[Marika (OP)]

Dan says:

"In space, no one can hear you scream." I think we've all heard that quote.

The sun sends light to the Earth, and although space is near absolute zero, we still feel the heat from the sun here on Earth. So light is able to travel through space and maintain its heat, right?

Much like light travels, If an astronaut screams in their space helmet, would the sound energy leave the helmet and go into space? So if another astronaut was close enough, would they be able to hear the scream?

What do you think?

[PmbPhy]

Dan says:

"In space, no one can hear you scream." I think we've all heard that quote.

The sun sends light to the Earth, and although space is near absolute zero, we still feel the heat from the sun here on Earth. So light is able to travel through space and maintain its heat, right?

Much like light travels, If an astronaut screams in their space helmet, would the sound energy leave the helmet and go into space? So if another astronaut was close enough, would they be able to hear the scream?

What do you think?

Sound is the propagation of disturbances in a gas such as air. No gas, no sound.

[Bill S]

Sound is the propagation of disturbances in a gas such as air. No gas, no sound.

I’ve always accepted that as a “given”, but one of the good things about this sort of forum is that reading posts like this sometime sparks new thoughts about familiar things.

My thought is, if sound propagates by disturbing the molecules of the gas, such that waves are formed, and that it is these waves that propagate; how closely “packed” do the molecules have to be to allow the waves to form?

Space is not empty, but, presumably is too rarefied for wave formation.
As a gas expands, is there a cut-off point beyond which sound will no longer propagate through it?

[Bored chemist]

how closely “packed” do the molecules have to be to allow the waves to form?

Of the order of the wavelength of the sound.

In space someone might (just) hear you scream if your helmets were touching.
They would also hear you if they were in the same spacesuit:-)

[chiralSPO]

I’ve always accepted that as a “given”, but one of the good things about this sort of forum is that reading posts like this sometime sparks new thoughts about familiar things.

My thought is, if sound propagates by disturbing the molecules of the gas, such that waves are formed, and that it is these waves that propagate; how closely “packed” do the molecules have to be to allow the waves to form?

Space is not empty, but, presumably is too rarefied for wave formation.
As a gas expands, is there a cut-off point beyond which sound will no longer propagate through it?

I think the mean free path of the gas particles would have to be somewhat shorter than the wavelength of the waves to be propagated.

On the surface of the earth (760 mmHg), the mean free path of the air molecules is on the order of 100 nm, while on the surface of the moon (10^–12 mmHg), it is closer to 5 km  (https://en.wikipedia.org/wiki/Mean_free_path).

The longest waves that are audible have wavelengths of about 20 m.

EDIT: oops crossed with bored!

[jarvisss]

When I am watching spacebattles in the Star Wars I turn off the sound to make it look more realistic 

[Halc]

When I am watching spacebattles in the Star Wars I turn off the sound to make it look more realistic 

Might as well leave the sound on.  The battles are in no way realistic, and actually depict WW2 airplane battles.  All the physics was modeled after close quarters aircraft, not spacecraft at all.

Can't say there is much improvement anywhere else for that matter.  They've not yet made a movie of Forever War and they'll probably screw up the battles if they do since the cinema-goers like their standard where it is.

[Janus]

When I am watching spacebattles in the Star Wars I turn off the sound to make it look more realistic 

Fun fact.   Originally, the fly by of the Enterprise in the opening credits of Star Trek was going to be silent (no sound in space).  However upon viewing, it felt flat.   We are just too used to expecting a sound when something goes by fast. Without it something seemed lost.
That being said, there was a 1989 movie "Moon Trap" (coincidentally starring Walter Koenig),   Which had a number of action scenes that took place on the Moon, all in perfect silence.

[alancalverd]

You can't scream in space because your lungs will be empty. You can scream in a space suit, and as long as you have selected "VOX" or pressed the "TX" button, your buddies will hear you.

[Bored chemist]

You can't scream in space because your lungs will be empty.

You can scream once- and you probably would.

[Bill S]

Fun fact.   Originally, the fly by of the Enterprise in the opening credits of Star Trek was going to be silent (no sound in space).  However upon viewing, it felt flat.   We are just too used to expecting a sound when something goes by fast. Without it something seemed lost.

The Enterprise banks into its turn; how realistic is that in space?

[alancalverd]

Essential. If the ship suddenly changed direction without banking, the crew would all be squished to one side,or fall over, depending on what artificial gravity system they use to keep them upright in straight flight.

[Bored chemist]

Essential. If the ship suddenly changed direction without banking, the crew would all be squished to one side,or fall over, depending on what artificial gravity system they use to keep them upright in straight flight.

The (magical) system they have which stops them getting mashed when they accelerate to impossible speeds would be able to keep their feet on the floor when they turned a corner.

[Petrochemicals]

What is happening in starwars is the radiation and gravity are affecting the a space ship and producing the sound in the air inside the ship..

[PmbPhy]

Sound is the propagation of disturbances in a gas such as air. No gas, no sound.

I’ve always accepted that as a “given”, but one of the good things about this sort of forum is that reading posts like this sometime sparks new thoughts about familiar things.

My thought is, if sound propagates by disturbing the molecules of the gas, such that waves are formed, and that it is these waves that propagate; how closely “packed” do the molecules have to be to allow the waves to form?

Space is not empty, but, presumably is too rarefied for wave formation.
As a gas expands, is there a cut-off point beyond which sound will no longer propagate through it?

This is like asking "Is the kitchen table flat?"  Well with a micrometer used to measure the flatness then its flat. If you use a tunneling electron microscope then nothing is flat.

[Bill S]

Essential. If the ship suddenly changed direction without banking, the crew would all be squished to one side,or fall over, depending on what artificial gravity system they use to keep them upright in straight flight.

That's how I saw it until I talked to someone whose maths/physics knowledge was far in advance of mine.  He insisted that banking would be necessary only in an atmosphere, and that their artificial gravity and inertial dampers would keep the occupants from ending up in a heap.

[Bill S]

This is like asking "Is the kitchen table flat?"  Well with a micrometer used to measure the flatness then its flat. If you use a tunneling electron microscope then nothing is flat.

That makes good sense to me. 

Relating it to my question: "As a gas expands, is there a cut-off point beyond which sound will no longer propagate through it?"  This seems to say: "Yes, there is, but good luck finding it."

[Bored chemist]

This seems to say: "Yes, there is, but good luck finding it."

Not so much "luck" needed, more a matter of reading the thread, and finding out that the cut off is where the mean free path is of the same order as the wavelength.

[Bill S]

Not so much "luck" needed, more a matter of reading the thread, and finding out that the cut off is where the mean free path is of the same order as the wavelength.

I think the mean free path of the gas particles would have to be somewhat shorter than the wavelength of the waves to be propagated.

I get that, but wouldn't know how to start applying it to space.  So, you are right, "not luck", just more knowledge than I have.