Bohr received numerous honours and accolades.

Liquid droplet theory

Bohr had felt the consequences of the Nazi regime almost as soon as Adolf Hitler came to power in Germany in , as several of his colleagues there were of Jewish descent and lost their jobs without any prospect of a future in their home country. After the discovery of fission, Bohr was acutely aware of the theoretical possibility of making an atomic bomb.

However, as he announced in lectures in Denmark and in Norway just before the German occupation of both countries in April , he considered the practical difficulties so prohibitive as to prevent the realization of a bomb until well after the war could be expected to end.

Even when Heisenberg at his visit to Copenhagen in told Bohr about his role in a German atomic bomb project, Bohr did not waver from that conviction. In early Bohr received a secret message from his British colleague James Chadwick , inviting Bohr to join him in England to do important scientific work.

Still convinced of the infeasibility of such a project, Bohr answered that there was greater need for him in occupied Denmark. After being warned about his imminent arrest, Bohr escaped by boat with his family across the narrow sound to Sweden. In Stockholm the invitation to England was repeated, and Bohr was brought by a military airplane to Scotland and then on to London.

Upon being briefed about the state of the Allied atomic bomb project on his arrival in London, Bohr changed his mind immediately about its feasibility. Concerned about a corresponding project being pursued in Germany, Bohr willingly joined the Allied project. Taking part for several weeks at a time in the work in Los Alamos, New Mexico , to develop the atomic bomb, he made significant technical contributions, notably to the design of the so-called initiator for the plutonium bomb.

His most-important role, however, was to serve, in J. Bohr set out on a solitary campaign, during which he even succeeded in obtaining personal interviews with British Prime Minister Winston Churchill and U. He was unable to convince either of them of his viewpoint, however, instead being suspected by Churchill of spying for the Russians. Bohr was allowed to return home only after the atomic bomb had been dropped on Japan in August In Denmark he was greeted as a hero, some newspapers even welcoming him with pride as the Dane who had invented the atomic bomb.

He continued to run and expand his institute, and he was central in postwar institution building for physics. Internationally, he took part in the establishment of CERN , the European experimental particle physics facility near Geneva , Switzerland, as well as of the Nordic Institute for Atomic Physics Nordita adjacent to his institute. Bohr left behind an unsurpassed scientific legacy , as well as an institute that remains one of the leading centres for theoretical physics in the world.

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Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed. Jan 3, See Article History. Niels Henrik David Bohr. Learn More in these related Britannica articles: In the Danish physicist Niels Bohr presented the first theoretical model that could give quantized energy levels that were in quantitative agreement with measurements of the hydrogen spectrum.

Bohr rejected the idea of light quanta, and he searched for ways to explain the Compton effect and the photoelectric effect by arguing that the momentum and energy conservation laws need to be satisfied only statistically in the time average.

In he stated that…. Bohr held a lectureship in physics at Copenhagen University from to and went on to hold a similar position at Victoria University in Manchester from to He went back to Copenhagen University in to become a professor of theoretical physics. In , he was appointed the head of the Institute for Theoretical Physics. Combining Rutherford's description of the nucleus and Planck's theory about quanta, Bohr explained what happens inside an atom and developed a picture of atomic structure.

This work earned him a Nobel Prize of his own in Later in life, he became president of the Royal Danish Academy of Sciences, as well as a member of scientific academies all over the world. He spent the last two years of the war in England and the United States, where he got involved with the Atomic Energy Project. It was important to him, however, to use his skills for good and not violence.

He dedicated his work toward the peaceful use of atomic physics and toward solving political problems arising from the development of atomic weapons of destruction. He believed that nations should be completely open with one another and wrote down these views in his Open Letter to the United Nations in Bohr's greatest contribution to modern physics was the atomic model. The Bohr model shows the atom as a small, positively charged nucleus surrounded by orbiting electrons.

Bohr was the first to discover that electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element. The chemical element bohrium Bh , No. Bohr's theoretical work contributed significantly to scientists' understanding of nuclear fission. The rise of Nazism in Germany prompted many scholars to flee their countries, either because they were Jewish or because they were political opponents of the Nazi regime.

In , the Rockefeller Foundation created a fund to help support refugee academics, and Bohr discussed this programme with the President of the Rockefeller Foundation, Max Mason , in May during a visit to the United States.

Bohr offered the refugees temporary jobs at the Institute, provided them with financial support, arranged for them to be awarded fellowships from the Rockefeller Foundation, and ultimately found them places at institutions around the world.

In this form, they were stored on a shelf at the Institute until after the war, when the gold was precipitated and the medals re-struck by the Nobel Foundation. Bohr kept the Institute running, but all the foreign scholars departed. Bohr was aware of the possibility of using uranium to construct an atomic bomb , referring to it in lectures in Britain and Denmark shortly before and after the war started, but he did not believe that it was technically feasible to extract a sufficient quantity of uranium During this meeting the two men took a private moment outside, the content of which has caused much speculation, as both gave differing accounts.

