In this original and revolutionizing discussion, Nikola Tesla gives
us something really new to think about. First - Does the moon
rotate on its axis? Second - Is the Franklin pointed lightning rod
correct in theory and operation? Third - Do -wireless signals fly
thru space by means of so-called Hertzian waves in the ether, or
are they propagated thru the earth at prodigious velocity by means
of earth-bound oscillations? World-famous conundrums these
questions which have been answered in many ways by some of the
greatest scientists. Dr. Tesla explains these three predominant
scientific fallacies in a masterly way, so that everyone can
FOR over a century and a half the whole world, educated and
otherwise, thought that the moon revolved around its axis. Nikola
Tesla in the present highly instructive article disproves that
theory and will convince scientists and all others alike that the
moon does no such thing.
For thousands of years it was thought that the sun and stars
revolved around the earth and all kinds of experimental proofs were
furnished to substantiate this theory. The illustrious Galileo
thought different, and everyone today knows that the earth revolves
around the sun.
So it is with Tesla's discovery. Tesla also, in the second part of
the present paper, shows us that the ancient and time-worn theory
advanced by Benjamin Franklin as to the lightning conductor is not
substantially correct as viewed by latter day science. It will come
as a shock even to our professors that the lightning rod actually
aids the lightning in hitting the building.
The reason is that the lightning rod helps in ionizing (making
conductive) the surrounding air.
Mr. Tesla has devised a lightning conductor with no points, and
there is no doubt whatsoever that his theory is right. Scientists
the world over will acknowledge this very shortly.
In a third section of the same paper Tesla explodes still another
popular delusion, viz., that wireless waves follow the curvature of
the earth when messages are transmitted, let us say from a point in
the United States to a point in Europe. In his revolutionary
arguments, supported by facts as well as by logic, Tesla shows why
the currents do not travel around the earth but directly thru it.
In other words.
Tesla maintains that wireless communication is accomplished ONLY
thru the medium of the earth itself. His contention seems very
sound. If it were not so, let every wireless station, commercial or
otherwise, do away with its ground connection. None could then
operate as is well known, except perhaps over very limited
Mr. Tesla's present article will arouse world-wide comment due to
the revolutionary philosophy contained therein. We are sure our
readers will appreciate Mr. Tesla's most timely and illuminating
article on this but little understood subject.
Famous Scientific Illusions
By NIKOLA TESLA
Written specially for the Electrical Experimenter
THE human brain, with all its wonderful capabilities and power, is
far from being a faultless apparatus. Most of its parts may be in
perfect working order, but some are atrophied, undeveloped or
missing altogether. Great men of all classes and professions -
scientists, inventors, and hardheaded financiers - have placed
themselves on record with impossible theories, inoperative devices,
and unrealizable schemes. It is doubtful that there could be found
a single work of any one individual free of error. There is no such
thing as an infallible brain.
Invariably, some cells or fibers are wanting or unresponsive, with
the result of impairing judgment, sense of proportion, or some
other faculty. A man of genius eminently practical, whose name is a
household word, has wasted the best years of his life in a
visionary undertaking, a celebrated physicist was incapable of
tracing the direction of an electric current according to a
childishly simple rule. The writer, who was known to recite entire
volumes by heart, has never been able to retain in memory and
recapitulate in their proper order the words designating the colors
of the rainbow, and can only ascertain them after long and
laborious thought, strange as it may seem. Our organs of reception,
too, are deficient and deceptive. As a semblance of life is
produced by a rapid succession of inanimate pictures, so many of
our perceptions are but trickery of the senses, devoid of reality.
The greatest triumphs of man were those in which his mind had to
free itself from the influence of delusive appearances. Such was
the revelation of Buddha that self is an illusion caused by the
persistence and continuity of mental images : the discovery of
Copernicus that, Contrary to all observation, this planet rotates
around the sun; the recognition of Descartes that the human being
is an automaton, governed by external influence and the idea that
the earth is spherical, which led Columbus to the finding of this
continent. And tho the minds of individuals supplement one another
and science and experience are continually eliminating fallacies
and misconceptions, much of our present knowledge is still
incomplete and unreliable. We have sophisms in mathematics which
cannot be disproved.
