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Is quantum mechanics materialist?
Quantum: Einstein, Bohr and the great debate about the nature of
reality
By Manjit Kumar
Published by Icon Books, 2008, £20
Reviewed by
Pete Mason
WHAT DOES quantum mechanics, the study of atoms and
subatomic phenomena, tell us about the world? In the 1920s and 1930s,
the founders of quantum mechanics fell out among themselves over how to
interpret the strange discoveries of this new science.
Take quantum leaps, a concept which Albert Einstein
helped define in 1905. An electron can appear to be in one place in an
atom and then, "as if by magic, reappear in another without ever being
anywhere in between". It was like a tree disappearing in London and
suddenly reappearing in Paris or New York.
Accessible to the non-scientist, Manjit Kumar’s
Quantum draws a detailed study of Einstein’s objections to the orthodox
interpretation of quantum mechanics, termed the ‘Copenhagen
interpretation’. Kumar argues that, in 1927, the leading exponents of
quantum mechanics, primarily Niels Bohr and Werner Heisenberg, abandoned
realism, which holds that the world exists independently of us, a basic
premise of materialism.
In 1958, Heisenberg wrote that the Copenhagen
interpretation had "led physicists far away from the simplistic
materialist views that prevailed in the natural sciences of the 19th
century". Einstein, he said, wished to return to "the idea of an
objective, real world", where subatomic particles "exist objectively in
the same sense as stones or trees exist, independently of whether or not
we observe them". (Physics and Philosophy, pp82-83)
But the discovery of quantum leaps challenged
previous, simplistic views of the world. A more sophisticated model of
reality is emerging. Kumar tends to blur rather than clarify
Heisenberg’s distinction between the certain existence of stones or
trees and the strange world of the quantum where things are not so clear
cut.
The contradictions in the subatomic world forced
Bohr and Heisenberg to break through the old materialist preconceptions
of solid particles with definite positions and orbits. For this work,
Heisenberg won a Nobel prize. Kumar complains that Heisenberg’s method,
"vitiated all attempts to unearth regular patterns in nature or any
causal connection", and "marked the end of a golden age in physics". But
the method was a means to an end. Kumar’s objections reflect the
influence of an ossified trend of Marxism, which argues that modern
science is riven with ‘subjective idealism’.
Quantum mechanics has provided descriptions of many
previously unexplained phenomena while unearthing new paradoxes. In
Physics and Philosophy, Heisenberg is specific: it was the ‘simplistic’
materialist views of the 19th century which could not account for 20th
century observations. For Marxists, there is no immutable materialist
ontology, that is, what comprises existence (such as matter, energy or
motion). Old, simplistic materialist concepts have to be abandoned in
the light of new discoveries. Friedrich Engels attacked the "shallow,
vulgarised form" of materialism which persisted in the mid 19th century,
explaining that with each epoch-making discovery materialism has to
change its form.
Quantum mechanics was, and remains, epoch-making. It
discovered phenomena which led scientists to construct a new theory or
interpretation of the physical world which stepped outside of the
philosophical constructs of all previously existing human society. It
created the possibility of a new materialism. Technically, it led to
lasers, transistors and computers which have transformed society.
However, in the 1920s and 1930s, Einstein looked for
ways in which quantum mechanics might make predictions that were
inconsistent with reality as he defined it. Kumar strongly supports
Einstein’s views, but steps beyond them into idealism. Attacking Bohr,
he states: "For Bohr the theory came first, then the philosophical
position, the interpretation constructed to make sense of what the
theory says about reality. Einstein knew that it was dangerous to build
a philosophical world-view on the foundations of any scientific theory".
