Humanities Core Course Spring 2011 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 Germany and was officially involved in the Nazi efforts to produce atomic bombs. Those efforts were unsuccessful, and at least one major book (Heisenberg’s War, by Thomas Powers) was written to make the case that Heisenberg stayed behind and participated in the project with the explicit purpose of stalling it. Whether this explanation is correct or not it is certainly not for us to decide here; but we can say with equal certainty that from that time (if not from before) no one has been able to claim with any level of plausibility that science and scientists are innocent, that there are no moral implications to what they do.

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 19^th 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.