Ball lightning

Descriptions vary, but reports commonly depict a glowing sphere near the ground during or after a lightning storm. Witnesses have described different colours, sizes, motion and durations, and accounts are not always consistent. Because the phenomenon is rare and unpredictable, reliable direct measurements have been scarce, making it difficult to establish which observations share the same cause.

Researchers have proposed explanations involving plasma, electrical or magnetic fields, and chemical processes, among others; no single model is generally accepted. A 2014 paper reported optical and spectral measurements of a luminous event observed during a thunderstorm in China, associated with a cloud-to-ground lightning strike. Such an observation provides data for investigation, but does not by itself settle the mechanism or show that every reported ball-lightning event has the same explanation.

Laboratories have produced short-lived glowing spherical objects using electrical discharges, including experiments at the Max Planck Institute for Plasma Physics that create plasma objects above water. These are useful for studying possible physical or chemical processes, but they are experimental analogues; their differences from witness reports mean they should not automatically be identified as natural ball lightning. Establishing the phenomenon's nature requires further reproducible observations and measurements under natural conditions.