MACH Numbers at Various Altitudes

[DarkWanderer]

Sound isn't defined as something you can hear, it is defined an oscillating pressure wave - and yes, those huge rippling pressure waves in space are sound.

GG, you're showing yourself incompetent. Sound is a travelling pressure wave perceptible by a human, any other transmitted oscillation is infrasound, ultrasound or shock wave. Moreover, simple mechanics of continua cannot be applied when range between molecules of the medium is comparable to the wave length. So, a supernova shock wave it's not a sound in both senses.

I hope, this applies only to your physics knowledge.

Edited July 7, 2009 by DarkWanderer

[GGTharos]

Space is not a vacuum. The scale of things might be different, but that's all there is to it. The point is that there are pressure waves in space and they are transmitted, and they do go places. We cannot detect them using our traditional means - that is, our ears, but they are still created by the exact same physics that cause what we hear as sound, and as such this is exactly what they are. The mechanics are the same.

 

Kinda like light and infrared, though that example doesn't have a particularly unimaginable shift in scale. ;)

 

I will also point out to you the summary of an article:

http://adsabs.harvard.edu/abs/2009ApJ...691..963C

 

Scientists in this particular field (Astronomy) use the word 'supersonic'.

 

Having to hear something in order for it to be sound, and that it must happen on our scale is an archaic notion.

 

GG, you're showing yourself incompetent. Sound is a travelling pressure wave perceptible by a human, any other transmitted oscillation is infrasound, ultrasound or shock wave. Moreover, pressure waves cannot be transmitted in space - only in medium.

I hope, this applies only to your physics knowledge.

Edited July 7, 2009 by GGTharos

[DarkWanderer]

They are still not perceptible - hence, it is no sound. Period.

[GGTharos]

... which is precisely why we have so many applications of 'sound' that we cannot hear ... right? ;)

[DarkWanderer]

... which is precisely why we have so many applications of 'sound' that we cannot hear ... right?

Wrong. Because it is infrasound, ultrasound and shock waves. See above.

[RvEYoda]

If we go by Wiki definition

http://en.wikipedia.org/wiki/Sound

 

sound is defined as vibration within audible frequencies.

 

But wiki is wiki...in this case though, it is probably somewhat acceptable

of a definition, at least imo.

 

Can someone explain to me what the definition of "infra--" and "ultra--" are?

are they latin? greek? some other stuff?

 

I know what they mean for EM / sound waves (infra, freq below human

percievable and ultra, freq above human perceivable)

[GGTharos]

A good number of people with somewhat high academic credentials apparently don't care for your definition.

It seems in the modern world sound turns out to be a particular mechanical process that is rather independent of the human ear. Hm. :)

 

But alright, I'll cede. How about 'stellar sound', though 'Cosmic sound' might sound better. ;)

[DarkWanderer]

I know what they mean for EM / sound waves (infra, freq below human

percievable and ultra, freq above human perceivable)

infra (lat.) = low, lower (than)

ultra (lat.) = over, higher (than)

Simple as that.

A good number of people with somewhat high academic credentials apparently don't care for your definition.

They are obviously not mathematicians or physicists. And you aren't as well - an addition to said above, pressure waves (including sound) in rigid bodies do not involve macroscopic matter movement.

Edited July 7, 2009 by DarkWanderer

[RvEYoda]

Believing something too much is set in stone often just increases the force

of the fall when it some day inevitably occurs ;). I aint saying I have a better

description (various physics = various world descriptions/models), but I find it

akward you would claim we are not mathematicians or physicists and everything

is so discrete in its existance/definition. I wonder Is there truelly a general

accepted definition of "sound"??

What degree do you need ;) ?

 

"pressure waves (including sound) in rigid bodies do not involve macroscopic matter movement."

Like I was saying, particle oscillations. (where avg position for molecules stay constant in some frame

of reference)

Edited July 7, 2009 by =RvE=Yoda

[A.S]

:lol:

 

....once, back in days i asked a girlfriend what the difference between a musicinstrument (a guitar in that case) and a girl is.... she looked wondering, while i revealed the answer: " the art, how you play it"

where she then vehement replied back: No. The Sound :huh:!! (both laughed)

 

Why bothering with little definitions, if you can feel the vibrations :smilewink:

Edited July 7, 2009 by A.S

[Kuky]

You can feel the earthquake vibrations but you can't hear them. Sound should not be defined as vibrations of any matter of any frequency as then even you moving around with your hand left/right at say few Hz would be clasified as sound but its not. Anything that is not audible is not clasified as sound. There are EM waves in all kinds of spectrum, a certain range of wavelengths that is visible to human eye is defined as light, anything infra or ultra of that range gets clasified as another type of EM wave.

