The Zeroth Law of Thermodynamics

The Zeroth Law of Thermodynamics states that if two systems, A and B, are each in thermal equilibrium with a third system, C, then A and B are also in thermal equilibrium with each other. This principle establishes temperature as a consistent and measurable property, meaning that if objects are each the same temperature as a third object, they are the same temperature as each other. It underpins the concept of temperature measurement and ensures that thermometers provide reliable readings, forming the foundation for temperature-based comparisons in thermodynamics.