Quantum mechanics - Pianeta Scuola Gallery

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THE
AUTHOR
characters
FRAYN’S
COPENHAGEN
THE PLAY
plot
comments
HISTORICAL
BACKGROUND
SCIENTIFIC
BACKGROUND
from the beginnings of
modern atomic theory
to Hiroshima
MICHAEL FRAYN: biography
• English dramatist, columnist, reporter
and translator, Michael Frayn was
born on September 8, 1933, in the
suburbs of London.
• Growing up in Ewell, South London,
he soon revealed a talent for music
and poetry and, by the time he was a
teenager, he knew that he wanted to
be a writer of some sort.
• Frayn attended the University of
Cambridge, where he graduated in
1957 with a degree in moral science.
MICHAEL FRAYN: biography
• He started working as a reporter and a columnist for
the Manchester Guardian and The Observer.
• He has written several plays for the theatre and
Copenhagen is one of them, Frayn has also translated
Chekhov, and written some screenplays, including
Clockwise, Make and Break and Benefactors which
have been filmed for UK television.
• He won several prizes for his works.
• He is married to the biographer and critic Claire
Tomalin and they live in London.
THE PLAY: PLOT, CHARACTERS AND COMMENTS
Copenhagen, a thought-provoking
drama by Michael Frayn, re-enacts
the 1941 visit of Werner
Heisenberg, who was then in charge
of the Nazi nuclear power
programme, to Niels Bohr, his
mentor and collaborator in creating
quantum mechanics,
complementarity, and the
uncertainty principle, in German –
occupied Denmark.
The third character in the play is
Bohr’s wife Margrethe.
• Margrethe didn’t like Heisenberg and was particularly suspicious
of that meeting in 1941, expressing the view of those who
suspected Heisenberg of wrong doing and were hostile in their
view of his actions and behaviour.
• Frayn has Bohr, his wife Margrethe and Heisenberg re-enact and
examine the meeting, discussing, in the process, how science,
politics and morality may intertwine.
• "Re-enact" is not really the right word, for no one now alive
appears to know what actually took place during the visit, and
Frayn does not try to solve the mystery.
• More historical investigation and speculation than high drama,
the events in Copenhagen are driven by a single question: what
drove German physicist Werner Heisenberg to visit his former
mentor, the half-Jewish Niels Bohr, in occupied Denmark in
1941?
• There was a meeting. Why?
• Was Heisenberg after help with the Nazi nuclear research
programme, or seeking information about US and Allied
progress on atomic research … or something else?
• Did Heisenberg want to warn Bohr, and through him the Allies,
that the Germans were working on an atomic bomb and if so to
what end?
• Was it to convey the impression that Germany was about to
succeed and that the Allies should therefore make peace with
Hitler… or was it say that he had given up on an impossible
task and that therefore the other side shouldn’t try either?
• Did Heisenberg want to find out whether the Allies were
actually working on an A - bomb?
• Or did he hope to convince Bohr to issue a joint declaration
with him denouncing efforts to build a bomb and pledging not
to work on it?
• “The idea for Copenhagen came to me out of my interest
in philosophy.” Frayn declared in a BBC interview “It was
when I read a remarkable book called Heisenberg's War by
Thomas Powers, that I came across the story of Werner
Heisenberg's visit to Niels Bohr in 1941. As soon as I read
it I began to think that this story reflected some of the
problems that I had been thinking about in philosophy for a
long time.
• How do we know why people do what they do, and even
how one knows what one does oneself?
It's a
fundamental question... this is the heart of the play. (…)
We can never know everything about human thinking.
• I wanted to suggest with Copenhagen that there is some
kind of parallel between the indeterminacy of human
thinking, and the indeterminacy that Heisenberg introduced
into Physics with his famous Uncertainty Principle.
Though I'm not trying to say they're exactly parallel.
• The Uncertainty Principle says that there is no way,
however much we improve our instruments, that we can
ever know everything about the behaviour of a physical
object. And I think it's also true about human thinking.”
MICHAEL FRAYN
Sources:
· Copenhagen in New York by Harry Lustig and Brian B. Schwartz.
· Interview with Michael Frayn, BBC 28.8.2003.
