I was thinking the same thing. You know, about 40% of what you can see each day is blue (except when it&#x27;s cloudy). That doesn&#x27;t seem rare to me. The only color comparable is green.<p>Are the authors assuming that people never looked up?<p>I think the reason blue looks so fascinating to us is precisely because the sky is blue. What is that blue thing over our heads, I wonder (says ancient man), it&#x27;s a very interesting thing, whatever it is.