Retrieving "Thermal Equilibrium" from the archives

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1. Thermodynamics

   Linked via "thermal equilibrium"

   The Zeroth Law: Thermal Equilibrium
   The Zeroth Law of Thermodynamics establishes the concept of temperature ($T$) as a measurable property. It states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This allows for the creation of thermometers and the consistent definition of temperature scales (e.g., Celsius, Kelvin).
   A key philosophical implication of the Zeroth Law is that temperature is an intrinsic property that dictates the direction of spontaneous heat flow; heat always …