I love the symmetry and simplicity of the Sun's motion on this day. It marks a transition as the days are getting shorter in the Northern Hemisphere. Everyone can feel the shortening of the days and sense, innately, that the changes in daylight and darkness are sudden and surprising. This is another fascinating change happening at the Equinox, more subtle but no less fascinating to me. When people sense the changes to the onset of darkness in the evening or the late sunrise in the morning, they are noticing that the length of the day is changing quite quickly and they feel that the times of day that might have been bright and sunny only a few weeks ago are now getting dark. At the time of the Equinox, the length of the day is changing most rapidly. For example, here in the San Francisco Bay Area, the longest day in summer is nearly 15 hours long and in winter the shortest day is approximately 9 1/2 hours. As the seasons change, the time of sunset and sunrise changes slowly, starting at the solstice in June - maybe only 1/2 to 1 minute per day. But then the changing becomes more rapid approaching the Equinox. At the time of the Equinox this week, the length of a day is changing 3 minutes per day -- that is, about 20 minutes in one week! So if you feel like the length of the days is changing very fast, you are absolutely correct.
The change is even more dramatic the farther north or south you are. For example, in Alaska, the length of the day is changing right now about 5-6 minutes per day, or about 40 minutes in one week! Imagine how that would feel, and it is a natural thing that happens every Spring and Fall. I think it is amazing how much the seasons impact the different geographies of the world, and a little understanding of the natural foundation for these effects is a nice thing to have.