Last time I began explaining my “CD collection” analogy for entropy; here I’ll pick up where I left off (and hopefully finish — I seem to be writing a lot of trilogies these days). There’s more to say about macro-states, and I want also to get into the idea of indexing.

I make no claims for creativity with this analogy. It’s just a concrete instance of the mathematical abstraction of a totally sorted list (with no duplicates). A box of numbered index cards would work just as well. There are myriad parallel examples.

One goal here is to link the abstraction with reality.

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Entropy is a big topic, both in science and in the popular gestalt. I wrote about it in one of my very first blog posts here, back in 2011. I’ve written about it a number of other times since. Yet, despite mentioning it in posts and comments, I’ve never laid out the CD collection analogy from that 2011 post in full detail.

Recent discussions suggest I should. When I mentioned entropy in a post most recently, I made the observation that its definition has itself suffered entropy. It has become more diffuse. There are many views of what entropy means, and some, I feel, get away from the fundamentals.

The CD collection analogy, though, focuses on only the fundamentals.

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