[TCML] Would a Tesla coil work in a vaccum?

[Alice]

Hi Bill, Greg and all,

I have been asking around a lot about this.  I was wondering why all the 
varieties of color.  Someone told me the purple/violet colors are the weaker 
sparks.  Every time I see a color photo or film of someone having sparks 
shoot off their finger tips this is the case.  In the case of a nice big 
coil, the bolts look blue/white when they hit the ground.  They tell me 
those are the ones that are the most powerful.  The kind of gas/air makes 
the color, which, has made me wonder, what color would the sparks be if a 
Tesla coil was sitting on the surface of Mars?  Could one even work on Mars 
in its ultra thin atmosphere?  This raises another question, is gravity an 
issue?  If someone brought a Tesla coil to try out at the International 
Space Station, would the zero gravity affect it?

Becky

----- Original Message ----- 
From: "G Hunter" <dogbrain_39560 at yahoo.com>
To: "Tesla Coil Mailing List" <tesla at pupman.com>
Sent: Saturday, April 17, 2010 3:48 PM
Subject: Re: [TCML] Would a Tesla coil work in a vaccum?


> From: Bill Noble <william_b_noble at msn.com>
> sparks can only be visible when
> there is matter in the intervening space to be
> ionized. In a perfect vacuum, there would be no
> visible sparks or plasma
>
> --------------------------------------------------

Hi Bill,

Interesting stuff, which raised still more questions in my slowly 
calcifying, middle-aged brain.  For example, why are Tesla coil sparks the 
color they are?  Presumably, ionized air contributes the color.  But if 
that's all there is to it, why aren't all TC sparks the same color?  Even in 
my own coils, I've observed discharges of violet, violet-white, purple, 
blue, and various shades of blue-white.  Likewise, Jacob's ladder sparks are 
orange and flaming, while TC spark gap sparks are intense blue-white.  How 
can an ionized 80/20 Nitrogen/Oxygen mix at 1 atm glow at so many different 
colors?  Is it just a matter of temperature?  What about impurities?  I 
suppose the JL uprights might contribute metal ions and metal vapor, which 
could explain the dramatic color difference.

Oddly, what the camera sees and what I see don't always agree.  Sparks that 
look blue-white to me may render as violet in photographs, or vice-versa. 
This is troubling as my cameras and I tend to agree very well on the colors 
of other subjects.  Why the disagreement on the color of TC discharges?

Regarding the ultra-high vacuum situation:  what about a thermionic electron 
tube?  Is a visible discharge inside such a tube possible?  I'm assuming the 
answer is "no", but what about a very high current through a hard vacuum? 
Still invisible?  I guess I'm just fishing around for an answer to the 
ultimate question:  What color is an electron???

Greg




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