Science Where Magic Failed
Where magic has failed, science succeeds. For centuries, man has dreamed of being able to see things happening hundreds of miles away. Sorcerers concocted magic brews, soothsayers gazed long and hard into crystal balls, and magicians tossed mystic powders into pools of clear water—all to no avail. Not until the development of television, was man able to see as well as hear distant events in his own home as they happen.
How is this possible? How can these pictures and sounds, move invisibly through space, then suddenly become visible to us on a fluorescent screen?
The wave is quicker than the eye
Let’s imagine that we have a pool of water and a stone. If you toss the stone into the water, ripples or waves travel outward from the place where the stone entered the water in ever-widening circles. These ripples or waves diminish in height as they get farther away from the starting point.
Sending and receiving sound and pictures through the air consists of creating and detecting electromagnetic waves in a great pool of space.
If we look at those ripples on the water more closely we notice that there is a definite distance from the crest of one ripple to the crest of the next. This is called wave length. Even though they are not visible, electrornagnetic waves have a wave length, or a definite distance from crest to crest. Scientific instruments measure the distances in meters and centimeters.
The frequency of a wave is the number of waves which occur in a second. If a wave is said to have a frequency of 10,000 cycles a second, it means that 10,000 of those: waves will pass a given point in one second. We cannot send or receive sound or pictures without considering both the wave lengths and their frequency.
The electronic highway
Ordinary alternating electric current used in homes reverses its direction of flow in the wires 60 times a second. Therefore, we can say that such a current produces an electro-magnetic wave of 60 cycles a second.
This is too low a frequency for radio or television because at this frequency electromagnetic waves travel only very short distances. By increasing the frequency to about 10,000 cycles (10 kilocycles) a second, we find waves suitable for transmitting radio programs. We can use the range up to 300,000,000 cycles (300 megacycles) and higher for sending sound and pictures.
We can keep going along the electronic highway until the waves increase in frequency to a point where they begin to have a heating effect, at about 1,000,000 megacycles per second. These are heat waves or infrared rays.
When the frequency reaches 375,000,000 megacycles, electromagnetic waves become visible, and we have light waves. Beyond 750,000,000 megacycles we can no longer see these waves for they become ultraviolet rays, which cause a healthy sunburn if you are exposed to them long; enough.
Just for the fun of it, we can keep going along the electronic highway to a point where we come to rays which can penetrate the body and metals and wood. We call them X rays. As we move along, the frequency becomes even greater, and we reach the gamma rays, such as radium produces. Finally we reach cosmic rays at the known end of the electronic highway. These waves have frequencies as high as 10,000,000,000,000,000,000,000,000 cycles per second.
Dissecting the spectrum
From this journey up the electronic highway we can see that only a small part of the highway is used for radio and television. This portion, from 10,000 cycles (10 kilo-cycles) to 30,000,000,000 cycles. (30,000 megacycles), is called the radio spectrum.
If we think of this part of the electronic highway as having a definite length, like five inches measured on a yardstick, the problem becomes apparent. Since each radio and television station occupies a certain portion of the highway rather than just a point on the dial, clearly there is space in the radio spectrum for only a certain number of them.
The amount of space turned over to any one service will depend upon the importance and the extent of the service. There is a constant clamor for parts of the radio spectrum. Not only do radio broadcasters want as much space as they can get, but marine, aviation, FM, television, police, government, fire, and amateur broadcasters want as much space as they can use.
In the United States, as we pointed out earlier, non-governmental users of space in the radio spectrum receive their allocations from FCC. However, the United States is not the only nation using radio. Progress in the field of communications has been greatly accelerated within the last two and a half years, and soon after the war it will be necessary for all nations to participate in a world communications conference to discuss the allocation of radio wave bands to television, FM, and other radio services.
Otherwise, for example, Great Britain might set aside a certain section of the radio spectrum for the use of maritime radar anticollision devices, and the United States might set aside the same section for television. A British ship entering New York harbor on a foggy night and using the radar detector at British frequencies would disrupt the local television programs, and television would gum up the radar device. This is just one illustration of the difficulties ahead unless an international conference determines just what portions of the radio spectrum will be set aside for the various types of communication.
How important is television compared to standard broadcasting? Will television eventually take the place of regular radio? Should radio set and television equipment manufacturers wait until a world conference has been held before going ahead and producing their products?