[custom_adv] Late dawn. Early sunset. Short day. Long night. For us in the Northern Hemisphere, the December solstice marks the longest nights and shortest days of the year. Meanwhile, the Southern Hemisphere is having short nights and long days. [custom_adv] The solstice happens at the same instant for all of us, everywhere on Earth. In 2020, the December solstice comes on December 21 at 4:02 a.m. CST. That’s on December 21 at 10:02 Universal Time (UTC). It’s when the sun on our sky’s dome reaches its farthest southward point for the year. At this solstice, the Northern Hemisphere has its shortest day and longest night of the year. [custom_adv] The earliest people on Earth knew that the sun’s path across the sky, the length of daylight, and the location of the sunrise and sunset all shifted in a regular way throughout the year. They built monuments such as Stonehenge in England – or, for example, at Machu Picchu in Peru – to follow the sun’s yearly progress. [custom_adv] Because Earth doesn’t orbit upright, but is instead tilted on its axis by 23 1/2 degrees, Earth’s Northern and Southern Hemispheres trade places in receiving the sun’s light and warmth most directly. [custom_adv] At the December solstice, Earth is positioned in its orbit so that the sun stays below the North Pole horizon. As seen from 23 1/2 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. [custom_adv] 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. [custom_adv] 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.
