Alan Turing: The Enigma (56 page)

There was no time for social relaxation. It was the peak of the war effort, and they were all working for up to twelve hours a day. Alex Fowler would have liked to find the time and energy to entertain Alan, but it was out of the question. Like many people, he was also afraid of boring him. Alan meanwhile was accommodated in a hotel. He told a joke about how he tried going to read in the toilet when the black-out was on, but found to his chagrin that the lights went out there too.

Greenwich Village in 1943 was, perhaps more exciting than Princeton in 1938. Alan later told a story about a man in the hotel having made a sexual approach, amazing him by its casualness. No hint of anything like this was heard in Bell Labs, though Alan once said, ‘I’ve spent a considerable portion of time in your
subway
. I met someone who lived in your
Brooklyn
who wanted me to play
Go
.’ Another time he said: ‘I had a
dream
last night. I dreamt I was walking up your Broadway carrying a flag, a
Confederate
flag. One of your
bobbies
came up to me and said, “See here! You can’t do that,” and I said, “Why
not?
I fought in the
War between the States”.’
Alan’s curious English voice, like the X-system encoding his information by frequency rather than by amplitude, made a vivid impression on his temporary colleagues.

By the end of February Alan had gained more familiarity with the electronic equipment that was used in the laboratory. Although his work was primarily theoretical, he asked many questions about oscilloscopes and frequency analysers, such as they were using for breaking speech encipherment systems, and left them impressed with the amount of knowledge he had picked up. He also took advantage of the theoreticians at Bell Labs, for instance learning from Nyquist his theory of feedback, which was a new departure making use of the complex numbers.

But another significant interaction of his visit was the one he made every day at teatime in the cafeteria. Here he met a person who had been able to
take the part of an academic, philosophical engineer, the role that Alan might have liked had the English system allowed for it. This was Claude Shannon, since 1941 working for Bell Laboratories and producing ideas of a breadth which would find scant encouragement in any British company. While Friedman was Alan’s opposite number in terms of direct responsibility for cryptanalytical work, Friedman was an older and more old-fashioned figure: a code and cipher fanatic, rather than someone who had looked at cryptology through the eyes of modern science as Alan had. In intellectual depth it was Shannon who was Alan’s opposite number, and they found a good deal in common.

People had thought about machines since the dawn of civilisation, but
Computable Numbers
had come up with a precise, mathematical definition of the concept of ‘machine’. People had thought equally long about communication, but here again it needed a modern mind, in this case Claude Shannon’s, to provide a precise definition of the concepts involved. These were somewhat parallel developments. Shannon had completed his first paper
⁸
in this direction in 1940, and by 1943 his fundamental ideas were beginning to be used in Bell Laboratories, in whose mathematical department he was now employed. He was consulted about the design of the X-system, which posed some of the questions answered by his work.

The transmitter, the ionosphere, and the receiver, were a
communication channel
, in his terms; a channel with a limited capacity, and a channel plagued by noise. Into this channel had to be squeezed a signal. Shannon found ways to define channel capacity, noise, and signal, in terms of a precise measure of information. The problem of the communication engineer was that of encoding the signal in such a way as to make best use of the channel, and to prevent it being distorted by the noise; Shannon found new precise theorems which placed limits upon what could be achieved.

There was not only a parallel between his work and Alan Turing’s; there was a sort of reciprocity. On his side Alan, although his main strength was in the logic of machines, had dipped into the study of information. Not only was this true in general terms of all his cryptological work, but there was an even more specific point of contact. Shannon’s measure of information was essentially the same as the Turing ‘decibans’. A
ban
of weight of evidence made something ten times as likely; a binary digit or
bit
of information made something twice as definite. There were fundamental connections between the theories, although they were not free to discuss them. Shannon only knew by implication why Alan was at Bell Labs at all.

