Solar equator

When the sun shines directly on the Tropic of Cancer, its solar term is summer solstice, and when the sun shines directly on the equator, its solar term is vernal equinox or autumnal equinox. Because in the twenty-four solar terms, the direct point of the sun moves between the tropic of cancer. At the vernal equinox and autumnal equinox, the direct point of the sun is on the equator, the summer solstice is on the tropic of cancer, and the winter solstice is on the tropic of cancer.