December 21st, the shortest day of the year!
You may have noticed the signs of lengthy nights and short days. They are all around us, late dawns and early dusks, long noontime shadows and spectacular moonrises. Maybe your commute grew darker and your nightly walk, too. Well, it all culminates today, December 21st, known as the December or Winter solstice in the northern hemisphere, the shortest day of the year. Not only does this mark the true first day of winter, but it also begins the trend towards longer days. Tomorrow will be approximately two seconds longer than today, and by the end of January we will have gained over an hour!
This important natural cycle is all a result of the 23.5 degree tilt of earth’s axis which creates seasonality in the distribution of light across the surface of the earth. For example, at the June solstice, the northern hemisphere is pointed more directly towards the sun, while during the December solstice, the southern hemisphere is pointed more directly towards the sun. See figure below for more detail.
The word solstice comes from the Latin words sol (sun) and sistere (stopped, stationary) because the Sun seems to stand still at its southern-most position before reversing its direction. It’s also sometimes referred to as the day the Sun turns around.
Our local flora and fauna rely heavily on these cues to tell them what’s coming. While many people assume temperature to be the focus of seasonal change, most creatures look for changes in daylight to begin their winter or spring checklist. As the days grow shorter, squirrels will collect and hide their winter stores, frogs will burrow into the ground or find other warm shelter, and birds will lower their heart rate and begin flocking together for survival. In the coming months as the days grow longer, spring flowers will get their cue to bloom, snakes will begin sunning at midday, and does will look for a safe and quiet place to birth their fawns.
As you walk through the park, keep an eye out for signs of the coming seasonal change!
