Henrik David Bohr was born in Copenhagen on October 7, 1885, as the
son of Christian Bohr, Professor of Physiology at Copenhagen University,
and his wife Ellen, née Adler. Niels, together with his younger
brother Harald (the future Professor in Mathematics), grew up in an
atmosphere most favourable to the development of his genius - his father
was an eminent physiologist and was largely responsible for awakening
his interest in physics while still at school, his mother came from
a family distinguished in the field of education.
at the Gammelholm Grammar School in 1903, he entered Copenhagen University
where he came under the guidance of Professor C. Christiansen, a profoundly
original and highly endowed physicist, and took his Master's degree
in Physics in 1909 and his Doctor's degree in 1911.
a student, the announcement by the Academy of Sciences in Copenhagen
of a prize to be awarded for the solution of a certain scientific problem,
caused him to take up an experimental and theoretical investigation
of the surface tension by means of oscillating fluid jets. This work,
which he carried out in his father's laboratory and for which he received
the prize offered (a gold medal), was published in the Transactions
of the Royal Society, 1908.
studies, however, became more and more theoretical in character, his
doctor's disputation being a purely theoretical piece of work on the
explanation of the properties of the metals with the aid of the electron
theory, which remains to this day a classic on the subject. It was in
this work that Bohr was first confronted with the implications of Planck's
quantum theory of radiation.
In the autumn
of 1911 he made a stay at Cambridge, where he profited by following
the experimental work going on in the Cavendish Laboratory under Sir
J.J. Thomson's guidance, at the same time as he pursued own theoretical
studies. In the spring of 1912 he was at work in Professor Rutherford's
laboratory in Manchester, where just in those years such an intensive
scientific life and activity prevailed as a consequence of that investigator's
fundamental inquiries into the radioactive phenomena. Having there carried
out a theoretical piece of work on the absorption of alpha rays which
was published in the Philosophical Magazine, 1913, he passed on to a
study of the structure of atoms on the basis of Rutherford's discovery
of the atomic nucleus. By introducing conceptions borrowed from the
Quantum Theory as established by Planck, which had gradually come to
occupy a prominent position in the science of theoretical physics, he
succeeded in working out and presenting a picture of atomic structure
that, with later improvements (mainly as a result of Heisenberg's ideas
in 1925), still fitly serves as an elucidation of the physical and chemical
properties of the elements.
Bohr held a Lectureship in Physics at Copenhagen University and in 1914-1916
a similar appointment at the Victoria University in Manchester. In 1916
he was appointed Professor of Theoretical Physics at Copenhagen University,
and since 1920 (until his death in 1962) he was at the head of the Institute
for Theoretical Physics, established for him at that university.
of his work on the structure of atoms came with the award of the Nobel
Prize for 1922.
in his Institute were since 1930 more and more directed to research
on the constitution of the atomic nuclei, and of their transmutations
and disintegrations. In 1936 he pointed out that in nuclear processes
the smallness of the region in which interactions take place, as well
as the strength of these interactions, justify the transition processes
to be described more in a classical way than in the case of atoms (Cf.
»Neutron capture and nuclear constitution«, Nature, 137
A liquid drop
would, according to this view, give a very good picture of the nucleus.
This so-called liquid droplet theory permitted the understanding of
the mechanism of nuclear fission, when the splitting of uranium was
discovered by Hahn and Strassmann, in 1939, and formed the basis of
important theoretical studies in this field (among others, by Frisch
contributed to the clarification of the problems encountered in quantum
physics, in particular by developing the concept of complementarily.
Hereby he could show how deeply the changes in the field of physics
have affected fundamental features of our scientific outlook and how
the consequences of this change of attitude reach far beyond the scope
of atomic physics and touch upon all domains of human knowledge. These
views are discussed in a number of essays, written during the years
1933-1962. They are available in English, collected in two volumes with
the title Atomic Physics and Human Knowledge and Essays 1958-1962 on
Atomic Physics and Human Knowledge, edited by John Wiley and Sons, New
York and London, in 1958 and 1963, respectively.
