1 Physics has never existed
Yang Dong was a physicist. A string theorist. And she killed herself.
Her note was only one line long:
Physics has never existed, and will never exist.
A sentence like that does not belong in a suicide note. It belongs as the opening line of a metaphysics textbook. But to Yang, it was not philosophy. It was despair.
For Wang Miao, a nano-material scientist, the note was incomprehensible. How could physics never have existed, when it is the skeleton of modern life? Lasers, satellites, GPS, semiconductors—all monuments to physical laws. What did Yang see that broke her faith so completely?
When asked, Yang’s partner, the physicist Ding Yi, did not answer with words. He answered with a demonstration.
1.1 The Pool Table
Science has always loved metaphors of colliding spheres. Newton used them to explain light,1 Maxwell sketched them to understand Saturn’s rings,2 and Einstein invoked them in discussions of Brownian motions.3 Ding Yi continued the tradition—since the 19th century, billiards have been routinely used in physics textbooks for illustration.
He placed the ball at one end of the table, struck it with the cue at a fixed angle and force, and watched it collide with the side cushions. The rebound was predictable. Then he placed the ball elsewhere, struck again with the same angle and force. The collisions traced out an identical pattern. He did it again. And again.
Five times. Five experiments.
Each yielded the same result.
“Aren’t you shocked by the results?” Ding asked rhetorically. Wang did not know how to respond.
“Come on, let’s celebrate. We’ve discovered a great principle of nature: The laws of physics are invariant across space and time.”
This was no trivial statement. It is one of the great articles of faith in science: that laws are not local customs, but universal decrees. Strike a ball here, or there, today or tomorrow—it doesn’t matter. The physical laws remain the same.
Try it yourself. Ding Yi’s pool table has been reconstructed here.
Drag the ball anywhere you like. Release it. A cue will strike with the same direction and force each time. Watch the numbers: position, velocity, acceleration. Try it again, and again.
Notice how the experiment becomes boring. That boredom is the signature of a law.
1.2 The Seduction of Invariance
Science seduces us with boredom. That is its secret charm. We want the universe to behave, not to surprise. Every replication, every repeated experiment that yields the same result, feels like a reassurance that we live in an orderly cosmos.
Philosophers gave this reassurance a name: the Principle of the Uniformity of Nature. David Hume, the great skeptic, articulated it in the 18th century: the assumption that the future will resemble the past; that nature tomorrow will behave like nature today; that “the course of nature continues always uniformly the same.”4
Across cultures and centuries, thinkers spontaneously embraced the principle without hesitation. Thales sought a single element to ground the flux of the world. Aristotle believed nature’s motions could be classified because they followed regular causes. Xunzi wrote 天行有常—“the heavens move with constancy.”5 The Stoics saw the cosmos ordered by logos. Aquinas and medieval scholastics argued that God’s creation was rational and therefore reliable. Galileo, Kepler, and Newton all assumed their laws applied everywhere.6 Bacon made nature a system governed by its own laws and the very source of knowledge. And knowledge is power.
This conviction—that the rhythm of nature is reliable, and thus knowable—is what keeps us from superstition. However framed—through omen or through reason—the majority have trusted that the world follows patterns so that we are not at the mercy of whimsical gods.
That trust is what makes science possible. Once we believed in order rather than caprice, knowledge could accumulate. Experiments became expected to repeat, results communicable, and science emerged as a shared project. This conviction, more than any single discovery, is what allowed the modern worldview to take root.7
Without the Principle of Uniformity of Nature, replication collapses, prediction is impossible, and “law” becomes an empty word. With it, the modern scientific worldview takes shape: not pleasing the gods, but trusting that the world itself is knowable, and that what we learned here and now will apply tomorrow and elsewhere.
Ding Yi concluded forcefully,
… a great principle of nature: The laws of physics are invariant across space and time. All the physical laws of human history, from Archimedes’ principle to string theory, and all the scientific discoveries and intellectual fruits of our species are the by-products of this great law.
But here is the scandal: Hume could never prove it. No one has. The uniformity of nature is not a discovery. It is a bet. A metaphysical faith disguised as an empirical law.8 Even in the twentieth century, Einstein marveled that “the most incomprehensible thing about the universe is that it is comprehensible.”9
1.3 The Lawful Table
Now, physicists don’t spend their lives rolling pool balls the same way over and over again. They juggle a zoo of variables—spin, friction, imperfections, air currents, hidden quirks of the felt—each one a potential troublemaker, each one an invitation for variance and disorder.
