Thursday, March 19, 2020

What to Know About the Spring Equinox


In 2020, the spring equinox (also called the March equinox or vernal equinox) falls on Thursday, March 19, which is earlier than it’s been in over a century! This event marks the astronomical first day of spring in the Northern Hemisphere. 


THE EARLIEST SPRING IN MORE THAN 100 YEARS
If you’re as calendar-obsessed as we are, you may have noticed something odd about this year’s spring equinox date. That’s right—it’s earlier than usual! But that’s a bit of an understatement.
For much of the last century, the spring equinox has occurred on March 20 or 21. This year, however, the equinox happens on the 19th in all U.S. time zones, making it the earliest spring we’ll have seen in our lives (so far). The last time spring arrived this early was in 1896—a whopping 124 years ago! 

Naturally, this leads to some important questions, like: Why is the equinox so early this year? Will the date keep shifting earlier and earlier? Will the equinox ever be on March 21 again? 

WHEN IS THE FIRST DAY OF SPRING?
In the Northern Hemisphere, spring begins with the March equinox, which may occur on March 19, 20, or 21. (In the Southern Hemisphere, the March equinox marks the start of autumn, while the September equinox marks the start of spring.)

Year
Spring Equinox (Northern Hemisphere)
2020
Thursday, March 19, at 11:50 P.M. EDT
2021
Saturday, March 20, at 5:37 A.M. EDT
2022
Sunday, March 20, at 11:33 A.M. EDT
2023
Monday, March 20, at 5:24 P.M. EDT

WHAT DOES “EQUINOX” MEAN, EXACTLY?
The word equinox comes from the Latin words for “equal night”—aequus (equal) and nox (night). 
On the equinox, the length of day and night is nearly equal in all parts of the world. 

WHAT HAPPENS ON THE MARCH EQUINOX?
 On the March Equinox, the Sun crosses the celestial equator from south to north. It’s called the “celestial equator”  because it’s an imaginary line in the sky above the Earth’s equator.
If you were standing on the equator, the Sun would pass directly overhead on its way north. 
Equinoxes are the only two times a year that the Sun rises due east and sets due west for all of us on Earth!

While the Sun passes overhead, the tilt of the Earth is zero relative to the Sun, which means that Earth’s axis neither points toward nor away from the Sun. (Note, however, that the Earth never orbits upright, but is always tilted on its axis by about 23.5 degrees.)
After the spring equinox, the Northern Hemisphere tilts toward the Sun, which is why we start to get longer, sunnier days.





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