Bohr's numerous writings (some 115 publications), three appearing as
books in the English language may be mentioned here as embodying his
principal thoughts: The Theory of Spectra and Atomic Constitution, University
Press, Cambridge, 1922/2nd. ed., 1924; Atomic Theory and the Description
of Nature, University Press, Cambridge, 1934/reprint 1961; The Unity
of Knowledge, Doubleday & Co., New York, 1955.
Nazi occupation of Denmark in World War II, Bohr escaped to Sweden and
spent the last two years of the war in England and America, where he
became associated with the Atomic Energy Project. In his later years,
he devoted his work to the peaceful application of atomic physics and
to political problems arising from the development of atomic weapons.
In particular, he advocated a development towards full openness between
nations. His views are especially set forth in his Open Letter to the
United Nations, June 9, 1950.
end, Bohr's mind remained alert as ever; during the last few years of
his life he had shown keen interest in the new developments of molecular
biology. The latest formulation of his thoughts on the problem of Life
appeared in his final (unfinished) article, published after his death:
"Licht und Leben-noch einmal", Naturwiss., 50 (1963) 72: (in
English: "Light and Life revisited", ICSU Rev., 5 ( 1963)
Bohr was married, in 1912, to Margrethe Nørlund, who was for
him an ideal companion. They had six sons, of whom they lost two; the
other four have made distinguished careers in various professions -
Hans Henrik (M.D.), Erik (chemical engineer), Aage (Ph.D., theoretical
physicist, following his father as Director of the Institute for Theoretical
Physics), Ernest (lawyer).
died in Copenhagen on November 18, 1962.
David Bohr (October 7, 1885 – November 18, 1962) was a Danish
physicist who made essential contributions to understanding atomic structure
and quantum mechanics.
Born in Copenhagen
to Christian Bohr and Ellen Adler, Bohr received his doctorate from
Copenhagen University in 1911. He then studied under Ernest Rutherford
in Manchester, England. Based on Rutherford's theories, Bohr published
his model of atomic structure in 1913, introducing the theory of electrons
travelling in orbits around the atom's nucleus, the chemical properties
of the element being largely determined by the number of electrons in
the outer orbits. Bohr also introduced the idea that an electron could
drop from a higher-energy orbit to a lower one, emitting a photon (light
quantum) of discrete energy. This became the basis for quantum theory.
In 1916, Bohr
became a professor at the University of Copenhagen, and director of
the newly constructed "Institute of Theoretical Physics" in
1920. In 1922, he was awarded the Nobel Prize in physics for developing
the Copenhagen interpretation of quantum mechanics.
largely affected by the philosophy of Søren Kierkegaard of sharp
sudden "quality" changes and rejection of the continuous changing.
These concepts were manifested in Bohr's quantum theory.
conceived the principle of complementarity: that items could be separately
analyzed as having several contradictory properties. For example, physicists
currently conclude that light is both a wave and a stream of particles
- two apparently mutually exclusive properties - based on this principle.
Bohr also found philosophical applications for this daringly original
principle. Albert Einstein much preferred the determinism of classical
physics over the probabilistic new physics of Bohr and Max Planck. He
and Bohr had good-natured arguments over the verity of this principle
throughout their lives. One of Bohr's most famous students was Werner
Heisenberg, a crucial figure in the development of quantum mechanics,
but also head of the German atomic bomb project.
and his wife Margrethe had several children, one of whom, Aage Niels
Bohr, also became a very successful physicist: like his father, he won
a Nobel prize.
the German occupation of Denmark in World War II, Bohr was visited by
Heisenberg in Copenhagen and apparently learned something of the German
plans. In 1943 he escaped to Sweden to avoid arrest by the German police,
then travelled to London.
at Los Alamos, New Mexico, USA, on the Manhattan Project, where, according
to Richard Feynman, he was known by the assumed name of Nicholas Baker
for security reasons. However his role in the project was minor. He
is quoted as saying "That is why I went to America. They didn't
need my help in making the atom bomb." He was seen as a knowledgeable
consultant or "father confessor" on the project . After
the war he returned to Copenhagen, advocating for a peaceful use of
nuclear energy. He died in Copenhagen in 1962.
