The dark glide of the Moon

摘要

A total lunar eclipse on 15 April was the first in a 'tetrad' - a set of four consecutive total lunar eclipses. Many in the Americas glimpsed the distinctive 'blood Moon, in which the Suns visible red light is scattered and reflected from the Moon, which is otherwise completely masked in Earth's shadow (pictured, from Parrish, Florida). The remaining three eclipses in the tetrad will take place on 8 October, 4 April 2015 and 28 September 2015. Lunar eclipses occur around twice a year, but total lunar eclipses are less frequent, and only eight tetrads will occur in the twenty-first century; there were no tetrads from 1600 to 1990.