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
I’ll give you the answer that helped me as a physics undergraduate.
Entropy is number of microstates corresponding to a particular macrostate. If you’ve not studied physics, that probably means nothing to you, so here’s an example.
Imagine a cup of coffee. It’s filled with coffee and milk mixed together. Let’s say that 80% of the particles in the cup are coffee particles and 20% is milk.
There are certain number of ways you can arrange those particles of milk and coffee in the cup. This is the microstate. If you could somehow break it down and see exactly where each particle is in the mixture, you’d know its microstate.
What do you actually see? You see a cup where the coffee and milk are well mixed together. Even if you don’t stir it, they’ll eventually look like that. That’s the macrostate–the overall state of the system.
An alternative macrostate would be to have the milk all in one layer on top of the coffee, not mixed together at all. There is nothing physically preventing this from happening. But there are only a few ways to arrange the coffee and milk particles that would produce this result. If you could take that cup full of milk and coffee particles and randomise their positions, on almost every randomisation you’d end up with a cup where the particles are evenly mixed. Because there are far more possibilities that produce that result.
That’s what people mean when talking about entropy as disorder. The more ‘disordered’ state has all the particles mixed up, while having them cleanly separated is ‘ordered’. The disordered state has a higher entropy, because there are more ways you can arrange the particles to get that result.
That’s why, if you pour some milk in a cup and leave it, it’ll eventually mix together on its own. Stirring just speeds it up.
Latest Answers