And yet, beneath the clutter, the pursuit is the same: change the knobs, keep the laws. Find that invariance that stands like granite.
Set the ball, pick an angle, choose a force, slide the friction. Watch the ball run like a wild child across the felt. Then, look to the right: the number that refuses to panic: total energy. The surface changes, the invariant doesn’t. Complexity multiplies, but the promise of invariance holds. That’s what a law feels like from the inside.
Physics hides its treasures in invariants. They are its balance sheets. No matter how wild the day’s trading—balls ricocheting, particles colliding—the books close clean. Energy in, energy out. Momentum tallied to the last decimal.
1.4 The Lawful Coin
A curious reader might object: not all outcomes are replicable the way billiard collisions are. What about random events—like flipping a coin? Where is the invariance there?
Let’s try it.
Flip the coin as many times as you like. At first, the results look noisy, even chaotic. Ten flips tell you nothing. But flip a hundred, a thousand, and something remarkable happens: the wildly fluctuating ratio between heads and tails begins to settle. Chaos turns into pattern. Noise reveals order.
Pop the champagne—you’ve just discovered the Law of Large Numbers. It states that the average outcome of a random experiment approaches its expected value as the number of trials increases. This is the invariance of chance: the more experiments you run, the closer you get to the hidden probability of the coin. It isn’t merely a statistical curiosity; it’s a bedrock principle—the universe’s quiet promise of consistency, assuring us that even in the realm of chance, a hidden invariance governs.
Jacob Bernoulli, who first proved this and published it posthumously in 1713,10 called it his golden theorem. Casinos thrive on it. Insurance companies rely on it. Weather forecasts whisper it. The law promises that randomness itself contains a rhythm, and that with enough patience, averages will converge.
But hidden in the proof is an often overlooked clause: each trial must be independently and identically distributed. Your previous toss must not interfere with the next toss; a toss here or there, today or tomorrow, it makes no difference, as if all these tosses are drawn from the same deck. This is Hume’s Principle in disguise: uniformity all over again. The law of large numbers depends on the same bet—that nature behaves consistently, yet probabilistically, across time and space.
It looks like victory: even in randomness, invariance survives. Only when such invariance holds can statistics, probability, and the sciences built on them exist at all.
1.5 Emmy Noether’s Gift
Physics is built on a particular type of invariance, called symmetry. We know the idea from everyday life: my left hand mirrors my right. If I flip one over, it overlays the other—a transformation that demonstrates the symmetry.
Physicists extended this notion beyond mirror-images: a symmetry means the property of remaining invariant under any transformation. If a system remains the same from one moment to the very immediate next, that is time symmetry. If it holds the same here as it does elsewhere—whether a nanometer or a million kilometers away, that is spatial symmetry. If it behaves the same no matter how we rotate it—even by the tiniest imperceptible angle, that is rotational symmetry. These are what physicists call continuous symmetries: sameness that holds not only in great leaps, but through every tiny shift so small that transformation is smooth.
Symmetry allows all branches of physics promises us some kind of conservation, promises that follow Noether’s Theorem.
In 1915, Emmy Noether, German mathematician and lecturer at University of Göttingen without pay—merely because she was a woman—discovered a secret mathematical architecture beneath the laws of physics. She proved that, loosely speaking, whenever a physical system behaves the same regardless of where it is, when it is, or how it is oriented, there must exist a law of conservation.11
Every continuous symmetry guarantees a conservation law. Time symmetry guarantees energy is conserved. Spatial symmetry guarantees momentum is conserved. Rotational symmetry guarantees angular momentum is conserved.
1.6 The Ghost Particle
Now, imagine you are a particle detective on a cosmic crime scene: when a radioactive nucleus undergoes beta decay, transforming a neutron into a proton and emitting an electron, something doesn’t add up. The emitted electrons don’t always carry the expected amount of energy and their trajectories don’t always align with the conservation of momentum. What do you conclude?
