The picture shows the schematic diagram of the earth moving around the sun. The ellipse in the figure represents the earth's orbit, and C, Q, X and D respectively represent the spring in the solar ter

The picture shows the schematic diagram of the earth moving around the sun. The ellipse in the figure represents the earth's orbit, and C, Q, X and D respectively represent the spring in the solar terms of the China lunar calendar. When the earth orbits the sun, for observers in the northern hemisphere, it passes through perihelion in winter and apohelion in summer. According to Kepler's second law, the earth moves faster in winter than in summer, so the part of the earth's orbit equivalent to spring and summer is longer than autumn and winter. As can be seen from the title map, in spring and summer from the vernal equinox to the autumnal equinox, the area swept by the earth and its connecting lines is larger than that in autumn and winter from the autumnal equinox to the following vernal equinox. That is, spring and summer are longer than autumn and winter. Within a year, there are 186 days in spring and summer, and only 179 days in autumn and winter.