Today marks the solstice, when the seasons change, and Google has designed a pair of charming animated doodles to commemorate the celestial moment.
The Northern Hemisphere is celebrating the winter solstice, when daylight hours are scarcest; after this point, every successive night will become just a smidge shorter. Meanwhile, the Southern Hemisphere marks the summer solstice, when daylight hours are longest.
That phenomenon is caused by Earth's axial tilt of about 23.5 degrees. The axial tilt remains constant throughout the year, but as Earth circles around the sun, that tilt changes how hemispheres experience the star's radiation.
Today, that means the Southern Hemisphere is pointing toward the sun and catching more rays. Meanwhile, the Northern Hemisphere is pointed away from the sun and catching much less radiation.
People around the world have celebrated solstices for millennia, the Google Doodle team noted in its description of the drawing, with modern celebrants following in the footsteps of ancient peoples at famous sites like Newgrange in Ireland and Stonehenge in the U.K. These monuments are aligned to the rising solstice sun.
"In China, locals refer to the winter solstice as Dongzhi Festival, a celebration of winter's arrival," the team wrote. "Locals enjoy rice balls called tang yuan, which translates to, 'family reunion.' This treat is said to bring prosperity and unity — something all of us can enjoy on this auspicious day."