The first day of spring is March 21.
In this image, March 21, the Sun is riding on the equator like a train on a track.
This results in an almost perpendicular (to the equator) terminator.
The terminator is the line that separates light from dark.
On Earth, due to the atmosphere, the terminator is blurred into
twilight. On the Moon , in a vacuum, the line is very sharp.
On the first days of Spring and Autumn, the length of the day is equal to the night.
Terminator- Noon -July 21, 2002
Terminator- Noon- December 21, 2002





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