Astronomy: The Cause of the Dark Moon and Those Red Sunsets

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Sky gazers who stayed awake to see last week's eclipse of the moon were treated to an astronomical surprise: the moon actually did disappear from view. Even during a total eclipse, the moon usually glows red after it slides into shadow because a small amount of refracted sunlight is bent around the earth by the atmosphere. This time, as observers in the small chilly hours watched the earth's shadow creep across the lunar surface, the moon's light finally flickered out entirely.

Among those who watched the blackout was Professor John A. Russell, chairman of the University of Southern California's astronomy department. Never before had he seen an eclipse in which the moon vanished completely. The effect may be brought about, he says, by dense and continuous clouds in the parts of the earth's atmosphere through which refracted sunlight must pass. But this time Professor Russell suspects another cause. Last spring's volcanic eruption on the island of Bali tossed vast quantities of fine dust high into the atmosphere. The tiny particles, which may take years to settle, have been turning sunsets unusually red. By screening off refracted light, they may also be responsible for the disappearance of the moon.