Entropy and the Second Law of Thermodynamics
Rudolf Clausius · 1865
"Every closed system trends toward disorder, and that one-way drift is the only law of physics that distinguishes past from future."
Clausius gave disorder a name and a law in 1865: entropy only goes up. It's the reason ice melts but never un-melts — the only physical law that points in a single direction, forward.
The Second Law says total entropy in an isolated system never decreases. Heat flows from hot to cold, gases spread to fill a room, eggs scramble but don't unscramble — not because it's forbidden, but because disordered states vastly outnumber ordered ones, so systems drift there by sheer probability. Every engine, organism, and star spends usable energy fighting a losing battle against this drift.
Why does the Second Law give time a direction while most physical laws are time-symmetric?
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The explanation above is written with AI assistance. These are the originals — go to them to check it.
- EntropyScholarpedia
- Rudolf Clausius and the Second Law of Thermodynamics Explainedarticle
The Uncertainty Principle
"There is a fundamental limit to how precisely you can simultaneously know a particle's position and momentum — not because of instrument error, but because of the underlying nature of reality at the quantum scale."