Have We Abandoned the Physical Theory of Nature?
| Scientific Paper | |
|---|---|
| Title | Have We Abandoned the Physical Theory of Nature? |
| Read in full | Link to paper |
| Author(s) | Burniston Brown |
| Keywords | physical theory of nature, mathematical theory of nature, causation, energy, action at a distance |
| Published | 1956 |
| Journal | Science Progress |
| Volume | 44 |
| No. of pages | 16 |
| Pages | 619-634 |
Read the full paper here
Abstract
The Greek philosophers showed that in the study of Nature there were three fundamentally different theories which could be put forward to account for the obvious and extensive characteristics of stuff and change: the physical, the mathematical, and the functional theories...
Overview
This is the substance of a lecture G. Burniston Brown gave to the Royal Institute of Philosophy in October 1955, published the following year in Science Progress. It is not a technical paper but a diagnosis of what had gone wrong with twentieth-century physics, argued historically. Brown's thesis is that physics has quietly swapped one metaphysics for another: the physical theory of Nature, in which permanent bodies exert forces on one another and those forces are the causes of what we observe, has been displaced by the mathematical theory, in which mathematical relations are themselves treated as causes. He takes the epigraph from Newton — "Our business is with the causes of sensible effects" — and uses it as the standard against which he measures Eddington, Jeans, Milne and the quantum theorists.
The departure from the mainstream account is total but unusually well-mannered. Brown does not say relativity or quantum mechanics is arithmetically wrong; he says they are not explanations at all, because "mathematical relations (equations) do not exert force and cannot cause even a speck of dust to change its motion." Where the orthodox view treats the abandonment of mechanical models as intellectual progress, Brown treats it as the return of a medieval error, and — following Spengler — as a symptom of cultural decline. He ends by sketching his own alternative: a delayed action-at-a-distance force law that he claims does the work of relativity without any of its apparatus.
The argument
The three Greek theories
Brown opens with a taxonomy. Thales noticed that Nature is composed of objects with the quality of permanence; Heraclitus emphasised that Nature contains change. Parmenides argued that change must be motion rather than generation, and that motion required a "where-it-is-not" — an objection Leucippus and Democritus answered by making the "stuff" many and adding the void. This is the physical theory: eternal atoms moving in absolute space.
The mathematical theory descends from Pythagoras, Eudoxus and Plato, and has three consequences Brown emphasises: causal primacy is given to relations; a distinction is drawn between the apparent world of bodies in motion and an underlying real world of mathematical form; and, since that underlying world is not directly observed, "reason and 'harmony' are better guides to knowledge than experiment and observation."
The functional theory arose from the study of living things — Hippocrates, Empedocles, Aristotle — and requires form as a cause alongside matter, leading to the principle of "becoming". Brown sets it aside after noting Whitehead as its modern advocate; his subject is the two-thousand-year contest between the first two.
How the mathematical theory returned
The historical core of the paper follows the mathematical theory from Nicholas of Cusa and Bruno through Kepler and Galileo — for whom the primary qualities of bodies were just those expressible mathematically — to Newton, with whom the physical theory "finally became dominant and was placed on a firm foundation, the position of mathematics being solely that of a method". Brown stresses, against the usual picture, that Newton did not share the belief that the world is essentially mathematical, and quotes Universal Arithmetic to the effect that there may be problems mathematics cannot handle.
The turn back came, on Brown's reading, through the ether. Optical and electromagnetic phenomena demanded a medium, but the medium had to be given properties unlike those of any known substance, so investigators took to describing it in general terms without specifying its mechanical action. What made this possible was the invention of energy: the potential function, invented by Lagrange purely to simplify calculation from Newton's law, later became potential energy, and kinetic energy and action were added. Brown quotes Green in 1838 excusing himself on the grounds that "we are so perfectly ignorant of the mode of action of the elements of the luminiferous ether on each other" that a general principle is safer than an assumed mechanism; and MacCullagh admitting that his hypotheses "are nothing more than fortunate conjectures". Airy went a step further, describing his equations not as giving a mechanical explanation but as showing that "the phenomena may be explained by equations". That, Brown says, is the moment the mathematical theory re-emerged.