Even in pure reasoning, free of the shortcomings of symbolic
processes, we are often arrested by doubt which the strongest
intelligences have been unable to dispel.
Experimental science itself, most positive of all, is not
unfailing. In the following I shall consider three exceptionally
interesting errors in the interpretation and application of
physical phenomena which have for years dominated the minds of
experts and men of science.
I. The Illusion of the Axial Rotation of the Moon.
It is well known since the discovery of Galileo that the moon, in
traveling thru space, always turns the same face towards the earth.
This is explained by stating that , while passing once around its
mother-planet the lunar globe performs just one revolution on its
axis. The spinning motion of a heavenly body must necessarily
undergo modifications in the course of time, being either retarded
by resistances internal or external, or accelerated owing to
shrinkage and other causes. An unalterable rotational velocity thru
all phases of planetary evolution is manifestly impossible. What
wonder, then, that at this very instant of its long existence our
satellite should revolve exactly so, and not faster or slower. But
many astronomers have accepted as a physical fact that such
rotation takes place. It does not, but only appears so; it is an
illusion, a most surprising one, too.
I will endeavor to make this clear by reference to Fig. 1, in which
E represents the earth and M the moon.
The movement thru space is such that the arrow, firmly attached to
the latter, always occupies the position indicated with reference
to the earth. If one imagines himself as looking down on the
orbital plane and follows the motion he will become convinced that
the moon does turn on its axis as it travels around. But in this
very act the observer will have deceived himself. To make the
delusion complete let him take a washer similarly marked and
supporting it rotatably in the center, carry it around a stationary
object, constantly keeping the arrow pointing towards the latter.
Tho to his bodily vision the disk will revolve on its axis, such
movement does not exist. He can dispel the illusion at once by
holding the washer fixedly while going around. He will now readily
see that the supposed axial rotation is only apparent, the
impression being produced by successive changes of position in
But more convincing proofs can be given that the moon does not, and
cannot revolve on its axis. With this object in view attention is
called to Fig. 2, in which both the satellite, M, and earth, E, are
shown embedded in a solid mass, M1 (indicated by stippling) and
supposed to rotate so as to impart to the moon its normal
translatory velocity. Evidently, if the lunar globe could rotate as
commonly believed, this would be equally true of any other portion
of mass M1, as the sphere M2, shown in dotted lines, and then the
part common to both bodies would have to turn simultaneously in
opposite directions. This can be experimentally illustrated in the
manner suggested by using instead of one, two overlapping rotatable
washers, as may be conveniently represented by circles M and M2,
and carrying them around a center as E, so that the plain and
dotted arrows are always pointing towards the same center. No
further argument is needed to demonstrate that the two gyrations
cannot co-exist or even be pictured in the imagination and
reconciled in a purely abstract sense.
The truth is, the so-called "axial rotation" of the moon is a
phenomenon deceptive alike to the eye and mind and devoid of
physical meaning. It has nothing in common with real mass
revolution characterized by effects positive and unmistakable.
Volumes have been written on the subject and many erroneous
arguments advanced in support of the notion. Thus, it is reasoned,
that if the planet did not turn on its axis it would expose the
whole surface to terrestrial view; as only one-half is visible, it
The first statement is true but the logic of the second is
defective, for it admits of only one alternative. The conclusion is
not justified as the same appearance can also be produced in
another way. The moon does rotate, not on its own, but about an
axis passing thru the center of the earth, the true and only one.
The unfailing test of the spinning of a mass is, however, the
existence of energy of motion. The moon is not possest of such vis
viva. If it were the case then a revolving body as M1 would contain
mechanical energy other than that of which we have experimental
evidence. Irrespective of this so exact a coincidence between the
axial and orbital periods is, in itself, immensely improbable for
this is not the permanent condition towards which the system is
tending. Any axial rotation of a mass left to itself, retarded by
forces external or internal, must cease. Even admitting its perfect
control by tides the coincidence would still be miraculous. But
when we remember that most of the satellites exhibit this
peculiarity, the probability becomes infinitesimal.
