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GPS Observables in Newtonian Spacetime or Why We Do Not Need 'Physical' Coordinate Systems
History and Philosophy of Physics · Submitted 11 Oct 2024
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim In this sense, I conclude that the 'observable' view of general relativity is unmotivated.
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The abstract, sentence by sentence
Some authors have defended the claim that one needs to be able to define 'physical coordinate systems' and 'observables' in order to make sense of general relativity. Moreover, in Rovelli (Physical Review D, 65(4), 044017 2002), Rovelli proposes a way of implementing these ideas by making use of a system of satellites that allows defining a set of 'physical coordinates', the GPS coordinates. In this article I oppose these views in four ways. First, I defend an alternative way of understanding general relativity which implies that we have a perfectly fine interpretation of the models of the theory even in the absence of 'physical coordinate systems'. Second, I analyze and challenge the motivations behind the 'observable' view. Third, I analyze Rovelli's proposal and I conclude that it does not allow extracting any physical information from our models that wasn't available before. Fourth, I draw an analogy between general relativistic spacetimes and Newtonian spacetimes, which allows me to argue that as 'physical observables' are not needed in Newtonian spacetime, then neither are they in general relativity. In this sense, I conclude that the 'observable' view of general relativity is unmotivated.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Some authors have defended the claim that one needs to be able to define 'physical coordinate systems' and 'observables' in order to make sense of general relativity. | background 1.00 | 0.03 | 0.02 | asserted 0.81 |
| s1 | Moreover, in Rovelli (Physical Review D, 65(4), 044017 2002), Rovelli proposes a way of implementing these ideas by making use of a system of satellites that allows defining a set of 'physical coordinates', the GPS coordinates. | background 1.00 | 0.03 | 0.02 | asserted 0.97 |
| s2 | In this article I oppose these views in four ways. | contribution 0.95 | 0.76 | 0.05 | asserted 0.97 |
| s3 | First, I defend an alternative way of understanding general relativity which implies that we have a perfectly fine interpretation of the models of the theory even in the absence of 'physical coordinate systems'. | contribution 0.95 | 0.80 | 0.15 | asserted 1.00 |
| s4 | Second, I analyze and challenge the motivations behind the 'observable' view. | contribution 0.95 | 0.85 | 0.04 | asserted 0.70 |
| s5 | Third, I analyze Rovelli's proposal and I conclude that it does not allow extracting any physical information from our models that wasn't available before. | result 0.83 | 0.87 | 0.18 | asserted 1.00 |
| s6 | Fourth, I draw an analogy between general relativistic spacetimes and Newtonian spacetimes, which allows me to argue that as 'physical observables' are not needed in Newtonian spacetime, then neither are they in general relativity. | contribution 0.48 | 0.82 | 0.14 | asserted 0.96 |
| s7 | In this sense, I conclude that the 'observable' view of general relativity is unmotivated. | interpretation 0.78 | 0.76 | 0.85 | asserted 1.00 |
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Original abstract
Some authors have defended the claim that one needs to be able to define 'physical coordinate systems' and 'observables' in order to make sense of general relativity. Moreover, in Rovelli (Physical Review D, 65(4), 044017 2002), Rovelli proposes a way of implementing these ideas by making use of a system of satellites that allows defining a set of 'physical coordinates', the GPS coordinates. In this article I oppose these views in four ways. First, I defend an alternative way of understanding general relativity which implies that we have a perfectly fine interpretation of the models of the theory even in the absence of 'physical coordinate systems'. Second, I analyze and challenge the motivations behind the 'observable' view. Third, I analyze Rovelli's proposal and I conclude that it does not allow extracting any physical information from our models that wasn't available before. Fourth, I draw an analogy between general relativistic spacetimes and Newtonian spacetimes, which allows me to argue that as 'physical observables' are not needed in Newtonian spacetime, then neither are they in general relativity. In this sense, I conclude that the 'observable' view of general relativity is unmotivated.
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What it cites · 2 sentences without a confident label
Cites as support 1 paper
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Moreover, for some simple toy models it is easy to see[See the discussion of the double harmonic oscillator model in [ref] .] that no non-trivial `observables' in this technical sense can be defined, while one has a perfectly fine interpretation of these models.
Reassessing the problem of time of quantum gravity · Gauge and `observables' · 0.98
Cites as background 1 paper
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In some more technical definitions of spacetime models[See for instance the definitions in [ref] of Newtonian models or the recent comparison in [ref] of general relativistic models and models of teleparallel gravity, which essentially differ in the connections employed in each of these models.] one also includes the affine connection $∇$ as one of the ingredients of the model, but here I will just assume that the connection for general relativistic models is the Levi-Civita connection and I won't be paying much more attention to it.
Torsion in the Classical Spacetime Context · A brief discussion of how to interpret general relativity · 0.94
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