"He was a man weighed down with a conscience"

- Supreme Court Justice Felix Frankfurter's description of Niels Bohr

Niels Bohr was "...the wisest and most lovable of men" according to his colleague J. Rud Nielson (J. Rud Nielson, Memories of Niels Bohr, Physics Today, Oct. 1963, pg. 22). Many others who knew Bohr would agree. But Bohr was also one of the most foresighted of men, and one of the few who not only thought ahead about the post-World War II implications of the atomic bomb but who personally urged President Franklin Roosevelt and Prime Minister Winston Churchill to prepare for the nuclear future.

Bohr lived in Copenhagen, Denmark, where he founded the Institute for Theoretical Physics in 1921 (now known as the Niels Bohr Institute). For many years he had been one of the most respected physicists in the world, and he had won the Nobel Prize in physics in 1922 for his work on the structure of the atom (Abraham Pais, Niels Bohr's Times, in Physics, Philosophy, and Polity, pg. 171, 214-215).

In Jan. 1939 Bohr embarked on a four month stay in the United States as a visiting professor. Shortly before sailing for the U.S. he learned of the successful uranium fission experiment that had been conducted in Germany in Dec. 1938. Bohr brought the exciting news to the U.S., and in 1939 the physics world revolved around nuclear fission.

Bohr became one of the key fission researchers, determining in 1939 that the rare U-235 isotope was the isotope that made uranium fissionable and which made a chain reaction theoretically possible. But because U-235 comprised less than 1% of uranium and was so difficult to separate from the rest of the uranium, he felt an atomic bomb could not be made in the near future. "It would take the entire efforts of a country to make a bomb", Bohr explained to his colleagues (quoted by Barton Bernstein in Helen Hawkins, G. Allen Greg, and Gertrud Weiss Szilard, editors, Toward a Livable World: Leo Szilard and the Crusade for Nuclear Arms Control, pg. xxix). Even Bohr could not have known that something like that would soon occur. (For an excellent account of how Bohr spread the news of fission to the U.S., see Roger Stuewer, Bringing the News of Fission to America, Physics Today, Oct. 1985).

In April of 1940 the Nazis occupied Denmark. This put Bohr at great risk, for altho he was not a religious man, his mother was Jewish. In spite of the danger, he turned down offers to live safely in other countries. Bohr explained his reasons when he declined an offer from the British government to come to Great Britain:

But in Sept. 1943 the order came to arrest Jews in Copenhagen. Word was leaked to Bohr that he would soon be arrested by the Nazis. His escape late that month and passage to Great Britain in early Oct. are the stuff that adventure movies are made of. For brevity's sake, I will just offer a few sources of information on his escape: his son, Aage Bohr, in S. Rozental, editor, Niels Bohr: His Life and Work As Seen By His Friends and Colleagues, pg. 195+; Pais, pg. 478+ and 487+; French and Kennedy, pg. 280+; Richard Rhodes, The Making of the Atomic Bomb, pg. 482+.

Yet Bohr's adventure was only beginning. Upon arriving in Great Britain he was given direct access to high level advisors in the British government, who informed him of the Manhattan Project. Bohr was surprised; he later wrote: " was a revelation to me to learn...about the advanced stage the work had already reached" (J. Robert Oppenheimer papers, Box 34, Bohr memorandum to President Roosevelt, July 3rd, 1944, Library of Congress).

Bohr and his son Aage were soon asked to join the Manhattan Project. They arrived in the U.S. on Dec. 6, 1943 (Pais, pg. 496). But Bohr was thinking beyond the invention of the atomic bomb.

Previous conversations with colleagues from Germany and Russia had led him to believe those countries were working on an atomic bomb. This had seemed like only a distant possibility to him - until he learned how far along the British and Americans had gotten. Now even though it was probably too late for the Germans to make an a-bomb, he knew the Russians would eventually be able to make one. And once Germany was defeated, Russia would be aided by knowledge from captured German scientists. Aage later related,

During his visits to Los Alamos Bohr served mainly as a "scientific father confessor" to the scientists, clarifying their problems with the atomic bomb and offering possible approaches that might be taken (Richard Hewlett and Oscar Anderson, The New World: A History of the United States Atomic Energy Commission, Vol. 1: 1939-1946, pg. 310). But his primary concern was the prevention of a nuclear arms race: "That is why I went to America. They didn't need my help in making the atom bomb" (quoted in Nielson, pg. 28-29).