Three theories have been advanced for the origin of the moon.
According to the oldest suggested by the great German philosopher
Kant, and developed by Laplace in his monumental treatise
"Mecanique Celeste", the planets have been thrown off from larger
central masses by centrifugal force. Nearly forty years ago Prof.
George H. Darwin in a masterful essay on tidal friction furnished
mathematical proofs, deemed unrefutable, that the moon had
separated from the earth.
Recently this established theory has been attacked by Prof. T. J.
I. See in a remarkable work on the "Evolution of the Stellar
Systems", in which he propounds the view that centrifugal force was
altogether inadequate to bring about the separation and that all
planets, including the moon, have come from the depths of space and
have been captured. Still a third hypothesis of unknown origin
exists which has been examined and commented upon by Prof. W. H.
Pickering in "Popular Astronomy of l907", and according to which
the moon was torn from the earth when the later was partially
solidified, this accounting for the continents which might not have
been formed otherwise.
Undoubtedly planets and satellites have originated in both ways
and, in my opinion, it is not difficult to ascertain the character
of their birth. The following conclusions can be safely drawn:
1. A heavenly body thrown off from a larger one cannot rotate on
its axis. The mass, rendered fluid by the combined action of heat
and pressure, upon the reduction of the latter immediately
stiffens, being at the same time deformed by gravitational pull.
The shape becomes permanent upon cooling and solidification and the
smaller mass continues to move about the larger one as tho it were
rigidly connected to it except for pendular swings or vibrations
due to varying orbital velocity. Such motion precludes the
possibility of axial rotation in the strictly physical sense. The
moon has never spun around as is well demonstrated by the fact that
the most precise measurements have failed to show any measurable
flattening in form.
2. If a planetary body in its orbital movement turns the same side
towards the central mass this is a positive proof that it has been
separated from the latter and is a true satellite.
3. A planet revolving on its axis in its passage around another
cannot have been thrown off from the same but must have been
II. The Fallacy of Franklin's Pointed
The display of atmospheric electricity has since ages been one of
the most marvelous spectacles afforded to the sight of man. Its
grandeur and power filled him with fear and superstition. For
centuries he attributed lightning to agents god-like and
supernatural and its purpose in the scheme of this universe
remained unknown to him.
Now we have learned that the waters of the ocean arc raised by the
sun and maintained in the atmosphere delicately suspended, that
they are wafted to distant regions of the globe where electric
forces assert themselves in upsetting the sensitive balance and
causing precipitation, thus sustaining all organic life. There is
every reason to hope that man will soon be able to control this
life-giving flow of water and thereby solve many pressing problems
of his existence.
Atmospheric electricity became of special scientific interest in
Franklin's time. Faraday had not yet announced his epochal
discoveries in magnetic induction but static frictional machines
were already generally used in physical laboratories. Franklin's
powerful mind at once leaped to the conclusion that frictional and
atmospheric electricity were identical. To our present view this
inference appears obvious, but in his time the mere thought of it
was little short of blasphemy. He investigated the phenomena and
argued that if they were of the same nature then the clouds could
be drained of their charge exactly as the ball of a static machine,
and in 1749 he indicated in a publisht memoir how this could be
done by the use of pointed metal rods.
The earliest trials were made by Dalibrand in France, but Franklin
himself was the first to obtain a spark by using a kite, in June,
1752. When these atmospheric discharges manifest themselves today
in our wireless station we feel annoyed and wish that they would
stop, but to the man who discovered them they brought tears of joy.
The lightning conductor in its classical form was invented by
Benjamin Franklin in 1755 and immediately upon its adoption proved
a success to a degree. As usual, however, its virtues were often
exaggerated. So, for instance, it was seriously claimed that in the
city of Piatermaritzburg (capital of Natal, South Africa) no
lightning strokes occurred after the pointed rods were installed,
altho the storms were as frequent as before. Experience has shown
that just the opposite is true. A modern city like New York,
presenting innumerable sharp points and projections in good contact
with the earth, is struck much more often than equivalent area of
Statistical records, carefully compiled and publisht from time to
time, demonstrate that the danger from lightning to property and
life has been reduced to a small percentage by Franklin's
invention, but the damage by fire amounts, nevertheless, to several
million dollars annually. It is astonishing that this device, which
has been in universal use for more than one century and a half,
should be found to involve a gross fallacy in design and
construction which impairs its usefulness and may even render its
employment hazardous under certain conditions.
