The Wireless Era - The Marvels of Modern Physics
By Rogers D. Rusk, B. Sc.
The Wireless Era is a name frequently given to the scientific period upon
which we are now entering, by people who realize only vaguely themselves
what they actually mean by it. In reality there is a surprising relation
between wire and wireless transmission. That they are not distinctly
different phenomena may put new meaning in the phrase, "Wireless Era."
The question has often been asked "Will all wires be done away with in
the future?" Now the theory most generally accepted at present is that
the energy of an electric current in ordinary wire transmission does not
reside in the wire, but in the ether surrounding the wire, and that the
wire is, as its name implies, merely a conductor to conduct or lead the
current here or there. To make this clear, let us imagine a current
moving in the wire in Fig. 1, from A to B and returning by the ground.
The dotted spiral lines represent the strain in the ether due to the
electro-static and the electromagnetic lines of force about the wire. The
important point to notice is that the current, without this field, would
be lifeless and inert because the magnetic field represents the energy of
motion of the current; it would then have no energy of motion, for the
energy is really stored up in the ether and is transmitted by it.
Let us look beneath the surface a moment at wireless transmission. In
Fig. 2, the wireless waves are represented as traveling from aerial A to
B. We cannot doubt for a moment but what the energy is transmitted by the
ether, as no conducting medium is present. Therefore, the main difference
between wire and wireless transmission seems to be that while in wire
transmission the energy is directed to a definite point, in wireless it
spreads out and dissipates itself in all directions.
A further study of Figs. 1 and 2 may reveal the reason for this. In a
steady direct current the field is steady and continuous.
Change this current, however, to an alternating one and the field or
ether strain varies accordingly, producing an undulatory motion of the
ether. That is, the field about the wire rises and falls periodically.
With an ordinary alternating current the strain in the ether is most
noticeable just about the wire and becomes negligible a short distance
away, although theoretically the waves may travel at each reversal a long
distance before being dissipated. Let us raise the potential and
frequency, however, and see what happens. The field rises to full
strength in a very short time, and the waves follow each other at a
greater speed. This means that radiation is going to amount to much more
than before. The waves are going to be stronger, and their number will be
multiplied many times. If instead of using a wire to direct the energy
from A to B, we shorten the circuit very much, making it merely a local
circuit at A, and if we put another small or local circuit at B, then
some of the radiant energy from A will be intercepted at B, and these
waves passing B will induce a slight current at B.
This is wireless transmission. See what a gradual step it is instead of a
very sudden one from wire to wireless transmission. In one case we have a
small radiation factor, due to a real current in a conductor. In the
other case we have a high radiation factor due to the absence of a long
conductor. In the first the energy is directed; while in the second, it
spreads out in all directions.
The medium of transmission of the energy is the same in either case. The
result is that in one case a large per cent of the energy reaches its
destination, while in the other case only a very small per cent does.
The field about a wire carrying a direct current acts quite like an
invisible whirlpool which pulls the electrons, or charged particles in
the wire, along. The field, in turn, grows with the current, for the
action is an inter-dependent one, and the result is a continuous current.
If, with an alternating current, the oscillation frequency is high, the
current does not have time between reversals to penetrate the wire
deeply, and it is found that the current exists only on the surface of
the wire. This is the well known skin effect and shows again that the
energy must reside in the external field, and that it takes some
appreciable time to start the electrons in motion. This is what we call a
current in a wire.
Wireless telegraphy came into prominence in 1896, when Dr. Guglielmo
Marconi first demonstrated its commercial value. Since then its
importance has increased by leaps and bounds. The submarine has been
directed from the shore by wireless; the human voice has been transmitted
hundreds and thousands of miles; and various kinds of mechanism have been
controlled by it.
However, the glaring predictions of a wireless era for a while somewhat
unduly inflamed the imagination of the public. Let us look at the facts.
It is very significant that one prediction of a few years ago has not
been realized, and that was concerning the wireless transmission of
power. Power and energy are two different things. Energy is any capacity
for doing work, while power is the rate at which work is done.
Now sufficient energy may be sent across the ocean to easily operate a
delicate detector, but the rate at which any work is done is ridiculously
minute. Energy has been transmitted but the power was negligible. When a
submarine is controlled at a distance, it is not power from the shore
which operates the machinery, but rather power from some source on board
the boat itself which is controlled by the energy transmitted from the
shore. The strength of the waves decrease too rapidly with the distance
to allow of any great amount of energy being transmitted.
