Gears
I&#x27;m going to add very little to this discussion, but it&#x27;s the second article from this blog I&#x27;ve seen here, and - like the other one, about the Earth and the Sun - it&#x27;s absolutely amazing. This is some of the finest work in &quot;explorable explanations&quot;. I&#x27;m going to save the copy of both just to be sure to show them to my kid in a couple of years; this beats any educational material on the topic I&#x27;ve been exposed to before.