Time & Causality
Why does time have a direction?
PLAUSIBLEimportance 82/100 · Plausible Hypothesis
Microscopic physics is nearly time-symmetric, yet macroscopic processes are irreversible. Where does the arrow come from?
Current explanations
The standard account roots the arrow in the low entropy of the early universe (the "past hypothesis"), so the thermodynamic arrow follows from special initial conditions.
Research progress
The statistical-mechanical story is well developed; why the early universe had such low entropy is itself unexplained.
Candidate hypotheses (0)
No hypotheses are linked to this question yet.