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What Makes lightning?

Lightning is a giant electric spark in the sky.

Electric charges exist in everything, including the air around us. We usually do not notice the electric forces created by the atmosphere. However when they become strong enough, the results are dramatic.

Storm clouds strengthen the electric forces created in the atmosphere. As drops of water rise through storm clouds, the electric charges in these drops are separated (no one is exactly sure how this happens).

Close-up of lightning strike
magnifyClose-up of lightning strike

When the sky's electric forces become strong enough, air breaks down into a 'soup' of electric charges, called a plasma. Normally air is a gas that does not allow much electricity to flow. As a plasma, air can conduct massive electric sparks.

The air changes into a plasma in small steps, starting from the cloud and heading towards the ground. When the plasma channel nears the ground, one or more return strokes leap from the ground to the cloud. This is the lightning we see.

Cloud to cloud lightning
magnifyCloud to cloud lightning

Actually, only one lightning strike in five reaches the ground—most happen between one cloud and another.

A lightning stroke lasts for about half a second. In this time a single lightning strike can release as much power as a large coal-burning power station.

Kite experiment
magnifyKite experiment

Charge separation in thunderstorms
magnifyCharge separation in thunderstorms

Yoy Lang power station
magnifyYoy Lang power station
© Museum Victoria Australia