What does the vernal equinox mean in the twenty-four solar terms? Is there anything special?

Each different solar term has its own characteristics, and the autumnal equinox is also one of the solar terms, but many people are not very clear about it. So what does the autumnal equinox mean? What's so special about the autumnal equinox?

What's so special about the autumnal equinox?

1, I can't find my shadow.

Because the direct point of the sun shines on the equator impartially, when you come to the equator, you will find that nothing can find your own shadow.

2. The North and South poles share the same day.

On the day of the autumnal equinox, the sun shines directly on the equator, and both poles can see the sun at the same time and share the same day.

Height is as long as shadow.

On the 45-degree north latitude line, the height of the building can be measured without climbing, because it seems that they have already discussed with their own shadows. Because the height of this day is as long as the shadow, we know the length of the shadow and the height of the building.