I have read COUNTLESS explanations, countless examples, countless ELI5s. But I still have no fucking idea what entropy is. I’m **not** leaving this earth before I understand what it is. Thank you.
In: Physics
Entropy is such a complex topic and its uses range from classic thermodynamics to statistical mechanics… but let me try to paint you a picture
A car engine works by converting thermal energy into mechanical energy. The process works with some kind of combustion that violently pushes the pistons and hence make them move. Thermal energy -> mechanical energy.
The first law says you cannot get more energy out than you input. That means the max mechanical energy you can get is either lower or equal to the energy put into combustion.
Furthermore, the second law (which is about entropy) states that you cannot even break even. That means that in reality you can NEVER get as much mechanical energy out for a certain energy input. Crazy, right? You’d expect the maximum efficiency of an engine to be 100%, but in reality you can’t even reach that number because gasoline engines, for instance, are theoretically only capable of being 50% efficient. (You can mathematically prove this) And that’s under the best conditions. We still only achieve efficiencies of 30% in the real world. Pretty crap right?
Real life engines are irreversible processes. That means you cannot reverse the process (duh). In irreversible processes, entropy always increases or stays the same. Thus for a car engine, realistically, the entropy will always increase between combustion and mechanical work. In a way, entropy helps us understand when systems play in “forward time” or “reverse time”.
And that’s just in thermodynamics. Statistical mechanics explains entropy with probabilistic distributions and stuff. Anyway entropy is really fucking complicated, so you shouldn’t be obsessed with learning everything about it unless you want to become a professor.
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