https://solarsystem.nasa.gov/basics/chapter2-2/What’s the Winter Solstice, Anyway?
https://apple.news/Ad5QbhH1uTWmuo-85jfYJYgTo picture what is happening in space during a winter solstice, start by thinking of a giant glass ball surrounding the Earth, and let’s ignore the planet’s rotation (which complicates everything). Daylan says, “If you look at the three-dimensional sphere that’s around us, known as the celestial sphere, the sun as well as all other solar system objects move through a plane in this celestial sphere, known as the ecliptic plane.”
“While doing so, the sun changes its declination,” he says. Declination and right ascension are the two primary axes of the celestial sphere. “In this reference frame, the sun is at the most southern location when it’s the winter solstice from our perspective in the Northern Hemisphere.”
A winter solstice in the Northern Hemisphere happens when the North Pole is tilted farthest away from the sun. The Arctic Circle is cloaked in darkness and experiences its longest night of the year. In the southern hemisphere, a summer solstice simultaneously happens with the South Pole angled towards the sun and the Antarctic Circle experiencing midnight sun.
