Niels Bohr

J.J. Thomson
One day, in late September 1911, as Bohr was crossing the Great Belt, he wrote to his fiancee, "I am taking off with all my silly fierce spirit".

Financed by a stipend from the Carlsberg Foundation (a Danish institution) for a year's study abroard, he was on his way to Cambridge to start postdoctoral research under J.J. Thomson, the director of the Cavendish. In his baggage he carried the poor translation of his Ph.D thesis, which he had helped prepare a little earlier.

Bohr knew of Thomson's ideas on atomic structure, since these are mentioned in one of Thomson's books which Bohr had quoted several times in his thesis. When asked why he had gone there for postdoctoral research, he replied : "First of all I had made this great study of the electron theory. I considered Cambridge as the center of physics and Thomson as a most wonderful man." In other words, Bohr looked forward above all to discuss with Thomson matters related to his thesis.

Several physicists have given me an account of Bohr's first meeting with Thomson. It went about as follows. Bohr entered Thomson's office, carrying one of Thomson's books, opened it on a certain page, and politely said : "This is wrong". This first encounter with Thomson did not lay the basis for the relationship Bohr had hoped for. Later, Bohr reminisced

It was a disappointment that Thomson was not interested to learn that his calculations were not correct. That was also my fault. I had no great knowledge of English and therefore I did not know how to express myself. I could say only that this is incorrect. He was not interested in the accusation that it was not correct.

Thomson was a genius who actually showed the way to everybody. Then some young man could make things a little better.

The whole thing was very interesting in Cambridge, but it was absolutely useless.

Then, while still attached to Cambridge, Bohr met Rutherford. His life changed.

Message from England
A courier from Stockholm had arrived in Copenhagen with a communication from England to the Danish general staff, to the effect that an important message for Prof. Bohr was to come via the general staff offices. It was requested to ascertain whether Bohr would be willing to receive that message, which was to be written on a piece of ultramicrofilm hidden in a hollowed-out section of a key attached to a bunch of other keys. Only after receipt of a signal that Bohr would accept the message would the bunch of keys be sent to Copenhagen.

Gyth was charged with contacting Bohr. He was an officer in the information division of the Danish general staff who at the same time was deeply involved with the Danish resistance movement. Thus came about Gyth's visit to Bohr, the beginning of a secret operation codenamed '213'.

Bohr declared himself willing to accept the message. But it took another three weeks before a sufficiently well qualified courier was found to bring the material from Stockholm to Copenhagen.

After receipt of the keys, Gyth managed to locate the microdot which was the size of a pinhead. He put it under a microscope and transcribed it.

"I have heard in a roundabout way that you have considered coming to this country if the opportunity should offer. I need not tell you how delighted I myself should be to see you again."

"Indeed I have in my mind a particular problem in which your assistance would be of the greatest help. Darwin and Appleton are also interested in this problem and I know they too would be very glad to have your help and advice."

"All I want to do is to assure you that if you decide to come, you will have a very warm welcome and an opportunity of service in the common cause"

"Yours sincerely, J. Chadwick. Physics Laboratories - The University of Liverpool"

Bohr declined the invitation. At Bohr's request, Gyth returned the next day to pick up a reply to Chadwick. He saw to it that this letter was reduced to 2 x 3 mm size. Next, it was wrapped in metal foil and handed to a courier. Then it went to a dentist who inserted the message in a hollow tooth of the courier, then covered it with a filling.

"In spite of the times, it was possible to continue undisturbed both the experimental and the theoretical work."

"I have to the best of my judgment convinced myself that in spite of all future prospects, any immediate use of the latest marvelous discoveries of atomic physics is impracticable."

But two weeks later he called Gyth again. Further reflection had led him to believe he saw a method for practical uses of fission. He had committed his idea to paper and asked Gyth if he could help him once again to get his message to the British. Gyth obliged and this time the letter was sent in secret, but less dramatic ways.

The escape
In mid-September Bohr was informed by Swedish diplomatic sources in Copenhagen that arrest of refugees was imminent. In the following days, it became increasingly clear that Bohr own fate was also at risk. All this led him to contact the Danish underground, especially the biochemist Kaj Linderstrøm-Lang. Linderstrøm-Lang arranged for an escape route to Sweden.

On 29 September 1943 Bohr and his wife left Carlsberg on foot to walk to a small house in the Musikby, part of the Sydhavn quarter, where they arrived in the early evening. That was the place of assembly for about a dozen people who, together with the Bohrs, were to make the illegal crossing over the Øresund in the same boat. Toward ten o'clock everyone left the little house, crawling on all fours part of the way, to get to the beach. Everybody boarded a little fishing boat that brought them on to the Øresund. Linderstrøm-Lang, who kept an eye on the Bohrs, all the way from Carlsberg to the boat, now departed.

