I wrote:

By the way, lightning rods are not supposed to "draw the lightning"
\ away from the protected structure. Any wire you might use would be
far too flimsy to carry such a load. What a lightning rod does is
to slowly discharge the atmosphere surrounding it


"w_tom" wrote in message

This is the scam promoted by the Early Streamer Emission
industry.

Actually, this is the scam first promoted by Benjamin Franklin. Turns out he
was wrong. So was I in my previous posting, so I may well be the first
newsgroup poster in history to admit to error. Being somewhat elderly, I
tried to recall what we learned about lightning in physics class, and got it
mixed in with what we learned about Franklin in history class. It seems even
Ben realized later in his life that lightning rods do not discharge clouds,
but merely provide a safe path to ground for the lightning.

The US Army defines in TM5-690 a wire size sufficient to
discharge lightning without damage. 10 AWG. This makes
complete sense once one learns a direct lightning strike has
so little energy.

Hmmmm. It seems to me knocking bricks off of buildings, or splitting trees,
or making very loud noises and bright lights suggests more than "so little
energy". Various non commercial websites suggest that a typical lightning
strike releases 250 KWH of energy. A big one may release 10 times that much.
That is a lot of energy. Admittedly, most of that is dissipated in the air
above where it strikes, but I think it is disingenuous to characterize it as
"little". It is not a lot, for example, compared to what it takes to light
New York city. On the other hand, that amount of energy is concentrated in
less than a millisecond, so it is very intense.

notes, and are based upon decades of experience. If lightning
vaporizes wires, then Ben Franklin did not exist to sign the
Declaration of Independence.

Ben's kite did not actually get struck by lightning, but just picked up the
cloud charge. His kite string was not a copper conductor and did not conduct
a large current.

A lightning rod above the pond and properly earthed by 10
AWG or heavier wire is more than sufficient to intercept and
divert lightning to earth without pond damage.

Most lightning rod manufacturers use 2 or 0 gauge wire as the down wire. 10
gauge seems to me a little flimsy. Given that a 10 gauge copper wire has a
resistance of about 1 ohm per 1000 feet, and given a total length of wire
of about 50 feet, we are dealing with 0.05 ohms of resistance. Given also
that an average lightning strike can have a current of 10,000 amps (NASA has
measured at least one strike of 100,000 amps)(and that the conductor takes
the entire current) we are dealing with a dissipated power of 10000^2*.05
or 5 million watts. Or 100,000 watts per foot of wire. Admittedly this is
for a very short time. But I submit that 100000 watts applied to a foot of
this wire over a millisecond will melt or otherwise seriously damage that
wire.