There was also a brief self-indulgent self-parody by the director Christopher Nolan in Oppenheimer that the audience could easily miss, so it might be forgivable. In the scene, Oppenheimer took off his army uniform in exchange for his trademark wide-brim fedora hat, tie and tobacco pipe laid neatly before him. That was Bruce Wayne discovering his true self with the Batman suit hung before him in one of those previous Nolan blockbusters.

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So, what’s my new takeaway after watching it a second time? Well, it brings back a memory in Hong Kong. When an old neighbour, a retired professor – his father-in-law was the first Chinese from the mainland to earn a PhD in physics in the United States – learned that I studied philosophy in college, he said, “Boy, your dad must have lots of money [to waste].” He didn’t actually say the last two words, but that was what he meant.

Why this memory? Because I couldn’t think of two more opposite academic subjects, one being pretty useless while the other is so powerful it produced weapons that could wipe out humanity.

For a very long time, I avoided telling people what I studied in college. It was a bit like telling them you had herpes. Now, though, I don’t care. That’s the good thing about impending old age – you care less and less about anything. There was another bad memory.

You know how with the new-style online porn, the director or cameraman sometimes interviews the porn star before the actions. I once watched a clip where the lady was asked about her level of education. College, she replied. What did you major in? Well, you can guess her answer! That was a complete turn-off; I didn’t watch the rest of the clip.

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Nowadays, though, I feel less useless or IQ-challenged having studied philosophy. I am actually kind of glad I did, because philosophy now is more like a hobby such as carpentry, not a discipline, unless you are an academic, and there is nothing to be ashamed of if you love playing with wood.

After watching Oppenheimer, I took out an old copy of Werner Heisenberg’s Physics and Philosophy: The Revolution in Modern Science. Hey, if the great Heisenberg thinks the two disciplines can be paired together, philosophy can’t be that useless.

Right from the start, he asks where Nolan completely left off with his movie: what’s the importance of modern physics besides producing the atomic bomb? Well, it turns out, “reality” itself is at stake; and hence the title of the book, which was a collection of public lectures for a non-scientific audience after the second world war. I didn’t get the message when I first read it fresh out of high school. Now I kind of do, up to a point!

Heisenberg then talked for a long time about the history of quantum theory, which you probably knew a little bit about from popular science books, and the history of Western philosophy, which was pretty pedestrian and disappointing.

He only came into his own when he started discussing Immanuel Kant’s Critique of Pure Reason and how modern physics, of which Heisenberg was one of the founders, undermined Kant’s philosophy.

But of course, every educated German was Kantian in some way just like it was once said that every Frenchman was a Cartesian, at least back when pre-university European schooling was rigorous and of a very high standard.

Heisenberg then explained how the concepts of space, time and causality (cause and effect) in Euclid’s geometry, Newton’s physics and Kant’s philosophy – which pretty much underpinned the entire Western conception of reality, or rather the very possibility of considering something as “real” at all – has been questioned, if not undermined, by the [then-] new physics.

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Now I know this story has been told many times in many books, some very well, some very badly. But it’s nothing like hearing a founder of modern physics recounting the revolution, like reading Leon Trotsky’s History of the Russian Revolution.

It’s funny how like most people, I still feel, experience and make sense of the physical environment in three-dimensional Euclidean space and the one single absolute space and time of Newton, and through the simple or simplistic cause and effect of Kant.

Consider this sentence: Putin started (cause) the war (effect) in Ukraine (space) more than a year ago (time). Whatever you think about the war and Putin, you just can’t get away with using these categories, which were once thought to be fundamental but are not, according to quantum theory.

For sure, the technologies of which we are all consumers are post-Einsteinian and post-Heisenberg, from GPS to smartphones. But I just use them and have no idea how they actually work. Our cognition may be long past its use-by date.

Force, at least in the Western tradition, has been another fundamental causal factor, as something we can feel, exert and be pained by. But in his book on the history of the concepts of force, physicist Max Jammer points out you can’t “feel” the fundamental “forces” of nature. In fact, “force” has no real meaning in modern physics other than as a shorthand for ease of communication.

Besides thermonuclear weapons, we can thank Einstein, Heisenberg and a few of their fellow geniuses for all that – turning reality on its head.