Kumar criticises Bohr for putting concepts arising
from physical observations before philosophical speculation, and he
attributes this criticism to Einstein. But there is a difference between
attempting to defend a set of principles scientifically, as Einstein
did, and relying primarily on a philosophical world-view while rejecting
scientific theory if it violates it, which Kumar tends towards. Einstein
clearly states: "The elements of physical reality cannot be determined
by a priori philosophical considerations, but must be found by an
appeal to the results of experiments and measurements". (Can
Quantum-Mechanical Description of Physical Reality Be Considered
Complete? Einstein, Podolsky and Rosen, Physical Review, 15 May 1935)
There is sometimes a blurring of the line between fact and comment in
Quantum.
Kumar identifies three ‘elements of reality’ which
Einstein attempted to defend. One is causality. Kumar compares the
random radioactive decay of atoms to an apple falling. Once the apple is
let go, Kumar writes, it falls to the ground, caused by gravity.
However, in the quantum world, Kumar asserts, there is no causality, and
the apple would hover for an unknown period of time in the air before
falling.
But this is misleading. In an apple orchard, the
apples fall in autumn and we know the cause. Similarly, quantum
mechanics has revealed the causes of atomic decay. Yet we do not know,
precisely, when each apple will fall, just as we do not know, precisely,
when each atom will decay. The wind blowing the apples down is chaotic
and cannot be predicted precisely, nor can the atrophy of the cells in
the stems of individual apples. It is not at all clear that there is a
difference between causality as we commonly experience it and causality
at the atomic or subatomic level as understood by quantum mechanics.
Furthermore, this atrophy cannot be studied without
interfering with the apple and causing a change in its time of falling.
Scientists cannot carry out experiments without interfering with nature
at the atomic level, and this appears to have a degree of general
validity. This illustrates the discovery that the separation of
experimenter and subject, another element of reality which Einstein
defended, appears to be an idealised concept.
The third element was locality, the belief that
things in separate localities cannot be in instantaneous touch with each
other in the way quantum mechanics appeared to suggest. Einstein derided
this "spooky action at a distance" of quantum mechanics, yet it has
since been proved experimentally. Isaac Newton’s gravity also had
appeared to be this kind of spooky action. Ironically, to truly explain
gravity, Einstein abandoned the concept of absolute time and space,
which his contemporaries had thought was an element of reality.
Consequently, Einstein’s relativity was considered a denial of
materialism and objective reality by philosophers and some prominent
scientists at the time.
Experiments in the 1980s demonstrated that if two
photons are simultaneously emitted from an atom they are ‘entangled’ or
in instantaneous touch with each other. Even though they travel away
from each other at the speed of light, they are somehow still part of
the same entity. Experiments performed on one photon appear to instantly
affect the other. Just like the quantum leap of electrons, which appear
to defy our concepts of space and time by disappearing from one place
and reappearing in another without passing in between, these entangled
objects appear to disregard space and time. They act as if they do not
acknowledge the existence of separate localities. In scientific terms,
they are non-local. Kumar downplays the great significance of this
discovery.
In general terms, Einstein was the loser in the
great debate about the nature of physical reality. What troubled
Einstein, Kumar concludes, is the "renunciation of the representation of
a reality thought of as independent of observation". It is at this point
that one realises that Kumar’s study largely passes over some vital
experimental results. The physicist Richard Feynman stated that the
results from Young’s ‘two-slit’ experiments (which demonstrate the
inseparability of the wave and particle characteristics of light and
other quantum particles) are "absolutely impossible to explain" using
the concept of reality Kumar wishes to preserve at the subatomic level.
The omission of a discussion of these experiments makes it very
difficult for the reader unfamiliar with them to judge Kumar’s
conclusions objectively.
One day, a new theory will reveal the deeper reality
behind subatomic particles, in the same way as the discovery of
electromagnetic radiation helped us understand the transient nature of
rainbows. But this reality will be non-local. As US physicist Nick
Herbert pointed out, insisting that subatomic particles have an
independent existence is like insisting that rainbows are solid objects
and have some definite place in space irrespective of the observer. We
know that rainbows appear to be in different places depending on the
position of the observer. Kumar will never find that pot of gold at the
end of the rainbow. Quantum is a fine book in many ways, but not an
objective account.
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