In January 1957 J Robert Oppenheimer was on holiday in the Caribbean when he received a telegram from the Nobel-prize-winning physicist Chen-Ning Yang informing him that experimentalists had discovered that parity is not conserved in the weak interaction.

“Walked through door,” Oppenheimer cabled back to Yang.

Reactions to unexpected events, whether in science or otherwise, are often loosely lumped together as instances of surprise. Philosophers, however, discern several different ways to experience the unforeseen. Oppenheimer’s reaction to what’s called “parity violation”, for instance, I’d say is an example of shock. Shock is when your trusted set of basic assumptions slams into an equally trustworthy finding.

The vast majority of physicists, it’s safe to say, experienced that emotion in January 1957. Until then, they had assumed that every process in physics remains the same if you reverse all three spatial co-ordinates, and had now learned that it wasn’t true. Yang once told me that, for physicists, the discovery of parity violation was like having the lights switched off and being left in such total confusion that you were unsure if, when the lights came back on, you’d be in the same room.

After this particular discovery, the room didn’t look too different to before. What interests me, though, is the shock – the momentary sense that foundational assumptions could be undermined. It’s a physicist’s emotional acknowledgment of the abyss.

Experiencing the unexpected

A different way to experience the unexpected is to be bewildered. Bewilderment also involves a conflict between a finding and your assumptions, but this time your gut goes with those assumptions. You strongly suspect that something’s wrong with an experiment or finding, but you aren’t entirely sure. Think of your reaction to the “discovery” of cold fusion in 1989 or faster-than-light neutrinos in 2011.

I’m aware that I’m using ordinary words such as “shock” and “bewilderment” to describe phenomena that, to philosophers like me, have particular technical characteristics. But then physicists do the same if you think of how you use terms like “friction”, “impulse” or “power”. These names might be colloquial but they’re not arbitrary, and are used because of their loose relation to their technical meaning. So pay less attention to the words I’m about to use and more to the experiences that they point to.

In an essay in the 2018 book Surprise: an Emotion?, Anthony Steinbock – a fellow philosopher at Stony Brook University – characterizes “surprise” as being attentively and expectantly attuned to something, which then catches you off-guard and throws you back on your own experience. You accept, let’s say, both the unexpected findings and the assumptions embedded in your physics practice. But in contrast to both shock and bewilderment, you presume they can nevertheless be integrated.

Surprise involves “a believing what I cannot believe”, Steinbock writes. Think of the reaction when two teams of experimental particle physicists announced, on 11 November 1974, that they’d measured a spike in the number of particles produced at energies of 3.1 GeV indicating the existence of a long-lived particle now known as the J/ψ. As the Italian physicist Giuliano Preparata wrote: “It was as if one found in some remote region of the Earth a human race whose life expectancy was not 70 but rather 70,000 years!” Yet nobody in the physics community doubted either the findings or quantum electrodynamics.

Tell me you weren’t awed last year by the first photos of a black hole, or by the 2016 data demonstrating the existence of gravitational waves

Surprise is different from “awe”, which is a deep respect for a fundamental phenomenon when it abruptly emerges strongly and directly. Tell me you weren’t awed last year by the first photos of a black hole, or by the 2016 data demonstrating the existence of gravitational waves. Neither event was a surprise or shock in the sense of challenging fundamental assumptions. You knew these things were surely there. What was unexpected was that they appeared so magnificently and so suddenly.

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This is the critical point

“Amazement”, meanwhile, is the experience of a phenomenon that puts in an unexpected appearance but then never goes away. Think of the idea that energy comes in discrete quantities. At the beginning of the 20th century, the “quantum” was regarded as a troublesome but isolated phenomenon that might eventually disappear, but which kept repeatedly turning up, like a peculiar uninvited guest who stalks you and eventually joins your inner circle of friends.

Then there’s “astonishment”, which is the experience of something that you did not believe was even possible – not in the perceptual cards, so to speak – and forces you to reconfigure your experience. In 1895, for example, when the German physicist Wilhelm Röntgen first saw his cathode-ray tube making his fluorescent screen glow, he thought he was hallucinating. Only after elaborate exploration could he believe it was real. But Röntgen remained so mystified about his observation that he called it an “X-ray”.

The critical point

Shock, bewilderment and the other reactions I’ve mentioned are a familiar part of ordinary life. So why am I bothering to point out that they’re a familiar part of physics as well? The reason is that these reactions shed light on the differences and similarities between ordinary activities and physics. For example, in physics, time is a scalar quantity – a measurable sequence of discrete moments. In ordinary life, however, we live time as a flow in which we must simultaneously anticipate and remember.

So when physicists experience surprise, it dramatizes the presence of ordinary time in their activities. You can only find something surprising in the present because you have assumptions (the past) and expec-tations (the future). At its most exciting, therefore, physics is an encounter with the potentially strange, and when the strange arrives the encounter cannot help but be emotional. 

But are these phenomena I’ve described familiar to you? If so, or if you have better names or other experiences, send them in and I’ll write about them in a future column.