Question explored with the scientific record
Conversation so far
- 1 What is energy itself, using "real science" to answer? + a private exchange
- 2 Yes, but not consistent with your just previous reply. "Energy is a conserved scalar derived from time-translation symmetry, not a physical substance. Confidence: high—this is settled physics, confirmed across quantum mechanics, relativity, and thermodynamics.
- 3 Yes, but still inconsisytent with what seemms to be your insistence of saying it is fundamental to physics.
- 4 Why does physics insist in providing an answer for something it cannot objectively identify?
Answered on this page ↓
Why does physics insist in providing an answer for something it cannot objectively identify?
The asker's objection is consistent: if physics cannot "objectively identify" what energy is, why does it insist energy provides answers?
The retrieved evidence does not help here. It covers concrete uses of "energy" as a tool—a metric to detect fatigue cracks [1], a conserved quantity in computational fluid dynamics [2], a calibration target for particle detectors [3]. None of these records define what energy is in an ontological sense. They treat energy as a measured or calculated number that works for engineering. That is the standard physics answer: energy is a conserved quantity that you can compute, not an object you can point to.
The asker's challenge goes to the heart of how physics operates. Physics does not need to identify what energy "really is" to use it. It treats energy as a property that is defined operationally—by how it is measured or calculated. The same is true for time, electric charge, and probability amplitude. These concepts are defined by their mathematical relationships and empirical consequences, not by a direct description of their "substance."
So the answer to "why does physics insist on using it?" is that energy works. It is a conserved quantity in every known physical process down to the precision experiments can test. That makes it the most reliable constraint in physics, more reliable than any specific theory of what it "is." Physics trades in operational definitions and predictive success, not metaphysical certainty. The asker's point is not a refutation of the concept; it is a correct identification of the epistemology that physics actually uses. The insistence is earned by the track record, not by a proof of what energy "really is."
My call: Energy is an operationally defined conserved quantity that predicts outcomes reliably. "What it is" is a question physics does not try to answer. Confidence: high about the epistemology of physics practice. The asker's critique is correct about the limits of what physics can say, but it does not undermine the practical use of the concept.
Sources used 3
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Fatigue crack growth monitoring using high-frequency guided waves
Noncontact laser interferometry detects fatigue crack growth at a fastener hole via a measurable energy drop in the high-frequency guided ultrasonic wave behind the crack, and finite-difference simulations support approximate defect sizing.
DOI: 10.1177/1475921713498532 -
Non-body-fitted fluid–structure interaction: Divergence-conforming B-splines, fully-implicit dynamics, and variational formulation
Divergence-conforming immersed boundary (DCIB) method yields negligible incompressibility errors on the Eulerian grid, minimizes spurious solid-volume changes, and improves energy conservation in immersed FSI with co-dimension zero solids, outperforming prior immersed methods.
DOI: 10.1016/j.jcp.2018.07.020 -
The overview of the ATLAS local hadronic calibration
The paper describes the ATLAS local hadronic calibration, a sequential Geant4-simulation-based procedure that corrects topological clusters to particle level and, in simulations, restores single-pion energy and recovers jet linearity up to 92% in di-jet events.
DOI: 10.1088/1742-6596/160/1/012079