AN HISTORICAL PERSPECTIVE ON THE
BACKGROUND AND THE CHARACTERS
Though the details of their famous meeting may be in
dispute, Niels Bohr and Werner Heisenberg are certainly
well-documented historical persons, both very much a part
of their times.
They were intimately involved in the evolution of modern
atomic physics.
They survived not one but two devastating world wars,
and they lived well into the 20th Century under the threat
of the Cold War, a war chiefly fought with the terror of
nuclear annihilation, whose basic scientific concepts they
had helped discover.
So, what was Heisenberg trying to tell Bohr during this
meeting, and what did he want from Bohr?
The broader historical setting and a fuller appreciation of
Heisenberg’s outlook and relationship to the war and to
fission research strongly suggest that he wanted…
• First: to convince Bohr that the seemingly inevitable
German victory would not be so bad for Europe after all.
The alternative, as Heisenberg later noted to his horrified
Dutch colleagues, was a Europe ruled by the Soviet Union.
Having witnessed a traumatic Soviet revolution in Bavaria
as a teenager, Heisenberg always considered Soviet
domination an even worse evil than Nazi domination.
• Second: he apparently wanted Bohr to use his influence to
prevent Allied scientists, who were surely far behind the
Germans, from working towards building a bomb that
could be used against Germany.
Bohr immediately sensed Heisenberg’s intentions and
broke off the conversation. Heisenberg returned home to
Germany intent on continuing fission research. Heisenberg
had already resigned himself to the march of events, and
events after the visit to Bohr now appeared to be marching
toward a possible nuclear war, regardless of what he may
or may not have wanted.
However, just three months later, the German Army
decided to abandon its fission project on the
recommendation of its closest advisors, choosing to
concentrate instead on rockets and jet aircraft.
It was the beginning of the end of any German hopes for
sweeping success in fission research.
• Why did the Germans not make an atomic bomb?
• Why, as became known as a result of Samuel Goudsmit’s
Alsos mission at the end of the War, were they, under
Heisenberg, not even trying, but were working instead to
build a nuclear reactor for the production of energy?
• Was it because of incompetence?
• Was Heisenberg dragging his feet or denying the feasibility
because he didn’t want Hitler to have the bomb?
• Who had more on his conscience? Heisenberg? Whose
work in nuclear physics during the War did not result in the
death of a single human being…or Bohr? Who at Los
Alamos contributed to building the atomic bomb, which
did kill thousands of people.
Bibliography:
A historical Perspective on Copenhagen by Dr. David C. Cassidy.
SCIENTIFIC BACKGROUND
• Frayn’s play is a drama in which Physics (quantum
mechanics, atomic physics , etc) is in the background
throughout. One merit of Frayn’s play is it makes Physics
accessible to the audience.
• Bohr’s wife is in the play mostly for this reason, because
she had no scientific training and yet her husband
discussed all his work with her. She is like our
representative there, someone who is not a scientist and to
whom everything must be made plain, that means easier
for us to be understand.
• All his life, Niels Bohr struggled as he tried to express his
thoughts and put them on paper, either in Danish or
English or German. It did not help that he mumbled and
often could not be heard, leave alone understood, by his
listeners.
• Michael Frayn’s play "Copenhagen" admirably conveys
the torment that Bohr and his friends put themselves
through as they groped their way toward a formulation of
quantum mechanics that eventually changed how we do,
teach, and learn physics.
• Bohr won the Nobel Prize in 1922, at age 37, "for his
investigations of the structure of atoms and the radiations
emanating from them".
• In the following years, through the twenties and early
thirties, he devoted most of his time and energy to a fuller
understanding of the meaning of quantum mechanics.
• People began to speak of the "Copenhagen school", the
"Copenhagen interpretation" of quantum mechanics, the
"Spirit of Copenhagen", and more recently and sometimes
unkindly of the "Copenhagen orthodoxy".*
*in the student’s book you will find an extract of a lecture on this point given by
Professor Eugen Merzbacher - University of North Carolina .
FROM THE BEGINNING OF MODERN ATOMIC THEORY TO
HIROSHIMA: AN OUTLINE SKETCH OF THE SCIENTIFIC AND
HISTORICAL BACKGROUND TO THE PLAY.
