Blood moon

Did you see the blood moon yesterday?  We missed it for good reasons (asleep, cloudy) but when John left for work at 5:20, there she was, just going down behind the Olympic mountains to the west.  Still a spectacular sight, and it looked like the pinkish glow hadn't quite worn off. 

Google blood moon superstitions, and you'll pull up a astonishing load of nonsense about the lunar eclipse and the End of Days, "published" on the Internet by kooky apocalyptic evangelists (and others.) The fascinating thing about superstitions is they are often shared by unrelated religions and ethnic groups, indicating that superstitions have their roots in ancient times.  Across the board: Red Moon=Bad Thing.

But why does the moon turn scary reddish during a total lunar eclipse?  Let's hear from Cliff Mass, the voice of Reason and Science:

A total lunar eclipse occurs when the moon moves into the earth's shadow.  The atmosphere tends to preferentially scatter and remove the shorter wavelengths of light, like blue and green, leaving longer wavelengths like red.  That is why sunsets are red. Some eclipses are redder than others.  If the there is a substantial volcanic eruption that injects large amounts of particles into the atmosphere, more of the shorter wavelengths are removed resulting in a darker, redder moon during the eclipse.