremely thin gas between
galaxies, but within the cluster. I do not see how there can be
sound waves in it. I would expect the cavities shown in the
Chandra images to be the extent of it. The IGM should pile up
at the edges of the cavities, not propagate sound waves.

I presume that the "B flat" characterization of the waves is
derived from the distance between crests and their speed.
The distance between crests must be derived from the angular
separation between them and the assumed distance to the
cluster. So if the assumed distance to the cluster is off, the
note will be something other than B flat.

I just thought about it for a few more seconds. I can't believe
those are really sound waves. I think they must be clouds of
gas on ballistic trajectories away from the black hole.

-- Jeff, in Minneapolis

Jens
2010-Jun-04, 06:21 AM
Agreed. The shuttle crew have reported before that the thrusters make a bit of a 'twang' sound when fired. Clearly the sound can propagate through the structure of the vehicle, and into the air of the cabin.

I don't think you have to go to space to find out that is true. I forgot what you call those things, but when two plastic cups are attached to the ends of a string, you can clearly hear sounds transmitted through the string. Also, if a person taps a metal railing you can hear the sound very clearly even if it's so far away that you could barely hear it through the air.

Spoons
2010-Jun-04, 06:31 AM
Another example many may be aware of, though in this day and age it'd probably get you arrested, is when we were kids we'd lean down and put our ear to the railway lines and you can hear the train coming from a much greater distance.

George
2010-Jun-04, 02:18 PM
I'm still not happy calling them sound waves but I guess that is just my blind prejudice. After all I don't think of density waves in spiral galaxies as sound waves either.I remember being very surprised when the article first came out. I wouldn't have ever guessed "sound" propogation would travel such distances.

Yet sound is a longitudnal wave and we know that when gas is compressed then it will subsequently expand, which is how a wave pattern can be formed since this expansion will cause recompression, though diminished.

So, as wild as it sounds (accidental pun), the Bb propogation isn't so crazy after all.

George
2010-Jun-04, 02:19 PM
I don't think you have to go to space to find out that is true. I forgot what you call those things, but when two plastic cups are attached to the ends of a string, you can clearly hear sounds transmitted through the string. Also, if a person taps a metal railing you can hear the sound very clearly even if it's so far away that you could barely hear it through the air.
Yes, it is just a matter of degree of density and the ISM is not a total vacuum, which others have mentioned already.

Luckmeister
2010-Jun-04, 06:56 PM
Have you watched Forbidden Planet (http://www.imdb.com/title/tt0049223/)? It would fit right in to the sound effects in that movie.

Absolutely! I watched it in its first theatrical release in 1956 and it has remained one of my favorite sci-fi movies ever since. A lot of people assume the Theremin was used in the film, but it was a ring modulator circuit designed specifically for the sound track.

Mike

George
2010-Jun-06, 01:10 AM
Absolutely! I watched it in its first theatrical release in 1956 and it has remained one of my favorite sci-fi movies ever since. A lot of people assume the Theremin was used in the film, but it was a ring modulator circuit designed specifically for the sound track.
That entire movie was great in every respect. I am surprised a major re-make has not been done.

Spaceman Spiff
2010-Jun-06, 07:37 PM
Perhaps this is a picky point, but "sound" (pressure) waves can indeed be transmitted through the Galaxy. A necessary (but insufficient for the human ear) requirement of such is that the wavelengths of the pressure disturbance(s) must be much larger than the mean free path distances between the colliding particles. Otherwise, such disturbances are damped exponentially and so quickly die out (such a system is a damped oscillator). Astronomers calculate and use "sound speeds" within gas clouds of the interstellar medium (ISM), and when disturbances move faster than this speed a shock wave can then propagate.

Take our atmosphere, for example. The average particle density near sea-level is about 2.7e19 molecules per cubic cm. The typical mean free path (mfp) distance between molecular collisions is something like 7e-6 cm ( proportional to ( n * d2)-1 ), where n is the number of molecules per unit volume and d is the particle diameter. Typical air sound speeds are ~343 m/s or 343,000 cm/s. So if wavelengths that successfully propagate must be much larger than the molecular mean free path, the frequencies must be much smaller than 49 GHz. This isn't a problem for most pressure waves of interest in Earth's atmosphere.

But in the ISM, the particle (mostly H atoms) number densities are ~1e20 times smaller, and the particles are smaller (being H atoms) by a factor of ~3, thus the mean free paths of the particles is then maybe 1e21 times greater, or ~7e15 cm (or about ~50 astronomical units). Sound speeds are typically ~100,000 cm/s or so. Thus if wavelengths of pressure disturbances must exceed the particle mfp substantially, the resulting required frequencies should be smaller than 1e-11 Hz.

Also: sound waves, as they are normally thought of in Earth's gaseous atmosphere (and heard by the human ear), are longitudinal waves (rather than transverse).

George
2010-Jun-07, 04:04 PM
Take our atmosphere, for example. The average particle density near sea-level is about 2.7e19 molecules per cubic cm. The typical mean free path (mfp) distance between molecular collisions is something like 7e-6 cm ( proportional to ( n * d2)-1 ), where n is the number of molecules per unit volume and d is the particle diameter. Typical air sound speeds are ~343 m/s or 343,000 cm/s. So if wavelengths that successfully propagate must be much larger than the molecular mean free path, the frequencies must be much smaller than 49 GHz. This isn't a problem for most pressure waves of interest in Earth's atmosphere.
Thanks for the details. The "supersonic" speeds within clouds can play an important role in stellar formations.

danscope
2010-Jun-07, 11:42 PM
Yes...yes, of course, of course, BUT...... if you were in a space capsule and a meteor several hundred feet across whizzed by you at some extraordinary velocity, you would never the less 'not' hear it . Isn't this true, gentlemen? isn't this true? Hmmm...

Shaula
2010-Jun-08, 06:35 AM
Yes...yes, of course, of course, BUT...... if you were in a space capsule and a meteor several hundred feet across whizzed by you at some extraordinary velocity, you would never the less 'not' hear it . Isn't this true, gentlemen? isn't this true? Hmmm...
What would be there to hear? That has little to do with sound propagation per se but with the fact that there is no air for it to displace to generate a rushing noise. OK that happens to severely limit sound propagation as well, but...

George
2010-Jun-08, 12:49 PM
Yes...yes, of course, of course, BUT...... if you were in a space capsule and a meteor several hundred feet across whizzed by you at some extraordinary velocity, you would never the less 'not' hear it . Isn't this true, gentlemen? isn't this true? Hmmm... Yes, audible sound requires much greater density. [Of course, instrumentation could detect inaudible sound waves and convert them.]

danscope
2010-Jun-08, 04:51 PM
Hi, Well, surely that must be a case for experiment. :) But I shall not volunteer to be in the capsule! LOL
Best regards,
Dan