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What is the speed of lightning?

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September 22, 2014 10:00PM

Light travels at 186,000 miles per second in a vacuum. So the light from a flash of lightning travels at the speed of light in air, which is slightly less than the speed of light in a vacuum (e.g. space)

But lightning itself travels nowhere near as fast as the speed of light. Lightning is an electrical discharge and is bound by the laws of physics. Its speed depends on many factors, including the conductivity of the medium it is travelling through. Careful scientific measurements of many lightning flashes have revealed that the electricity moves at different speeds at different stages of its journey in the lightning flash. Also, its returning upstroke is much faster than its downstroke.

Speed of Propagation

The Guinness Book of Answers indicates maximum speeds around 87,000 miles per second. Also, the US Department of Energy gives the speed of lightning as 93,000 miles per second, which may be based on the 'half the speed of light' principle. Neither is considered accurate for atmospheric discharges.

Observed Velocity

Propagation of high-altitude lightning observed from space was measured at a speed of 50 kilometers per second (112,000 mph). This is considerably slower than the 670 kilometers per second (1,500,000 mph) maximum return stroke velocity reported in an IEEE report in 2006. In a paper published in 2007, wide variations in stroke speeds were reported, up to 4000 kilometers per second (9,000,000 mph). While incredibly fast, these show that the average lightning speed is considerably slower than the speed of light.

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lightning is able to strike 100 times per second.