For explanation of this curious fact I may first refer to Fig. 3,
in which s is a metallic sphere of radius r, such as the capacity
terminal of a static machine, provided with a sharply pointed pin
of length h, as indicated. It is well known that the latter has the
property of quickly dissipating the accumulated charge into the
To examine this action in the light of present knowledge we may
liken electric potential to temperature. Imagine that sphere s is
heated to T degrees and that the pin or metal bar is a perfect
conductor of heat so that its extreme end is at the same
temperature T. Then if another sphere of larger radius, v1, is
drawn about the first and the temperature along this boundary is
T1, it is evident that there will be between the end of the bar and
its surrounding a difference of temperature T - T1, which will
determine the outflow of heat. Obviously, if the adjacent medium
was not affected by the hot sphere this temperature difference
would be greater and more heat would be given off. Exactly so in
the electric system. Let q be the quantity of the charge, then the
sphere-and owing to its great conductivity also the pin-will be at
ference of potential between the point of the pin and the medium
around the same
the large sphere is used. In many scientific tests and experiments
this important observation has been disregarded with the result of
causing serious errors. Its significance is that the behavior of
the pointed rod entirely depends on the linear dimensions of the
electrified body. Its quality to give off the charge may be
entirely lost if the latter is very large. For this reason, all
points or projections on the surface of a conductor of such vast
dimensions as the earth would be quite ineffective were it not for
These will be elucidated with reference to Fig. 4, in which our
artist of the Impressionist school has emphasized Franklin's notion
that his rod was drawing electricity from the clouds. If the earth
were not surrounded by an atmosphere which is generally oppositely
charged it would behave, despite all its irregularities of surface,
like a polished sphere. But owing to the electrified masses of air
and cloud the distribution is greatly modified. Thus in Fig. 4, the
positive charge of the cloud induces in the earth an equivalent
opposite charge, the density at the surface of the latter diminishing
with the cube of the distance from the static center of the cloud. A
brush discharge is then formed at the point of the rod and the action
Franklin anticipated takes place. In addition, the surrounding air is
ionized and rendered conducting and, eventually, a bolt may hit the
building or some other object in the vicinity. The virtue of the
pointed end to dissipate the charge, which was uppermost in
Franklin's mind is, however, infinitesimal. Careful measurements show
that it would take many years before the electricity stored in a
single cloud of moderate size would be drawn off or neutralized thru
such a lightning conductor. The grounded rod has the quality of
rendering harmless most of the strokes it receives, tho occasionally
the charge is diverted with damaging results.
But, what is very important to note, it invites danger and hazard
on account of the fallacy involved in its design. The sharp point
which was thought advantageous and indispensable to its operation,
is really a defect detracting considerably from the practical value
of the device. I have produced a much improved form of lightning
protector characterized by the employment of a terminal of
considerable area and large radius of curvature which makes
impossible undue density of the charge and ionization of the air.
These protectors act as quasi-repellents and so far have never been
struck tho exposed a long time.
Their safety is experimentally demonstrated to greatly exceed that
invented by Franklin. By their use property worth millions of
dollars which is now annually lost, can be saved.
III. The Singular Misconception of the Wireless.
To the popular mind this sensational advance conveys the impression
of a single invention but in reality it is an art, the successful
practice of which involves the employment of a great many
discoveries and improvements. I viewed it as such when I undertook
to solve wireless problems and it is due to this fact that my
insight into its underlying principles was clear from their very
In the course of development of my induction motors it became
desirable to operate them at high speeds and for this purpose I
constructed alternators of relatively high frequencies. The
striking behavior of the currents soon captivated my attention and
in 1889 I started a systematic investigation of their properties
and the possibilities of practical application. The first
gratifying result of my efforts in this direction was the
transmission of electrical energy thru one wire without return, of
which I gave demonstrations in my lectures and addresses before
several scientific bodies here and abroad in 1891 and 1892.
