Uploaded February 2025 | Updated September 2026, 7 hours ago
Pressure under pressure: on the status of the classical pressure in relativity
Much of the century-old debate surrounding the status of thermodynamics in relativity has centered on the search for a suitably relativistic temperature; recent work by Chua (2023) has suggested that ‘the’ classical temperature concept — consilient as it is in classical settings — ‘falls apart’ in relativity. However, these discussions have still tended to assume an unproblematic Lorentz transformation for ‘the’ pressure concept (specifically, this is presumed to be Lorentz invariant). Here I argue that, just like ‘the’ classical temperature, ‘the’ classical concept of pressure breaks down in relativistic settings. This situation suggests a new thermodynamic limit — a ‘rest frame’ limit — without which an unambiguous thermodynamic description of systems does not emerge. I end by briefly discussing how thermodynamics, in requiring preferred frames, bears on the idea of ‘symmetry-to-reality’ inferences.
Pressure under pressure: on the status of the classical pressure in relativity
Much of the century-old debate surrounding the status of thermodynamics in relativity has centered on the search for a suitably relativistic temperature; recent work by Chua (2023) has suggested that ‘the’ classical temperature concept — consilient as it is in classical settings — ‘falls apart’ in relativity. However, these discussions have still tended to assume an unproblematic Lorentz transformation for ‘the’ pressure concept (specifically, this is presumed to be Lorentz invariant). Here I argue that, just like ‘the’ classical temperature, ‘the’ classical concept of pressure breaks down in relativistic settings. This situation suggests a new thermodynamic limit — a ‘rest frame’ limit — without which an unambiguous thermodynamic description of systems does not emerge. I end by briefly discussing how thermodynamics, in requiring preferred frames, bears on the idea of ‘symmetry-to-reality’ inferences.
