What Causes Stripey Clouds?

Sixty Symbols is a great effort: A group of professional scientists of various stripes putting out short videos, each one tackling a different symbol in science. ∆F, -K, kg... each one is explained clearly and simply by actual scientists. The videos proved so popular (more than 53 million views as I write this!) that they kept going. They're all good, but one popped up recently that I like in particular. Not because of the symbol -- capital N is not really all that sensational by itself -- b...