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Posted by Heathcliff on June 10, 2008, 1:44 pm
>
> > ...
> > Thats incorrect. And blunt rods being better would be some remarkable new
> > science.
> > ...
> > If you discharge the static electricity, then you can stop lightning. So
> > the claim that discharging the clouds/ground will stop lightning is 100%
> > scientific and correct. The flaw is that you can't guarantee that you can
> > discharge it fully, or continuously or fast enough.
>
> > We may share the same resonings because what I state is based on the laws
> > of physics. So my statements are true.
>
> Your statements are based in popular myth - with no basis in laws of
> physics. Is it knowledge because the urban myth is popular? That
> same lesson (flawed but popular reasoning) also proved Saddam's
> mythical WMDs. A fact does not exist due to popular belief.
>
> First, the myth is that sharp (pointed) rods are better. Science and
> numbers say blunt rods make better lightning rods. From a 1999 paper
> in Journal of Applied Meteorology by Moore, Rison, Mathis, and Aulich
> (published May 2000):
>
> > Following tradition, however, sharp-tipped Franklin rods are
> > widely installed despite evidence that, on occasion, lightning
> > strikes objects in their vicinity. In recent tests of various
> > tip configurations to determine which were preferentially struck
> > by lightning, several hemispherically tipped, blunt rods were
> > struck but none of the nearby, sharper rods were "hit" by
> > lightning.
>
> Second: myth that a lightning rod dissipates static charges also was
> repeatedly criticized as junk science. From Wikipedia:
>
> > Lightning dissipators have been widely discredited and
> > criticized by lightning researchers over the last 30 years.
>
> Numerous peer reviewed papers also discredit that "discharge the
> static electricity, then you can stop lightning" theory. Again, NFPA
> was quite blunt about it. There exists zero supporting facts or
> research for this "discharge the static electricity" myth. None.
> NFPA said:
>
> > Accordingly, based on the Bryan Panel Report and the record
> > before it, the Council, in its most recent consideration of the
> > question whether to issue a standard for the ESE systems,
> > concluded, as it had in the past, that there was no basis for
> > the Council to issue a standard for ESE lightning protection
> > systems, and that given the lack of validation of the primary
> > claims made for the ESE technology, renewed standards development
> > activities for ESE systems was not appropriate.
>
> Even worse, that 'discharge the air' theory creates a human safety
> risk. From Hartono and Robiah entitled "A Long Term Study on the
> Performance of Early Streamer Emission ...":
>
> > The failure of the ESE air terminals to intercept nearby
> > lightning strikes posed an unacceptable risk to public safety.
> Furthermore:
> > The case studied submitted to the NFPA provided indisputable
> > evidence that lightning do strike the buildings after they
> > were installed with the ESE air terminals. ... the presence
> > of several ESE air terminals ... still resulted in lightning
> > strikes on one or more of those buildings. ...
> > The case studies highlight the very close proximity of some
> > lightning strikes to the ESE air terminals, shoring that
> > they are unable to protect buildings as claimed by their
> > manufacturers.
>
> If those ESE terminals discharged air, then why so many lightning
> strikes even near the ESE air terminals? Because air terminals that
> discharge static are based in junk science reasoning.
>
> Not only was the NFPA roundly critical of that 'discharge the air'
> myth. NFPA also cited numerous studies (ie Hartono and Robiah) that
> showed "discharge the static electricity" devices provided NO
> protection. Speculation that lightning rods protect by discharging
> the air is only junk science and is not found in science. We learned
> this same lesson from history: Saddam's WMDs. Popular belief does not
> create fact. Facts come from learning the science. Static
> discharging does not provide protection.
>
> How many sources completely discredit this 'discharge the air'
> myth? Science (laws of physics and experiments) says blunt rods are
> superior. Discharging inches of air around a lightning rod neither
> stops nor averts nor reduces lightning strike frequency. Lightning
> strikes are made irrelevant by connecting / diverting / channeling /
> conducting that inevitable lightning strike into earth. Protection is
> about dissipating that energy harmlessly in earth. That energy must
> be dissipated somewhere. Inside a building (destructively) or inside
> earth? Discharging static charges is the same logic that also proved
> "Saddam's WMDs" - junk science reasoning promoted by popularity. How
> many science sources need be quoted?
Good explanation and thanks for the citations. I think there is also
something to be gained by looking at the sequence of events. From
what I have read, for most cloud-to-ground strikes you first have a
dart leader descending from the cloud in stepwise fashion. (you can
sometimes hear it as the crackling or 'cosmic zipper' sound before the
main boom of a nearby strike) When the dart leader gets within a
hundred meters or so of the ground, the local static field becomes
very intense and things on the ground within a 50 or 100 meter radius
beneath the dart leader send up small positive-ion streamers. When
one of these connects with the dart leader then the channel is
complete and the main discharge begins. So in essence, meteorological
events determine where and when the dart leader comes down, and when
it nears earth then there is a sort of target zone beneath it; only
then do conditions on the ground come into play to determine exactly
where in that target zone will the strike occur.
As for what makes for a vigorous ground streamer that is likely to
connect up with the dart leader, I don't think I have seen any
articles on that. Anecdotally, I know when I lived in an area with
well and septic water systems, people used to often talk about their
wells being struck by lightning. That would seem to argue that good
grounding is a factor, since the well (an iron pipe sunk a couple
hundred feet into the ground) only stuck up maybe six inches or so,
and certainly there would be taller structures (trees, houses)
nearby. -- H
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