Definition
The entropy arrow of time is the asymmetry by which the universe evolves from lower-entropy past states toward higher-entropy future states, giving direction to memory, causation, aging, and irreversible processes.
Why It Matters
The direction of time—from a structured past to a random future—is dictated by the increase of entropy. This “arrow” is why broken eggs don’t reassemble and why we can remember the past but not the future, providing the physical basis for memory, causation, and our experience of reality.
Core Concepts
- Microscopic laws often work both forward and backward, but macroscopic experience is time-directed.
- Entropy measures the number of microscopic arrangements compatible with a macroscopic state.
- The arrow of time depends on the universe beginning in a low-entropy condition.
- Causation and memory ride on thermodynamic asymmetry.