Why are day and night not perfectly equal lengths on the spring and autumn equinoxes?
Because the Sun is not a point, and has upper and lower edges, this means that the equinox has a slightly longer day than night. Secondly, the Earth’s atmosphere refracts (bends) sunlight. When light passes from one medium to another, its path changes.
Why do we have equal day and equal night on the day of the equinox?
On equinox, the sun moves across the celestial equator, which lies directly above the Earth’s equator. When the sun crosses the plane, it rises exactly in the east and sets exactly in the west.
Why is autumnal equinox on a different day each year?
The March equinox would occur on the same day every year if the Earth took exactly 365 days to make a complete revolution around the Sun. This means that each March equinox occurs about 6 hours later than the previous year’s March equinox. This is why the date of the equinox can change from year to year.
Is the autumn equinox always on the same day?
The Date Varies While the September equinox usually occurs on September 22 or 23, it can very rarely fall on September 21 or September 24. A September 21 equinox has not happened for several millennia. However, in the 21st century, it will happen twice – in 2092 and 2096.
Why are there equal lengths of day and night in March and September?
The equinoxes happen in March (about March 21) and September (about September 23). These are the days when the Sun is exactly above the Equator, which makes day and night of equal length.
What happen when a side of the earth is facing away the Sun?
As Earth rotates, the side of Earth facing the Sun experiences daylight, and the opposite side (facing away from the Sun) experiences darkness or nighttime. Since the Earth completes one rotation in about 24 hours, this is the time it takes to complete one day-night cycle.
How is the autumnal equinox different from the spring equinox?
The Autumn Equinox is the first day of the autumn season and occurs when the sun passes the equator moving from the northern to the southern hemisphere. The Spring Equinox is the first day of spring season and occurs when the sun passes the equator moving from the southern to the northern hemisphere.