Plasma globes, or plasma lamps (also called plasma

Plasma (physics)

In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...

 balls, domes, spheres, tubes or orbs, depending on shape), are novelty items that were most popular in the 1980s. The plasma lamp was invented by Nikola Tesla

Nikola Tesla

Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...

 after his experimentation with high-frequency currents

Electric current

Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...

 in an evacuated glass tube

Vacuum tube

In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...

 for the purpose of studying high voltage

High voltage

The term high voltage characterizes electrical circuits in which the voltage used is the cause of particular safety concerns and insulation requirements...

 phenomena, but the modern versions were first designed by Bill Parker

Bill Parker (MIT)

William P. Parker is an artist, scientist, and entrepreneur, best known for inventing the modern design of the plasma lamp. The invention occurred in 1971, when Parker was working as a student in a physics laboratory at the Massachusetts Institute of Technology and accidentally filled a test...

. Tesla called this invention an inert gas

Inert gas

An inert gas is a non-reactive gas used during chemical synthesis, chemical analysis, or preservation of reactive materials. Inert gases are selected for specific settings for which they are functionally inert since the cost of the gas and the cost of purifying the gas are usually a consideration...

 discharge tube.
Most commonly, plasma globes are available in spheres or cylinders

Cylinder (geometry)

A cylinder is one of the most basic curvilinear geometric shapes, the surface formed by the points at a fixed distance from a given line segment, the axis of the cylinder. The solid enclosed by this surface and by two planes perpendicular to the axis is also called a cylinder...

.