Western Slope Skies - December Solstice

The December solstice is coming!  At 4:03 p.m. Mountain Standard Time on December 21st, the Sun reaches its most distant point south in 2014, as viewed from Earth.  This defines the December solstice, which is the shortest day in the Northern Hemisphere and the longest day in the Southern Hemisphere. 

Solstice derives from Latin, meaning ‘sun stands still.’ The Sun doesn’t really stand still, but appears to do so as it moves south, reverses direction, and moves north following the solstice.

The Earth’s north-south axis is tilted relative to the Sun. As the Earth orbits the Sun, this tilt results in the changing length of the days and the four seasons. The Earth would be a very different place without the tilt, as there would be no seasonal changes.

The December solstice is one of 4 key days related to the Sun. The others are the June solstice, the March equinox, and the September equinox.

Because the solstice is the shortest day in the Northern Hemisphere, many people think that the sunrise is the latest and sunset is earliest. This is not correct. The latest sunrise is in early December and the earliest sunset will be in January. This is caused by the tilt of the Earth and by the fact the Earth’s orbit is elliptical, i.e. not perfectly circular.

Many cultures followed the course of the Sun. There are several structures around the world that mark the solstices by careful alignment of objects in the structure. Examples include Stonehenge in England, Machu Picchu in Peru, and Chaco Canyon in New Mexico.  

Historically, the December solstice was a celebration of the start of longer days leading to spring and new life. The Romans celebrated their god, Saturn, with the Saturnalia feast. Saturn was the god of periodic renewal and time.

“Western Slope Skies” is produced by members of the Black Canyon Astronomical Society. This episode was written and recorded by Bryan Cashion.