During that period, while working with my oscillation transformers
and dynamos of frequencies up to 200,000 cycles per second, the
idea gradually took hold of me that the earth might be used in
place of the wire, thus dispensing with artificial conductors
altogether. The immensity of the globe seemed an unsurmountable
obstacle but after a prolonged study of the subject I became
satisfied that the undertaking was rational, and in my lectures
before the Franklin Institute and National Electric Light
Association early in 1893 I gave the outline of the system 1 had
conceived. In the latter part of that year, at the Chicago World's
Fair, I had the good fortune of meeting Prof. Helmholtz to whom I
explained my plan, illustrating it with experiments.
On that occasion I asked the celebrated physicist for an expression
of opinion on the feasibility of the scheme. He stated
unhesitatingly that it was practicable, provided I could perfect
apparatus capable of putting it into effect but this, he
anticipated, would be extremely difficult to accomplish.
I resumed the work very much encouraged and from that date to 1896
advanced slowly but steadily, making a number of improvements the
chief of which was my system of concatenated tuned circuits and
method of regulation, now universally adopted. In the summer of
1897 Lord Kelvin happened to pass thru New York and honored me by a
visit to my laboratory where I entertained him with demonstrations
in support of my wireless theory. He was fairly carried away with
what he saw but, nevertheless, condemned my project in emphatic
terms, qualifying it as something impossible, "an illusion and a
snare." I had expected his approval and was pained and surprised.
But the next day he returned and gave me a better opportunity for
explanation of the advances I had made and of the true principles
underlying the system I had evolved. Suddenly he remarked with
evident astonishment: "Then you are not making use of Hertz waves?"
"Certainly not," I replied, "these are radiations.
No energy could be economically transmitted to a distance by any
such agency. In my system the process is one of true conduction
which, theoretically, can be effected at the greatest distance
without appreciable loss." I can never forget the magic change that
came over the illustrious philosopher the moment he freed himself
from that erroneous impression. The skeptic who would not believe
was suddenly transformed into the warmest of supporters.
He parted from me not only thoroly convinced of the scientific
soundness of the idea but strongly exprest his confidence in its
success. In my exposition to him I resorted to the following
mechanical analogues of my own and the Hertz wave system.
Imagine the earth to be a bag of rubber filled with water, a small
quantity of which is periodically forced in and out of the same by
means of a reciprocating pump, as illustrated. If the strokes of
the latter are effected in intervals of more than one hour and
forty-eight minutes, sufficient for the transmission of the impulse
thru the whole mass, the entire bag will expand and contract and
corresponding movements will be imparted to pressure gauges or
movable pistons with the same intensity, irrespective of distance.
By working the pump faster, shorter waves will be produced which,
on reaching the opposite end of the bag, may be reflected and give
rise to stationary nodes and loops, but in any case, the fluid
being incompressible, its inclosure perfectly elastic, and the
frequency of oscillations not very high, the energy will be
economically transmitted and very little power consumed so long as
no work is done in the receivers. This is a crude but correct
representation of my wireless system in which, however, I resort to
Thus, for instance, the pump is made part of a resonant system of
great inertia, enormously magnifying the force of the imprest
impulses. The receiving devices are similarly conditioned and in
this manner the amount of energy collected in them vastly
The Hertz wave system is in many respects the very opposite of
this. To explain it by analogy, the piston of the pump is assumed
to vibrate to and fro at a terrific rate and the orifice thru which
the fluid passes in and out of the cylinder is reduced to a small
hole. There is scarcely any movement of the fluid and almost the
whole work performed results in the production of radiant heat, of
which an infinitesimal part is recovered in a remote locality.
However incredible, it is true that the minds of some of the ablest
experts have been from the beginning, and still are, obsest by this
monstrous idea, and so it comes that the true wireless art, to
which I laid the foundation in 1893, has been retarded in its
development for twenty years.
