Note: Please do not attempt to
recreate any of the experiments shown here. Flying a kite with a
wire line can result in death by electricution from atmospheric
electricity or power lines!
Ben Franklin is probably the best known of the early experimenters who
investigated atmospheric electrostatics. Most who have heard of
his experiments (possibly performed in 1752) with the kite and the key
think that he was struck by lightning, which is not true. He was
fortunate not to be struck by lightning, as it would have resulted in
severe injury or death. What Ben Franklin experienced was a jolt
of atmospheric electricity which is always present, to some degree,
even in the absence of an electrical storm.
Ben Franklin originally proposed to use a metal rod to conduct
atmospheric electricity to a "sentry box" holding a man. At the
time, Franklin lacked the funds to contruct the device. Plans for the
proposed experiment were published in England in 1751. A French
naturalist, D'Alibard, reading a French translation of Franklin's
proposal, built a "sentry box" and by 1752 had sucessfully tested it in
Marly, France.
Details surrounding Ben Franklin's kite experiment are not well
documented. Some researchers insist that he may not have
conducted the experiment at all.
One version of the story is as follows: A few weeks after
D'Alibard's experiment, Franklin, holding an insulating silk
ribbon, flew a kite with a wet hemp string in stormy weather.
The atmospheric electricity was conducted by the wet string and
passed to a key attached to the string. Supposedly, Ben touched
the key and received a mild shock.
Other early experimenters such as Professor Georg Richmann were not so lucky:
On August 6, 1753, Professor Georg Richmann of St. Petersburg tried
with a colleague, M. Sokolaw, engraver to the Academy at St.
Petersburg, to attract the lightning. He attached a wire to the top of
his house and led it down to an iron bar suspended above "the
electrical needle" and a bowl of water partly filled with iron filings.
"The Professor," stated a letter from Moscow which Franklin published
in The Pennsylvania Gazette, "judging from the Needle that the Tempest
was at a great Distance, assured M. Sokolaw that there was no Danger,
but that there might be at the Approach. M. Richmann stood about a Foot
from the Bar, attentively observing the Needle. Soon after M. Sokolaw
saw, the Machine being untouched, a Globe of blue and whitish Fire,
about four inches Diameter, dart from the Bar against M. Richmann's
Forehead, who fell backwards without the least Outcry. This was
succeeded by an Explosion like that of a small Cannon which also threw
M. Sokolaw on the Floor, feeling as it were some Blows on his Back. It
has since been found that the Wire breaking, some Bits had hit him
behind, and left the Marks of Burning on his Clothes," Professor
Richmann was killed-- "his body [being] found in the midst of his
apparatus, like an artilleryman dead under the wreck of his gun,"
From http://www.todayinsci.com/R/Richmann_Georg/RichmannGeorgExp.htm
Source: Benjamin Franklin, A Biography, by Ronald W. Clarke. Random House (1983) p. 87.
Richmann Image Source: http://fargo.itp.tsoa.nyu.edu/~lewis/electricity/pages/franklin.html
Some researchers assert that atmospheric electricity originates from an
excess of positive ions present in the lower 3 km of the atmosphers.
The ionization of the atmosphere is believed to be caused by
cosmic rays and radon. Other theories point to the friction
generated as air molecules pass one another and the surface of the
earth. As a result, static electricity builds up and contributes
to the potential, which may be as high as 100 volts per meter of
altitude above the earth's surface.
In a quest to determine the electrical potential of the atmosphere,
Dangerous Laboratories engineers procured a kite, wire line, and a deep
sea fishing reel.
Item
Source
Specifications
Cost ($)
32" "SkyDog" Diamond Kite
Hobby Shop
32" X 31"
15.00
Mason Multistrand Trolling Wire
Ebay
45 Lb test/1000 feet
Weight of line 361 g
50.00
Penn #49 Super Mariner Fishing Reel
Ebay
Used
55.00
The kite was flown several times in fair weather, location Golden,
Colorado (8/30/2010). The reel was grounded with a cheap
multimeter. No voltage was detected, even with 500 feet of line
out.
The following day, the a 7' delta kite was flown. Just as our
engineers were getting discouraged, a significant shock in the forearms
of the operator was felt when flying the kite at less than 100 feet
altitude. The reel was quickly grounded with a wire, and the
shocks ceased. The grounding clip was unhooked and held about 1
cm from the reel. A noticible continuous spark and buzzing sound
was observed (see photo below). The source of the high voltage was most likely a
localized rainstorm (not thunderstorm) which appeared about 2.5
km from the kite. As the wind was gusting up to 25 mph, it was
decided that the 7' delta was too big for this type of experiment.
The storm went on to hang around for another hour and produce a beautiful rainbow.
The spark is barely visible in the low-resolution movie:
Later that week, the SkyDog diamond kite was flown on top of North
Table Mountain by Dangerous Laboratories Engineer Philip H who noted
electrical shocks.
