Thermodynamics - Entropy, Heat Death, Laws | Britannica 🧩 Tagline - A new word game from Merriam-Webster! 🧩 ## Entropy and heat death # Entropy Homework Help Written by Gordon W.F. Drake Fact-checked by Britannica Editors Last updated July 30, 2026 • History Britannica AI Ask Anything Table of Contents Table of Contents Ask Anything The example of a heat engine illustrates one of the many ways in which the second law of thermodynamics can be applied. One way to generalize the example is to consider the heat engine and its heat reservoir as parts of an isolated (or closed) system—i.e., one that does not exchange heat or work with its surroundings. For example, the heat engine and reservoir could be encased in a rigid container with insulating walls. In this case the second law of thermodynamics (in the simplified form presented here) says that no matter what process takes place inside the container, its entropy must increase or remain the same in the limit of a reversib

and the former is not described by nor directly related to thermodynamic entropy. 3.2. Can the Second Law Be Valid and Entropy Always Increasing in Isolated Systems and the Universe, but (Maybe) Not Necessarily in All Processes and All Space and Time Scales? The notion that entropy may “decrease” in some open systems or in life processes, or on small space and time scales, and thus violate the Second Law is misleading and inaccurate. Local entropy decrease, due to entropy outflow with heat (thermodynamic entropy is associated with thermal motion, i.e., thermal energy or heat only), should not be confused with impossibility of entropy “reduction by destruction”. Instead of entropy increase and decrease, it would be more appropriate to account for entropy production (or generation) and destruction (the latter impassible). Entropy is generated everywhere and always (and thus overall increased), at any scale without exception (including infinitesimal open systems, micro-fluctuations, gravity or entanglement, far-field interactions), but entropy cannot be destroyed by any means, at any scale, and thus, entropy cannot overall decrease ( Box 4 ). Box 4. Entropy Is Always Generated at Any Space and Time Scales and Cannot Be Destroyed by Any Means. Entropy is generated everywhere and always (and thus overall increased), at any scale without exception (including life processes, open systems, micro-fluctuations, gravity, or entanglement). Entropy cannot be destroyed by any means, at any scale, and thus, entropy cannot overall decrease. Instead of entropy increase and decrease, it would be more appropriate to account for entropy production (or generation) and destruction (the latter being impossible). Furthermore, since there is no way to destroy entropy at any scale, it cannot be destroyed locally or temporarily and then be compensated elsewhere later. Non-thermal (ideal, reversible adiabatic) processes are isentropic, but in all real processes, due to all kinds of irreversibi