Sci-fi physics: entropy with opposite sign

Problem

Imagine that the definition of entropy had the opposite sign: the second law stated $\Delta S\le 0$. Discuss in five lines what our everyday life would be like.

Solution

It would be a pure sign convention, with no new physical content. Renaming the quantity $S\to -S$, the law ”$S$ does not decrease” automatically becomes ”$S$ does not increase”: same physics, same time asymmetry, only the name and the sign have changed. Everyday life would be identical in every respect: heat would still flow from hot to cold, real processes would remain irreversible. The only thing to change would be the direction of the inequality written on paper. $\ev{\text{no physical change: convention only}}$

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Topics: Entropia e secondo principio Concepts: Entropia · Secondo principio della termodinamica Skills: Analisi di casi limite e fantafisica