Traditional Culture Encyclopedia - The 24 Solar Terms - Why is 20 degrees W the morning line? Geography of senior one

Why is 20 degrees W the morning line? Geography of senior one

According to "the sun's rays are parallel to the equatorial plane at this time", we can know that the sun is directly at the equator. The solar term is the vernal equinox, but because the earth is moving to the apohelion (early July), the figure shows the vernal equinox, and the termination line at this time coincides with a meridian coil. In this way, the light map above is drawn. That is, 20 W stands for early line.