Werner Karl Heisenberg
Article
by: J J O'Connor and E F Robertson (University of St. Andrews, Scotland)
Werner
Karl Heisenberg
Born: 5 Dec 1901 in Würzburg,
Germany
Died: 1 Feb 1976 in Munich, Germany
Werner Heisenberg's father was August Heisenberg and his mother was
Anna Wecklein. At the time that Werner was born his father was about to progress
from being a school teacher of classical languages to being appointed as a Privatdozent
at the University of Würzburg. Anna's father, Nikolaus Wecklein, was the headmaster
of the Maximilians Gymnasium in Munich and it was while August Heisenberg was
a trainee teacher at that school that he had met Anna. August and Anna were married
in May 1899. Werner had an older brother Erwin, born in March 1900, who was therefore
nearly two years older than his brother.
August Heisenberg was [3]:-
...
a rather stiff, tightly controlled, authoritarian figure.
He
was an Evangelical Lutheran and his wife Anna had converted from being a Roman
Catholic to make sure there were no religious problems with their marriage. August
and Anna, however, were only religious for the sake of convention. A Christian
belief was expected of people of their status so for them it was a social necessity.
In private, however, they expressed their lack of religious beliefs, and in particular
they brought up their children to follow Christian ethics but showed total disbelief
in the historical side of Christianity.
In September 1906, shortly before his
fifth birthday, Werner enrolled in a primary school in Würzburg. He spent three
years at that school but then in 1909 his father was appointed Professor of Middle
and Modern Greek at the University of Munich. In June 1910, a few months after
his father took up the professorship, Werner and the rest of the family moved
to Munich. There he attended the Elisabethenschule school from September, spending
only one year at this school before entering the Maximilians Gymnasium in Munich.
This of course was the school where his grandfather was the headmaster.
In
1914 World War I began and the Gymnasium was occupied by troops. Lessons were
arranged in different buildings and as a result of the disruption Heisenberg undertook
much independent studying which probably had a beneficial effect on his education.
His best subjects were mathematics, physics and religion but his record throughout
his school career was excellent all round. In fact his mathematical abilities
were such that in 1917 he tutored a family friend who was at university in calculus.
During this period he belonged to a paramilitary organisation which operated in
the Gymnasium with the intention of preparing the young men for later military
service.
Heisenberg also worked on farms as his contribution to another voluntary
organisation which sent the boys to help in the fields in spring and summer. This
work took him away from home for the first time in 1918 when he was sent to work
on a dairy farm in Upper Bavaria. It was a time of great hardship with long hours
of labour made worse since there was insufficient food. He spent his spare time
playing chess, which he did to a very high standard, and also read mathematics
texts he had taken with him. In fact by this time he had become interested in
number theory and he read Kronrcker's work and tried to find a proof of Fermat's
Last Theorem.
After the war ended in 1918 the situation in Germany became unstable
with different factions trying to take power by force. Heisenberg took part in
the military suppression of the Bavarian Soviet forces but, although it was a
very serious business, the young men probably almost treated it almost as a game.
He later wrote [4]:-
I was a boy of 17 and I considered
it a kind of adventure. it was like playing cops and robbers ...
In
the Gymnasium Heisenberg led a youth movement and he later led a movement within
the Young Bavarian League. In 1920 he took his Abitur examination and was one
of two pupils entered from the Maximilians Gymnasium for a Bavarian wide competition
for a scholarship from the Maximilianeum Foundation. Eleven scholarships were
available and Heisenberg just made it by coming in eleventh place. His examination
results in mathematics and physics were classed as extraordinary, but his essay
on "tragedy as poetic art" was much less impressive. He declined the offer of
free accommodation from the Foundation, preferring to live with his parents.
In
the period between taking his Abitur examination and entering the University of
Munich Heisenberg went off hiking with his youth group. He nearly died of typhoid
which he contracted after spending the night in a castle which had been used as
a military hospital. He recovered, despite the problems of obtaining suitable
food, in time to begin his university studies. During the summer of 1920 Heisenberg
was, as he had been for some time, intending to study pure mathematics at university.
He had read Weyl and also Bachmann's text which gave a complete survey of number
theory and this was to be his intended research topic for his doctorate. He approached
Ferdinand von Lindemann to see if he would be his research supervisor.
Had
the interview with Lindemann been a success then Heisenberg might today be known
as an outstanding number theorist. However, the interview did not go well, almost
certainly since Lindemann was only two years off retiring and had only agreed
to see Heisenberg as a favour to his father who was a friend and colleague. Following
this Heisenberg had an interview with Sommerfeld who happily accepted him as a
student.
