A flash of lightning is a lightning between the ground and a cloud. The gigantic "short circuit" is caused by a voltage of more than 100 million volts between the thundercloud and the ground. Most flashes of lightning begin on the ground and then spread upwards. Lightnings between ground and cloud add up to just a small part of all lightnings. Most of the lightnings take their way between the clouds and are not dangerous. A flash of lightning, on the contrary, can cause devastating damage. It splits up trees and can set houses on fire or destroy electronic devices Even if a lightning strikes at a distance of about 10 metres; it can paralyze or even kill a person.