What is ball lightning? | BBC Science Focus Magazine


Ball lightning is a mysterious and unexplained form of lightning which has confused weather watchers throughout history and continues to intrigue researchers today. The phenomenon is generally described as a ball of light that appears during thunderstorms.

The size of the ball varies, from a golf ball to larger than a football, and it tends to hover over the ground. Its lifetime varies too, from a few seconds to a few minutes, with larger and dimmer balls tending to last longer.

Observations go far back in history. Luminous balls feature in the legends of the Argentinean and Chilean Mapuche culture, but the earliest known written reference comes from an English monk in 1195. He described “a dense and dark cloud, emitting a white substance which grew into a spherical shape under the cloud, from which a fiery globe fell towards the river”. Tsar Nicholas II even reported witnessing the phenomenon in a church in St Petersburg as a young child.

A study conducted in the 1960s for the US Atomic Energy Commission found that ball lightning has been seen by 5 per cent of the world’s population – about the same proportion as those who have seen a bolt of normal lightning strike up close.

Scientists think that ball lightning is real, but how it happens is an open question. In 2014, Chinese scientists captured a video of ball lightning while trying to record normal lightning. Their readings show a mixture of silicon, iron and calcium atoms in the ball, all common components of soil.

This lends weight to the theory that when lightning strikes soil, it creates a vapour of silicon nanoparticles. These particles react with air to generate light and heat at relatively low temperatures. However, it does not explain observations of ball lightning passing through walls, or aircraft cockpits. Further research will be needed to finally unravel this mystery.

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Asked by: Oscar Brown, via email

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