Abstract
In this note, I argue that a dynamically shifted world—i.e. a world identical to our own except for a fixed constant difference in the absolute acceleration of each object—is nomically impossible in a Newtonian world populated by finitely many objects. A dynamic shift however seems to be nomically possible in a world populated by infinitely many objects, but only in a broad sense of nomic possibility.
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Notes
As an anonymous referee for this journal has pointed out, it should be noted that the case under consideration is one in which forces act on the centres of mass of extended bodies. If every particle of matter accelerated at the same rate (e.g. if the whole universe was in free fall in a uniform gravitational field), then there would be no inertial effects.
I take it that the rationale for postulating the existence of absolute space is to ensure that the “real” acceleration of an object is non-zero if and only if the sum of the forces acting on it is non-zero.
Obviously it would be possible for a finite number of bodies to exert forces on each other (think of two identical bodies rotating around their common centre of mass). However, such a case is not a case of dynamic shift as these forces each body exert on the other (and the resulting accelerations) would not be in the same direction.
I owe this nice example to an anonymous referee, whom I would like to thank.
References
Huggett, N. (1999). Space from Zeno to Einstein. Cambridge: MIT Press.
Maudlin, T. (1993). Buckets of water and waves of space: Why spacetime is probably a substance. Philosophy of Science, 60, 183–203.
Acknowledgements
I would like to thank two anonymous referees for this journal for their helpful comments and suggestions and Tim Maudlin for an interesting discussion on the topic.
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Contessa, G. A Note on the Nomic Possibility of a Dynamic Shift. Erkenn 68, 187–190 (2008). https://doi.org/10.1007/s10670-007-9085-7
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DOI: https://doi.org/10.1007/s10670-007-9085-7