This is the reason why the "statics" have proved unconquerable, why
the wireless shares are of little value and why the Government has
been compelled to interfere.
We are living on a planet of well-nigh inconceivable dimensions,
surrounded by a layer of insulating air above which is a rarefied
and conducting atmosphere (Fig. 5). This is providential, for if
all the air were conducting the transmission of electrical energy
thru the natural media would be impossible. My early experiments
have shown that currents of high frequency and great tension
readily pass thru an atmosphere but moderately rarefied, so that
the insulating stratum is reduced to a small thickness as will be
evident by inspection of Fig. 6, in which a part of the earth and
its gaseous envelope is shown to scale. If the radius of the sphere
is 12 1/2", then the non-conducting layer is only 1/64" thick and
it will be obvious that the Hertzian rays cannot traverse so thin a
crack between two conducting surfaces for any considerable
distance, without being absorbed.
The theory has been seriously advanced that these radiations pass
around the globe by successive reflections, but to show the
absurdity of this suggestion reference is made to Fig. 7 in which
this process is diagrammatically indicated. Assuming that there is
no refraction, the rays, as shown on the right, would travel along
the sides of a polygon drawn around the solid, and inscribed into
the conducting gaseous boundary in which case the length of the
side would be about 400 miles. As one - half the circumference of
the earth is approximately 12,000 miles long there will be,
roughly, thirty deviations. The efficiency of such a reflector
cannot be more than 25 per cent, so that if none of the energy of
the transmitter were lost in other ways, the part recovered would
be measured by the fraction (1/4)30. Let the transmitter radiate
Hertz waves at the rate of 1,000 kilowatts.
Then about one hundred and fifteen billionth part of one watt is
all that would be collected in a perfect receiver. In truth, the
reflections would be much more numerous as shown on the left of the
figure, and owing to this and other reasons, on which it is
unnecessary to dwell, the amount recovered would be a vanishing
Consider now the process taking place in the transmission by the
instrumentalities and methods of my invention. For this purpose
attention is called to Fig. 8, which gives an idea of the mode of
propagation of the current waves and is largely self - explanatory.
The drawing represents a solar eclipse with the shadow of the moon
just touching the surface of the earth at a point where the
transmitter is located. As the shadow moves downward it will spread
over the earth's surface, first with infinite and then gradually
diminishing velocity until at a distance of about 6,000 miles it
will attain its true speed in space. From there on it will proceed
with increasing velocity, reaching infinite value at the opposite
point of the globe. It hardly need be stated that this is merely an
illustration and not an accurate representation in the astronomical
The exact law will be readily understood by reference to Fig. 9, in
which a transmitting circuit is shown connected to earth and to an
antenna. The transmitter being in action, two effects are produced:
Hertz waves pass thru the air, and a current traverses the earth.
The former propagate with the speed of light and their energy is
unrecoverable in the circuit. The latter proceeds with the speed
varying as the cosecant of the angle which a radius drawn from any
point under consideration forms with the axis of symmetry of the
At the origin the speed is infinite but gradually diminishes until
a quadrant is traversed, when the velocity is that of light. From
there on it again increases, becoming infinite at the antipole.
Theoretically the energy of this current is recoverable in its
entirety, in properly attuned receivers.
Some experts, whom I have credited with better knowledge, have for
years contended that my proposals to transmit power without wires
are sheer nonsense but I note that they are growing more cautious
every day. The latest objection to my system is found in the
cheapness of gasoline. These men labor under the impression that
the energy flows in all directions and that, therefore, only a
minute amount can be recovered in any individual receiver. But this
is far from being so. The power is conveyed in only one direction,
from the transmitter to the receiver, and none of it is lost
elsewhere. It is perfectly practicable to recover at any point of
the globe energy enough for driving an airplane, or a pleasure boat
or for lighting a dwelling. I am especially sanguine in regard to
the lighting of isolated places and believe that a more economical
and convenient method can hardly be devised. The future will show
whether my foresight is as accurate now as it has proved
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