With his fellow student Pauli, Heisenberg began to study theoretical
physics under Sommerfeld in October 1920. At first he was cautious, taking mostly
mathematics classes and making sure that he could revert to mathematics if the
theoretical physics went badly. He avoided courses by Lindemann, however, so his
mathematical interests moved from number theory to geometry. Soon his confidence
in theoretical physics was such that by the second semester he was taking all
of Sommerfeld's courses. He also took courses in experimental physics, which were
compulsory, and he began to plan to undertake research in relativity. However
Pauli, who was at that time working on his major survey of the theory of relativity,
advised him against doing research in that topic. On atomic structure, however,
Pauli explained, much needed to be done since theory and experiment did not agree.
In [6] Heisenberg wrote of his early days at university:-
My
first two years at Munich University were spent in two quite different worlds:
among my friends of the youth movement and in the abstract realm of theoretical
physics. Both worlds were so filled with intense activity that I was often in
a state of great agitation, the more so as I found it rather difficult to shuttle
between the two.
In June 1922 he attended lectures by Niels Bohr
in Göttingen. Returning to Munich, Sommerfeld gave him a problem in hydrodynamics
to keep him busy while he (Sommerfeld) spent session 1922-23 in the United States.
Heisenberg presented preliminary results on the problem on turbulence at a conference
in Innsbruck before going again to Göttingen to study with Born, Franck, and Hilbert
while his supervisor was away. There he worked with Born on atomic theory, writing
a joint paper with him on helium. His doctoral dissertation, presented to Munich
in 1923, was on turbulence in fluid streams.
After taking his doctorate Heisenberg
went on a trip to Finland then, in October 1923, he returned to Göttingen as Born's
assistant. In March 1924 he visited Niels Bohr at the Institute for Theoretical
Physics in Copenhagen where he met Einstein for the first time. Returning again
to Göttingen he delivered his habilitation lecture on 28 July 1924 and qualified
to teach in German universities.
Heisenberg later wrote:-
I
learned optimism from Sommerfeld, mathematics at Göttingen, and physics
from Bohr.
From September 1924 until May 1925 he worked, with
the support of a Rockefeller grant, with Niels Bohr at the University of Copenhagen,
returning for the summer of 1925 to Göttingen. Heisenberg invented matrix mechanics,
the first version of quantum mechanics, in 1925. He did not invent these concepts
as a matrix algebra, however, rather he focused attention on a set of quantised
probability amplitudes. These amplitudes formed a non-commutative algebra. It
was Max Born and Pascual Jordan in Göttingen who recognised this non-commutative
algebra to be a matrix algebra.
Matrix mechanics was further developed in a
three author paper by Heisenberg, Born and Jordan published in 1926. In May 1926
Heisenberg was appointed Lecturer in Theoretical Physics in Copenhagen where he
worked with Niels Bohr. In 1927 Heisenberg was appointed to a chair at the University
of Leipzig and he delivered his inaugural lecture on 1 February 1928. He was to
hold this post until, in 1941, he was made director of the Kaiser Wilhelm Institute
for Physics in Berlin.
In 1932 he was awarded the Nobel Prize in physics for:-
The creation of quantum mechanics, the application of which has
led, among other things, to the discovery of the allotropic forms of hydrogen.
In the presentation speech H Pleijel said:-
Heisenberg
... viewed his problem, from the very beginning, from so broad an angle that it
took care of systems of electrons, atoms, and molecules. According to Heisenberg
one must start from such physical quantities as permit of direct observation,
and the task consists of finding the laws which link these quantities together.
The quantities first of all to be considered are the frequencies and intensities
of the lines in the spectra of atoms and molecules. Heisenberg now considered
the combination of all the oscillations of such a spectrum as one system, for
the mathematical handling of which, he set out certain symbolical rules of calculation.
It had formerly been determined already that certain kinds of motions within the
atom must be viewed as independent from one another to a certain degree, in the
same way that a specific difference is made in classical mechanics between parallel
motion and rotational motion. It should be mentioned in this connection that in
order to explain the properties of a spectrum it had been necessary to assume
self-rotation of the positive nuclei and the electrons. These different kinds
of motion for atoms and molecules produce different systems in Heisenberg's quantum
mechanics. As the fundamental factor of Heisenberg's theory can be put forward
the rule set out by him with reference to the relationship between the position
coordinate and the velocity of an electron, by which rule Planck's constant
is introduced into the quantum-mechanics calculations as a determining factor.
