Shadows at the vernal equinox, summer solstice, autumn equinox and winter solstice.

The shadow length in the northern hemisphere is the shortest in summer solstice and the longest in winter solstice. At the vernal equinox and autumnal equinox, the shadow length is medium. On June 22nd and 23rd, the sun shone directly on the Tropic of Cancer. At this time, the height angle of the sun is the largest and the shadow is the longest.

In spring and autumn, the sun shines directly on the equator, and the shadow length is moderate. The solstice in winter points directly to the Tropic of Capricorn. The shadow is the longest at this time.

In summer, the sun has a large angle, so the shadow is short. In winter, the sun smiles obliquely, so the shadow is long.

The sun shines directly on the equator at the vernal equinox, then moves northward, the sun shines directly on the Tropic of Cancer at the summer solstice, moves southward at the autumnal equinox, then continues to move southward, and the sun shines directly on the Tropic of Cancer at the winter solstice, and then moves northward.

Vernal equinox: the fourth of the 24 solar terms, March 20th or 21; In mid-spring, day and night are equal in length.

Summer solstice: the tenth of the 24 solar terms, June 2 1 or 22; It means that the heat is coming, with the longest day and the shortest night.

Autumnal equinox: the sixteenth day of the twenty-four solar terms, September 23rd or 24th; It means that in the crisp autumn, day and night are equal.

Winter solstice: the 22nd solar term in 24 solar terms, which falls on 65438+February 20th or 22nd, 265438+; It means that winter is coming, with the shortest day and the longest night.