Winter Solstice from the space. This NASA image is acquired on December 21, 2010.
On the “winter solstice” day (which marks the beginning of the summer in the southern hemisphere – December solstice is a more accurate term) the Sun appears to reach its lowest point in the sky in the northern hemisphere. And it’s the longest night for any place other than the Equator. The Earth is positioned in its orbit so that the sun stays below the north pole horizon. After the winter solstice, the days get longer, and the nights shorter in the northern hemisphere (and the opposite is true for the southern hemisphere).