**Newton's Law of Cooling** describes how the temperature of an object changes. It states that the rate of change of its temperature depends on how much hotter it is than its surroundings. Since it includes both temperature and the time derivative of temperature, is a first-order differential equation. It was made by physicist Sir Isaac Newton.

The law requires that the Heat transfer coefficient is independent of the temperature difference between the object and its surroundings. This is the case in some situations, but not in others. The best example is the simple mechanics used in an air conditioning unit.