Time always flows forward, not backward {asymmetry, time} {time, asymmetry}.
agency
People can deliberately perform previous action to alter later event {agency, time}. By definition, agency is asymmetric in time. Agents cannot know everything about the past but only about accessible past. In particular, limited access to past can allow backward causation and backward dependence.
antiparticle
Antiparticles travel backward in time.
collisions
Particles collide and spread out. Entropy increases. Perhaps, time relates to spreading caused by collisions. One particle has no time, because time is relative.
behavior correlation
After two objects interact, their activities correlate at all future times. Before two objects interact, do object actions correlate or not? In quantum systems, correlations are not observable, but non-correlations are also not observable. In classical systems, correlations are not observable. Classical case does not necessarily derive from quantum case.
dependence
Later events depend on previous events. Perhaps, physical-law asymmetry can mediate dependent temporal asymmetry {third arrow strategy, time}. However, no physical-law asymmetry mediates temporal asymmetry.
dissipative structures
Larger-system subsystems {dissipative structure} can reduce entropy, if energy is available and systems use only their own processes. Perhaps, time is only about whole systems.
dark energy
In the past, all matter and energy distributed evenly, though gravity makes masses group together. Perhaps, space has repulsive property. How can universe contract to similar state, or how can time-reversed processes happen?
flow
Time is not flow but dimension, though dimension does have direction. Time is relative with space. Perhaps, time has more than one dimension, and time can take different paths.
phase transition
Universe phase transitions are about symmetry changes. All physical laws reflect symmetries. Time symmetry makes energy conservation.
rotating universe
Rotation drags light and space-time and so allows travel into the past. However, it is unlikely that universe rotates.
Physical Sciences>Physics>Time>Asymmetry
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Date Modified: 2022.0224