In article , Ohioguy wrote:

I noticed something funny about the neon light on my Dad's basement
light switch. When I put my finger anywhere even NEAR the tip of the
switch, the neon light appears to *JUMP* away from the end back towards
the base of the switch. I assume there is something of a charge on my
hand, and that is causing the neon gas 'plasma' or whatever you call it
to move away? I never really investigated this, but found it very
interesting.

It is common for neon lamps to be operated with the cathode/negative
glow not completely covering an electrode. In any given glow discharge
lamp, this glow layer has some sort of natural current density in mA per
square centimeter. If the current is low enough to incompletely cover the
electrodes at that current density "rate", then the electrodes are
incompletely covered by glow.

And, it is easy to cause the glow to move around. In some neon lamps
operated with glow incompletely covering their eectrodes, the
cathode/negative glow layer even jumps around on its own. The best
example of this is "flicker flame" neon lamps.

With AC, some trace of current can flow through insulators (such as the
glass bulb) due to "capacitive coupling". Each electrode has to re-fire
60 times per second with usual AC in North America (50 times per second in
Europe). It sounds to me plausible for touching some neon lamps to cause
their glow pattern to shift.

--
- Don Klipstein )