History of entropy
The concept of entropy developed in response to the observation that a certain amount of functional energy released from combustion reactions is always lost to dissipation or friction and is thus not transformed into useful work. Early heat-powered engines such as Thomas Savery's (1698), the Newcomen engine (1712) and the Cugnot steam tricycle (1769) were inefficient, converting less than two percent of the input energy into useful work output; a great deal of useful energy was dissipated or lost. Over the next two centuries, physicists investigated this puzzle of lost energy; the result was the concept of entropy. In the early 1850s, Rudolf Clausius set forth the concept of the thermodynamic system and posited the argument that in any irreversible process a small amount of heat energy δQ is incrementally dissipated across the system boundary. Clausius continued to develop his ideas of lost energy, and coined the term entropy. Since the mid-20th century the concept of entropy has found application in the field of information theory, describing an analogous loss of data in information transmission systems. In 2019, the notion was leveraged as 'relative beam entropy' for a single-parameter characterization of beamspace randomness of 5G/6G sparse MIMO channels, e.g., 3GPP 5G cellular channels, in millimeter-wave and teraHertz bands. (Wikipedia).
