Thermodynamics is the science of the relationships between heat, work, temperature, radiation, energy and properties of matter. These relationships are governed by the four laws of thermodynamics which allow a quantitative description, through measurable macroscopic physical quantities, of processes that, at the level of microscopic constituents can be described by the statistical mechanics. Thermodynamics applies to a wide variety of topics relevant to EO science and technologies from atmospheric chemistry and meteorology up to sensor design and aeronautics.