bliksem

Bliksem is the Dutch word for lightning, a sudden discharge of electricity in the atmosphere during thunderstorms. It occurs when electrical charges build up and separate within cumulonimbus clouds or between a cloud and the Earth's surface, and the electrical impedance of the air breaks down, allowing a rapid current to flow. The flash is the optical manifestation of this discharge, and the accompanying thunder is the audible shock wave produced by the rapid heating of air.

Origin of the term: In Dutch, bliksem not only names the natural phenomenon but also appears in idioms and as an exclamation.

Physical process: Charge separation within storms leads to regions of positive and negative charges. When the electric field becomes strong enough, air ionizes along a path called a leader; a return stroke then travels along this channel, producing the bright flash. The current can be tens of kiloamperes and the channel may extend over kilometers. Temperatures in the discharge can reach around 30,000 kelvin.

Types: The most common form is cloud-to-ground lightning, where charge moves from cloud to the ground. Other varieties occur within a single cloud or between clouds, and are collectively referred to as intra-cloud or inter-cloud lightning.

Safety: If a thunderstorm approaches, seek shelter in a substantial building or a vehicle with the windows closed. Avoid open fields, tall objects, water, and metal conductors. If trapped outdoors, crouch low but do not lie flat.