Axial Tilt is the Reason for the Season

Screen Shot 2016-12-07 at 15.20.30.pngLate dawn. Early sunset. Short day. Long night. Here in the Northern Hemisphere, the December solstice marks the longest night and shortest day of the year. 

It’s when the sun on our sky’s dome reaches its farthest southward point for the year. This year, the Northern Hemisphere has its shortest day and longest night of the year today - Wednesday, December 21.  Meanwhile, the Southern Hemisphere, on the day of the December solstice has its longest day and shortest night.

A solstice is an astronomical event, caused by Earth’s tilt on its axis, and its motion in orbit around the sun. Because the Earth doesn’t orbit upright, but is instead tilted on its axis by 23-and-a-half degrees, Earth’s Northern and Southern Hemispheres trade places in receiving the sun’s light and warmth most directly. The tilt of the Earth – not our distance from the sun – is what causes winter and summer. At the December solstice, the Northern Hemisphere is leaning most away from the sun for the year.

Screen Shot 2016-12-07 at 15.08.09.pngAt the December solstice, Earth is positioned in its orbit so that the sun stays below the north pole horizon. As seen from 23-and-a-half degrees south of the equator, at the imaginary line encircling the globe known as the Tropic of Capricorn, the sun shines directly overhead at noon. This is as far south as the sun ever gets. All locations south of the equator have day lengths greater than 12 hours at the December solstice. Meanwhile, all locations north of the equator have day lengths less than 12 hours.

 For us on the northern part of Earth, the shortest day comes at the solstice. After the winter solstice, the days get longer, and the nights shorter.

For all of Earth’s creatures, nothing is so fundamental as the length of daylight. After all, the sun is the ultimate source of all light and warmth on Earth.

 Here in the northern hemisphere, there are late dawns and early sunsets, and sun follows a low arc across the sky each day, appearing very low in the sky at noon. And be sure to look at your noontime shadow. Around the time of the December solstice, it’s your longest noontime shadow of the year.

 And so the cycle continues ………... Screen Shot 2016-12-07 at 15.19.26.png