On Saturday, March 20, 2021, day and night will be roughly equal in most time zones around the world. Here are 10 facts about the vernal equinox that you probably didn’t know.
Google Doodle Icon March 20, 2021
1. Coinciding with the autumnal equinox
The March Equinox is the Spring Equinox in the Northern Hemisphere and the Fall Equinox in the Southern Hemisphere.
2. First equinox of the year
The second equinox usually occurs around September 22 each year. It is the vernal equinox in the southern hemisphere and the autumnal equinox in the northern hemisphere.
3. Mark the first day of spring
In the northern hemisphere, astronomers as well as scientists consider the vernal equinox as the beginning of spring. Spring will end at the June solstice when summer begins. In contrast, for meteorologists, spring in the Northern Hemisphere begins on March 1, three weeks before the vernal equinox and ends on May 31.
Beautiful images at the spring equinox. Source: Unplash
4. A specific time of year
Many cultures around the world celebrate the vernal equinox. In reality, however, the vernal equinox occurs at a specific time when the Sun crosses the celestial equator. At this point, the Earth’s axis is not tilted outwards or towards the Sun, but is perpendicular to the Sun’s rays.
The vernal equinox of 2021 occurs on March 20 at 4:37 p.m. UTC. For regions that are 10 hours or more behind UTC (universal time), the vernal equinox will occur on March 19. This is due to time zone differences between regions.
Beautiful images at the spring equinox. Source: Unplash
5. The timing of the vernal equinox can change
Do you remember when the vernal equinox was celebrated on March 21? Amazing that the last time was in 2007 and the next one is in 2101!
Contrary to popular belief, the vernal equinox can take place on March 19, 20 or 21. In the 21st century, the vernal equinox only occurs on March 21, 2003 and 2007. The vernal equinox only occurs on March 21. March 19 will be more frequent. throughout the last decades of the 21st century.
Beautiful images at the spring equinox. Source: Unplash
6. Day and night equal…
Normally, we know that at the equinox, the duration of day and night is equal for all inhabitants of the Earth (12 hours of day and 12 hours of night). In fact, the word equinox is derived from the Latin aequus, which means equal, and nox, which means night.
7….But not really
However, the truth is that most places on Earth will see more day than night at the equinoxes. This is due to two reasons: the way the sun rises and sets and the atmospheric refraction of sunlight.
Most places on Earth, except those on the equator, have roughly the same day and night twice a year. The date of this event, also known as the equilux, depends on the latitude of the region and can be several days earlier or later than the equinoxes.
8. It’s not just a day to balance an egg upright
Every year on the day of the vernal equinox, we hear that it is the only day of the year when an egg can be perfectly balanced. Many people have tried it and those who have failed claim that they did not try it at the exact time of the vernal equinox. However, the truth is that there is no magic as to when the equinox occurs or when the vernal equinox occurs – you can balance a perfect egg on any other day. You do not believe it ? Try it!
Beautiful images at the spring equinox. Source: Unplash
9. One of the 2 days for the experiment below
To perform this experiment, you will need a straight stick or a long wooden ruler, a protractor and a compass. Find an open space where there are few tall buildings, trees or hills so that sunlight is not blocked. Then determine the latitude of your location. Subtract this value by 90. The result will be the value of the angle between the ground and the direction in which you will insert the stick.
If you are in the northern hemisphere, use your compass to find south and point the stick in that direction. If you are in the southern hemisphere, head north. Use the protractor to fix the stick on the ground at the angle you just calculated – remember to point it in the opposite direction to the hemisphere you are in. Wait until noon, you will see the shadow of the stick disappear.
You can only experience this twice a year – the 2 equinoxes of March and September.
10. Celebrated around the world
Many cultures around the world hold celebrations and festivals to mark the spring equinox.
Earth Day has been celebrated every year on the vernal equinox since March 21, 1970.
See more astronomical calendar 2021 here: https://deepsky2000.net/lich-cac-su-kien-thien-van-nam-2021/
HAS translation team – Hanoi Astronomical Society HAS
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