This was a profound crisis for physicists in the 1930s. By Noether’s theorem, it implies one of the following two possibilities. One possibility is that, somehow for beta decay reactions, the continuous spatial and time symmetries don’t hold. In other words, for beta decay alone, space and time are discrete, forming a kind of lattice, as if particles are jumping on an infinite chessboard from one grid to another. The other possibility is that something is missing. This was indeed physicist Wolfgang Pauli’s proposal: an unknown particle carries away the missing energy and momentum like a thief who had made off with some of the loot.
Yet the second possibility is equally mysterious. This unknown particle would have to be able to escape detection, meaning that it doesn’t interact with an electron or a nucleus that it encounters. Pauli concluded, this particle, like a ghost, can pass through the entire earth without interacting.
Pauli himself was troubled by his own untestable hypothesis, acknowledging that he had committed the worst mistake a physicist could commit: postulating a particle that cannot be subjected to experimental scrutiny.12 He wrote in a letter in 1930, “I agree that my remedy could seem incredible because one should have seen these particles much earlier if they really exist. But only the ones who dares can win and the difficult situation, due to the continuous structure of the beta spectrum, is lighted by a remark of my honoured predecessor, Mr Debye, who told me recently in Brussels: ‘Oh, it’s well better not to think about this at all, like new taxes.’ From now on, every solution to the issue must be discussed. Thus, dear radioactive people, look and judge.”13
For decades, the ghost particle remained a phantom. It was finally confirmed via experiments in 1956 by Clyde Cowan and Fredrick Reines, and gained the name neutrino. It turns out that neutrinos, ghostlike as they are, indeed have traces. There is a very small, but non-zero chance that neutrinos interact with a nucleus. So physicists pile an enormous amount of nuclei in front of a beam of neutrinos, and wait, listening to that faintest creak of the floor boards in vast haunted houses.
Noether’s Theorem, and with it, the beautiful architecture of physics, was saved. Nobel Laureate, physicist Leon Lederman, and theoretical physicist Christopher Hill wrote,
We should add that experimentalists still often look for missing energy and momentum in their detectors in particle collisions, but this is always interpreted nowadays as evidence for a new particle, never as evidence for the breakdown of the conservation laws of energy and momentum. Our faith, or should we say confidence (as science is not faith-based), in the symmetries of the structure of space and time, and Noether’s theorem would, at this point, be very hard to shake.14
Even though the universe sometimes presents us with puzzles that seem to defy our most cherished laws, the answer often lies not in the breakdown of those laws, but in a deeper, more complete understanding of the underlying reality. Symmetry is the premise; conservation the promise.
The universe, though mysterious, ultimately plays fair.
1.7 Through the Looking-Glass, and What Alice Found There
Alice who adventured in Wonderland once again steps across the threshold. This time, she climbs through a large looking-glass, a mirror. The world in the mirror should look the same, only reversed. The left hand becomes right, the teacup is still a teacup, the chessboard is still a chessboard. The mirror reassures: the rules are unchanged, only inverted.
This is the promise of parity in physics. Flip space like a mirror, and the equations should hold. North and south, left and right, clockwise and counterclockwise—no preferred side, no sacred orientation. Nature, impartial, does not distinguish between her reflection and herself.
For decades, physicists assumed this symmetry was absolute. It was not just an assumption, but an article of faith: nature’s mirror never lies. The very idea that the reflection could misbehave—that the rules inside the glass might be different—was unthinkable. Space, time, rotation, parity, charge—pillars of invariance. Break them and the temple of physics shakes.
But then came a puzzle that cracked the mirror.
In the early 1950s, physicists once again noticed something strange. Two subatomic particles, known as the tau and the theta, looked identical in every measurable way—same mass, same charge, same lifetime. They should have been the same particle. But they weren’t. The tau decayed into three pions; the theta decayed into two. Their only difference lay in parity, their mirror identity, as if Nature decides mirror images should differ.
The resolution came in 1956—the same year when neutrino was confirmed—with the bold, yet revolutionary suggestion by Tsung-Dao Lee and Chen-Ning Yang. The young Chinese American scientists proposed that parity, the symmetry between a physical system and its mirror image, might not be conserved.15
Theory is cheap. Experiment is king. Lee and Yang talked to experimental physicist Chien-Shiung Wu, or Madame Wu, as she is universally known. She, like Alice before her, looked into the mirror by freezing cobalt nuclei in near absolute zero, aligning them, and watching them spit electrons. If parity were sacred, the spray would be symmetric. It wasn’t. The electrons came out lopsided, as if the universe had a preferred hand.
