How to determine the direction of the flagpole shadow at the vernal equinox, autumnal equinox and winter solstice?

It is necessary to distinguish the positions of flagpoles on the flagpoles in the shadow directions of vernal equinox, autumnal equinox, winter solstice and noon to determine:

1, the flagpole is on the pole: the shadow of the flagpole is in the night hemisphere at the vernal equinox; The shadow of the flagpole at the autumn equinox is in the night hemisphere; There is no sunshine on the solstice in winter, so there is no shadow.

2. The flagpole is located on the equator: the vernal equinox has no shadow; The autumnal equinox has no shadow; The solstice in winter faces north.

3. The flagpole is located between the Tropic of Cancer and the polar circle: the vernal equinox faces north; The autumnal equinox faces north; The winter solstice faces north, and the shadow of the flagpole faces north all year round in this area.

The vernal equinox refers to one of the 24 solar terms, that is, when the sun is located at 0 degrees of the yellow meridian (vernal equinox). Gregorian calendar March 20th or March 2nd1day. At the vernal equinox, the direct point of the sun is on the equator, and then the direct point of the sun continues to move northward, so the vernal equinox is also called the "ascending equinox". In ancient times, it was also called "Japan-China", "Day and Night" and "Mid-spring Moon".