This was the question my niece asked me a while ago, and with a reason. We’re used to the fact that astronomical events are “fix”, like the duration of the day and night, the revolution of the Earth around the Sun, the Moon’s rotation and so on. But if you check it out, the date of the Vernal Equinox (and Solstices too, by the way) shifts over the years, and you can have in on 19, 20, or 21 March.
Why something in kind does happen? Simple: this is due to the duration of the Earth’s year, which is not 365 precisely, but 365.256 days, a fact that in history has created a few issues with calendars (one day I’ll write about
In 2019 the Vernal (=Spring) Equinox is today, 20 March, with a fantastic, final Supermoon of 2019 and the third Supermoon in a row. What better way to celebrate than watching it online?
You can check out here at Slooh, for instance, from Canary Island Observatory. This is what you’re going to see on their site:
“Supermoons are all about perigee; the Moon’s closest approach to Earth as it orbits around us each month. This year we got the closest to our most influential satellite in February, but this event will be visually just as stunning, and with enough gravitational force to make ocean tides lower and higher than at other points during the year. ‘Equinox’ comes from the Latin for ‘equal night’, which means we get equal parts of daylight too. It is the official start of spring in the Northern Hemisphere, and autumn in the Southern. Above the Earth’s equator in space is a line we call the celestial equator. When the Sun crosses this humanmade line in March, the Vernal equinox is at hand, and six months later in September the same happens again, but with seasons reversed at the Autumnal Equinox. Wherever we are on the planet during a Vernal Equinox, we do well to look at the amount of light left at day’s end, and not at lingering cold temperatures or frost keeping spring flowers from peeking through. ”
Also worth checking is this video:
In any case, Happy Worm Moon!
I find the impossible attempts to reconcile solar and lunar calendars through history, especially where Passover and later Easter are concerned, fascinating.
The general rule for deciding Easter, for example, varies between Orthodox and Western Christianity as well as with Jewish Passover, but I tend to remember it as the first Sunday after the full moon after the spring equinox.
Clearly this year it’s not the case, perhaps with the equinox and the full moon virtually coinciding.
You literally read my mind. This might be the reasons we have never had (for what I know at least) Equinox on 22 March… but this is worth another post (and more research). Oh, history! 😀
As you say, Steph – this is a fascinating subject and I look forward to that post about the history of the different calanders…
Thanks and… hopefully soon 🙂