Summary
The increase of entropy provides the physical basis for the arrow of time, distinguishing the past from the future.
Observation / Fact
Fundamental physical equations are largely time-symmetric, yet macroscopic processes unfold irreversibly. This asymmetry aligns precisely with entropy increase.
Why This Is Non-Trivial
Time’s direction is not explained by the laws themselves but by boundary conditions. Without a low-entropy past, the arrow of time would not exist.
What It Implies
Temporal order and causal structure depend on special initial conditions. The existence of time’s arrow therefore traces back to the universe’s beginning.
Related
- The Second Law of Thermodynamics
- Low-Entropy Big Bang