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Tesla's Colorado Springs Lightning Observations
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From Feed Line No. 6
TESLA'S COLORADO SPRINGS LIGHTNING OBSERVATIONS
by Gary L. Peterson
As seen from a present day perspective, the time which Nikola Tesla
invested into his 1899 Colorado "expedition" appears to have been
some of his most productive. This might be because he had considered
the previous ten years of research as practice for the work that
was being conducted at the now well-known Experimental Station.
Or perhaps it is from the many recorded observations dating from this
period and the group of important patents would appear over the next
few years. In fact, work on the applications for these fundamental
radio patents began while Tesla was still in Colorado. One major account
that is related in the Colorado Springs Notes and in an article
titled "The Transmission of Electrical Energy Without Wires,"
has to do with an unusual natural
radio phenomenon that Tesla observed during and after an intense
thunder storm which passed close by his Colorado lab.
The receiver that he used appears to have built around an oscillatory
transformer similar to the type employed for high frequency lighting.
(See Nikola Tesla: Lecture Before the New York Academy of Sciences
� April 6, 1897 for details about these devices.)
Located on the primary side of the transformer were a sensitive device
known as a rotating coherer and a mica condenser both connected
to an elevated terminal and to ground. The primary side of the circuit
also included a battery for placing a small dc voltage
across the coherer and a mechanical switch known as a "break."
During normal operation the make-and-break device would open
and close about 72 times per second. In the secondary side of
the circuit was another coherer and battery plus a delicate relay
which responded by closing every time a lightning discharge occurred
in the general vicinity. This type of receiver was extremely
sensitive, being capable of recording effects as distant as an
estimated 500 miles.
On July 4 Tesla writes that his observations began as the
storm was approaching and still at a distance of 80 to 100 miles.
The relay on the elegantly simple receiver must have begun to chatter
practically as soon as all the connections were made.
As the storm came closer, the relay continued to respond even as
it was adjusted to its least sensitive setting.
As the storm continued on past the lab is when, in Tesla's word's,
"the most interesting and valuable observation was made."
The relay was once again adjusted to be more sensitive and
it continued to respond for a while and then stopped.
After an unspecified time had passed the relay again responded
for a while and then once again ceased to play.
As recorded by Tesla this on-again off-again action
continued to repeat itself with a period of about 30 minutes,
at the very least six or seven times, on into the evening.
He writes, "most of the horizon was clear by that time."
A number of people have speculated as to what, exactly,
Tesla had seen that summer long ago. One proposal,
put forth in the Proceedings of the Tesla Centennial Symposium,
is that mechanical vibrations were being detected which were
the result of terrestrial piezoelectric interactions associated
with the lightning strikes. Another theory has it that the
varying ground currents were the result of stationary waves
created by reflections off the Pikes Peak mountain range.
Tesla himself considered two other possibilities for the creation
of what he believed were stationary waves anchored to their
moving point of origin. The first and, at the time,
to him least probable, was that they were the result of reflections from
the point of the earth's surface diametrically opposite to the storm.
More likely, in his mind, was that they resulted from
reflections which took place within the storm itself,
at a point very close to the origin of the initial wave packets.
In 1994 a new premise was set forth by Kenneth and James Corum
in a paper presented at the biennial Tesla Symposium in
Colorado Springs. The proposed model is an adaptation of
waveguide theory and draws upon a method of treating radiation
sources in a waveguide that calls for the existence of "images"
which mirror an assumed dipole source. These images in
combination with the source itself can be said to form what
appears to be broadside array of radiating elements.
Furthermore, the radiation from these sources, being coherent,
can interfere and cast side lobes that appear as maxima and
nulls along the waveguide walls.
It is proposed that rather than registering the existence of
stationary waves, Tesla might have been seeing a wave interference
phenomenon similar to that described above. The nodes and antinodes
which passed by his point of observation might have been
due to the superposition of partially coherent lightning induced
VLF waves radiating from the primary source and an adjacent
image and propagating down along the earth-ionosphere waveguide.
This model bears more than passing resemblance to Tesla's
preferred scenario that did not call for the reflection of waves
from the antipodes. At the same time it is important to note
that in the specifications for his Patent No. 787,412,
Art of Transmitting Electrical Energy Through Natural Media Tesla stated
that the lightning produced waves provided "unmistakable evidence
that the disturbances created had been conducted from their
origin to the most remote portions of the globe and had been
thence reflected..." In the ten short months between July 4, 1899
and the May 16, 1900 application date what had caused this tremendous
shift of opinion to where he now believed and practically
recorded as fact what before had been assigned the lesser probability?
Tesla himself gave us the answer in 1929 when he wrote:
"The chief discovery which satisfied me thoroughly as to the
practicability of my plan was made in 1899 in Colorado Springs,
where I carried on tests with a generator of 1500 KW capacity
and ascertained that under certain conditions the current was
capable of passing across the entire globe and returning from
the antipodes to its origin undiminished in strength.It was a
result so unbelievable that the revelation at first almost stunned me."
The Corums' 1994 analysis provides us with a highly plausible physical
model to explain Tesla's lightning related observations
during the stormy summer of 1899. It is also quite apparent that
that year's ground breaking experiments with a specially designed
high power electrical oscillator thoroughly convinced Tesla that
he was seeing indications of electrical earth resonance.
This raises the question: while in he was in Colorado Springs did
Tesla ever observe any indications of interference between the
outgoing waves that were induced by his experimental VLF transmitter
and incoming waves reflected from the antipode?
The rotating coherer and associated circuitry
Tesla's VLF receiver must have been very similar to the circuit
illustrated here. Each of the two coherers c and c' were constructed
from a short section of 3/8 inch I.D. glass tubing capped with
two brass plugs. The intervening space was partially filled
with course nickel chips. The two adjacent batteries B and B' were
adjusted with resistors r and r' to strain the devices to a
point where they were just about to break down and become conducting.
An incoming signal would drive the potential across the device beyond
its threshold causing a much stronger battery current to flow.
A clockwork drive mechanism was used to continuously
rotate the small glass cylinders thus decohering the chips after
each received impulse. It is now believed that coherers
are uniquely suited to detect the particular type of natural
radio phenomenon that Tesla observed in 1899.
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