Humanities Core Course Spring 2013 Instructor: Bencivenga
LECTURE NOTES
Lecture 6.
Let us continue with some of the ways in which
quantum mechanics revolutionizes our ordinary understanding of the world. It is
common to think that the world is composed of some basic elements. For the
ancient Greek philosophers Leucippus and Democritus (as well as, you know by
now, for Epicurus), these elements were the atoms—literally, the “indivisibles.”
For contemporary physics, they are the elementary particles; and Heisenberg
claims that we are actually wrong in calling atoms by that name because our atoms
can be, and have been, divided. Whatever these basic elements are, anyway, they
are supposed to be different from one another, and each to contribute in its
own different way to the constitution of larger objects. But, again,
contemporary physics challenges this view. In it, there are no basic things out of which everything else is
made. There is matter, of course, whose ultimate material constituents are
elementary particles; there is energy, which is hardly a thing at all; and there is constant transformation of the one into
the other, and vice versa. Favoring the side of energy in this exchange,
Heisenberg says:
Energy is a substance, since
its total amount does not change, and the elementary particles can actually be
made from this substance as is seen in many experiments on the creation of
elementary particles. Energy can be changed into motion, into heat, into light
and into tension. Energy may be called the fundamental cause for all change in
the world. (p. 37).
But, of course, the reverse process can also
occur: material objects (nuclei of atoms, say) can split or even disintegrate,
releasing energy; so what we seem to be left with is something close to the
picture of old Anaximander, for whom the fundamental substance of the universe
was undifferentiated being, from which various specific things originate at one
time or another, only to eventually return back into the undifferentiated state
(see pp. 34-35). Or, we could also say, our current picture is close to that of
Heraclitus, who thought of change as the fundamental principle and of fire as
the basic element. “If we replace the word ‘fire’ by the word ‘energy’ we can
almost repeat his statements word for word from our modern point of view” (p.
37)
Even
more radically, Heisenberg thinks that contemporary physics may come to agree
with Pythagoras and Plato that reality is not constituted by matter at all—differentiated
or undifferentiated—but rather by mathematical form. A modern atom is mostly
empty; the electrons orbiting in it have virtually no mass; the solidity of a
material object or the fluidity of a liquid are
ultimately to be explained in terms of their mathematical structure. Pythagoras
thought that all things were numbers and Plato thought that the world was made
of geometrical figures; but that was because their mathematics was fairly
simple. Our mathematics is much more intricate, and yet Heisenberg has no doubt
that in quantum mechanics “the elementary particles will finally also be
mathematical forms, but of a much more complicated nature” (pp. 45-46). Which
is, indeed, quite radical, because we think that matter is accessible to our
bodies but mathematical forms are only accessible to our minds; if matter
reduces to mathematical forms, then nature is really only accessible to our
minds.
Quantum
mechanics does not just challenge traditional ideas; it challenges the language
itself in which those ideas were phrased—it challenges our ordinary language.
This language, Heisenberg says, “was formed during the
prehistoric age among the human race as a means for communication and as a
basis for thinking” (p. 142). It can hardly be expected that an instrument
formed through this process will be adequate to the demands of rigorous
science; so for centuries people have attempted to refine it, to make it more
logical and precise (at the risk of also making it too narrow; see the quote
from Faust on pp. 144-145), to add
new technical terms to it, and to introduce mathematical symbolism into it. But
quantum mechanics seems to undo the very fabric of this language, however
refined it might have been. In language we state facts; we say, for example,
“The desk is brown,” which means, among other things, that the desk is not blue
or white. And in quantum mechanics it does not seem possible to state facts
that way. We can say that an electron was
observed to have a certain position; but can we actually say that it was an
independent, objective fact that the electron had that position? If the
electron had not been observed, quantum mechanics says, it would not have had
any particular position. Also, in our statements there is typically a
subject—what we are talking about—and a predicate—what we say of the subject.
