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Thread: Vacuums

  1. #1 Vacuums 
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    Are vacuums all relatively so?

    Does a sound wave actually travel in space to an imperceptible degree?

    If a container is evacuated gradually is there a point at which it can be said that the wave will no no longer pass through?

    Is this where quantum tunneling comes into play perhaps?


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  3. #2  
    Brassica oleracea Strange's Avatar
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    There have to be enough atoms/molecules that the movement back-and-forth (sound) can be transferred from one particle to another. If they are too "spaced out" then they won't be able to bump into one another and the sound won't be transmitted.


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    Bullshit Intolerant PhDemon's Avatar
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    There is no such thing as a perfect vacuum, there is always some matter present.

    For a sound wave to travel, there needs to be a certain minimum density in the material it is passing through, the density of space is too low for sound to be transmitted.

    Tunnelling (https://en.wikipedia.org/wiki/Quantum_tunnelling) has nothing to do with sound waves, but matter waves (https://en.wikipedia.org/wiki/Matter_wave) and is irrelevant when discussing sound.
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    Brassica oleracea Strange's Avatar
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    That got me thinking, is there the possibility of sound waves tunnelling... Well, almost: Tunneling across a tiny gap | MIT News
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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  6. #5  
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by geordief View Post
    Are vacuums all relatively so?

    Does a sound wave actually travel in space to an imperceptible degree?

    If a container is evacuated gradually is there a point at which it can be said that the wave will no no longer pass through?
    It really is tied to the relationship between the wavelength of the Sound, and the length of the free mean path of the particles of the medium.
    Sound travels by particles jostling each other in a way that creates alternate compression and rarefactions. This is because particles don't have to travel very far before encountering another. As the medium becomes more rarefied, particle can travel longer and longer distances before striking another. In fact, they can bypass a good number of closer particles along the way. If you try to create a sound, it generally ends up changing the velocities of randomly dispersed particles rather then producing a coherent pattern.
    Now if you push on a whole bunch of particle over a long period of time, you could produce a denser reqion of particle, which could propagate. What you are doing is making a "sound" wave with a much longer wavelength than the average distance a individual particle in likely to travel before hitting another.
    Our own galaxy has density waves that slowly move through it and help generate star formation. ( the spiral arms you see in galaxies are causes by these density waves.) In a sense you could say that they are extremely low frequency, low wavelength "sound" waves moving through the galactic medium.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  7. #6  
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    Quote Originally Posted by Janus View Post
    Quote Originally Posted by geordief View Post
    Are vacuums all relatively so?

    Does a sound wave actually travel in space to an imperceptible degree?

    If a container is evacuated gradually is there a point at which it can be said that the wave will no no longer pass through?
    It really is tied to the relationship between the wavelength of the Sound, and the length of the free mean path of the particles of the medium.
    Sound travels by particles jostling each other in a way that creates alternate compression and rarefactions. This is because particles don't have to travel very far before encountering another. As the medium becomes more rarefied, particle can travel longer and longer distances before striking another. In fact, they can bypass a good number of closer particles along the way. If you try to create a sound, it generally ends up changing the velocities of randomly dispersed particles rather then producing a coherent pattern.
    Now if you push on a whole bunch of particle over a long period of time, you could produce a denser reqion of particle, which could propagate. What you are doing is making a "sound" wave with a much longer wavelength than the average distance a individual particle in likely to travel before hitting another.
    Our own galaxy has density waves that slowly move through it and help generate star formation. ( the spiral arms you see in galaxies are causes by these density waves.) In a sense you could say that they are extremely low frequency, low wavelength "sound" waves moving through the galactic medium.
    I think I got that
    Mayflow would like that;a hotline to God.The Sound is out there
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  8. #7  
    exchemist
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    Quote Originally Posted by geordief View Post
    Quote Originally Posted by Janus View Post
    Quote Originally Posted by geordief View Post
    Are vacuums all relatively so?

    Does a sound wave actually travel in space to an imperceptible degree?

    If a container is evacuated gradually is there a point at which it can be said that the wave will no no longer pass through?
    It really is tied to the relationship between the wavelength of the Sound, and the length of the free mean path of the particles of the medium.
    Sound travels by particles jostling each other in a way that creates alternate compression and rarefactions. This is because particles don't have to travel very far before encountering another. As the medium becomes more rarefied, particle can travel longer and longer distances before striking another. In fact, they can bypass a good number of closer particles along the way. If you try to create a sound, it generally ends up changing the velocities of randomly dispersed particles rather then producing a coherent pattern.
    Now if you push on a whole bunch of particle over a long period of time, you could produce a denser reqion of particle, which could propagate. What you are doing is making a "sound" wave with a much longer wavelength than the average distance a individual particle in likely to travel before hitting another.
    Our own galaxy has density waves that slowly move through it and help generate star formation. ( the spiral arms you see in galaxies are causes by these density waves.) In a sense you could say that they are extremely low frequency, low wavelength "sound" waves moving through the galactic medium.
    I think I got that
    Mayflow would like that;a hotline to God.The Sound is out there
    Just don't anyone tell Quantumologist!
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