Characteristically, Bohr thought that while the threat of nuclear annihilation could become the "greatest disaster", it could also become "one of the greatest boons to mankind". (J. Robert Oppenheimer papers, Box 34, Felix Frankfurter memorandum to Sec. of War Stimson, April 26, 1945, Library of Congress).

Let's take a moment to list some of Bohr's key points from 1944:

Among Bohr's friends was Supreme Court Justice Felix Frankfurter. Frankfurter was so convinced by Bohr's ideas that he relayed them to his friend, President Roosevelt. Roosevelt appeared to agree with Bohr's views and asked to have Bohr, in Frankfurter's words, "tell our friends in London that the President was anxious to explore ways for achieving safeguards in relation to X" [the atomic bomb] (J. Robert Oppenheimer papers, Box 34, Felix Frankfurter memorandum to Sec. of War Stimson, April 26, 1945, Library of Congress).

Bohr had already convinced some high level British officials that international control of nuclear weapons was essential for world security. Now they set up an appointment for him with the Brit whose opinion mattered most - Prime Minister Winston Churchill.

On May 16, 1944 Bohr met with Churchill and Lord Cherwell, Churchill's closest advisor. But when Bohr returned from the meeting he told a friend that Churchill had "scolded us like two schoolboys!" (R.V. Jones in French and Kennedy, pg. 284-285). Churchill apparently felt the purpose of the meeting was to criticize how he had dealt with Roosevelt on nuclear matters, and he lit into Bohr and Cherwell before Bohr could explain his views. Churchill's tirade took up most of Bohr's allotted time, and it did not help matters that Bohr was a notoriously poor speaker. Plus, when it came to Russia, Churchill was interested in nuclear coercion, not nuclear cooperation. After the meeting Churchill distrusted Bohr, fearing he might tell other nations of the Manhattan Project (Aage Bohr in Rozental, pg. 204; Martin Sherwin, A World Destroyed, pg. 107-108, 110).

Bohr returned to the U.S. in June and told Frankfurter of his failed meeting with Churchill. Frankfurter in turn spoke to FDR. Now the President asked to meet with Bohr.

Bohr's Aug. 26, 1944 meeting with Roosevelt was just the opposite of his meeting with Churchill. According to Bohr's son,

But when Roosevelt and Churchill met on Sept. 18, it was Roosevelt who agreed to Churchill's views on the matter. And to top that off, they decided that Bohr should be investigated and "steps taken to ensure that he is responsible for no leakage of information, particularly to the Russians". (Sherwin, pg. 109-110, 284).

Bohr eventually surmised that nothing good had come of his meeting with Roosevelt. He made one final attempt, via letter, to influence FDR. But before the letter could be delivered, Roosevelt died. Bohr gave the letter to Vannevar Bush, who had been Roosevelt's main science advisor. In June 1945 Bohr left the United States (Aage Bohr in Rozental, pg. 209-210).

During World War II Bohr did not argue against using the atomic bomb, unlike fellow Manhattan Project physicist Leo Szilard. Instead, he stayed focused on his message of international control and scientific openness. But after the atomic bomb was used on Japan Bohr told friends, "The frightening thing was... that it was not necessary at all" (Niels Blaedel, Harmony and Unity: The Life of Niels Bohr, pg. 233). British nuclear historian Margaret Gowing wrote that Bohr's son Aage said his father "privately deplored the spirit in which the bomb had been used" (Gowing in French and Kennedy, pg. 275).

Bohr continued to work for international control of nuclear weapons until his death in 1962.

Bohr once summarized his approach to life, in his softspoken manner, when he said:

- Doug Long

For further information:

A.P. French and P.J. Kennedy, editors, Niels Bohr: A Centenary Volume

Margaret Gowing, Britain and Atomic Energy, 1939-1945

J. Robert Oppenheimer papers, Box 34, Felix Frankfurter/Niels Bohr folder, Library of Congress

Abraham Pais, Niels Bohr's Times, in Physics, Philosophy, and Polity

Richard Rhodes, The Making of the Atomic Bomb

S. Rozental, editor, Niels Bohr: His Life and Work As Seen By His Friends and Colleagues

Martin Sherwin, A World Destroyed

Niels Henrik David Bohr, a web site by the School of Mathematics and Statistics at the University of St. Andrews

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