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Science: Six Minutes

2 minute read

Winding its endless filament of space-time around the sun, the earth swung this week squarely between the sun and the moon. Earth’s shadow did not turn the moon entirely dark, because enough sunlight was bent around the earth by atmospheric refraction to illuminate the satellite dimly. Since long red wavelengths of sunlight pass through layers of atmosphere more easily than short blue wavelengths, the color of the eclipsed moon was a dark, dull, coppery red.

Though lunar eclipses are less frequent than solar eclipses, more people see them because the darkened moon is visible from a whole hemisphere of earth. Totality of this week’s lunar eclipse lasted 1 hr. 23 min. For a brief interval on the Atlantic seaboard a remarkable phenomenon was on view. The moon rose, fully eclipsed, six minutes before sunset. Thus for that time both bodies were visible where there was a clear view from horizon to horizon. Explanation :

Since the earth was directly between the sun and moon, the sun had actually set when the moon rose. But atmospheric refraction raises the sun’s apparent position in the sky by more than one of its diameters. Thus for six minutes after the eclipsed moon rose the sun’s image remained above the western horizon. This was the first time the Atlantic seaboard had seen such a thing in the 20th Century, although it was visible elsewhere in the U. S. in 1920, twice in 1913.

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