• Electrons: 1895 Thomson discovers the electron, the extremely light,
negatively charged particles orbiting inside the atom which give it its
chemical properties.
• Quantum Theory : 1900 Planck discovers that heat energy is not
continuously variable, as chemical physics assumes. There is smallest
common coin in the currency, the quantum and all transactions are in
multiples of it.
• Photons: 1905 Einstein realises that light, too, has to be understood
not only as waves but as quantum particles, later known as photons
• The Nucleus:1910 Rutherford shows that the electrons orbit around a
tiny nucleus, in which almost the entire mass of the atom is
concentrated.
• The Quantum Atom: 1915 Bohr realises that quantum theory applies
to matter itself. The orbits of the electrons about the nucleus are
limited to a number of separate whole number possibilities, so that the
atom can exist only in a number of distinct and definite states. (The
incomplete so-called “old quantum theory”)
• Matter as Waves: 1924 De Broglie in Paris suggests that, just as
radiation can be treated as particles, so the particles of matter can be
treated as a wave formation.
• The Wave Equation: 1925 Schrödinger finds the mathematical
equation for the wave interpretation, and proves that wave and matrix
mechanics are mathematically equivalent.
• Quantum mechanics: 1925 Heisenberg abandons electron orbits as
unobservable. Max Bohn finds instead a mathematical formulation in
terms of matrices for what can be observed – the effects they produce
upon the absorption and emission of light.
• Uncertainty: 1927 Heisenberg demonstrates that all statements about
the movement of a particle are governed by the uncertainty relationship:
the more accurately you know its position, the less accurately you know
its velocity, and vice versa.
• The Copenhagen Interpretation: 1928 Bohr relates Heisenberg’s
particle theory and Schrödinger’s wave theory by the complementary
principle, according to which the behaviour of an electron can be
understood completely only by description in both wave and particle
form. Uncertainty plus complementary become established as the pillars
of the Copenhagen (or “orthodox”) interpretation of quantum
mechanics.
• Neutrons: 1932 Chadwick discovers the neutron – a particle
which can be used to explore the nucleus because it carries
no electrical charge, and can penetrate it undeflected.
• Into the Nucleus: 1932 Heisenberg opens the new era of
nuclear physics by using neutrons theory to apply quantum
mechanics to the structure of the nucleus.
• Transmutation: 1934 Fermi in Rome bombards uranium with
neutrons and produces a radio-active substance which he cannot
identify.
• The liquid drop: 1937 Bohr explains the properties of the
nucleus by analogy with a drop of liquid.
• Identification: 1939 Hahn and Strassmann in Berlin identify the
substance produced by Fermi’s bombardment as barium, which
has only about half atomic weight of uranium.
• Fission: 1939 Lise Meitner and Frisch in Sweden apply Bohr’s
liquid drop model to the uranium nucleus, and realise that it has
turned into barium under bombardment, by splitting into two,
with the release of huge quantities of energy.
• The Neutrons Multiply: 1939 Bohr and Wheeler at
Princeton (US) realise that fission also produces free
neutrons. These neutrons are moving too fast to fission
other nuclei in U-238, the isotope which makes up 99% of
natural uranium, and will fission only the nuclei of the U235 isotope, which constitutes less than 1% of it.
• The Chain Reaction: 1939 Joliot in Paris and Fermi in
New York demonstrate the release of two or more free
neutrons with each fission, which proves the possibility of
a chain reaction in pure U-235.
• The War: 1939 The Second
World War begins and Germany
at once commences research
into the military possibilities of
fission
• The Critical Mass: 1940
Frisch
and
Peierls
in
Birmingham (UK) calculate,
wrongly but encouragingly, the
minimum amount of U-235
needed to sustain an effective
chain reaction.
• The Manhattan Project: 1942
The Allied atomic bomb
programme begins.
• The Reactor: 1942 Fermi in
Chicago achieves the first selfsustaining chain reaction, in a
prototype reactor.
• The Bomb: 1945 The bomb is
successfully tested in July, and
in the following month used on
Hiroshima and Nagasaki
(Japan).
• Germany Defeated: 1945 The
Allied advance into Germany
halts the atomic programmes
there.
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