Parity symmetry is violated. Nature is left-handed, after all.
Lee and Yang won the Nobel Prize in the same year. This discovery was a seismic event in physics, challenging a deeply held “article of faith” in the scientific community. Wolfgang Pauli wrote in a letter, “Now after the first shock is over, I begin to collect myself. Yes, it was very dramatic.”16 Feynman who lost $50 dollars to a fellow scientist in 1956 on a bet that parity symmetry would not be violated, even in his 1985 book, still expressed disbelief and hope that “a more beautiful and, hence, more accurate understanding” of things will emerge.
This discovery was disturbing philosophically. Physicist A. Zee later made it clear,
The crucial idea which came to Lee and Yang is that Nature may respect parity in many of her laws, but not in the laws governing the weak interaction between particles. Imagine that one of the fundamental principles of our legal system, that the accused is presumed innocent until proven otherwise, is decreed to hold only for certain crimes, while for other crimes the opposite is to be the case. Just as judicial philosophers would surely cringe at this notion, physicists find Nature’s selective violation of parity rather discomforting philosophically.17
1.8 Beyond the Mirror: CP, T, and CPT
Parity was gone, but physicists clung to hope. Maybe if you combined a mirror with antimatter—in technical jargon, charge conjugation plus parity, or CP—the universe would be restored. A mirrored world of antiparticles should behave like ours. That was the creed of the 1960s.
Until it wasn’t.
In 1964, James Cronin and Val Fitch found that neutral kaons—particles flickering between matter and antimatter—sometimes decayed in ways forbidden by CP symmetry. Not often. Just rarely enough to unsettle faith. CP, too, was broken. This won them the Nobel Prize in 1980.
If CP fails, then by the structure of physics, time reversal (T) must fail too. Imagine a movie of particles colliding—play it backward. For most forces, the reversed movie looks physically possible. But in the weak interaction, it doesn’t. Time itself, at the microscopic level, is not fully reversible.
And yet, there is one last covenant: CPT symmetry. Combine all three—charge, parity, and time—and nature holds steady. CPT means this: if you flip left and right, swap matter for antimatter, and reverse the arrow of time all at once, the world plays fair again. This is not just a guess; it is a theorem. As long as physics obeys the basic assumptions of relativity and quantum fields, CPT cannot fail. And in every experiment ever performed, CPT holds.
So yes, symmetry after symmetry has fallen. Parity. Charge. CP. Time. Each one, once thought sacred, turned out to be conditional. But CPT remains unbroken.
That survival is not trivial. It is what gives us hope that the laws of physics are still coherent. It is why matter and antimatter have the same mass, why conservation still feels real, why the edifice of physics hasn’t collapsed into Yang Dong’s despair.
Just as important: these violations are reproducible. Wu’s cobalt electrons always shoot left. Kaons always betray CP at the same tiny fraction. The movie of time reversal always fails in the same way. Scandalous, yes—but scandal written into law. The mirror lies, but it lies consistently.
This was the reassurance: nature might break her covenants, but she does so predictably. A broken law is still a law if its violations can be written down and repeated.
Even in the ruins of symmetry, some structure endures.
1.9 Breaking Symmetry
No matter where you set the ball on the lawful pool table, the energy conserves because there is spatial symmetry. But what if we broke the spatial symmetry?
Try again, but this time, on a demon’s pool table where you can choose how to break the spatial symmetry.
Enable the Size Field and drag the ball across the table, you’ll notice its size alters. Hit it with a cue, watch how the kinetic energy bounces up and down as the ball moves across the table from left to right and right to left—when it is supposed to stay constant. The ball doesn’t look the same anymore when moving. Spatial symmetry is broken. Energy doesn’t conserve.
Enable transmutation, and even worse things happen. The concept of energy doesn’t even apply anymore. The conservation law does not break. It evaporates.
Only in this case, you own the pool table and can control whether and how to break symmetry. But imagine what scientists of pool tables have to face!
1.10 The Unlawful Table
“I still don’t understand what you’re getting at,” Wang asked. How is the pool table relevant to Yang’s suicide?
