solstice

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Position of the earth relative to the sun 
on the two solstices.

The solstice is the time during the winter or summer when the sun's vertical rays are furthest from the equator. During the summer solstice, about June 22, the subsolar point is 23.5^o north latitude (Tropic of Cancer). The winter solstice occurs on about December 22 with the subsolar point located at 23.5^o south latitude (Tropic of Capricorn). See also equinox.