A return stroke (the very bright visible flash that we see as lightning) travels at about 60,000 miles per second back towards the cloud, with one flash consisting of as many as 20 return strokes. When the oppositely-charged leader and streamer connect, a powerful electrical current begins flowing (hence why it is ill-advised to stand under a tall object during a thunderstorm!). As it nears the ground, the negatively charged stepped leader is attracted to a channel of positive charge reaching up, a streamer, usually through something tall, such as a tree, house, or telephone pole. This stepped leader is invisible to the human eye and travels to the ground in a millisecond. In CG lightning, a channel of negative charge, called a stepped leader, will zigzag downward in a ‘forked’ pattern - hence it is sometimes called forked lightning. Lightning can strike the ground, the air, or inside clouds, but there are roughly 5 to 10 times more cloud flashes than cloud-to-ground flashes. This, as well as its starting and ending points and direction of movement, give rise to different ‘types’ of lightning. The polarity of lightning discharge can affect how it spreads and branches in space and time. A beautiful and deadly natural phenomenon, lightning is simply a sudden, electrostatic discharge - a ‘spark’ or ‘flash’ as charged atmospheric regions temporarily equalise themselves through this discharge.
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