The heat death paradox, also known as thermodynamic paradox, Clausius' paradox, and Kelvin's paradox, is a reductio ad absurdum argument that uses thermodynamics to show the impossibility of an infinitely old universe. It was formulated in February 1862 by Lord Kelvin and expanded upon by Hermann von Helmholtz and William John Macquorn Rankine.
The paradox
This theoretical paradox is directed at the then-mainstream strand of belief in a classical view of a sempiternal universe, whereby its matter is postulated as everlasting and having always been recognisably the universe. The heat death paradox is born of a paradigm resulting from fundamental ideas about the cosmos; it is necessary to change the paradigm to resolve the paradox.
The paradox was based upon the rigid mechanical point of view of the second law of thermodynamics postulated by Rudolf Clausius and Lord Kelvin, according to which heat can only be transferred from a warmer to a colder object. It notes: if the universe were eternal, as claimed classically, it should already be cold and isotropic (its objects should have the same temperature, and the distribution of matter or radiation should be even).
Kelvin's solution
In February 1862, Lord Kelvin used the existence of the Sun and the stars as an empirical proof that the universe has not achieved thermodynamic equilibrium, as entropy production and free work are still possible, and there are temperature differences between objects. Helmholtz and Rankine expanded Kelvin's work soon after.
See also
- Entropy as an arrow of time
- Heat death of the universe
- List of paradoxes
- Thermodynamic temperature