Lightening

In the turbulent atmosphere of a thunderstorm, the conducting characteristics of any little cubic inch or cubic foot of air changes constantly, going from a relatively good to really lousy conductor and back in fractions of a second. What matters is a snapshot of the conductive characteristics in the microsecond of the lightening strike. If there is a "pretty good" path to ground through the air 10 feet from a tree, and an excellent partial path to ground through the tree, but a horrible path between the tree and the pretty good path, the pretty good path will win and the tree will be bypassed. The tree is like an insulated wire, a good conductor wrapped in a poor conductor. This analysis is supported by the fact that often trees are struck by lightening in the middle rather than at the top. Swirling branches and leaves are not as good an overall conductor as a nice, solid, wet tree trunk, so often the branches are bypassed by a path through the air. I lost a tree this way. The tree was taller than my two-story house, so somewhere in the 20-30 ft range. Lightening hit it 9 feet off the ground and blew out half of the trunk at that height. The upper part of the tree keeled over as if I had cut a pie wedge into the trunk with a chain saw. Missed the house by inches. Got over one cord of firewood out of it.

Lightening rods increase the probability that a protected structure will not take a direct hit, but with lightening *nothing* is guaranteed.

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