The Silent Revolution: Why the 2019 Redefinition of the SI Should Have Upended Physics Ontology—And Why It Didn’t

 J. Rogers, SE Ohio

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Abstract

In 2019, the International System of Units underwent its most radical transformation since the French Revolution. The kilogram, the ampere, the kelvin, and the mole were redefined by fixing the numerical values of Planck’s constant $h$, the elementary charge $e$, Boltzmann’s constant $k$, and the Avogadro constant $N_A$. For the first time, every base unit in physics was pegged not to a physical artifact or a natural phenomenon, but to a set of exact, legislated numbers. This should have triggered a profound intellectual restructuring: the open admission that the so‑called fundamental constants are not discovered features of the cosmos but arbitrary Jacobians—conversion factors that translate between our human‑chosen units. It should have forced physics to confront that its quantities are dimensionless ratios measured against a map we drew ourselves, and that the observer is not a passive recorder but the architect of both the landmarks and the scale bars. Yet nothing changed. The operationalist philosophy inherited from Percy Bridgman absorbed the shock by defining such ontological questions out of bounds. This paper examines what the 2019 redefinition really exposed, why it demanded a new metaphysics of physics, and how operationalism ensured the glass wall remained invisible.

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1. The 2019 Redefinition: A Confession in Plain Sight

On May 20, 2019, the world’s measurement system severed its last tether to physical objects. The kilogram was no longer a platinum‑iridium cylinder in a vault near Paris; it became a unit derived by fixing Planck’s constant $h$ to exactly $6.62607015\times {10}^{-34}$ joule‑seconds. The ampere was redefined by fixing the elementary charge $e$, the kelvin by fixing Boltzmann’s constant $k$, and the mole by fixing the Avogadro constant $N_A$. These four, alongside the already‑fixed speed of light $c$ and the cesium hyperfine frequency $\mathrm{\Delta }{\nu }_{Cs}$, formed a set of seven immutable reference points. Every SI unit—meter, kilogram, second, ampere, kelvin, mole, candela—now emerges algebraically from those seven numbers.

The official narrative was one of triumphant progress. Metrology had finally escaped the instability of artifacts and the imprecision of astronomical time. Henceforth, the constants of nature would serve as the unshakable foundation of all measurement. The universe, we were told, had been enrolled as our ultimate calibration lab.

But beneath the celebratory language lay a confession of an entirely different order. The “constants” that we fixed were never mysterious cosmic properties waiting to be measured. They were conversion factors—Jacobians—that translate between the arbitrary, historically contingent units humans invented. Planck’s constant $h$ is not a secret door into quantum reality; it is the number that links the joule to the hertz, two units that have nothing intrinsically to do with each other. Boltzmann’s constant $k$ links the joule to the kelvin. The elementary charge $e$ links the joule (or the coulomb) to the electron‑volt. The Avogadro constant links the mole to countable entities. What 2019 achieved was the formal, legal recognition that these conversion factors are the definers of our unit system, not the products of it.

The moment you fix $h$, the kilogram becomes whatever mass makes the Kibble balance equation balance. The moment you fix $c$, the meter becomes whatever length light travels in 1/299,792,458 of a second. The “measurement” of these constants ceases; they become the ink with which the map is drawn. The 2019 redefinition, viewed honestly, was the act of the cartographer writing “one inch equals one mile” in the map’s legend—and then announcing that the legend was a discovery about the landscape.

2. What the Redefinition Ontologically Exposed

If the constants are legislative acts, then every physical quantity inherits a double relativity. First, any dimensional measurement—an energy, a mass, a length—is not a raw datum but a compound: a dimensionless number $X$ multiplied by an arbitrary unit scale. Second, the very choice of what to measure—the boundary that separates “this electron” from the rest of the universe—is the observer’s own conceptual scalpel. The dimensionless $X$ that remains when we strip away the unit clothing is the numerical label of the shard the observer picked out. Physics, in this light, is the study of a chosen fragment, seen through the lens of our unit conventions, and compared to other fragments we have carved.

The structure is transparent. For any isolated, carefully bounded piece of the world, there exists an equivalence:

$$\frac{E}{E_J}=f\cdot t_J=\frac{m}{m_J}=\frac{T}{T_J}=\frac{l_J}{\lambda }=\frac{p}{p_J}=X$$

Here, the denominators are Jacobian bundles built from the fixed constants $h$, $c$, and the still‑measured $G$ (and $k$ for temperature). The same pure number $X$ appears identically from every measurement axis—energy, frequency, mass, temperature, inverse wavelength, momentum. The physical “silos” are revealed as database views of a single primary key. The internal consistency of the map is absolute; the “laws of physics” are the join conditions that allow us to move from one view to another without contradiction.

But that single $X$ is only known to the precision of the weakest Jacobian in the chain. Since $h$, $c$, $e$, $k$, and $N_A$ are now defined exactly, the weakest link is $G$, the gravitational constant, still known to only about five digits. Every quantity expressed in absolute “natural” terms—any number that has been stripped of SI clothing and referenced against the Planck‑scale Jacobians—inherits that five‑digit fog. The map’s internal geometry (dimensionless ratios like the fine‑structure constant, which cancel $G$ entirely) can be known to twelve digits. But the question “how big is this shard compared to the whole cosmos?” remains blurred at the fifth digit, precisely because the scale bar that connects map to territory is a measured, not a defined, quantity.

