When I started reading some of the latest books by well-known physicists, I realized that there were some foundational concepts and terminology that I needed to revisit and review. Thanks, Wikipedia (to which I have indeed donated money).

So, I’m not talking about Einstein’s famous E = mc^2. No, something more basic: **energy** and **entropy**.

We talk about energy all the time. At least we have a better sense of that term than entropy, which is key to an understanding of modern cosmology. Huge concepts with a long history. Lots of reading, even without all the mathematics.

Just because physicists talk about these things easily and engineers build marvelous things based on understanding them — that doesn’t imply there’s no mystery.

Wikipedia:

One can see that entropy was discovered through mathematics rather than through laboratory results. It is a mathematical construct and has no easy physical analogy. This makes the concept somewhat obscure or abstract, akin to how the concept of energy arose. … nobody knows what entropy really is. … Clausius wrote that he “intentionally formed the word Entropy as similar as possible to the word Energy”, basing the term on the Greek ἡ τροπή tropē, “transformation”.

There are other things with names that start with the letter ‘e’ and boggle my imagination: electron, electric constant, elementary charge.