I will probably try the resistor experiment first. How would I identify such a resistor?
Have you made friends with Google yet?
Here is the result of using this search string: "47k ohm resistor". However, based on your responses so far, it is clearly too dangerous for you to be messin' around with mains voltages at this time. You are safely
insulated from the voltages that are used to produce the plasma ball by its glass envelope. Not so if you go poking around a convenience outlet energized with mains power. Best to stick with "vintage electronics art" and stay away from any direct contact with electricity until you know a LOT more about it.
When I went to hook up another vintage light bulb it lit with only one of the two wires connected. I don't understand how this can be. Does it not take a complete circuit to light a bulb? Please explain if you can.
Yes, it does take a complete circuit to light the bulb. Sometimes the circuit path is not obvious though. For example, when atmospheric lightning comes down from the sky to strike something on the ground, where is the "return path" to complete the circuit?
For your lamp, the circuit is from the central "plasma ball" electrode through the ionized gas inside the globe, then through the glass wall of the globe via capacitive coupling, then back to "ground" through whatever is touching the outside of the globe. By "ground" I mean the other terminal of the high-voltage power supply that is energizing the plasma ball. It is probably not obvious where that is, but the metal framework supporting the plasma display globe and its power supply should be a "gud enuf ground" for your purposes.
The resistance of this path is very high, millions of ohms, because of the insulating glass sphere which is always in between the plasma ball in the center of the globe and "ground" on the outside. That is why you see random discharges of "lightning streamers" inside the globe, and why those streamers appear to be attracted to fingers placed on the outside of the globe. Your body (or other objects) represent a low-resistance connection to the ground-return that completes the circuit. When you bring your fingers (or other objects) close to the glass globe, their low resistance appears in parallel with all other paths to ground.
Placing copper electrodes on the two wire leads of your lamp should
not cause it to light up unless one of the leads, or the surrounding plastic case, is connected to ground, typically by you holding the plastic case or touching one of the two leads with your fingers. Alternatively, you can wrap aluminum or copper foil around the outside of the plastic case and then connect that foil to ground. Or connect just one, but not both, of the two leads to ground. Try visiting
this Internet page for more information on plasma globes.
Yes, free space does have an impedance 376.73 Ohms. Look it up on Wikipedia under the title "Impedance of free space".
This is the
radiation impedance of free space, for purposes of coupling electromagnetic energy into it, typically by means of an impedance-matched antenna. It has nothing to do with how a plasma globe works.