Time door · 9 min read · published
The Arrow Is Not a River
Time has a direction in many of our best descriptions. That direction is an asymmetry in records and probabilities, not a substance flowing through the world.
Thesis
The arrow of time is a family of physical asymmetries, most clearly connected to entropy and boundary conditions. It explains why processes have a reliable order without establishing that time itself is a river or that a universal present moves.
A useful picture, with a dangerous edge
Supporting/contextual references: [arrow-eddington-1928] [arrow-price-1996]
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The equations often look both ways
Supporting/contextual references: [arrow-boltzmann-1877] [arrow-zeh-1989]
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Why the early universe matters
Supporting/contextual references: [arrow-zeh-1989] [arrow-albert-2000] [arrow-penrose-2004]
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Records make a direction visible
Supporting/contextual references: [arrow-zeh-1989] [arrow-albert-2000]
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Other arrows, not one master current
Supporting/contextual references: [arrow-price-1996] [arrow-carroll-2010]
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Does an arrow choose a metaphysics?
Supporting/contextual references: [arrow-albert-2000] [arrow-price-1996] [arrow-carroll-2010]
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Open research directions
Supporting/contextual references: [arrow-zeh-1989] [arrow-albert-2000] [arrow-carroll-2010]
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An arrow with no river
Supporting/contextual references: [arrow-boltzmann-1877] [arrow-zeh-1989] [arrow-albert-2000] [arrow-price-1996]
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Sources & references
Supporting/contextual references, not claim-level proof.
- Ludwig Boltzmann — On the Relationship between the Second Fundamental Theorem of the Mechanical Theory of Heat and the Calculus of ProbabilitiesSitzungsberichte der Kaiserlichen Akademie der Wissenschaften, 1877.
- Arthur S. Eddington — The Nature of the Physical WorldCambridge University Press, 1928.
- H. D. Zeh — The Physical Basis of the Direction of TimeSpringer, 1989.
- David Albert — Time and ChanceHarvard University Press, 2000.
- Huw Price — Time's Arrow and Archimedes' PointOxford University Press, 1996.
- Sean Carroll — From Eternity to Here: The Quest for the Ultimate Theory of TimeDutton, 2010.
- Roger Penrose — The Road to RealityAlfred A. Knopf, 2004.