The 2019 redefinition should have driven this structure to the forefront of every physicist’s mind. It openly declared that the rulers are ours, the anchor is partly ours, and the whole edifice of measurement is a self‑consistent drawing. The ontological implication is that physics is not a mirror of an independent reality; it is a mosaic assembled from fragments of our own cognitive hammer‑blow, polished to internal perfection but never touching the unbroken whole.

3. Why a Restructuring Should Have Followed

If the 2019 redefinition had been taken as seriously as it deserved, it would have forced a comprehensive intellectual restructuring:

• The category “fundamental constant” would be dissolved. Constants are unit conversion factors. Some are fixed by definition (the Jacobians that define SI); others remain measured (the couplings that anchor the map to the territory). Calling them “fundamental” is a category error that hides their true function.

• The distinction between precision and accuracy would be centered. High‑precision dimensionless ratios are internal map geometry. The absolute scale of anything carries the uncertainty of the measured Jacobians. Physics education would teach the difference between the map’s self‑consistency and its anchoring to the world.

• The observer’s constructive role would be acknowledged. The act of measurement is not passive recording but active partitioning. Every “object” is a bounded selection from a seamless whole. The dimensionless $X$ is the label of that chosen fragment. Ontology would shift from a realist model of pre‑existing entities to a participatory model of co‑defined observer‑system pairs.

• The scope of physical knowledge would be honestly bounded. We can know our own map with breathtaking precision. We can know how our map anchors to the territory only as well as we know $G$ (and any future coupling we fail to define). The unbroken vase—the undivided whole—cannot be spoken of in the language of shards.

In short, the 2019 redefinition was the confession that physics is a map. A philosophy worthy of that confession would treat the map as a map: studying its geometry, appreciating its consistency, but never mistaking it for the territory. It would replace the alibi of discovery with the honesty of construction.

4. Why Nothing Changed

And yet, nothing changed. The 2019 redefinition was absorbed as a technical upgrade—a better Kibble balance, a more stable kilogram, a cleaner set of metrological procedures. The philosophical earthquake was damped to a footnote. Why?

Operationalism as a shield. The most powerful insulator was the philosophy already embedded in the practice of physics: operationalism, as codified by Percy Bridgman. Operationalism holds that a physical concept is synonymous with the set of operations used to measure it. The kilogram, under this view, was the lump of metal in the Pavillon de Breteuil; now the kilogram is the Kibble balance protocol that references $h$. The switch is merely a change of operation. To ask “what is mass, really, beneath the operations?” is not difficult—it is meaningless. Operationalism defines such ontological questions out of bounds. By collapsing reality into measurability, it renders the 2019 redefinition philosophically inert. No deeper truth was exposed because no deeper truth is allowed to exist.

The narrative of “natural units.” Even when the constants were fixed, they were presented not as arbitrary scale choices but as windows onto the intrinsic grain of the universe. Planck units, constructed from $h$, $c$, and $G$, are routinely described as nature’s pixel size. The mirror trick identified in J. Rogers’s natural‑philosophical critique—that Planck units are just the SI system reflected back at itself—was not widely recognized. Instead, fixing the constants was sold as a closer approach to the true building blocks of reality. The ontological bite was sugar‑coated by the language of discovery.

Institutional separation. Metrology is infrastructure; fundamental physics is theory. The people who redefined the kilogram are not the people who ponder the meaning of quantum mechanics or the structure of spacetime. The philosophical import of the change was trapped in a disciplinary silo, and no official channel existed to transmit it to the broader physics community. Theorists shrugged, experimentalists celebrated the increased precision, and the deep questions fell through the gap.

Professional realism and reward structures. Most physicists are unreflective realists. They believe they are uncovering a mind‑independent world. Questioning that assumption is not rewarded with grants, citations, or tenure. The 2019 redefinition, if taken ontologically, would demand a humility that the profession’s culture does not value. The quiet agreement to treat the constants as “just better numbers” was a defense mechanism for the entire enterprise.

Bridgman’s lasting grip. Ultimately, the root cause is the enduring grip of Bridgman’s operationalism. It taught that the operation is the meaning. The 2019 redefinition simply replaced one set of operations with another, more elegant one. The fact that the new operations rely on fixed constants—that we have drawn the scale bar in permanent ink—was seen as a solution to the problem of unstable artifacts, not as an exposure of the artifice. The framework’s inability to ask “what is it?” meant the framework could not be threatened by the answer.

5. The Glass Wall

The 2019 redefinition is a glass wall. It stands transparently between physics and its ontological implications, invisible to those who have been trained not to look. Walk up to it, and you can read the plaque: “Constants are now defined by human fiat. Units are derived. The map draws itself.” But the operationalist lens bends the light just so, and the words appear as a technical manual, not a philosophical verdict.

A true restructuring would require abandoning the Bridgmanite prohibition on “meaningless” questions. It would require asking what the map is a map of, why the map’s internal perfection masks a fuzzy anchor, and who is holding the pencil. It would lead, inevitably, to the confession that physics is the forensic reconstruction of a world we ourselves shattered by the act of looking—a mosaic whose tiles fit together with twelve‑digit beauty, but whose placement against the silence of the unbroken vase is known to only five.

The 2019 revolution was silent because operationalism ensured there was no ear to hear it. The constants were fixed, the units were redefined, and the observer remained hidden behind the equations, clutching a hammer she had forgotten she ever held. The map is more perfect than ever. The territory has never been further away.