A good hour later, all passengers were transferred to a large trawler. In the early hours of 30 September they were safely delivered in the harbour of Limhamn. From there, they were transported to Malmø, three miles to the north, where everyone was bedded down in the detention rooms of a police station. Bohr immediately contacted the rector of the University of Lund asking him to request an interview with the Swedish minister of foreign affairs in Stockholm. In the early afternoon of the same day, Bohr arrived by train in Stockholm. His wife stayed behind to await the arrival of the sons who came over shortly afterward with their families. At the station, Bohr was met by Prof. and Mrs. Klein -- who would be the Bohr's hosts -- by an intelligence officer of the Swedish general staff and by captain Gyth.

Gyth brought Bohr to the Kleins by taxi. In high Le Carre style, they first drove to a building used by the Swedish intelligence service, went up to the roof, walked over roofs to another building, then went down and took another taxi. Soon after arrival at the Klein home, a police officer arrived, with whom Gyth arranged security measures. One policeman to be present at all times in the home, one to be stationed in front of the houses, one to patrol nearby streets. That done, Gyth told Bohr of the British desire to have him come quickly.

For his own reasons, Gyth had had to flee to Swedien earlier in September. A few hours after Bohr's arrival, he had been told what had happened. At once he arranged for a communication to England of Bohr's escape. Almost immediately he received word that the British wanted Bohr to come over as soon as possible. The next day, an unarmed Mosquito bomber would be at Bohr's disposal at Stockholm's airport.

However, Bohr did not want to leave at once. First, he intended to intervene with the Swedish government on behalf of the Jews in Denmark. As it happened, for a few days, bad weather over the British Isles made his departure impossible anyway. Lasting thorugh 3 October, Bohr proposed modes of action to the Swedish minister of foreign affairs, King Gustaf V, the crown prince, and a number of other prominent Swedes. Meanwhile, Gyth had arranged for Bohr and his wife who had arrived in Stockholm to move to more spacious quarters provided by a member of the Danish embassy staff. Surveillance continued, now also including an armed Danish officer who during the night guarded the bedroom.

The time had now come for Bohr to fly to England. At ten o'clock on the evening of 4 October, Bohr said goodbye to his family.

After he had left, Gyth and the hosts broke open a bottle of champagne to celebrate the successful conclusion of this part of the adventure. Shortly after midnight, the bell rang. There stood Bohr. His plane had taken off alright but after a short while had to return because of engine malfunction. Bohr had taken a taxi back.

Since all security personnel had been dismissed, Gyth decided to guard the bedroom himself armed with the host's old revolver.

All was peaceful until in the early morning hours he heard soft steps on the stairs. Somebody approached the apartment door. Gyth stood at the ready, the revolver in one hand, a heavy candelabrum in the other.

Then, the morning newspaper dropped through the mail slot. Looking out of the window some moments later, Gyth saw an old newspaper lady wearing felt slippers so as not to wake her customers.

That evening, Bohr took off again via Stockholm's Bromma airport.

Bohr's plane flight to Britain had its hairy moments. When the plane reached the Kattegat near occupied Denmark, it increased altitude to avoid Nazi fighters and it became necessary to use the oxygen mask. By intercom, the pilot instructed Bohr, who was lying in the bomb bay separated from the cabin, to turn on the oxygen. But he got no response.

So the pilot took the plane down to near sea level. When it landed at a military airport in Scotland, in the early hours of 6 October, Bohr was in fine shape, telling that he had slept most of the way, which meant that he had been unconscious because of lack of oxygen.

Bohr spent the rest of that night in the home of the airport commander. The following morning he was flown to London's Croydon airport, where he was met by Chadwick and the secret service officer who had supervised his escape to Britain. They saw to it that Bohr was installed in the Savoy hotel.

Institute of Advanced Study
On 1948, Bohr arrived in Princeton after a trip by sea from Denmark. For about a week, he had had no opportunity to discuss scientific matters. He was quite pent up. Wolfgang Pauli and I were walking in a corridor of the Institute for Advanced Study when Bohr first came in. When he saw us, he practically pushed us into an office, made us sit down, said, 'Pauli, schweig' (Pauli, shut up). Then he talked for about two hours before either of us had a chance to interrupt him. Had Bohr's words been recorded, it would have constituted a fascinating document on the development of quantum theory.

A few weeks later, Bohr came to my office at the Institute of which I then was a temporary member. He was in a state of angry despair and kept saying 'I am sick of myself,' several times. I was concerned and asked what had happened. He told me he had just been downstairs to see Einstein. They had got into an argument about the meaning of quantum mechanics, but Bohr had been unable to convince Einstein of his views.