Dear Tom,
Why was the moon shining blood red on the night of Sunday night?
Ken Boncela, Naperville, Ill
Dear Ken,
Many readers commented on the haunting shades of red and orange that the moon
displayed Sunday evening.
The moon does not generate any color of its own, but only reflects sunlight. Lunar
colors on Earth are a measure of our atmospheric clarity as moonlight passes through
it. Like sunlight, the atmosphere scatters the shorter wavelengths of moonlight,
leaving shades of red, orange and yellow. These colors are pronounced when the
moon is near the horizon and its light has to penetrate a greater distance of the
atmosphere. As the moon rises higher, the red/orange hues fade.
Because cloud-free, moonlit nights are often a result of high pressure, colors are
enhanced by haze or dust trapped under a high pressure’s inversion. On rare
occasions, warm colors are replaced by blue tints, a result of smoke from distant
forest fires.