[Case]

I will also point out to you the summary of an article:

http://adsabs.harvard.edu/abs/2009ApJ...691..963C

 

Scientists in this particular field (Astronomy) use the word 'supersonic'.

Just to remind you that scientists in this particular field always have been a bit awkward when it comes to sticking to definitions... hell, we're still using cgs for crying out load :D

 

But it all comes down to semantics.

 

In science, the term 'sound speed' is typically used for about anything to do with (shock)waves propagating through a medium, because that speed (velocity actually), can be used for comparison, scaling, and other things and is a very important quantity in describing the physics of the waves and their propagation.

 

There are EM waves in all kinds of spectrum, a certain range of wavelengths that is visible to human eye is defined as light, anything infra or ultra of that range gets classified as another type of EM wave.

You'd be amazed how many times EM waves are called light... In fact, all EM waves, be it radio waves, microwaves, infrared, visible light, ultraviolet or gamma rays move with the speed of light... Edited July 7, 2009 by Case

[GGTharos]

But it all comes down to semantics.

 

In science, the term 'sound speed' is typically used for about anything to do with (shock)waves propagating through a medium, because that speed (velocity actually), can be used for comparison, scaling, and other things and is a very important quantity in describing the physics of the waves and their propagation.

 

 

Quite right - it has grown from 'I can hear stuff' with no physical explanation whatsoever (which is still used by many) to meaning the mechanics of a certain means of energy transfer. There's nothing special about the tiny sliver of frequencies that we can hear to differentiate it.

 

You'd be amazed how many times EM waves are called light... In fact, all EM waves, be it radio waves, microwaves, infrared, visible light, ultraviolet or gamma rays move with the speed of light...

 

Couldn't be 'cause it's all one and the same :D

It's not like it's all governed by the same mechanisms :D

[Kuky]

You'd be amazed how many times EM waves are called light... In fact' date=' all EM waves, be it radio waves, microwaves, infrared, visible light, ultraviolet or gamma rays move with the [i']speed of light[/i]...

 

Well actually I think the correct term should be that light travels at the speed of EM waves as light is just part of its spectrum. The card driver and passangers are travelling at the speed of the car they are in, not other way around. The term is just accepted because light was well known long before people learned of rest of EM waves.

[CHola]

Without a desire to correct or contradict anyone in this discussion, just a few remarks.

The speed of radio waves isn't the speed of light. The speed of light is ~3*10^8 m/s, while speed of radio waves is ~4*10^7 m/s...One may argue that for all intents and purposes, this is the same, but it isn't.

This is mainly the consequence of solar system we're in and the vacuum in our local space, isn't vacuum neither.

IIRC, the difference is rather small and on Earth's surface there's a 10^8 particles per cubic meter, while a half way to the Moon this density drops to 10^5 particles per cubic meter. Don't hold me for exact numbers, but the difference was surprisingly low, when I first learned it.

Deep space (beyond the Solar Wind) is something else, but I don't know, if we have measurement of that, available.

[RvEYoda]

the speed is the same, but the effective transmission speed is

not the same reason is that the photons/whathave you bump into obscacles

/interact along the way, with this and that. At least that is my understanding

of the subject.

 

if you look close into CHola's post, that is what he means ;). (he writes it like, since it is not pure vacuum)

[Kuky]

Yeah, actually all EM waves includng light travel slower in earths atmosphere compared to space because of more interaction with particles. I think maybe we've brain stormed a bit to much about this, I guess it all becomes relative depending how you define things, such as original topic about sound.

[GGTharos]

No, the original topic was about going fast in a jet or something.

 

 

I bet cool_t is loving this :D

[Kuky]

Ah yeah, the fast jets...

[CHola]

Sorry, for the digression. It's just that I find it fascinating, how, what we call space and need to wear pressurized suits for it, is actually full of matter and energy...Someone may even call that a life... :)

[Ells228]

And lets not start on string theory.

a very interesting debate, thanks guys.

[cool_t]

Mach speed changes with air temperature. It's not about drag, but the molecules interacting with one another. Colder air slows the speed of sound, so at high altitude, the speed of sound is slower than at sea level.

 

I don't know about the rest, I don't have the game yet.

 

Hummm...Friction = Drag....The colder the air the less friction...Like ICE..

[104th_Crunch]

No, the original topic was about going fast in a jet or something.

 

I bet cool_t is loving this :D

 

LMAO:rotflmao:

[cool_t]

I also have found that at higher altitudes the Jets burn less fuel meaning the jet does not need to work as hard; less friction = faster speeds and the rate of speed increase "Should" increase according to "Less" "Paracidic" drag... GG..Put some Tea on the boil please :)

[Kuky]

I've hurd that cold air is better for combustion