J. Robert Oppenheimer: Quantum Theory and Uncertainty

Reading the essays by J. Robert Oppenheimer in Atom and Void: Essays on Science and Community. In the essay Atom and Void in the Third Millennium I was struck by what these scientists he describes were going through as they struggled to interpret what they observed going on in quantum theory. As he says in one passage: “It did not seem reasonable, nor in fact has it ever proved possible, at a time when the very foundations of classical mechanics were being altered, to reinterpret this revolution in classical mechanics terms” (AV, p. 43).

The breakdown of classical mechanics, the quandaries of losing a vocabulary, the framework in ruins all while these scientists were daily discovering things about the universe that just didn’t make sense: wave/particle duality, states/affairs, etc.. Discovering that when one observed quantum interactions directly they did not behave as expected, but when one used probability and abstractions one observed what one expected. This counter-intuitive topsy-turvy world of quantum mechanics just didn’t seem logical at all. To know anything at all they had to link empirical data (waves) with knowledge (theory, math, rules, etc.) and then interpret this before the actual observation to align the theory and observation for the results. Everything was just the opposite of classical Newtonian mechanics they’d been taught in school. The world of cause and effect was blowing in the wind… Instead of stability, one was left with complexity and unsubstantial entities, abstractions, statistics, probabilities, guesses…

Assertions of probability and statistics rather than certitude. Ultimately these scientists came to the conclusion that reality itself, the reality we took for granted had vanished, the solid world of substance “of form’d Matter, solid, massy, hard, impenetrable, moveable Particles…” (Newton) that from the time of Lucretius inheritor of Leucippus-Democritus’s metaphysics was just plain wrong. Reality was not solid but was much stranger and less solid or massy, in fact reality was full of gaps and cracks, more of a Void. As Oppenheimer would remark, “it is not causal; there is no complete causal determination of the future on the basis of available knowledge of the present” (AV, pp. 47-48). In fact the law of quantum mechanics “restricts” but does not “in general define the outcome of an experiment” (AV, p. 48). The Newtonian universe of cause and effect had suddenly disappeared and in its place was statistical and probabilistic outcomes, base on uncertainty (Heisenberg). No one could no for sure what was happening at this level of reality. Nothing made sense under the old classical laws. As Oppenheimer declared:

This means that every observation on a system reveals some new knowledge as to what its state is that did not exist before, and could not by analysis and mathematical computation have been obtained. It means that every intervention to make a measurement, to study what is going on in the atomic world, creates, despite all the universal order of the world, a new, a unique, not a fully predictable, situation. (AV, p. 48)

Suddenly the world was open and incomplete, no longer a totality, a whole, but rather a realm where all our previous knowledge, our math, our ability to test, describe, control would no longer be of use. We were staring into a universe of contingent events that all our vast learning and mind tools had not prepared us for and were of little use. The frame of the world had entered an abyss. We had no way of describing this new realm, no vocabulary, no mathematical instruments. All we had were basic statistics and probabilities, mere estimations and hopeful fictions.

All the basic mathematical notation, concepts, theorems, etc. were of no use: “We have almost lost the concept of equations of motion, having discovered the very terms in which they are formulated – position, velocity, acceleration, and force – are not simultaneously applicable…” (AV, p. 48). It’s as if they’d been handed a blank page, emptied of all knowledge, unable to conceive even the rudimentary math needed to describe the events transpiring in the quantum world. Luckily they had Schrödinger theory of quantum mechanics which extends the de Broglie concept of matter waves by providing a formal method of treating the dynamics of physical particles in terms of associated waves. So rather than needing to know the motion as in the older Newtonian mechanics, they could treat it dynamically as particle/wave association.

The other issue is one people misunderstand most of the time, one that Oppenheimer clarifies which is the notion that the observer must be a part of the system observed, part of the equation. What he says is this is not about the “mind of man,” (AV, p. 49) being included, but rather about the apparatus: the “division between the object of study and the means (apparatus) used to study it” (AV, p. 49). The point of this is that the quantum world has not lost its objective quality; but it “attains this by those interlockings with experiments we use to define one or another its properties and to measure it” (AV. p. 49). So that objectivity is attained by the “interlocking” of experimental device which delimits and defines the properties and measurement of the data. Think of the new neurosciences and the imaging systems they use to define and delimit properties and measurement of the various patterns into charts, graphs, images to observe the brain in real time, etc.

One can feel the excitement in his voice as he describes what these quantum scientists had uncovered. The universe was a lot more complex than anyone had ever thought possible, that new tools, vocabularies, mathematical theorems, apparatuses, etc. would need to be developed to explore this heretofore unknown realm of being. When I think about it I’m astounded how it’s taken a few generations from the time of Oppenheimer to our own current generation to develop large enough Hadron Colliders to begin the latest phase in exploration of this sub-atomic world of quantum mechanics. Of course only in 2012 did they discover a new particle, the Higgs Boson. Like many other things in science this may not be the last. The more we probe into the depths the more we realize just how far down it goes. No one knows. But one thing for sure it was men like Oppenheimer who with their excitement and wonder at the universe, their determination to forge new tools, vocabularies, mathematical theorems and enter the unknown that still drives the sciences to this day. So many disparage the sciences because of the misuse. This is stupid. The sciences are a two-edged sword that can be used for good or ill. It’s up to us to decide which.

---

 

1. J. Robert Oppenheimer. Atom and Void: Essays on Science and Community.  Princeton University Press; UNABRIDGED VERSION edition (October 21, 1989)