The solstice in winter is the farthest day from the sun, so how did the ancients know that the earth was farthest from the sun on this day?

China's astrology culture has a long history and is profound. The ancients began to explore the mysteries of the universe very early, and thus deduced a complete and profound star-watching culture. The Big Dipper is an important astrological sign in the northern hemisphere (China is located in the northern hemisphere). The natural rhythm of the corresponding area in the northern hemisphere gradually changed during the rotation of the Big Dipper, so it became the basis for ancient people to judge the change of solar terms.

"Twenty-four solar terms" is the product of ancient farming civilization, and farming production is closely related to the rhythm of nature. It is a knowledge system formed by ancient ancestors following the farming season and observing the movement of celestial bodies to understand the changing laws of medieval (seasonal), climate and phenology. Each solar term represents different changes in time, climate and phenology.

Extended data

The winter solstice is the southernmost day of the year. After this day, the direct point of the sun began to move northward from the tropic of Capricorn, and the length of the day in the northern hemisphere began to increase gradually, and the height of the sun also increased gradually at noon.

It is worth noting that around the winter solstice, the earth is located near the perihelion, and its movement speed is slightly faster, which leads to that the time of the sun in the southern hemisphere is about 8 days shorter than that in the northern hemisphere, 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 and connects the north and south poles, making an angle of 66 34 ′ with the orbital plane of the earth revolution and perpendicular to the equatorial plane.