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The twins and the bucket: How Einstein made gravity rather than motion relative in general relativity

Janssen, Michel (2011) The twins and the bucket: How Einstein made gravity rather than motion relative in general relativity. [Preprint]

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    Abstract

    In publications in 1914 and 1918, Einstein claimed that his new theory of gravity somehow relativizes the rotation of a body with respect to the distant stars (a stripped-down version of Newton's rotating bucket experiment) and the acceleration of the traveler with respect to the stay-at-home in the twin paradox. What he showed was that phenomena seen as inertial effects in a space-time coordinate system in which the non-accelerating body is at rest can be seen as a combination of inertial and gravitational effects in a (suitably chosen) space-time coordinate system in which the accelerating body is at rest. Two different relativity principles play a role in these accounts: (a) the relativity of non-uniform motion, in the weak sense that the laws of physics are the same in the two space-time coordinate systems involved; (b) what Einstein in 1920 called the relativity of the gravitational field, the notion that there is a unified inertio-gravitational field that splits differently into inertial and gravitational components in different coordinate systems. I provide a detailed reconstruction of Einstein's rather sketchy accounts of the twins and the bucket and examine the role of these two relativity principles. I argue that we can hold on to (b) but that (a) is either false or trivial.


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    Item Type: Preprint
    Keywords: relativity of the gravitational field, twin paradox, rotating bucket, equivalence principle, kinematical relativity, general covariance.
    Subjects: Specific Sciences > Physics > Relativity Theory
    Depositing User: Michel Janssen
    Date Deposited: 11 May 2011 14:49
    Last Modified: 11 May 2011 14:49
    Item ID: 8605
    URI: http://philsci-archive.pitt.edu/id/eprint/8605

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