claimed in an interview after the war, when the author Robert Jungk
was working on the book Brighter Than a Thousand Suns, that he had tried
to establish a pact with Bohr such that scientists on neither side should
help develop the atomic bomb. He also said that the German attempts
were entirely focused on energy production, and that his circle of colleagues
tried to keep it that way.
saw this claim he disagreed wholeheartedly. He said that Heisenberg
had indeed let him know in Copenhagen that he was working on an atomic
bomb project, and that he thought that Germany would win the war. He
dismissed the idea of any pact as an after-the-fact construction. He
drafted several letters to inform Heisenberg about this but never sent
any of them.
play Copenhagen, which ran on Broadway for a time, explores what might
have happened at the 1941 meeting between Heisenberg and Bohr.
was born in Copenhagen on October 7, 1885. He was the older of the two
sons born to Christian Bohr and Ellen, née Adler. His father
was a Professor of Physiology at Copenhagen University. In his early
childhood his father helped to cultivate his interest in physics. Niels
attended Gammelholm Grammar School until 1903, when he enrolled in Copenhagen
University. It was at Copenhagen University where he met Professor C.
Christiansen. In 1909 Bohr earned his Master's degree in Physics, he
went on to get his Doctorate degree in 1911.
In his early
childhood Bohr was inspired by his teachers and his father to peruse
mathematics and physics in 1922 Bohr stated, “My interest in the
study of physics was awakened while I was still in school, largely owing
to the influence of my father.”(Niels Bohr, 1922)
a student, he conducted in his father's laboratory, an experimental
investigation of surface tension by using oscillating fluid jets. His
work won him the prize offered by the Academy of Sciences in Copenhagen,
and was published in the Transactions of the Royal Society, in 1908.
studies became much more theoretical. In fact his doctoral dissertation
on “the explanation of the properties of the metals with the aid
of the electron theory” was purely theoretical. To this day his
dissertation remains a classic on the subject. It was while doing this
work that Bohr was first confronted with Planck's quantum theory of
In 1911, under
Sir J.J. Thomson's guidance Bohr assisted in the experimental work going
on in the Cavendish Laboratory, and at the same time he continued to
pursue his own theoretical studies. In the spring of 1912 he went to
work at Professor Rutherford's laboratory in Manchester, where he preformed
theoretical work on the absorption of alpha rays, which was later published
in the Philosophical Magazine, in 1913. He then went on to study the
structure of atoms based on Rutherford's discovery of the atomic nucleus.
By introducing conceptions borrowed from Planck’s Quantum Theory,
he worked out a structure of an atom, which with later improvements
based on Heisenberg’s ideas in 1925, still is used. In recognition
of this work Bohr was awarded the Nobel Prize in physics in 1922.
In 1912 Bohr
married Margrethe Nørlund. Together they had six sons, of who
two died, the other four made distinguished careers in various professions:
Hans Henrik who became a doctor, Erik who became a chemical engineer,
Aage who followed his father as Director of the Institute for Theoretical
Physics, and Ernest who became a lawyer.
In 1916 Bohr
was appointed Professor of Theoretical Physics at Copenhagen University,
and from 1920 until his death in 1962, he was the head of their Institute
for Theoretical Physics.
activities in his Institute were directed toward research on the atomic
nuclei, and of their transmutations and disintegrations. In 1936 he
pointed out that the transition processes in atomic nuclei could be
described in a classical unlike the way that an atom is described. This
was in part due to the size of the transition, compared to the vastness
of the region that it occurred in. According to this view, a liquid
drop would give a very good picture of the nucleus; this was to become
the “liquid droplet theory”. In 1939 Hahn and Strassmann
used this theory to help further the understanding of nuclear fission
when they were working on splitting uranium.
Nazi occupation of Denmark in World War II, Bohr fled to Sweden and
then on to England and The U.S.A. While in the U.S. he became associated
with the Atomic Energy Project, and then in later years devoted his
work to the peaceful application of atomic physics. He also was active
in the politics that went with the development of atomic weapons. For
example on June 9, 1950, He sent a letter to the United Nations advocating
full openness between nations.
David Bohr died in Copenhagen on November 18, 1962.