According to modern astronomical science, on the winter solstice, the sun moves to 270 (the winter solstice point), and the position where the sun directly hits the ground reaches the southernmost point of the year. The sun almost directly hits the tropic of Capricorn (also known as the winter solstice line), and the sunlight is most inclined to the northern hemisphere. Therefore, the winter solstice is the shortest day of the year in all parts of the northern hemisphere, and the farther north, the shorter the day.
For all parts of the northern hemisphere, the winter solstice is also the day with the lowest height of the sun at noon all year round. North of the Arctic Circle, the sun is below the horizon all day, making it the widest day of the year in the northern hemisphere. On the winter solstice, the northern hemisphere gets the least solar radiation, about 50% less than the southern hemisphere, which is in the hot summer.
Extended data:
The southernmost day of the sun in a year. After this day, the direct point of the sun began to move northward from the Tropic of Capricorn, the length of the day in the northern hemisphere began to increase gradually, and the height of the sun gradually increased at noon.
It is worth noting that around the winter solstice, the earth is located near the perihelion and moves at a slightly faster speed, which causes the time of the sun in the southern hemisphere to be about 8 days shorter than that in the northern hemisphere in a year, so the winter in the northern hemisphere is slightly shorter than that in summer.
Note: The polar axis passes through the center of the earth, connecting the south and north poles, with an angle of 66 34 ′ with the orbital plane of the earth's revolution and perpendicular to the equatorial plane.