Niels Bohr - Danish Physicist Extraordinaire

Niels Henrik David Bohr was born October 7, 1885, in Copenhagen. His parents, Christian and Ellen (Adler) Bohr were from respected, well-to-do families. Christian Bohr was a professor of physiology at Copenhagen University. He enjoyed bringing educated, interesting people to his home for dinner and conversation, and his children were exposed to great ideas and current thinking. Ellen Bohr felt more comfortable giving birth to her children in her mother's home, a large house opposite Christiansborg Castle where the Danish parliament met. There were three children in the family. Bohr's sister was Jenny and his younger brother was Harald (who would win an Olympic silver medal in soccer and become a professor of mathematics). The brothers were inseparable throughout their lives. 

Bohr finished Gammelholm Grammar School in 1903. He was a good student and excelled in physics and mathematics. He was also a good athlete. It is probable that he learned a great deal from his father who gave him access to his laboratory. After graduation, Bohr began studies at Copenhagen University. He studied physics, mathematics, astronomy, and chemistry. He studied under Christian Christiansen, Harald Hoffding, and Thorvald Thiele. There was no physics laboratory at the university, so he did his research at the physiology laboratory in this father's department. In 1907, he was awarded the gold medal of the Royal Danish Academy of Sciences and Letters for his essay on determining the surface tension of liquids. 

Bohr received a master's degree in physics in 1909, and a doctor's degree in 1911. His doctoral thesis was on the electron theory of metals.

He received a grant from the Carlsberg Foundation and went to England in 1911 to study and conduct research with Sir J J Thomson (discovered the electron) at Cambridge. Bohr and Thomson were not well suited to each other, so after a few months, Bohr changed to Victoria University in Manchester (University of Manchester) working with Ernest Rutherford. Rutherford had just published a paper describing the theory that most of the mass of an atom was in its nucleus. 

He married Margrethe Nørlund on August 1, 1912. They had six sons, four of whom survived. One son is Aage Bohr, who also received a Nobel Prize in physics.

Bohr returned to the University of Copenhagen in 1912. He extended Rutherford's theory, using the quantum ideas of Planck, to describe how electrons in an atom travel around a nucleus in various set orbits, that the outer orbits hold more electrons than inner orbits, and that outer orbits determine the atom's chemical properties. Bohr also described how atoms might emit radiation when an electron jumped from an outer orbit to an inner orbit. He published three papers on the theory of the atom. In 1913, he was appointed a docent, which was not the job he wanted. He wrote to the university, asking them to create a new professorship in theoretical physics and to name him to the position. He received the recommendation, but his confirmation was delayed.

He returned to the University of Manchester, where he stayed from 1914 until 1916 as a lecturer. The confirmation was received in 1916, and Bohr returned to Copenhagen as professor of theoretical physics. In 1917 he was named a member of the Royal Danish Academy. He began work on planning an Institute of Theoretical Physics in Copenhagen, which opened in 1921. Bohr became the institute's first director. He remained there for the rest of his career. The institute was popular among physicists and welcomed visiting researchers.

In 1922, Bohr won the Nobel prize in physics for his work on the atom. His other research included the principle of complementarity, a theoretical description of the periodic table of elements, a theory of the atomic nucleus as a compound structure, and the function of the isotope 235 in uranium fission.

The Nazis entered Denmark in 1940. Bohr's position became uncertain since his mother's family was Jewish. Bohr learned from Lise Meitner, who had fled Nazi Germany, that the Germans were trying to split the atom. In 1943, he and his family escaped to Sweden on fishing boat, and then he and his son Aage flew as secret passengers in an unarmed military plane to England where he began working with a team trying to create a nuclear fission bomb. Within months, he and Aage moved with the team to Los Alamos, New Mexico, and began working on the Manhattan Project. He remained with the project from 1943 until 1945 when he returned to Denmark and his institute.

Bohr was very concerned about the possible catastrophic effects of the nuclear warfare, and in 1950 he wrote an "Open Letter to the United Nations" in which he urged that the weapons be placed under international control. In 1955, Bohr was named Chairman of the Danish Atomic Energy Commission.

Bohr died on November 18, 1962, at his home at Carlsberg.

Bohr was a personable man who was well liked and well respected. He had a grand sense of humor and is quoted:

"Never express yourself more clearly than you can think."

"Prediction is very difficult, especially about the future."

"An expert is a person who has made all the mistakes that can be made in a very narrow field."

Awards and Honors

• 1922, Nobel Prize for Physics
• 1926, Fellow, Royal Society
• 1938, Royal Society Copley Award
• President, Royal Danish Academy of Sciences
• President, Danish Cancer Committee
• Chairman of the Danish Atomic Energy Commission
• Foreign Member, Royal Society (London )
• Member of the Royal Institution, and Academies in Amsterdam, Berlin, Bologna, Boston, Göttingen, Helsingfors, Budapest, München, Oslo, Paris, Rome, Stockholm, Uppsala, Vienna, Washington, Harlem, Moscow, Trondhjem, Halle, Dublin, Liege, and Cracow
• Doctor, honoris causa, of many universities, colleges, and institutes

Sources

http://www.nobel.se/physics/laureates/1922/bohr-bio.html

http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Bohr_Niels.html

http://www.lucidcafe.com/library/95oct/nbohr.html

http://scienceworld.wolfram.com/biography/BohrNiels.html

http://www2.vo.lu/homepages/geko/atom/biogr.htm

http://hillion-tchernobyl.ifrance.com/hillion-tchernobyl/borh_en.htm

http://almaz.com/nobel/physics/1922a.html

http://www.pbs.org/wgbh/aso/databank/entries/bpbohr.html

http://www.sunderland.ac.uk/~hs0bcl/h_nb.htm

http://www.denmarkemb.org/bohr.html

http://encarta.msn.com/encnet/refpages/RefArticle.aspx?refid=761576813

http://www.pbs.org/hollywoodpresents/copenhagen/story/bohr.html