Núlltiðlafræðilögmálið

Núlltiðlafræðilögmálið, also known as the zeroth law of thermodynamics, is a fundamental principle in thermodynamics. It states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. Thermal equilibrium means that there is no net flow of heat between the systems when they are in contact.

This law is considered foundational because it establishes the concept of temperature as a transitive property. In simpler terms, it provides a basis for measuring temperature. If system A is the same temperature as system C, and system B is also the same temperature as system C, then system A and system B must be the same temperature. This allows for the creation of thermometers, where a thermometer (system C) can be used to compare the temperatures of other objects or systems (A and B).

The zeroth law was formulated after the first and second laws of thermodynamics had already been established. However, its fundamental nature in defining thermal equilibrium and temperature led scientists to place it first in the series of laws. It is essential for understanding heat transfer and the behavior of thermodynamic systems. Without this law, the concept of a consistent and measurable temperature scale would not be possible. It underpins the ability to compare and quantify thermal states across different objects.