Giant brains; or, Machines that think

by Edmund Callis Berkeley

NEW DEVICES FOR HANDLING INFORMATION

In the laboratories working on new mechanical and electronic brains, scientists are doing a lot of thinking about new devices for handling information. Research into devices for storing information shows that magnetic wire as used in sound recording is a rather good storage medium.

Magnetic Wire

For example, on a hundredth of an inch of fine steel wire we can “write” a magnetized spot by means of a small “writing” electromagnet. The electromagnet is simply some copper wire coiled around some soft iron shaped in a U. When current flows through the coil, the iron becomes a magnet, and the tips of the U magnetize the little section of the wire between them. The magnetized spot can be of two kinds, say north-south or south-north, depending on which way the current flows. We can “read” this difference by means of another small “reading” electromagnet. We can erase the spot by means of a stronger “erasing” magnet that produces a uniform magnetic state throughout the wire. The difference between north-south and south-north corresponds to the difference between 1 and 0, or “yes” and “no,” etc., and is a unit of information ([see Chapter 2]). Many other variations are possible. For example, the presence or absence of a magnetized spot may be the unit of information, or the “writing,” “reading,” and “erasing” electromagnets all may be the same.

Magnetic wire sound recordings made in the 1890’s are still good. This fact shows that magnetic wire may be a more permanent medium for storing information than is paper. Stray magnetic forces are likely to have no harmful effect on information stored on magnetic wire, for these forces would not be strong enough or detailed enough to change greatly the difference between the magnetized spot and its neighboring neutral area.

A reel of magnetic wire a mile long and ³/₁₀₀₀ of an inch thick costs about $5. At 80 magnetized spots to the inch, a mile of wire can store about 5 million units of information. Hence, the cost of storing one unit of information is about ¹/₁₀₀₀₀ of a cent. The time needed for changing a magnetized spot from 1 to 0 or from 0 to 1 is about ¹/₁₀₀₀₀ of a second.

Magnetic Tape

There is, however, a storage device that may be even more useful, and this is magnetic tape ([see Fig. 1]). The usual size of such tape is ¼ inch wide and 2 or 3 thousandths of an inch thick. Magnetic tape may be made of plastic with magnetic powder all through it, or it may be of paper coated with magnetic powder, or it may be of stainless steel or a magnetic alloy, or it may be of brass or a nonmagnetic alloy coated with a magnetic plating.

Magnetic tape has the added advantage that from 4 to 20 channels across the tape can be filled with magnetized spots, and the cost then becomes about ¹/₁₀₀₀₀₀ of a cent per spot. It seems possible that 1000 units of information can be stored in a quarter of a square inch of magnetic tape. This means that more than 1 million units of information can be stored in a cubic inch of space filled with magnetic tape, and about 2 billion units of information in a cubic foot, except that some of the space should be allotted to the reels and other equipment that hold the tape ([see Fig. 2]). This is closer packing than printed information in the telephone book, and yet with magnetic tape we can get to the information automatically.

Fig. 1. Magnetic tape.

Fig. 2. Tape reels.

Think of the enormous files in libraries, government, and business. Think of the problems of space and cost and access which these files imply. We can then see that this new development may well be of extraordinary importance.

Mercury Tanks

Fig. 3. Mercury tank.

Scientists are investigating other storage devices having still more remarkable properties, but these have the disadvantage that, when the power goes off, the information vanishes. One of these new storage devices is called a mercury tank ([see Fig. 3]). It consists mainly of a section of iron or steel pipe filled with mercury. At each end of this pipe, touching the mercury, is a thin slab of a crystal of quartz. Quartz, which is a common stone, and which nearly all sand is made of, changes its shape when pulsed with electricity. We put a pattern of electrical pulses into the quartz slab at one end of the mercury tank; for example, we could have the pattern 1101 meaning “pulse, pulse, no pulse, pulse.” The electrical pulses going into the quartz slab make the quartz vibrate. Thus ripples are produced in the mercury, and waves in the pattern 1101 meaning “wave, wave, no wave, wave” travel down the tank and strike the quartz slab at the far end. The quartz slab there changes its shape in the rhythm 1101, and it converts the waves back into electrical pulses in the same pattern. Then we take the pulses out of the far end along a wire, make them stronger again with an amplifier, give them the right form again, and feed them back into the front end of the mercury tank. The mercury tank is a clever use of the principle of an echo, as when you call across a valley and the rocks answer you back. We can store a pattern of 400 pulses (each a unit of information, a 1 or a 0, and each a millionth of a second in duration), in a mercury tank about 20 inches long. A mercury tank and an echo are examples of delay lines—“lines” along which waves are “delayed.”

Electrostatic Storage Tube

Another of the memory devices being developed is called an electrostatic storage tube ([see Fig. 4]). This is a big electronic tube with a screen across one end. The screen may be of two layers: one of copper, which conducts electricity, and one of mica, a material that does not. In the other end of the tube is a beam of electrons, which we can turn on and off and shoot at any of 2 or 3 thousand specific points or spots on the screen.

Fig. 4. Electrostatic storage tube.

There are two sizes of electric charge or quantity of electrons; we can call these 1 and 0. In about a millionth of a second, we can put either size of charge on one of the spots of the screen. With other circuits we can keep it there as long as we want, if the power does not flicker off. We can “remember” perhaps 2 or 3 thousand units of information in one of these electronic tubes. We can read, write, or erase any unit of information in a few millionths of a second.

Neither the mercury tank nor the electrostatic storage tube had, by the end of 1947, been put into a working mechanical brain. But there is good reason to believe that they will be successful devices and will open up a new era of speed in storing and referring to information. In fact, several laboratories are developing electronic calculating circuits using these devices which will perform up to 100,000 additions a second or 10,000 multiplications a second. Our minds certainly stagger at the thought of such speeds.