Change Without Change, and How to Observe it in General Relativity
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Change Without Change, and How to Observe it in General Relativity
Change Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativity Social Sciences,Tucson, AZ 85721,USA.Tel: (520)-621-3120Fax: (520>621-9559Email: rhealey@email.Arizona.eduAbstract• Many of the key ideas of this paper were developed in close collaboration with Jenann Ismael, who shares whatever credit IS due: I reserve to myself the blame foi not making adequate Change Without Change, and How to Observe it in General Relativityuse of her contributions. I thank also Shaughan Lavine, audiences in Oxford and the London School of Economics, and die referees for this journal forChange Without Change, and How to Observe it in General Relativity
their patience and constructive criticisms1Change Without ChangeAll change involves temporal variation of properties. There is change in the physical Change Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativityrld against two skeptical arguments recently presented by John Earman. Each argument imposes severe restrictions on what maycount as a genuine physical magnitude in general relativity. These restrictions seem justified only as long as one ignores the fact that genuine change in a relativistic world Change Without Change, and How to Observe it in General Relativityis framedependent. 1 argue on the contrary' that there are genuine physical magnitudes whose values typically vary with the time of some frame, and thChange Without Change, and How to Observe it in General Relativity
at these include most familiar measurable quantities. Frame-dependent temporal variation in these magnitudes nevertheless supervenes on the unchangingChange Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativityrame. Change is a significant and observable feature of a general relativistic world only because our situation in such a world naturally picks out a relevant class of frames, even if we lack the descriptive resources to say how they are realized by the values of basic underlying physical magnitudes Change Without Change, and How to Observe it in General Relativity.2change Without changeIntroductionMeldphysics began with Parmenides' denial of change. ĨL is templing today lo dismiss his argument as either fallaciChange Without Change, and How to Observe it in General Relativity
ous or else a reductio ad ubsurdum OÍ its premises. Surely we observe change all around US. Moreover, physical science seems to have provided US witliChange Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativity that has not changed is philosophers' practice of arguing among themselves about the best abstract analysis of change . But contemporary metaphysical discussions are almost uniformly descriptive rather than revisionary. As with Parmenides, McTaggart's argument for the unreality of time and change i Change Without Change, and How to Observe it in General Relativitys typically regarded as a simple reductio, resting on either fallacious reasoning or an incorrect analysis of change2. Unlike their illustrious predecChange Without Change, and How to Observe it in General Relativity
essors, today's philosophers complacently take for granted the existence of change, while leaving the investigation of concrete observable changes to Change Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativityonclusion that all the apparent changes we think we observe arc merely illusions-that no genuine physical magnitude ever changes—and that the lesson the general theory of relativity has to leach US is that all observable quantities in fact remain constant and unchanging.’ This shock may be just what Change Without Change, and How to Observe it in General Relativity is needed to highlight the fact that foundational physics is revisionary metaphysics under the guise of empirical science.Aller recovering from the sChange Without Change, and How to Observe it in General Relativity
hock, the next step must be to try to reconcile the overwhelming appearance of change in the world around US with the absence of any physical change aChange Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativityto show how real physical change in a general relativistic world can supervene on an unchanging physical basis, so that (to echo Wheeler) there is change without change. The second stage is to explain how we are able to observe physical change while remaining curiously unaware of its unchanging phys Change Without Change, and How to Observe it in General Relativityical basis.The argument that the deep structure of general relativity excludes change in genuine physical magnitudes hinges on technical features notChange Without Change, and How to Observe it in General Relativity
shared by other space-time theories. But it will nevertheless prove useful to begin by discussing the nature of change in a more familiar context of NChange Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativityhysical magnitudes even though these supervene on unchanging values of more fundamental physical magnitudes.The nature of this supervenience is best explained using the notion of a frame. Applied to a special relativistic world, this notion shows how a four-dimensional “block universe” may admit bot Change Without Change, and How to Observe it in General Relativityh change and its absence. Local frames are definable in any general relativistic world. Their definition permits one to describe a multiplicity of fraChange Without Change, and How to Observe it in General Relativity
me-dependent changes in such a world. A frame-dependent change is genuine: its occurrence is determined by the unchanging values of basic physical magChange Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativityc physical magnitudes whose unchanging values realize our occupation of it.Here's how the sections to follow lay out the argument of the paper. Section 1 offers a preliminary account of change intended to fit the idea of change in physical magnitudes in the context of contemporary metaphysical analy Change Without Change, and How to Observe it in General Relativityses of change. Section 2 uses physical examples to show how special relativity already forces US to get clearer on the notions of properties and timesChange Without Change, and How to Observe it in General Relativity
typically invoked by such analyses. Section 3 extends the analysis to general relativity4Change Without Change and shows how a traditional approach tChange Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativitylated arguments for the conclusion that, in a general relativistic world, no fundamental physical magnitude ever changes. Section 5 responds to the arguments by showing how to use fundamental magnitudes to define change in other, equally genuine, physical magnitudes, and explaining how we can observ Change Without Change, and How to Observe it in General Relativitye their changing values.1. ChangeA physical theory should tell US what kinds of things there are in the world, the properties they possess, and the reChange Without Change, and How to Observe it in General Relativity
lations they bear one another. The goal is to specify a set of basic entities, properties and relations. By permitting unrestrained recombination of tChange Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativityerties characterize them intrinsically, and the relations specify their arrangement. Any formally appropriate assignment of properties to basic individuals and specification of the external relations among them is allowed here. The physical laws distinguish those worlds that lie within the realm of Change Without Change, and How to Observe it in General Relativityphysical possibility.As a quantitative science, physics typically deals with magnitudes rather than properties. A physical magnitude is nothing more tChange Without Change, and How to Observe it in General Relativity
han a jointly exhaustive, mutually exclusive family of physical properties, with each property corresponding to an assignment of a value of the appropChange Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213 Change Without Change, and How to Observe it in General Relativity to another incompatible property in the associated family. Since each qualitative property simply corresponds to a 2-valued magnitude whose values are 1 (for “present") and 0 (for “absent”), I will move freely back and forth between talk of properties and talk of magnitudes.5https://khothuvien.cori Change Without Change, and How to Observe it in General Relativity!Change Without ChangeChange Without ChangeChange Without Change, and How to Observe it in General Relativity^Richard HealeyPhilosophy Department.University of Arizona,213Gọi ngay
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