Ding lit a cigarette, “Imagine another set of results. The first time, the white ball drove the black ball into the pocket. The second time, the black ball bounced away. The third time, the black ball flew onto the ceiling. The fourth time, the black ball shot around the room like a frighted sparrow, finally taking refuge in your jacket pocket. The fifth time, the black ball flew away at nearly the speed of light, breaking the edge of the pool table, shooting through the wall, and leaving the Earth and Solar system, just like Asimov once described. What would you think then?”
Indeed, a demon’s pool table.
After a long silence, Ding explained that physicists’ expensive “pool tables”—high-energy particle accelerators—constructed on different continents, have been consistently failing to yield the same results with the same experimental setup. If this were the case for all these physical experiments described earlier, we would not have been able to discover neutrino or symmetry violations.
Now imagine a similarly unlawful coin. When you flipped it, the first time, it gave you heads; the second time, it flew outside of the room; the third time, it hovered in midair humming like a hive of bees; the fourth time, it spun forever without landing, defying gravity’s grasp; the fifth time, it burst into flame and fizzled into ash, leaving only a scorch mark on the table.
… there seemed to be no pattern.
In the story, the leap from a lack of pattern to Yang Dong’s last words that “physics has never existed” is too quick. In reality, physicists are never afraid of “no obvious patterns” because they know they are dealing with complex situations with many knobs and with worlds governed by probabilities, not certainties, as exemplified by quantum physics.
In experiments with cobalt and kaons that support parity and CP violation above, at least physicists were able to repeatedly get the same result over and over again. Anomalies are still invariant on the lawful pool table. Invariant anomalies can still be written as laws.
Yang’s true crisis arises not from “no pattern” nor is it from simple replication failures, but from a fundamental betrayal of both scientific methods and their underlying principles.
1.11 Betrayal of Scientific Methods
Scientific method is not a single recipe but a set of practices.18 We design experiments so they can be replicated. We build theories so they can predict. We subject hypotheses to conditions where they might be falsified. We rely on measurement and quantification so that results can be communicated and compared. We use statistical inference so that from noisy samples we can draw stable generalizations. And we expose findings to peer scrutiny so that knowledge accumulates collectively, not privately. All these are parts of scientific methods that allow scientists to verify findings, build consensus, and gradually construct a towering edifice of knowledge about the universe, from the smallest particles to the largest galaxies.
However, all of these methods presuppose that the world itself is stable enough for yesterday’s data to apply tomorrow—uniformity of nature. Even failures to replicate previous results should be invariant. Without invariance, replication is meaningless, prediction impossible, falsification incoherent.
Yet, what Yang Dong and her peers were facing was a complete lack of patterns: identical setups yielded wildly different outcomes, so wild that even our best statistical tools could not capture the slight hint of invariance as if it were the demon’s coin.
Yang’s despair was not about complexity or chance—it was about the collapse of this scaffolding. A scientist can live with error and with noise; she cannot live with the treachery that makes her methods useless.
1.12 Apostasy of Symmetry
In our world, the mirrors crack but do not shatter. Even when symmetry fails, the failure repeats. Physicists can write down the fractions, build new theories, and live with scandal made consistent. In Yang Dong’s world, there is no such mercy. The experiment does not only violate symmetry—it refuses to give the same answer twice. Not scandal, but madness. Not law, but caprice. That is why she despaired.
For Yang, who had as much faith as any serious scientist does, this was the final betrayal. Symmetry was not just a mathematical trick but the deep covenant of nature. It was the bridge between invariance and conservation, the silent guarantor that science could still speak a coherent language.
From Yang Dong’s view, everything that we ever know from physics, from quarks to quasars, was an illusion. To see symmetry dissolve was to see the pillars of the temple collapse.
Physics has never existed, and will never exist.