Most everyone remembers the rule that the intensity of light varies
inversely as the square of the distance from the source. Applying this to
wireless, and neglecting other losses, at the distance of one mile the
energy would only be
of its original value. This in itself would stamp the wireless
transmission of power as impracticable unless a different method of
transmission than that now in use were discovered.
Nikola Tesla believed he had solved the problem and in 1905 took out
patents for a system of wireless transmission of power, with the ether as
the medium. In brief, by his system, he intended setting up powerful,
stationary, electric waves, setting the whole earth in vibration due to
the reflection and superimposition of waves from all parts of the earth.
The principle is similar to that of a string tied at one end and waved
back and forth by the hand at the other. Waves from the hand would travel
to the opposite end and be reflected back (see Fig. 4) creating nodes and
loops of vibration in the string. The proposition, it was claimed, had
been partially demonstrated, and on the strength of this a wonderful
station was built on Long Island.
Every reader of scientific periodicals is familiar with its picture and
history. At present it is deserted, but Tesla is still working upon the
subject. The problem, however, is as yet unsolved. We will not say it is
impossible of solution, for do we not have real wireless transmission of
power as an everyday occurrence in the ordinary transformer?
Though there is no metallic connection between the primary and secondary
coils, yet there is an immense transfer of power at only a slight loss.
Notice how near the ideal conditions are, however. The distance is
negligibly small, and even the medium itself is improved by the presence
of a soft iron core. It is too common a fact for us to consider it
wonderful, and yet the result is the same as that which has puzzled many
scientific minds to reproduce or duplicate through any great distance.
As wireless telegraphy and telephony supplement, rather than take the
place of the ordinary systems and as the transmission of power is the
back-bone of commerce and industry, it seems the wires are here to stay
for a long time to come. However, we must not disrespect the possibility
of just as revolutionary discoveries in the future as have occurred in
the past, hard as they are for us to even conceive of now.
Why, even wireless telegraphy would not have approached the success it
has, if the energy radiated directly by the Hertzian oscillator had been
depended upon. In the first place the decrease of energy, as shown by the
above law, would have been so great as to have been discouraging; and
secondly, the fact that radiation travels in straight lines would have
made long distance communication impossible, owing to the curvature of
Both of these theories were advanced early in the development of the
subject, and when approached near at hand were neither of them found as
forbidding as they had seemed. It was shortly found that when the sending
station was suitably grounded, that the waves actually follow the surface
of the earth, and the invention of sensitive detectors made the
transmission of a large amount of energy unnecessary for signaling.
Many such facts about wireless telegraphy are a mystery to the average
person, and although the mathematics of radiation were actually worked
out over sixty years ago by James Clerk Maxwell and his co-workers, many
of the exact physical actions which take place are but little understood
even by the brilliant scientists of the present day. Much more is known,
however, than formerly.
The wireless wave follows the earth as a huge conductor, because when the
oscillations occur in the aerial, shown in Fig. 3, the lines of force
moving up and down the aerial with the oscillating charge, throw off
loops as shown, which are waves traveling partly in and partly above the
earth. These travel off exactly like ripples on a pond, and also follow
the curvature of the earth.
They are much stronger than if radiated in all directions. It is evident
they are not as wireless as they might seem, for the earth acts as a huge
conductor. In early experiments between Lynn, Mass., and Schenectady,
N.Y., communication was found impossible, due to the dry rock mountains
intervening which acted as effective, non-conducting carriers. Not long
afterward communication was established between Clifden, Ireland, and
Buenos Aires, S.A., a distance of six thousand miles, the intervening
water being a good conducting medium.
Wireless telegraphy and telephony are now of immeasurable commercial
value, to say nothing of their importance from a purely scientific
standpoint. It may even be said that we have been approaching as a limit
the wire transmission of power for some years. In 1890 a power line was
established, thirteen miles long, at Portland, Oregon, which transmitted
current at 4,000 volts. In 1903, in Mexico, a line was built 104 miles
long, to operate at 60,000 volts, while in 1913 the Pacific Light &
Power Company of Los Angeles, Cal., began operating a line 240 miles long
at 150,000 volts.
This latter means a comparatively small current and a small conductor
acting more and more as a guide rather than a vehicle for the power. Has
a limit been reached; or will this record distance and voltage soon be
eclipsed? It is a problem the engineers and scientists will try to solve
in the near future.
The wireless era does not mean an era where wires are taken down and
thrown on the scrap heap. We must not look for scientific miracles for
nature follows natural laws. It means an age where an extra gift has been
given to man, enabling him to extend his influence beyond the sphere of
base matter; to annihilate distance and gain control over the finer
forces of nature.
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