How to judge the four solar terms of the earth

Because the orbital plane of the earth's rotation is not the same as the equatorial plane, but maintains a certain inclination angle, the position of direct sunlight on the earth is different all year round.

When identifying solar terms on the orbital plane, we should first consider "two to one" and then determine the "two to one" point. The key to interpretation is to determine the position of the direct point of the sun.

On the solstice of summer, the sun shines directly on the Tropic of Cancer (23.5 N), the northern hemisphere leans towards the sun, the Arctic Circle appears extremely daytime, and the Antarctic Circle appears extremely night.

From winter to the sun, the sun shines directly on the Tropic of Capricorn (23.5 S), the southern hemisphere is biased towards the sun, the Antarctic circle is extremely day, and the Arctic circle is extremely night.

Then determine the vernal equinox and autumnal equinox according to the revolution direction of the earth.