By Cameron Macphail, and Rozina Sabur (The Telegraph)
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.
In Japan, as spring approaches, the arrival of cherry blossom (Sakura) is hotly anticipated as the nation turning a shade of pink with the arrival. Months before they arrive, retailers switch into sakura mode,Danielle Demetriouw writes. The countdown excitement is heightened further by the televised Cherry Blossom Forecast which offers a petal-by-petal analysis of the advance of the blooms – known as the cherry blossom front – as they sweep from the south to the north of the archipelago.
The colourful Hindu festival of Holi is celebrated as the vernal equinox approaches. The ancient religious festival has become popular across the world, including celebrations across the UK, though it is mainly observed in India and Nepal. The celebrations begin with a bonfire the previous evening where revellers sing and dance. The following day involves participants throwing colour over each other, either with dry powder and water or coloured water-filled balloons. The festival signifies the victory of good over evil with the onset of spring and the end of winter.
Rabbits and hares have been associated with spring since ancient times. It is thought that the Anglo-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.
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 coloured 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