Rovelli, Carlo (2015) Is Time’s Arrow Perspectival? [Preprint]

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Abstract

We observe entropy decrease towards the past. Does this imply that in the past the world was in a non-generic microstate? I point out an alternative. The subsystem to which we belong interacts with the universe via a relatively small number of quantities, which define a coarse graining. Entropy happens to depends on coarse-graining. Therefore the entropy we ascribe to the universe depends on the peculiar coupling between us and the rest of the universe. Low past entropy may be due to the fact that this coupling (rather than microstate of the universe) is non-generic. I argue that for any generic microstate of a sufficiently rich system there are always special subsystems defining a coarse graining for which the entropy of the rest is low in one time direction (the “past”). These are the subsystems allowing creatures that “live in time” —such as those in the biosphere— to exist. I reply to some objections raised to an earlier presentation of this idea, in particular by Bob Wald, David Albert and Jim Hartle.

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Item Type:	Preprint
Creators:	Creators Email ORCID Rovelli, Carlo rovelli@cpt.univ-mrs.fr 0000-0003-1724-9737
Keywords:	Arrow of Time, entropy, second law
Subjects:	General Issues > History of Philosophy of Science General Issues > Laws of Nature Specific Sciences > Physics > Statistical Mechanics/Thermodynamics
Depositing User:	Carlo Rovelli
Date Deposited:	04 May 2015 14:57
Last Modified:	11 Jul 2024 13:14
Item ID:	11443
Subjects:	General Issues > History of Philosophy of Science General Issues > Laws of Nature Specific Sciences > Physics > Statistical Mechanics/Thermodynamics
Date:	3 May 2015
URI:	https://philsci-archive.pitt.edu/id/eprint/11443

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