Issac Newton laid the foundations for the corpuscular theory of light, which states that light is made up of small discrete particles called “corpuscles” (little particles). These corpuscles travel in a straight line with a finite velocity.↩︎
In 1859, Maxwell published his essay “on the stability of the motion of Staurn’s rings” (1859), which solved a mystery that had eluded scientists for 200 years—how they could remain stable without breaking up, drifting away, or crashing into Saturn. In this essay, Maxwell proved that a regular solid ring could not be stable, while a fluid ring would be forced to break up into blobs. He concluded that rings must be composed of numerous small particles. He was awarded the Adams Prize.↩︎
In 1905, Einstein provided the first quantitative explanation for Brownian motion, suspended pollen seeds in water moving in an erratic, random motion. In this essay (1905), he proposed that Brownian motion was caused by random bombardment of visible particles by invisible, constantly moving atoms and molecules.↩︎
Hume never named this principle as-is in his Treatise. He says, “if Reason determin’d us, it would proceed upon that principle that instances, of which we have had no experience, must resemble those, of which we have had experience, and that the course of nature continues always uniformly the same” (Hume 2000). For convenience, philosophers refer to this claim of similarity or resemblance between observed and unobserved regularities as the “Uniformity Principle,” “Resemblance Principle,” or the “Principle of Uniformity of Nature.” Read more in Henderson (2018).↩︎
Another translation: There is a constancy to the activities of Heaven, from Xunzi (2015, 175).↩︎
In 1638, Galileo Galilei published Discourses and Mathematical Demonstrations Relating to Two New Sciences (1914), his final book and a scientific testament. The first half of the book deals with the causes and mathematics of how bodies break and the acceleration of falling bodies. The second new science, described in the latter part of the book, deals with the mathematical descriptions and laws of local motions—motions of all matter. See more in Machamer and Miller (2021). In contrast, Kepler’s attitude is more ambiguous. But at least, he believes that his laws apply to all planets as he says, in his The Harmony of the World, “But it is absolutely certain and exact that the proportion between the periodic times of any two planets is precisely the sesquialterate proportion (i.e., the ratio of 3:2) of their mean distances…” (2021). Lastly, Newton wrote in the preface of The Mathematical Principles of Natural Philosophy, “I wish we could derive the rest of the phænomena of nature by the same kind of reasoning from mechanical principles; for I am induced by many reasons to suspect that they may all depend upon certain forces by which the particles of bodies, by some causes hitherto unknown, are either mutually impelled towards each other, and cohere in regular figures, or are repelled and recede from each other…” (1846).↩︎
It is extremely difficult—if not impossible—to pin down the exact date of such a naturalistic turn. Most history science textbooks agree that the origin of western science should at least start from the natural philosophy of ancient Greece, if not Egypt and Mesopotamia. See Lindberg’s The Beginnings of Western Science (2010) or McClellan III’s Science and Technology in World History (2015). However, the naturalistic turn does not mean that scientific naturalism is entirely free of references to God or the supernatural. See more in Science without God? by Harrison and Roberts (2019).↩︎
It is worth noting that not all philosophers agree that the Principle of Uniformity of Nature (PUN) is a metaphysical postulate. For example, Mill asserts that PUN is an empirical truth whereas Russell treats PUN as a postulate, a form of “wishful thinking.” See Salmon (1953).↩︎
This quote is adapted for readability. In his essay “Physics and Reality” (1936), Einstein wrote, “…the production of some sort of order among sense impressions, this order being produced by the creation of general concepts, relations between these concepts, and by definite relations of some kind between the concepts and sense experience. It is in this sense that the world of our sense experiences is comprehensible. The fact that it is comprehensible is a miracle.”↩︎
In a book titled Ars Conjectandi (The Art of Conjecturing) (2006)↩︎
Read more in Emmy Noether’s Wonderful Theorem (Neuenschwander 2017), Symmetry and the Beautiful Universe (Lederman and Hill 2011), and a recent biography Proving It Her Way (Rowe and Koreuber 2020).↩︎
Symmetry and the Beautiful Universe by Lederman and Hill (2011, 108).↩︎
Symmetry and the Beautiful Universe by Lederman and Hill (2011, 109)↩︎
More precisely, parity symmetry was proposed to be violoated in weak interactions. The “weak interaction” is one of the four fundamental forces of nature, alongside gravity, electromagnetism, and the strong force that binds nuclei. Unlike the others, it doesn’t push or pull in ways we can feel directly. Instead, it quietly governs certain rare processes—the slow disintegration of atomic nuclei, the burning of stars, the very fact that the Sun shines. It is called weak not because it is unimportant, but because, compared to the other forces, its grip is feeble and short-ranged.↩︎
Fearful Symmetry (Zee 2015, 29)↩︎
This is, of course, when we adopt views in Longino’s Science as Social Knowledge (1990).↩︎