Robert Frost was Wrong

Shortly after Niels Bohr produced his quantum model of the atom (1913), Robert Frost wrote (1916) his iconic poem, The Road Not Taken. Apparently a commentary on existential angst and the human condition, Frost’s poem can be read on an entirely different level. It raises questions that haunt the science of Quantum Mechanics (QM) to this day. 

Of course, that may not have been Frost’s intent; at that time the wide world was just beginning to learn about Relativity. But a poem is a poem is a poem. Once written, it transcends its author and even its milieu. We must meet the text head on, accept it on its own terms, regardless of the author’s subjective intent. 

A hundred plus years ago it was popular to think of the Universe as if it were a finely tuned Swiss timepiece, wound by God ‘in the beginning’ and left running mechanically ever since. Some 7^th Day: Gone fishin’!

But by 1900, a series of observations and experiments had already made this view untenable and eventually led to the discovery of Quantum Mechanics. QM showed that there is no pre-determined course of events, that what happens is more a function of probability than causality, and that Universe at its most fundamental level is best understood as a perpetual series of ‘choices’

In the realm of philosophy, this insight popped up as the Existentialist doctrine of Freedom. Jean Paul Sartre, the high priest of Existentialism, divided Universe into en-soi, which was perfectly deterministic, and pour-soi, which was perfectly free. He skirted the problem of dualism by defining en-soi as etre (being) and pour-soi as neant (nothingness). Le neant functioned as the negation of l’etre and in this way diversity was reconciled with solidarity.

Sartre understood that freedom, while absolute, could not be unbounded. For example, one is not ‘free’ to draw a square circle or fly to Mars just by flapping one’s arms. Facticity (the real world) imposes logical and physical limitations, but those limitations are external to the agent and do not in any way limit or qualify that agent’s perfect freedom. Limitations are part of en-soi, never pour-soi.

In The Road Not Taken, Robert Frost confronts a simple choice between two options (0, 1). He has a destination to reach and there are two roads that will take him there. Facticity excludes any other option: he cannot fly, he cannot tunnel, he cannot crawl for miles on his hands and knees through underbrush. If he is to accomplish his ‘project’ (arrive home by end of day), he has only two choices: there are only two roads he can take.

Frost’s preferred solution: travel both roads and still be one traveler. But with his imagination still bound by the limitations of classical physics, he rejects that notion as impossible. QM, however, suggests that such a strategy is possible. In fact, most current interpretations of QM assert that this is the only possibility. Given the existence of two equally attractive (i.e. equally probable) paths with identical start and stop points, Frost will travel both, whether he likes it, or is aware of it, or not. But how?

One possibility, supported by the various “double slit” experiments that gave QM its start, suggests that a quantum follows two or more paths simultaneously but does not ‘decide’ which path will be its ‘real’ path until it is reaches its destination and is observed (measured) by an external agent: “Daddy’s home!” or “I shall be telling this with a sigh…”

Mr. Frost can indeed “travel both and be one traveler”; there’s no other way to get where he’s going. But when he finally arrives at his destination, it will appear to all observers (including Frost himself who is now his own observer) that he has come by one path only. His arrival, once observed, collapses the Wave Function.

According to this model, Frost can experience both walks and then, at the very end, he can ‘decide’ which walk was more satisfying, select that walk, and make that his actual experience, his history, his biography. We imagine that we live in a world where the past determines the future. Frost shows how wrong this is. It is at least as true to say that the future selects its own the past. 

This interpretation has massive real world implications. Imagine, for example, how this might play out in a restaurant. “Waiter, bring me one order of everything on the menu and when I’ve finished, I’ll pay for whichever dish I liked best.”

Or what about a lifetime? You follow all courses open to you and then, at the end, you get to choose the one path that gets you the best result. How kool would that be!

But this option is not all it’s cracked up to be either. First, it isn’t really ‘Frost’ who makes the final decision. That decision is made by the whole experimental apparatus, the whole Universe for that matter, and is as much a function of mathematics (probability) as aesthetics (taste). 

Second, Frost will have no memory whatsoever of ‘the road not taken’. Similarly, I will have no memory of the dishes I decided not to pay for in your restaurant, or how they tasted. In a bizarre turn, you only get what you pay for after all. Cruel justice! 

Hugh Everett’s “Many Worlds Interpretation of Quantum Mechanics” modified this picture. According to Everett, every time Universe confronts a choice it bifurcates, splits. In one Universe, Choice A is made; in a second Universe, a perfect copy of the first save for this one decision, Choice B.

According to this view, Mr. Frost must “travel both”…but he is no longer “one traveler”. According to Everett’s theory, there are now two Frosts, entirely unaware of one another; sadly, according to Everett, they will never meet again. Everett’s theory allows Frost only one set of experiences, but he may (or may not) find consolation in the realization an alternate Frost is having the other set of experiences in an alternate universe. 

In any event, both Frosts arrive in the same town at the same time, but now it is really two different copies of the same town, each existing in its own Universe. What a waste! What is it about Nature that makes you think it might be that inefficient?

Once arrived, the town is the same in both universes, as is ‘the Frost’. So why can’t they pick back-up where they were before the split? Suppose we modify Everett’s model to allow Frost’s many trajectories to intersect, to become entangled, perhaps to recombine, to merge, radically constraining the proliferation of universes that so bedevils Everett’s scheme. This model allows the Universe to grow but at something approximating its currently observed rate, not exponentially as with Everett. 

This model begins to resemble Richard Feynman’s Sum Over Histories. According to Feynman, Mr. Frost travels both paths; but this time he remains one traveler. The two experiences merge only when he reaches his destination, but the final product is not a choice between, but a mash-up of, the two experiences. 

It might be more accurate to say that a part of Frost travels one path and another part travels the other path. Feynman’s model does not double the amount of experience Frost enjoys but it does combine experience from both pathways into a single outcome. According to our restaurant metaphor (above), we get to taste all the items on the menu…but only as samples, never as full meals.

Recently, a new interpretation has come along that builds on Feynman. In this thought experiment, known as the Cheshire Cat, quantum data is understood to show that certain properties (qualities) of the quantum follow one path while the particle itself (quiddity) follows the other. 

In Alice in Wonderland, the cat’s grin, a property, can appear separately from the cat itself. In the Cheshire Cat experiment, the particle’s spin can travel a different route from the rest of the quantum. In The Road Not Taken, perhaps Frost’s gait and affect travel one path while his body follows the other. Crazy, I know, but this is Quantum Mechanics! Convinced? Neither am I, but it’s one logical possibility.

Bottom line: The Road Not Taken is beautiful and ground breaking…but ultimately and unavoidably wrong! You can “travel both (roads) and be one traveler;” in fact, you must. But no one could have known it at the time. 

That said, there is a non-thetic intuition that suffuses this masterpiece that prepares us for what might be coming down the road. Perhaps it is a defining function of art to prepare us psychologically for impending upheaval. In any event,100 years later, no one is loosening their seat belt!

A hundred plus years ago it was popular to think of the Universe as if it were a finely tuned Swiss timepiece, wound by God ‘in the beginning’ and left running mechanically ever since. Some 7th Day: Gone fishin’!

Image: “Observation of a Quantum Cheshire Cat in a Matter-Wave Interferometer Experiment,” by Tobias Denkmayr et al., in Nature Communications, Vol. 5, Article No. 4492; July 29, 2014

David Cowles is the founder and editor-in-chief of Aletheia Today Magazine. He lives with his family in Massachusetts where he studies and writes about philosophy, science, theology, and scripture. He can be reached at dtc@gc3incorporated.com.

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