According to Heisenberg, he began to address nuclear energy, morality and the war, to which Bohr seems to have reacted by terminating the conversation abruptly while not giving Heisenberg hints about his own opinions. A Personal History of the Atomic Scientists. Heisenberg explained that he had visited Copenhagen to communicate to Bohr the views of several German scientists, that production of a nuclear weapon was possible with great efforts, and this raised enormous responsibilities on the world's scientists on both sides.

Michael Frayn 's play Copenhagen explores what might have happened at the meeting between Heisenberg and Bohr. In September , word reached Bohr and his brother Harald that the Nazis considered their family to be Jewish, since their mother was Jewish, and that they were therefore in danger of being arrested. The Danish resistance helped Bohr and his wife escape by sea to Sweden on 29 September.

On 2 October , Swedish radio broadcast that Sweden was ready to offer asylum, and the mass rescue of the Danish Jews by their countrymen followed swiftly thereafter. Some historians claim that Bohr's actions led directly to the mass rescue, while others say that, though Bohr did all that he could for his countrymen, his actions were not a decisive influence on the wider events.

By flying at high speed and high altitude, they could cross German-occupied Norway, and yet avoid German fighters. Bohr, equipped with parachute, flying suit and oxygen mask, spent the three-hour flight lying on a mattress in the aircraft's bomb bay.

He passed out from oxygen starvation and only revived when the aircraft descended to lower altitude over the North Sea. Bohr was warmly received by James Chadwick and Sir John Anderson , but for security reasons Bohr was kept out of sight.

He was given an apartment at St James's Palace and an office with the British Tube Alloys nuclear weapons development team. Bohr was astonished at the amount of progress that had been made. Bohr did not remain at Los Alamos, but paid a series of extended visits over the course of the next two years.

Robert Oppenheimer credited Bohr with acting "as a scientific father figure to the younger men", most notably Richard Feynman. Bohr recognised early that nuclear weapons would change international relations. In April , he received a letter from Peter Kapitza , written some months before when Bohr was in Sweden, inviting him to come to the Soviet Union.

The letter convinced Bohr that the Soviets were aware of the Anglo-American project, and would strive to catch up. He sent Kapitza a non-committal response, which he showed to the authorities in Britain before posting.

Oppenheimer suggested that Bohr visit President Franklin D. Roosevelt to convince him that the Manhattan Project should be shared with the Soviets in the hope of speeding up its results. Roosevelt suggested that Bohr return to the United Kingdom to try to win British approval. In June , Bohr addressed an "Open Letter" to the United Nations calling for international cooperation on nuclear energy. This award was normally awarded only to royalty and heads of state, but the king said that it honoured not just Bohr personally, but Danish science.

The Second World War demonstrated that science, and physics in particular, now required considerable financial and material resources. To avoid a brain drain to the United States, twelve European countries banded together to create CERN , a research organisation along the lines of the national laboratories in the United States, designed to undertake Big Science projects beyond the resources of any one of them alone.

Questions soon arose regarding the best location for the facilities. Bohr and Kramers felt that the Institute in Copenhagen would be the ideal site. Pierre Auger , who organised the preliminary discussions, disagreed; he felt that both Bohr and his Institute were past their prime, and that Bohr's presence would overshadow others.

The enthusiasm and ideas of the other people would not have been enough, however, if a man of his stature had not supported it. Meanwhile, Scandinavian countries formed the Nordic Institute for Theoretical Physics in , with Bohr as its chairman.

Bohr died of heart failure at his home in Carlsberg on 18 November Years later, his wife's ashes were also interred there. Bohr received numerous honours and accolades. Several other countries have also issued postage stamps depicting Bohr. From Wikipedia, the free encyclopedia. For other uses, see Bohr disambiguation. Bohr is on the right in the middle row, next to Max Born. List of things named after Niels Bohr. Archived from the original on 29 November Dart, James 27 July Retrieved 26 June Retrieved 14 February Retrieved 10 November Retrieved 12 February A Biographical Approach to Theoretical Entities.

University of Chicago Press. The establishment of an institute". Archived from the original on 5 April Retrieved 11 May Archived from the original PDF on 22 May Retrieved 18 February So too is a well-fortified atheism.

Bohr ended with no religious belief and a dislike of all religions that claimed to base their teachings on revelations. Jutarnji list in Croatian. Retrieved 13 August Istinu sam saznao od Margrethe, Bohrove supruge. Neither Bohr nor Heisenberg were the main characters of this encounter, but Carl Friedrich von Weizsaecker.

Von Weizsaecker's idea, which I think was the brainchild of his father who was Ribbentrop 's deputy, was to persuade Niels Bohr to mediate for peace between Great Britain and Germany. Archived from the original on 17 October Retrieved 21 December Archived from the original on Retrieved 4 June Retrieved 27 February Retrieved 3 March De frie Danske in Danish. Retrieved 18 November Government , pp.

Impact of Science on Society. Retrieved 12 June Bulletin of the Atomic Scientists. Massachusetts Institute of Technology. Retrieved 28 February Retrieved 13 March