Eddington, Jeans and the postulate method
On relativity Brown's complaint is specifically about method. Instead of drawing a physical conclusion from the Michelson–Morley null result — contraction of bodies with motion, or the non-existence of the ether and hence action at a distance — Einstein wrote down the constancy of the measured Speed of Light as a postulate, and the Lorentz transformations follow as relations between observers' measurements. "But no mention was made of any forces which would cause the instruments to read differently, the clocks to go slow, and so on." The relations between measurements, Brown insists, are conclusions from a genuine physical theory; they cannot be postulates.
He then presses Eddington hard, quoting the remark that all a physicist needs is one colour-blind eye to read pointers with, the redefinition of the physical universe as "the world which physical knowledge is formulated to describe", and finally the claim "that the fundamental laws and constants of physics are wholly subjective". Jeans is quoted asserting that "we live in a mathematical universe" and that the proton-to-electron mass ratio is a question for the mathematician. Brown notes that some mathematicians saw the danger: Poincaré on the mathematical method inspiring "a confidence nothing warrants", Eddington conceding that "in one sense deductive theory is the enemy of experimental physics", and Rutherford complaining that Continental physicists were content to explain everything on an assumption and "do not worry their heads about the real cause of a thing."
Cosmology gets the sharpest treatment. Milne built a model on metrical assumptions and argued that the actual universe must resemble it because reason could conceive no other — "Illusions of this kind, one would have thought, had died with Descartes." And Brown notes that some astrophysicists "do not hesitate to postulate the creation of matter from nothing, a hypothesis for which, it is hardly necessary to add, there is no evidence whatsoever" — a hit at continuous creation in the Steady State Theory.
Four practical dangers
Brown then lists the consequences he thinks follow from adopting the mathematical theory.
Loss of causation. The early mathematisers at least had a deity to make bodies conform to perfect relations. Revived without one, "all hope of causal explanation vanishes." Physicists feel the lack and paper over it by using causal language about fictions — "virtual mesons" that sound like objects but are not, and space-time, "a purely mathematical conception", spoken of as the cause of planetary motion.
Carelessness about constants. Brown singles out G, arguing that its appearance in the inverse-square law reflects a physical fact — on his account that the inertial mass of a body is about four thousand times its attractive mass — and that relativists who declare inertial and attractive Mass identical have overlooked the physical meaning of the constant.
Contempt for observation. If Newton's demand for "more experiments" becomes "narrow experimentalism", observations are made only to test theories already conceived, and the temptation is to find what you are looking for. His illustration is the eclipse test of light bending: some star images had moved towards the Sun, others sideways, hardly any radially; only the radial components were considered and the tangential ones "regarded as accidental errors and ignored"; the mean deflections and directions changed during the passage of the Moon's shadow; and Einstein's own formula for the variation of deflection with distance from the Sun was assumed in fixing the scale of the plates from which the deflections were then derived. He adds that the gravitational redshift had not been proved satisfactorily either, and that the perihelion advance was already known and might be accounted for otherwise. He also warns against splitting physicists into theoreticians and experimenters: the observer who is also the theory-maker sees at once when unexpected data invalidate the theory, whereas an experimenter who is not "may be quite strongly tempted to overlook them, and even not record them."
Misuse of language. This is the most quoted passage in the paper. Energy "is what it is defined to be, a product of some numbers obtained by measurement — a metrical feature of a physical process". Brown's analogy is man-hours: it is useful to know that building a ship takes ten million man-hours, "But we would not say that the cause of the appearance of the Queen Mary was that man-hours had flowed into the shipyard. Yet the statement that we are warmed by energy flowing to us from the Sun is quite common, and is just as absurd physically." Saying an atom cannot emit an electron until it has absorbed a certain quantity of energy "is just as absurd as saying that shipyards cannot emit ships until they have absorbed a certain quantity of man-hours." His conclusion: "Energy is not a thing, or an interaction between things"; it "can never be a causal agent in science; it can never take the place of force", and its use as one justifies Spengler's calling it "the great myth of Western science."
Brown's own alternative
In the last pages Brown sketches the theory he had published separately as "A Theory of Action-at-a-distance" (Proc. Phys. Soc. 68, 672, 1955). To atoms in motion acting by contact he adds forces which act at a distance but not simultaneously — after a time interval given by the distance divided by a constant of Nature "usually called the 'velocity of light'". The ether is then unnecessary and the Michelson–Morley and Kennedy–Thorndike results follow at once. The force also varies with relative motion as well as distance, and electromagnetism and gravitation are unified by extending the universality of gravitational force to all macroscopic forces.
