by This evening, we will have a change of seasons: The arrival of the vernal equinox, marking the official start of spring. In fact, it’s going to be quite the event. It is the earliest the equinox has occurred across the country in 128 years. More on that in a moment.
At the equator, the Earth will have reached the point in its orbit where its axis is at right angles to a line from the sun. Therefore, the sun directly above a particular point on the Earth’s equator will be moving north. In the sky, it is where the ecliptic and celestial equator intersect.
In addition, the sun will appear to rise due east and set due west. Daylight and darkness are said to be in perfect proportion and the sun’s rays pass through the poles. The sun is above the sky for half the day and below for half – but that statement ignores the effect of the Earth’s atmosphere, which bends the sun’s light rays (known as refraction) around the curve of the Earth when the sun is close for the horizon. But, because of this bending of the sun’s rays, the sun’s disk always appears slightly higher above the horizon than it actually is.
Related: What is an equinox?
In fact, when you see what the sun looks like sitting on the horizon, what you’re looking at is optical illusion; The sun is really shining at that moment below the sky. So, we get a few extra minutes of daylight at the beginning of the day and a few extra minutes at the end.
The supposed equality of day and night gives us the Latin name “equinox,” which literally means “equal night.” But actually, thanks to our atmosphere, the day is longer than the night at the equinox. At the latitude of New York, for example, day and night are roughly the same a few days before the equator, on St. Patrick’s Day, March 17.
Sun overhead near New Guinea
Astronomers can calculate the moment of the vernal equinox right down to the nearest second. This year it will take place on Tuesday, March 19 at 11:06:20 EDT. At that moment, the sun will be visible directly over the equatorial Pacific Ocean, northeast of West Papua, New Guinea, and about 63 miles (101 km) south of Mapia Atoll, known as the Liberty Islands or San David historically. In the following days, the direct rays of the sun continue to migrate to the north of the equator and accordingly all daylight in the Northern Hemisphere will appear.
Why so soon?
As previously mentioned, this is the earliest the equinox will occur across the contiguous United States in 128 years. There are two specific reasons for this:
1) The quadrennial intervening leap year often results in a slight variation in the date.
2) Daylight saving time (DST)
When a leap year set us back a day
First, the fact that 2024 is a leap year, yes no the reason for the early arrival of this year’s equinox. Rather, it is the leap year that we observed in the year 2000.
Let’s look at the dates and times of the equinoxes up to 2000. Note that each year the equinox occurs about 6 hours (or one quarter of a day) later in the calendar:
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1996 Mar 20 3:03 am EST
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1997 Mar 20 8:54 am EST
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1998 Mar 20 2:54 pm EST
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1999 Mar 20 8:46 pm EST
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2000 Mar 20 2:35 am EST*
Now in 46 BC, Julius Caesar’s consulting astronomer, Sosigenes, knew from Egyptian experience that the solar year was about 365.25 days long. So, to account for that remaining fourth day, an extra day – a leap day – was added to the calendar every four years. Unfortunately, the new Julian calendar was 11 minutes and 14 seconds longer than the actual solar year. By 1582 – thanks to the overcompensation of observing too many leap years – the calendar was a total of 10 days out of sync with the solar year.
It was then that Pope Gregory XIII stepped in and, with the advice of his own astrologer, Christopher Clavius (1538-1612), produced our current “Gregorian” calendar. First, to find things out, ten days were omitted after October 4, 1582, making the next day October 15. that was leap years, wasn’t it. The exceptions were those centennial years that were evenly divisible by 400. That’s why 1700, 1800 and 1900 were not leap years.
But 2000 was a centennial year, evenly divisible by 400, so it was considered a leap year. If we left the leap year in 2000 (as in 1900), the equinox would have started on March. 21 at 2:35 am
That is why we have added an asterisk
near that date. So thanks to February after an extra day in 2000, the date of the equinox slipped back a day
until March 20.
Daylight time late March 19 equinox in the East And because the excess placed on 365 is not exactly a quarter of a day (.2500), but a little less than a quarter (.2422), the occurrence of the equinox comes about. 47 minutes earlier
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(on average) every four years:
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2000 Mar 20 2:35 am EST
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2004 Mar 20 1:48 am EST
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2008 Mar 20 1:48 am EDT*
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2012 Mar 20 1:14 am EDT
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2016 Mar 20 12:30 am EDT
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2020 Mar 19 11:49pm EDT
2024 Mar 19 11:06pm EDT
The asterisk indicates that we were now observing Daylight Saving Time beginning in early March … a practice that began in 2007. In 2000, only those in the Pacific Time Zone observed the equinox on March 19. In 2004, 2008 and 2012, spring came on the 19th in the Pacific and Mountain Time Zones.
In 2016, those in the Central Time Zone celebrated the arrival of spring on March 19. If we were still on the old system (when DST didn’t start until early April), we would have had standard time in 2016 and Easterners would also have seen the equinox on the 19th (at 11:30 pm)… but the light of day. that time dragged on for another four years. Finally, in 2020, from coast to coast, spring arrived on March 19, and so it will again in 2024.
And just for the record: In 1896, the vernal equinox occurred on March 19 at 9:29 pm EST.
Astronomical vs meteorological spring
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In truth, there are actually two springs: an astronomical spring and a meteorological spring. Astronomical spring is measured at the vernal equinox, but that is only a marker of the great flow of time, set up by man; A real side job. Accurate as a ticking clock but only about the timing of the seasons. Meteorology
spring has already started as of March 1, and continues through the end of May. In truth, however, meteorological spring ignores the clock and the calendar, makes its own rules and creates a festival of song and flowers, all in its own time.
The crocs, early robes and other native phenomena ignore the hair-splitting details that signal the astrological arrival of the native consciousness. They all have their own way of knowing when spring really begins. Joe Rao serves as an instructor and guest lecturer at New York’sHayden Planetarium . He writes about astronomy forFree natural history magazine, the The Farmers’ Almanac
