Spring has Sprung! The Vernal Equinox

By Cameron Macphail and Rozina Sabur for The Telegraph

When does spring start in 2016?
The astronomical spring in the Northern Hemisphere begins today, Sunday, March 20.
The Spring (vernal) equinox in the Northern Hemisphere is also known as the March equinox. It’s called the “autumnal (fall) equinox” in the Southern Hemisphere.

The March equinox marks the moment the Sun crosses the celestial equator – the imaginary line in the sky above the Earth’s equator – from south to north.
This happens on March 19, 20 or 21 every year.

Why is it Called “Equinox”?
Since night and day are nearly exactly the same length – 12 hours – all over the world the event is called the equinox, which in Latin, literally means ‘equal night’ (equi – equal and nox – night).
In reality though, equinoxes do not have exactly 12 hours of daylight.
Solstices and equinoxes mark key stages in the astronomical cycle of the earth. In a year there are two equinoxes (spring and autumn) and two solstices (summer and winter).
The dates of the equinoxes and solstices aren’t fixed due to the Earth’s elliptical orbit of the sun. The Earth’s orbit around the sun means that in early January, the sun is closest (known as perihelion) and in early July it is most distant (aphelion).
What happens on an equinox?
The Earth’s axis always tilts at an angle of about 23.5° in relation to the ecliptic, i.e the imaginary plane created by the Earth’s orbit around the Sun.
On any other day of the year, either the Northern Hemisphere or the Southern Hemisphere tilts a litte towards the Sun but on the two equinoxes, the tilt of the Earth’s axis is perpendicular to the Sun’s rays.
The equinox happens at exactly the same time around the world.
The equinox occurs at the exact moment the Sun crosses the celestial equator – the imaginary line in the sky above the Earth’s Equator – from south to north. At this moment, the Earth’s axis is neither tilted away from nor towards the Sun.
In 2016, this happens at 4:30 am UTC (GMT).

The March equinox has long been celebrated as a time of rebirth in the Northern Hemisphere. Many cultures celebrate spring festivals and holidays around the March equinox, like Easter and Passover.

The Easter Bunny
Rabbits and hares have been associated with spring since ancient times. It is thought that the Ango-Saxon Goddess of Spring, Eostre, had a hare as her companion, which symbolised fertility and rebirth.
It’s hardly surprising that rabbits and hares have become associated with fertility as they are both prolific breeders and give birth to large litters in early spring.

Anglo-Saxon Goddess of Spring, Eostre

The legend of the Easter Bunny is thought to have originated among German Lutherans, where the ‘Easter Hare’ judged whether children had been good or bad in the run-up to Easter.
Over time it has become incorporated into Christian celebrations and became popular in Britain during the 19th century.
Many children believe that the Easter Bunny lays and hides baskets of colored eggs, sweets and sometimes toys in their homes or around the garden the night before Easter Sunday – much like Father Christmas delivering gifts on Christmas Eve.
This has given rise to the tradition of the Easter egg hunt which is still popular among children today.

 

 

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It’s a Bird? A Plane? No… it’s a Super Moon!

Three rare celestial events will occur this Friday, March 20, 2015. The people of Earth will experience a solar eclipse and a Supermoon during the Spring Equinox. For more, read the following article by Andrew Griffin of The Independent(UK): “As the eclipse plunges the UK and other places into darkness this Friday, two other rare if less spectacular celestial events will be taking place, too: a Supermoon and the Spring equinox. A Supermoon, or perigee moon, happens when the full or new moon does its closest fly-by of the Earth, making it look bigger than it normally does. And the spring equinox refers to the time of the year when the day and night are of equal duration, mid-way between the longest and shortest days. The solar eclipse refers to a phenomenon where the sun and moon line up, so that the latter obscures the former. And while it won’t be affected by the two other events, it is rare that the three events happen even individually.

Supermoon

In images from NASA in 2014, this supermoon is seen over the The Peace Monument on the grounds of the United States Capitol in Washington, DC. (Bill Ingalls/NASA via Getty Images)

Most of the time, there are between three and six Supermoons a year. There is set to be six in 2015, two of which have already happened. The next will take place on March 20, the day of the eclipse, and the others will come in August, September and October. Eclipses can only happen at new moon, when the moon appears is entirely in shadow. And the spectacular Supermoon images that are often spotted can only happen when the moon is full, since it can only be seen then. As a result, only the last three Supermoons of this year will be visible — because the moon is new rather than full on March 20, it won’t be seen. But it will be gliding past us closer than ever, and its shadow will be visible as it blocks out the sun on Friday morning.

Spring equinox

The equinox will also happen on March 20. While it won’t have any discernable, direct impact on how the solar eclipse looks, it will contribute to a rare collision of three unusual celestial events. On March 20, the Earth’s axis will be perpindecular to the sun’s rays — which only happens twice a year, at the two equinoxes. After that, it will start tipping over, making the days longer in the northern hemisphere. As such, the equinox has long been celebrated as a time of beginning and renewal, by a number of historic cultures, and is linked to Easter and Passover. The equinox will happen at the same time as a solar eclipse in 2053 and 2072, though it doesn’t always appear as close together as that.”

Snake of Sunlight

“The snake of sunlight” at Chichen Itza, Mexico.
©iStockphoto.com/CostinT

According to the website Time and Date.com, one of the most famous ancient Spring equinox celebrations was the Mayan sacrificial ritual by the main pyramid at Chichen Itza, Mexico. The main pyramid – also known as El Castillo – has four staircases running from the top to the bottom of the pyramid’s faces, notorious for the bloody human sacrifices that used to take place here. The staircases are built at a carefully calculated angle which makes it look like an enormous snake of sunlight slithers down the stairs on the day of the equinox. The Mayan calendar was very precise in this respect, but today the Mayan calendar is most famous for ending exactly at 11:11 UTC on the 2012 December Solstice. Knowledge of the equinoxes and solstices is also crucial in developing dependable calendars, another thing the Mayans clearly had got the hang of.