Energy
This Natural Philosophy wiki page disputes content found on Wikipedia page wikipedia:Energy
Energy is, in orthodox physics, a scalar quantity assigned to a physical system which has the useful property of being conserved: it may change form, but in a closed system the total does not change. It is measured in joules, it is calculated from the configuration and motion of matter, and no experiment has ever isolated it from matter. It is, in short, a number.
Much of the literature collected on this wiki holds that physics has forgotten this. The complaint is not that the quantity is wrongly calculated or that conservation is a bad rule; it is that a bookkeeping term has been quietly promoted into a thing — something that can exist on its own, fill space, travel, and act. Once that step is taken, the argument runs, entities such as "pure energy", the "energy of the vacuum" and dark energy follow as a matter of grammar rather than of evidence.
This article sets out what energy is on the standard account, the objection to its objectification as it is made by researchers documented here, the historical precedent that objection appeals to, and the places where the dispute has practical consequences.
The orthodox account
The point at issue is not controversial, and mainstream physics states it plainly when it is being careful. Energy is defined operationally: kinetic energy is a number computed from mass and speed, potential energy a number computed from position in a field, and the sum is found to be constant. Nothing in the definition requires or supplies a substance.
Richard Feynman put it as directly as anyone, in the Lectures on Physics:
It is important to realize that in physics today, we have no knowledge of what energy is. We do not have a picture that energy comes in little blobs of a definite amount. [...] It is an abstract thing in that it does not tell us the mechanism or the reasons for the various formulas.
Emmy Noether's theorem sharpens the same point: conservation of energy is a consequence of the time-translation symmetry of the laws, not the discovery of an indestructible fluid. On the orthodox account energy is therefore a property of systems, in the way that momentum or angular momentum is — a description of what matter is doing, not an inventory of what is present.
The objection to objectification
The case made on this wiki is that physics states the above when pressed but does not act on it. Glenn Borchardt gives the objection its sharpest formulation in "The Physical Meaning of E=mc2" (2009):
Energy actually does not exist and does not move. It is simply a mathematical description of the motion of matter. Matter does not "contain" energy, for matter only can "contain" other things in motion. Energy is simply a mathematical term necessary for describing and relating the various forms of the motion of matter.
Borchardt's argument rests on an assumption he calls inseparability: just as there can be no motion without matter, so there can be no matter without motion. Matter exists; motion occurs. Motion is not a part of the universe but what the parts do. To treat energy — a measure of motion — as an existing thing is therefore to commit a category error, and one that he traces through modern physics as a systematic "estrangement between matter and motion".
In "Einstein's Most Important Philosophical Error" (2011) he presses the same charge further back, arguing that the founding mistake was the objectification of motion itself, beginning with the treatment of light as a particle rather than as wave motion in a medium.
The consequences he identifies are specific. On this view, popular statements that matter is "converted into pure energy" describe nothing: what occurs is the transformation of one kind of matter in motion into another. The claim that the early universe was "filled with energy" before it contained matter is, on the same reading, not a bold hypothesis but a sentence with no referent. And the treatment of spacetime as a substance that can bend and ripple is the same error applied to a different matter-motion term.
The caloric precedent
The objection is not merely philosophical, and its force comes from the fact that physics has already made this exact mistake once and corrected it.
Heat was long held to be a substance — caloric, a weightless self-repelling fluid that flowed from hot bodies to cold ones. The theory was quantitative, it was successful, and it was wrong. Rumford's cannon-boring experiments and Joule's measurements established that heat is not a fluid contained in bodies but a measure of the motion of their parts. The substance was dropped; the bookkeeping survived intact, and thermodynamics lost nothing.
Borchardt draws the parallel explicitly, comparing the objectification of motion to "the theory that heat was a 'caloric fluid', instead of vibratory motion." The argument made here is that energy now occupies the position caloric once held: a quantity that is real as a measure and fictitious as a substance, but which is spoken of, and increasingly reasoned with, as though it were the latter.
Where the dispute has consequences
The distinction would be idle if nothing followed from it. Researchers here argue that a good deal does.
- Dark energy. The clearest case. A conserved bookkeeping quantity is given a density, an equation of state and a negative pressure, and is then made to act causally on the expansion of the universe. If energy is a measure of the motion of matter, then an "energy density of empty space" ascribes a property to the absence of the thing that bears it.
- Zero-point and vacuum energy. The same move at laboratory scale, and the source of the largest quantitative failure in physics: the discrepancy of some 120 orders of magnitude between the vacuum energy that quantum field theory predicts and the value cosmology reports.
- E = mc². Read as a conversion of matter into a matterless something, the equation licenses the whole vocabulary of "pure energy". Read as Borchardt reads it, it relates one form of matter in motion to another and no conversion into non-matter occurs.
- Spacetime. Once motion is objectified, the geometry describing it is objectified too, and a four-dimensional manifold is taken to be a constituent of the world rather than a description of it.
Conservation and its critics
A separate and narrower line of work on this wiki questions not the reality of energy but the universality of its conservation. Robert L Carroll's "The Non-Conservation of Energy" (1997) argues that energies are not additive in quantum or electromagnetic theory and reports that the decay energy of electron clusters exceeds the ballistic energy of their formation. Panos Pappas examined the status of the conservation principle in electrodynamics in his work on the cardinal law of electrodynamics (1988).
These arguments are logically independent of the objectification question — one may hold that energy is a mere descriptor and still expect the descriptor to balance — and they are recorded here as a distinct strand rather than as support for the first.
The contrary view
Not everyone documented here treats energy as a descriptor, and the disagreement should be recorded rather than smoothed over. David W. Talmage and colleagues argue the opposite case in "Energy is Everything: Quantum Explanation of Gravity and Inertia" (2002), taking energy as the fundamental ontological category and deriving gravity and inertia from the behaviour of a quantum field acting through a variable speed of light. On such accounts energy is not the abstraction and matter the reality, but the reverse.
Tuomo Suntola's zero-energy cosmology occupies a third position: it takes the energy bookkeeping entirely seriously and derives its cosmological results from the requirement that the total energy of the system be zero — treating energy as a constraint on what can exist rather than as a substance that exists.
Researchers on this wiki
- Glenn Borchardt — inseparability of matter and motion; the objectification of energy and spacetime
- Robert L Carroll — non-conservation of energy; non-additivity in quantum and electromagnetic theory
- Tuomo Suntola — zero-energy space; energy balance as a cosmological constraint
- Panos Pappas — conservation of energy in electrodynamics
Papers on this wiki
- 1988 — Panos Pappas, on the cardinal law of electrodynamics and the conservation of energy
- 1997 — Robert L Carroll, "The Non-Conservation of Energy"
- 2002 — David W. Talmage et al., "Energy is Everything: Quantum Explanation of Gravity and Inertia"
- 2007 — Tuomo Suntola, "Zero-Energy Space Cancels the Need for Dark Energy"
- 2009 — Glenn Borchardt, "The Physical Meaning of E=mc2"
- 2011 — Glenn Borchardt, "Einstein's Most Important Philosophical Error"