Then on his side, Shannon had also independently thought about logical machines. From 1936 to 1938 he had been working on the differential analyser at MIT, and had designed a logical apparatus with relays in connection with a particular problem. This in turn had led him to write a paper
⁹
in 1937 which drew the connection between the ‘switching’
operations of electromagnetic relays, and Boolean algebra – hence doing this just as Alan was designing his electric multiplier at Princeton.

Alan showed
Computable Numbers
to Shannon, which he read, immediately impressed. They also discussed the idea implicit in
Computable Numbers
, an idea of which they were independently convinced. Shannon had always been fascinated with the idea that a machine should be able to imitate the brain; he had studied neurology as well as mathematics and logic, and had seen his work on the differential analyser as a first step towards a thinking machine. They found their outlook to be the same: there was nothing sacred about the brain, and that if a machine could do as well as a brain, then it
would
be thinking – although neither proposed any particular way in which this might be achieved. This was a back-room Casablanca, planning an assault not on Europe, but on inner space.

Here at least was something they could speak of freely. Once Alan said at lunch, ‘Shannon wants to feed not just
data
to a Brain, but
cultural
things! He wants to play
music
to it!’ And there was another occasion in the executive mess, when Alan was holding forth on the possibilities of a ‘thinking machine’. His high-pitched voice already stood out above the general murmur of well-behaved junior executives grooming themselves for promotion within the Bell corporation. Then he was suddenly heard to say: ‘No, I’m not interested in developing a
powerful
brain. All I’m after is just a
mediocre
brain, something like the President of the American Telephone and Telegraph Company.’ The room was paralysed, while Alan nonchalantly continued to explain how he imagined feeding in facts on prices of commodities and stock, and asking the machine the question ‘Do I buy or sell?’ All afternoon the phone was ringing in his laboratory, with people asking who on earth it was.

On 2 February 1943, the German surrender at Stalingrad had marked the turning of the tide. But while the eastern front was turned by sheer brute force, the western powers had the space and time for developments in which force was not the only element. The intricacy and sophistication of their cryptanalysis was the most extreme example, but this was not the only sphere in which machinery was taking the war out of the old world of duty and self-sacrifice. In November 1942 the ground had been cleared at Los Alamos, and by March 1943 the first scientists were already moving in. The atomic bomb they planned to make would not release greater energy than the raids of 1943 already deployed against Germany. But it would make thousands of bombers redundant, thus mechanising the discipline and coordination of air offensives. The Manhattan Project would still depend upon an aircraft pilot – but then he, too, was being automated at Peenemünde, where the long predicted ‘monster cannons’ were on the way. The V-weapons would lack sufficient accuracy – but such problems of guidance were also being attacked at Germany’s back by the new techniques of proximity fuses, automatic celestial navigation, and automatic fire
control. People easily understood powerful guns, fast ships, impenetrable tanks, which extended human limbs. By now the secret of radar was out, and it could be understood how its manifold applications extended human eyesight to the longer wavelengths of the electromagnetic spectrum. But rapidly developing, and not only at Bletchley and Washington, was a new kind of machinery, a new kind of science, in which it was not the physics and chemistry that mattered, but the logical structure of information, communication, and control.

This development was not confined to warfare. In Dublin, Schrödinger was lecturing under the title ‘What is Life?’, and advancing the conjecture that the information defining a living organism must somehow be encoded in molecular patterns. In Chicago, two neurologists had read
Computable Numbers
, and were publishing
¹⁰
an idea that connected the definition of the logical machine with the actual physiology of brains. They had applied Boolean algebra to the properties of nerve-cells. As Hilbert died at Göttingen on 14 February 1943, a new kind of applied logic was taking shape. Against the distant thunder of the east, there were the first glimpses of a post-war science. This first half-serious, half-joking talk of ‘thinking machines’ reflected both the immensely wider horizon that the war had opened to science, and the fact that an end at last seemed possible.