The whole metrical content is one force formula between two particles, everything else following by superposition; substituting m1, m2 for e1, e2 in dynamical units converts the electrical case to the gravitational. Newton, Cavendish and Coulomb supplied the inverse-square term; electrodynamic experiments supply the velocity terms and radio experiments the acceleration terms. Brown claims the formula gives electromagnetic induction correctly and handles high-speed particles through the variation of electric force with velocity rather than a change in m — avoiding, he says, the anomaly in relativity where m varies with velocity while e does not. Magnetism, fields of force, displacement currents, retarded potentials, electromagnetic waves, absolute space and space-time "all disappear", and the eleven sets of Lorentz equations are replaced by one force formula. Inertia is accounted for by relative acceleration with respect to the total matter of the universe — a Machian move — and he claims quantitative agreement with the amount and distribution of known matter. A perihelion motion appears and can be fitted by adjusting a constant. Crucially, no gravitational bending of light is predicted: on this theory all "bending" is due to phase differences from superposition, though an increase in inertia near large masses should occur.
For microscopic physics he suggests abandoning waves — "which turn out to be waves of nothing or, worse still, waves of probability or even waves of knowledge" — and concentrating instead on frequency, proposing that quantum phenomena and matter diffraction might follow if all forces are intermittent at very high frequency.
Assessment
The paper's lasting value is the clarity of its central distinction. Brown puts his finger on something real: physics after 1905 increasingly answered "why" questions by exhibiting an equation, and the difference between exhibiting a relation and identifying a cause is a genuine philosophical difference that the working literature rarely acknowledges. The man-hours analogy is the best short statement of the reification objection to Energy in the twentieth-century literature — energy is a bookkeeping quantity conserved across processes, not a fluid that flows and does things — and it remains as sharp now as in 1955, since the textbook idiom of energy "flowing", "being stored" and "being carried" is unchanged. The warning about theory-laden observation, and about splitting observers from theorists, is likewise sound and is now standard in the philosophy of science, though Brown got there before it was fashionable. He also deserves credit for arguing his case from the historical record rather than from assertion; the sequence Green → MacCullagh → Airy is a real and well-chosen documentation of the drift he is describing.
The difficulties are of two kinds. First, the criticism of relativity is uneven. The 1919 eclipse complaint is his strongest empirical card, and the specific charges — tangential components ignored, plate scale fixed using the formula under test — are serious and were made by C. L. Poor at the time. But Brown wrote in 1955, and by then the light-bending result had been repeated at several eclipses; his own footnote concedes that improved methods "are held to indicate a displacement of the stellar images greater than the predicted value", which is a different complaint from the one his text is making. The gravitational redshift he dismisses as unproven was measured by Pound and Rebka in 1959, four years later, to about 10 % and subsequently to 1 %, and radio-interferometric and VLBI measurements of light deflection now confirm the general-relativistic value to better than 0.02 % — so the specific empirical case he rests on has not survived. He is also simply mistaken about G. The claim that the inertial mass of a body is "about four thousand times greater than its attractive mass" is asserted without derivation and has no evident meaning: the ratio of inertial to gravitational mass is dimensionless and has been shown equal to one by Eötvös-type torsion-balance experiments to a part in 1013. It is not a number that can be four thousand.
Second, the alternative theory is presented as a set of claims rather than a demonstration. Within the space of two pages Brown asserts that his force formula reproduces electromagnetic induction, high-speed particle behaviour, inertia from the mass distribution of the universe "quantitatively", and the perihelion advance — the last openly by adjusting a constant, which is curve-fitting rather than prediction and is precisely the kind of accommodation he criticises in others. The prediction that there is no gravitational bending of light, only phase-superposition effects, is a genuine falsifiable difference from general relativity, and it is now decisively refuted by Gravitational Lensing: multiply-imaged quasars, Einstein rings and cluster arcs are not phase effects in a beam, and the deflection has been measured directly against the general-relativistic value in solar-limb radio experiments. The suggestion that quantum phenomena might arise from forces intermittent at very high frequency is offered as a hint, not a theory, and nothing follows from it.
Read fairly, then, the paper is much stronger as criticism than as construction. Brown's methodological complaint stands on its own and does not depend on his force law being right; a reader may accept every word about causation, energy and theory-laden observation while rejecting the action-at-a-distance programme entirely. That the constructive half has since failed empirically does not blunt the diagnostic half, which is why the lecture is still worth reading.