Re: FW: Evanacence of Real History Re: Non-Radiative Evanescent Waves areba... (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Tue, 19 Jun 2007 00:40:32 EDT
From: Mddeming@xxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: FW: Evanacence of Real History   Re: Non-Radiative Evanescent
    Waves areba...

 
In a message dated 6/18/07 10:05:33 P.M. Eastern Daylight Time,  
tesla@xxxxxxxxxx writes:

I agree  you can get "longitudinal"/compression/sound waves in a plasma (a
highly  ionized gas).

However, this is absolutely _not_ a phenomena you can  observe in normal
breathable air, because:

* the density of ions in  air is normally very low, typical no more than a
few thousand per cubic  centimetre

* the mean free path (the distance an atom/ion/molecule  travels before a
collision) for air at sea level is approx 0.1um.

*  the charge on an individual ion is minute, typically just 1  electronic
charge (1.6 x 10-19 C).

These factors mean that random  collisions with neutral particles dominate
any electrostatic interaction  between ions by many many orders of magnitude.


Even if you keep the  ions but remove all the neutral particles (think a near
perfect vacuum  chamber with an incredibly tenuous cloud of ionized gas) the
density and  charge levels we are talking about are still far too low to
sustain waves,  with thermal motion totally dominating.

To get plasma waves in normal  pressure air requires near total ionization of
the medium (think nuclear  fireball or a huge electric arc).  Even if you do
manage to build a  device to do this to large volumes of air, I recon I'll
stick to my wires  for energy transmission rather than roasting everyone on
the planet.
So,  plasma wave in a plasma *YES*, "mechanical, longitudinal oscillation  of
ions" in normal breathable air  *NO*.

Colin.






Hi Colin,
 
Thank you for a breath of quantitative reality. Many ideas sound plausible  
until the orders of magnitude impinge upon them.
 
Matt D.



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