By 4 March Alan had completed a report on his suggestions regarding the RCA speech cipher, and had studied in great detail all the speech systems with which they were working. The head of the section had expressed concern that Alan might invent something which would create a tangle over patent rights, but Alan pooh-poohed this, saying that he wanted Bell Telephone to have anything that he thought of. ‘Hands across the sea’, he said. But what idea could possibly compare with those he had already handed across the sea, ideas far too important for any patent office to know existed? From 5 to 12 March he had to spend another week in Washington at the request of the Navy, to look after this side of his mission again. It was another critical point for the U-boat Enigma, for on 10 March the codebook for the short weather report signals, on which the December breakthrough had been based, was withdrawn. But the three months of successful decryption had allowed analysts to develop alternative methods in time, finding in particular that other ‘short signals’, allowed to remain in force, were also enciphered with the fourth wheel in its ‘neutral’ position. Again the German force threw away its advantage, and with more than sixty Bombes at Bletchley now, the Allied dependence upon this special trick was lessening. The change of 10 March was overcome in just nine days.

Returning to Bell Labs, Alan worked for a few more days on the RCA cipher. He wanted them to keep him informed on their progress after he had returned to England, and indicated two possible means of communication: either through Friedman, or through Professor Bayly, a Canadian engineer attached to British Security Coordination. At a quarter past four
on 16 March, he had a telephone call from BSC, telling him it was time to embark. He stopped work and left the West Street building within half an hour. His ship
¹¹
was not a
Queen
this time, but the 26,000 ton troop transporter
Empress of Scotland
. This British vessel could sustain
19
^1/2
knots, while packed with 3867 enlisted men, 471 officers – and just one civilian.

After a week’s delay, the
Empress of Scotland
left New York harbour on the night of 23 March. She steamed due east into mid-Atlantic, and then swung up to the north. Only one of the thousands carried into the midst of the battle knew the precarious system upon which so much depended – but that knowledge made no difference now. For a week Alan was ordinary again, having to take the risks and trust the authorities like everyone else. The danger was real enough: on 14 March the similar
Empress of Canada
had been sighted and sunk. Briefly he was on the receiving end of the system, and briefly he was relieved of responsibility for it.

In a sense he had stood upon the burning deck since 1939; but the sentiments of
Casabianca
, those of doing a patriotic duty contrary to inclination, were very remote from the spirit of Alan Turing’s war. He was doing what he had chosen to do, and was expressing himself, not subjecting himself. His mind continued to work away, fascinated by the problems, even during this voyage home. While briefly sharing in the helplessness, confinement and danger of the war, he spent his time studying a twenty-five-cent handbook on electronics, the
RCA Radio Tube Manual
, and invented a new way of enciphering speech.

If he dreamt about fighting in the War between the States, it was the reverse of the truth. He was committed to the Yankee side, and had seen no fighting. His struggle had all been behind the lines. But that was not quite the whole story. Once in conversation with his friend Fred Clayton, the question arose as to how scientists could have continued to work for Germany. With both personal honesty and political realism, Alan pointed out that in scientific research it was inevitable that one became absorbed in the work, and did not think of the implications. It was, in this respect, a Looking Glass war, with the
B. Dienst
analysts no less fascinated by their work.
^*
It could be an entrancing dream world, without connection with the issues of the war. But Fred did get him to admit that Germany raised other questions.

For Alan Turing’s generation, the First World War had been a War between the States, meaningless as Tweedledum and Tweedledee. The mirror symmetry of nationalism had disgusted Russell and Einstein, Hardy and Eddington, who saw only human beings with labels pinned upon them,
destroying each other. They longed to jump out of the system of
La Grande Illusion
, and in 1933 the new generation had voiced this longing openly. But Russell and Einstein came round to support of
this
war, the war for the Anti-War, the war that could be imagined not as the ‘national war’ but the world Civil War, a crusade against slavery. That it was primarily a war between two tyrannies; that it had massively reinforced national governments; that it had made mass slaughter respectable again; that it had militarised the advanced economies – these did not countervail. Against this enemy anything could be justified. In 1933 they had reviled the arms manufacturers above all others. But they were all arms manufacturers now.