...
Heisenberg's quantum mechanics has been applied by himself
and others to the study of the properties of the spectra of atoms and molecules,
and has yielded results which agree with experimental research. It can be said
that Heisenberg's quantum mechanics has made possible a systemization of spectra
of atoms. It should also be mentioned that Heisenberg, when he applied his theory
to molecules consisting of two similar atoms, found among other things that the
hydrogen molecule must exist in two different forms which should appear in some
given ratio to each other. This prediction of Heisenberg's was later also experimentally
confirmed. Heisenberg is perhaps best known for the Uncertainty Principle,
discovered in 1927, which states that determining the position and momentum of
a particle necessarily contains errors the product of which cannot be less than
the quantum constant h. These errors are negligible in general but become critical
when studying the very small such as the atom. It was in 1927 that Heisenberg
attended the Solvay Conference in Brussels. He wrote in 1969:-
To
those of us who participated in the development of atomic theory, the five years
following the Solvay Conference in Brussels in 1927 looked so wonderful
that we often spoke of them as the golden age of atomic physics. The great obstacles
that had occupied all our efforts in the preceding years had been cleared out
of the way, the gate to an entirely new field, the quantum mechanics of the atomic
shells stood wide open, and fresh fruits seemed ready for the picking.
Heisenberg
published
The Physical Principles of Quantum Theory in 1928. In 1929 he
went on a lecture tour to the United States, Japan, and India. In the 1930s Heisenberg
and Pauli used a quantised realisation of space in their lattice calculations.
Heisenberg hoped this mathematical property would lead to a fundamental property
of nature with a 'fundamental length' as one of the constants of nature.
In
1932 Heisenberg wrote a three part paper which describes the modern picture of
the nucleus of an atom. He treated the structure of the various nuclear components
discussing their binding energies and their stability. These papers opened the
way for others to apply quantum theory to the atomic nucleus.
In 1935 the Nazis
brought in a law whereby professors over 65 had to retire. Sommerfeld was 66 and
he had already indicated that he wanted Heisenberg to succeed him. It was an appointment
which Heisenberg badly wanted and in 1935 Sommerfeld again indicated that he wanted
Heisenberg to fill his chair. However this was the period when the Nazis wanted
"German mathematics" to replace "Jewish mathematics" and "German physics" to replace
"Jewish physics". Relativity and quantum theory were classed as "Jewish" and as
a consequence Heisenberg's appointment to Munich was blocked. Although he was
in no way Jewish, Heisenberg was subjected to frequent attacks in the press describing
him to be of "Jewish style".
In 1937 Heisenberg married Elisabeth Schumacher.
He met her through his music which was important to him throughout his life. An
excellent pianist, Heisenberg met Elisabeth Schumacher at a concert in which he
was performing at the house of a published friend. Elizabeth was only 22 when
they met, Heisenberg was 35. They were married on 29 April 1937, less than three
months after they first met. Heisenberg had been asked to take up the appointment
at Munich in March but had asked for the date to be delayed until August because
of his wedding. It was agreed that he should take up the appointment on 1 August.
He and his wife arrived in Munich in July but his appointment was blocked by the
Nazis.
During the Second World War Heisenberg headed the unsuccessful German
nuclear weapons project. He worked with Otto Hahn, one of the discoverers of nuclear
fission, on the development of a nuclear reactor but failed to develop an effective
program for nuclear weapons. Whether this was because of lack of resources or
a lack of a desire to put nuclear weapons in the hands of the Nazis, it is unclear.
After the war he was interned in Britain with other leading German scientists.
However he returned to Germany in 1946 when he was appointed director of the Max
Planck Institute for Physics and Astrophysics at Göttingen. In the winter of 1955-1956
he gave the Gifford Lectures "On physics and philosophy" at the University of
St Andrews. When the Max Planck Institute moved to Munich in 1958 Heisenberg continued
as its director. He held this post until he resigned in 1970.
He was also interested
in the philosophy of physics and wrote Physics and Philosophy (1962) and
Physics and Beyond (1971).
Heisenberg received many honours for his
remarkable contributions in addition to the Nobel Prize for Physics. He was elected
a Fellow of the Royal Society of London, and was a member of the academies of
Göttingen, Bavaria, Saxony, Prussia, Sweden, Rumania, Norway, Spain, The Netherlands,
Rome, the Akademie der Naturforscher Leopoldina, the Accademia dei Lincei, and
the American Academy of Sciences. Among the prizes he received was the Copernicus
prize.
Article by: J J O'Connor and
E F Robertson
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