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Gary Schafer wrote:
Well for a start, I would not stand next to a copper flag pole or a tree in a thunder storm. Side arcs can come just as easily from one as the other. Nor would I. My fault for not putting in a smiley face. But it is true that it would be safer to be nearer a grounded pole than a tree, owing to the reduced "surface effect" of the better conductor. That is to say: If one were somehow standing half way between a copper flagpole and a tree, it would be advisable to edge nearer the flag pole. That does not mean one should lean on it, though. There will be surface effect around even the best conductor. Lightning strikes can not be prevented. You can not "make anything disappear from the competition for lightning". Agree - not 'disappear', but unquestionably a proper air terminal and its corona discharge will reduce build-up of positive charge. If there is something in the area which is not so good at getting rid of charge, it will more likely be hit. See below: There is no such thing as bleeding of the charge. The earth can supply charge much faster than it is possible to bleed it off. "SUBSTANTIATION: In the years since Franklin Invented the sharp lightning rod, many physicists have shown that, under strong electric fields, the air around sharp rods becomes Ionized, creating space charges that act to weaken the fields. It has also been discovered that the strengths of the strong fields around the tips or sharp rods decrease so rapidly with distance that they become weaker than the fields over blunter rods at distances greater than about 1/4 in. .... From laboratory and field experiments, we have established that the critical field strengths for lightning Interception develop sooner around blunt lightning rods than around sharp ones around which the field strengths are limited by their charge emissions. In effect. sharp rods tend to protect themselves, by their charge emissions, against participating in lightning strikes." Charles B. Moore, Langmuir Laboratory, New Mexico Tech ------------------ A blunt air terminal is preferred over a sharp pointed one. A sharp point will encourage streamers to form sooner. They can actually attract a strike. This includes the toilet brushes mounted on the mast. Here is a quote from a study by scientists who were *trying* to attract lightning strikes: ------------ In strike-reception competitions over the past six years between sharp Franklin rods, sharp-tipped "ESE" air terminals, and blunt rods with hemispherical tips, all mounted on 6-mater high masts and separated horizontally by about 6 meters, none of the sharp-tipped air terminals has been "struck" by lightning but 12 of the blunt rods have taken strikes. ------------------------- SUMMARY (Dinner is on the table): You seem to have quite a bit of insight into lightning, but your message jumps around a bit, and this is all I have time for. My purpose was not a detailed rebuttal but to demonstrate that your original cryptic remark "...advice is bogus" was not in the best spirit or interst of reasoned dialog, nor was it true. From your follow-up message it appears you are more ready to bring more light than heat. Good. Grownups can disagree and discuss those points of contention without resorting to name-calling and invective. |
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