Today is the first day of spring 2019: but just what is the vernal equinox?
- 20 March is the first day of spring
- Despite popular belief there are not exactly 12 hours daylight
- Vernal equinox takes place at different times in different cities
So what is an equinox?
The word comes from Latin, meaning roughly 'equal night'. The vernal equinox usually occurs around 21 March in the northern hemisphere (south of the equator, it's the autumn equinox) and is the point at which the sun moves to be directly over the equator, appearing due south to us.
We won't be able to see that in Manchester, unfortunately, as the equinox is at 9.58pm in our city.
Equinox is a slight misnomer, however, as it usually exceeds 12 hours daylight a few days before - usually 17 or 18 March is the first of the year where day becomes longer than night.
Astronomically this is all important, but why does this signal the start of spring?
Being able to chart the seasons with a degree of accuracy is important agriculturally, as farmers need to prepare to plant their crops and have their livestock give birth. The sun crossing the equator and daylight outlasting night are good measures of when to define the start of the spring period.
There are some falsehoods connected with the equinox as well. Some people believe the equinox causes satellite disruption, which is easily disproved if you're reading this article. Others entertain the bizarre belief that an egg can be easily balanced on its end, when in reality it is no easier or harder to do this today than any other in the year.
The day has religious significance around the world, with the equinox marking the beginning of the season of fertility in many faiths. It is also used, for example, to calculate Easter, which always falls on the first Sunday after the first full moon after the equinox.
The equinox also has a link with people's wellbeing. Mental health is generally better with more daylight, and the amount of daylight increasing, as well as days getting warmer and on the vernal equinox you can start to notice both quite easily.
It also means, in Britain at least, that British Summer Time is just around the corner, so make sure you set your clocks forward on Sunday, 31 March!