In “The desk is brown,” “the desk” is the subject and “brown” (or “is brown”)
is the predicate. But what are we talking about in quantum mechanics? What are
the subjects of our statements? We know that electrons are either particles or
waves depending on how we see them and deal with them, so what indeed are we
talking about when we say “This electron has position p”? It seems that here it is not just a question of refining the
instrument, but of needing a new instrument altogether; and in fact Heisenberg says
that “no language existed in which one could speak consistently about the new
situation” created by quantum mechanics (p. 148) and describes the physicists’
inclination “to use an ambiguous rather than an unambiguous language, to use
the classical concepts in a somewhat vague manner …, to apply alternatively
different classical concepts which would lead to contradictions if used
simultaneously” (p. 153)—even getting to the point of drawing a connection
between this use of language and poetry (p. 153). He then gives a brief account
(in a passage I did not assign for reading) of the attempts made at building a
new logic especially appropriate for quantum mechanics—or quantum logic.
Finally,
quantum mechanics has undermined the scientist’s disinterested attitude as was traditionally conceived. By
contributing to the invention of nuclear weapons, it has created problems
scientists typically did not have before. “The political influence of science,”
Heisenberg says,
has become very much stronger than it was
before World War II, and this fact has burdened the scientist, especially the
atomic physicist, with a double responsibility. He can either take an active
part in the administration of the country in connection with the importance of
science for the community…. Or he may voluntarily withdraw from any
participation in political decisions; then he will still be responsible for
wrong decisions which he could possibly have prevented had he not preferred the
quiet life of the scientists. (p. 166)
Heisenberg himself experienced these
responsibilities directly; during World War II he stayed in
It is time to summarize the sense of these
lectures. Our natural environment is constantly either a resource or a threat
for us—in all cases an interlocutor, an Other in the
term used in this course. Through our entire civilization, the most
authoritative and efficacious means of encountering this interlocutor has been
through the discourse and practice of science. Especially in the last few
centuries, science has built a tremendous, even overwhelming reputation, which
permeates all aspects of our common conversation and decision-making. But I
have been arguing here that this reputation is largely based on an
old-fashioned conception of science, which goes back at least to the 19th
century. According to this conception, the world has a definite structure,
being constituted of basic components that obey necessary laws. Science
gradually but surely finds the truth about this structure, these components and
laws, and on the basis of the knowledge thus acquired promulgates recipes for
improving our life conditions. Such knowledge and recipes are perfectly
objective: they are what they are, independently of our beliefs, our emotions,
our observations, and even our knowledge itself. The earth rotates around the
sun, period—that is a fact, and would be a fact even if humans forever thought
otherwise. Galileo was one of the major promoters and popularizers of this
view; and the view seemed confirmed by the progress of
science until about a century ago. Then a revolution started, which is still
going on, and quite often scientists themselves are not quite sure what to say.
We have focused here on one major aspect of this revolution, quantum mechanics.
Heisenberg says on pp. 172-173 that similar points could be made about the
theory of relativity: Newton thought that space and time were absolute, and
that any object had an absolute location in them, but in the theory of
relativity every one of us is the origin of his/her own space, and all these
different spaces even have different geometries, depending on the masses
present there. Similar points could also be made about more recent theories,
such as chaos theory, which suggests that the world may be essentially
unpredictable, that there may be—in contrast with Laplace’s statement—no way of
subjecting all events to necessary laws. The most important moral that, I
think, we can draw from this brief exploration in the field of modern science
is that, in Heisenberg’s words, modern physics has turned “against the
overestimation of precise scientific concepts, against a too-optimistic view on
progress in general” (p. 175), and “has perhaps opened the door to a wider
outlook on the relation between human mind and reality” (p. 176). As Bohr put
it, we are not just spectators of a show put up for us by nature, trying to
figure out exactly what show it is; to some extent, we make nature what it is,
we produce the show and act in it—science itself, today, testifies to that. So
it may be useful, at least for comparison purposes, to consider other ways in
which this construction could be, or even has been, carried out.