A tiny ball of light created with a laser could help explain the mystery of ball lightning.
For centuries, witnesses have reported seeing glowing balls floating near the ground during a storm. Some are said to have moved through the air for several seconds before disappearing. This phenomenon, known as ball lightning, remains very difficult to study: it appears rarely, and eyewitness accounts do not always agree.
Fictional illustration
Chinese physicists decided to create something similar in the laboratory. They used a tungsten needle whose tip is much finer than a hair. An extremely brief laser sent a pulse of energy along the needle.
When it reached the tip, this energy became concentrated in a tiny space. It created an electric field intense enough to strip electrons from the atoms of argon gas placed nearby. The gas turned into plasma, a state of matter made up of electrically charged particles.
A small glowing sphere then appeared. It initially measured about 80 micrometers in diameter, less than a tenth of a millimeter, then grew to reach a few tenths of a millimeter. Its lifespan was about 100 nanoseconds, or one ten-millionth of a second.
That is extremely brief for us, but much longer than the pulse that created it. The researchers also observed that the sphere maintained its shape as it grew. Instead of dispersing immediately, it seemed to retain some of its energy in a luminous structure.
This organization corresponds to a physical phenomenon called a soliton: a wave that maintains its shape through the balance of several effects. Some scientists suspect that a related mechanism could explain ball lightning. The experiment shows that such a structure can indeed exist under certain conditions.
This advance primarily provides an experiment that scientists can repeat and measure. It could help them understand how energy remains concentrated in plasma, a question useful far beyond the mystery of ball lightning.