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Niels Bohr
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Niels Bohr in front of blackboard

Niels Bohr 1885 - 1962

Niels Bohr was one of the most influential scientists of the 20th Century and a major force in the field of quantum physics. He won the 1922 Nobel Prize in physics for his study of the structure and radiation of atoms. [See the animation of "The Bohr Atom", below, right.] Bohr recognized that Ernest Rutherford's model of the atom, in which electrons emitted radiation continuously, was unstable according to the laws of classical physics. Bohr postulated that radiation is emitted from atoms not as a result of the periodic motion of the electron in its orbit, but only when an electron "jumps" from one orbit to another losing energy that is emitted as radiation. Bohr's theory of the compound nucleus, in which the repulsion between positively charged protons is countered by huge amounts of energy in order to hold the nucleus together, helped lead to the hypothesis that splitting an atom would produce enough energy to fabricate a powerful weapon.

Bohr's father was a well-known Danish physiologist, his mother came from a wealthy family of Jewish bankers. Bohr earned his Ph.D. at the University of Copenhagen in 1911, then worked in Cambridge, England with J.J. Thomson, discoverer of the electron, and in Manchester with Rutherford, who proposed the first nuclear model of the atom.

In 1909 when his brother Harald left to pursue his own academic endeavors, Bohr hired Margrethe Norlund to type his numerous papers. One year later, the two became engaged and married in 1912. The marriage would produce six sons.
 
In 1921 Bohr was named director of the new Institute for Theoretical Physics in Copenhagen, which soon became a requisite destination for atomic physicists from around the world. During a lecture series in Gottingen, Germany, Bohr befriended the young Werner Heisenberg, [see video above] initiating their famous collaboration. In 1933, after the Nazis authorized German universities to fire staff on the grounds of politics and race, Bohr enabled young refugee physicists to come to his institute.

After Germany occupied Denmark, Bohr fled with his family to Sweden, and then to the United States where he helped develop the atomic bomb. As early as 1944, however, his concern about harnessing the power of nuclear energy led him to advocate control of nuclear weapons and world peace through the open sharing of knowledge among nations. He expressed these ideas to Winston Churchill and President Franklin Roosevelt, both of whom rejected his recommendations. After the war, he helped establish CERN, the European nuclear physics laboratory, and organized the first Atoms for Peace Conference in Geneva in 1955. He was the first recipient of the Atoms for Peace Award.

In 1956, Robert Jungk published a book, Brighter than a Thousand Suns, about the German atomic bomb effort during the war. The book included an excerpted letter from Werner Heisenberg detailing his recollection of his meeting with Bohr in Copenhagen in 1941. Heisenberg's recasting of the events so angered Bohr that he drafted a letter to Heisenberg renouncing his version of the meeting. However, the letter was never sent. But in February of 2002, in order to clarify Bohr's position about the meeting, the Bohr family posted on the internet the draft letter and other documents pertaining to the 1941 meeting.
 
Niels Bohr died in 1962 and is buried in Copenhagen.
 

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