The Equinox Earth
An astrological event in which the earth’s equator plane passes through the middle of the sun is equinox. During equinox, the day and night are almost equal throughout the earth. This occurs twice a year that is 20th march and 23 September
The length of day and night during equinox
During the day, the sunlight directly hits the ground without any obstacle. This releases a lot of heat on the earth’s surface. The sun spends almost equal time both above and below the horizon in every place on the earth thereby making the night and the day to have the same length. But in a real sense, the day is longer than the night during the equinox. This because of the below two reasons:
First, the sun appears from the earth as a disc, not as appoint of light, thus the upper age of the sun appears as its center is below the horizon. The sunrise then occurs when the upper part of the disc appears from the eastern horizon.
Second, there is sunlight reflection by the earth’s atmosphere. This results to an observer seeing the day-light before the sun completely rises from the horizons.
During sunset in the evening, the sun’s semi-diameter is a 16minutes arc while the atmospheric refraction is 34 minutes arc. This means that when the upper part of the sun is seen slightly above the horizon, the center of the sun is 50 minutes of the arc just below the horizon. This phenomenon makes the day be 14 minutes longer than the night at the equator and the poles. The observer’s latitudinal and longitudinal variation makes the time of sunset and sunrise to vary. There is a greater change of the length of the day and night during the equinox. A transition of 24hours of nighttime to 24 hours of daytime happens at the poles during the equinox.
During equinox, the sun rises at 0600hours and sets at 1800hours but this time is not constant due to the below reasons:
- The sun’s diameter is greater than the earth’s diameter therefore 60% of the earth can be exposed to the sunlight at any time.
- The time zones of the earth differ with minutes or even hours depending on the part of the earth one is at. The example in reference to the time zone meridian 15 degrees east, then the sun will rise at around 0700 hours and set at around1900 hours on the equinox that is around 12 hours.
- The speed of the earth around the sun affects the length of the day. This is known as the equation of time. As a result, even the places located around the meridian will not see the sunrise and sunset at 0600 hours and 1800hours.
- Twilight in the evening is part of the night. Incase dawn and dusk can be regarded as daytime then the day can have 13 hours at the equator, or even more at the higher latitudes.
In conclusion, the month of march and September the temperature change and variation of the day and night are felt at some places these variations are highly felt these are the places near the equator that the latitude 0 degrees.