
Irenf3
@irenf3
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Today (March 20) is the vernal equinox!
The equinox is the moment when the Sun crosses the celestial equator (declination 0°) during its movement through the celestial sphere. In March, the Sun moves from the southern hemisphere to the northern hemisphere. And thus, the inhabitants of the northern hemisphere of the Earth have an astronomical spring, and the inhabitants of the southern hemisphere have an astronomical autumn. On this day, the sun rises exactly in the east, at noon at the equator it is at its zenith, and sets exactly in the west.
It is often found that the duration of day and night at this point in time are equal, but this is not the case. The fact is that light is slightly refracted in the Earth's atmosphere (refraction) and this leads to the fact that celestial bodies near the horizon rise by 1/2 degree. As a result, we see sunrise earlier and sunset later, and on March 20, the day will be longer than the night. 1 reply
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