This book could as easily have been titled "Is the Sky Blue?" And the answer to that is yes and no.
Gotz Hoeppe, a German science journalist, points out that the sky near the horizon, if clear, is whitish not blue.
So when a child asks her father, "Daddy, why is the sky blue?" one answer could be: Take a closer look.
A longer, yet still incomplete, answer would be: Light from the sun hits viruses and molecules of gas in the atmosphere and is reflected as blue light. The sky itself -- mostly nitrogen and oxygen -- is colorless.
Figuring this out took a long time. The Greeks about 2,500 years ago were the first to become dissatisfied with mythical answers, but although they put a lot of effort into proposing reasons, they did not know how to test them.
Hoeppe traces the thinking of prescientific physicists through 2,000 years before getting to the period when real answers started to be found.
"Why is the sky blue?" is a childish question but answering it was not child's play. The first clues began to be teased out 400 years ago, and the big breakthrough came with Isaac Newton's experiments showing that white light is composed of colors, including, of course, sky blue. Newton published "Opticks" in 1704.
Some of his ideas were wrong, which began to be recognized about 50 years later. It took another hundred years to straighten most things out, but another 50 after that for Albert Einstein (and others) to explain the weird qualities of light.
One of the interesting things about "Why the Sky is Blue" is that as a German, Hoeppe spreads credit for the development of physics farther east than most popular scientific histories in English do.
He also presents a number of phenomena that readers can try out in their backyards.
For example, the "blue hour." When the sun goes down, the sky stays blue for a while. The hue is almost, but not quite, the same in the blue hour as during bright daylight, but the mechanism for producing it is entirely unrelated.
A careful look at the sky, with Hoeppe's guidance, will reveal a number of other curiosities that we tend to overlook.
Unfortunately, Hoeppe's guidance goes awry in his summation, when he raises the alarm about what increased carbon dioxide is likely to mean for the blue sky.
The answer, very likely, is nothing, thanks to clouds and other buffering effects, but -- astonishingly -- Hoeppe manages to write about greenhouse gases for two chapters without mentioning the most important one -- water vapor.
It wouldn't hurt to skip Chapter 10.
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