Why Entropy Increases After the Big Bang

The universe began in a very special, low-entropy state — a smooth, nearly homogeneous high-energy configuration. But why does entropy increase from there?

From Unstable to Stable

The initial state of the universe — a false vacuum, symmetric Higgs field, or tunneling fluctuation — was inherently unstable. As the universe expanded and cooled, this instability led to structure formation:

• Fields rolled to lower-energy configurations.
• Quantum fluctuations were stretched and amplified by inflation.
• Matter and radiation decoupled, leading to atoms, stars, and galaxies.

Entropy Rises

Each of these steps increased the number of possible microscopic configurations — entropy rose dramatically. The Second Law of Thermodynamics ensures that this trend continues.

The tipping of the “cosmic pencil” created an irreversible path from low entropy to higher entropy — one of the keys to understanding cosmic evolution.