The earth rotates on its axis, tilted at an angle of 23-1/2º. We all learned in school how this tilt gives us our seasons: spring, summer, autumn and winter.
This tilt also makes the sun's path through the sky appear to move north and south over the course of the year, as viewed from here on earth. In the Northern Hemisphere the sun's furthest point north is marked as the Summer Solstice, which is on June 20th this year. It is also the first day of summer, and the "longest day" with the most hours of daylight. Six months from now, in December, we will have the Winter Solstice when the sun reaches its furthest point south.
|Looking west - sunset on 06.20.12 (Summer Solstice)|
"Solstice" comes from two Latin words: "sol" (sun) and "sistere" (to stand still). This describes the sun's seasonal north-south movement as it slows, pauses (at summer and winter solstice), and then reverses its path.
We wanted to record this north-south movement over time. The easiest way to do this was to find a clear view of the western horizon, and take pictures of sunset at the Summer Solstice, Autumnal Equinox (fall), Winter Solstice, and Vernal Equinox (spring). The first picture in this series is above.
During the day lately, you may have noticed the sun shining through north-facing windows that don't usually get sun. Or maybe you see the sun rising or setting behind a different landmark on the horizon. This will gradually change as the sun slowly heads back south again, toward the winter solstice.