For the first time, engineers at Caltech have created a stable ring of plasma in open air—essentially capturing lightning in a bottle, but without the bottle.
Matter can exist in four distinct phases: solid, liquid, gas, and plasma. Plasmas are made of charged particles—ions and electrons—and occur naturally on Earth as lightning, in the weather phenomenon called St. Elmo’s fire (in which glowing balls of light sometimes appear on pointed objects during storms), and in man-made objects such as fluorescent light bulbs and plasma cutting torches.
Usually, plasmas do not have clearly defined shapes of their own. Lightning follows a path of least resistance through the air, creating wildly forking structures, while man-made plasmas are constrained by vacuum chambers or electromagnetic fields.