In the Dark

The Vernal Equinox, or Spring Equinox, (in the Northern hemisphere) takes place on Monday 20th March 2023, at 21.24 UTC (which is this evening at 9.24pm local Irish Time). I’m posting this 12 hours in advance of the big event to give you plenty of notice.

Many people regard the Vernal Equinox as the first day of spring; of course in the Southern hemisphere this is the Autumnal Equinox. The date of the Vernal Equinox is usually given as 21st March, but in fact it has only been on 21st March twice this century so far (2003 and 2007); it was on 20th March in 2008, has been on 20th March every spring from then until now, and will be until 2044 (when it will be on March 19th). This year, however, the Sun will already have set in Ireland before the Equinox, so sunrise tomorrow 21st March could reasonably be taken to be the first dawn of Spring.

People sometimes ask me how one can define the `equinox’ so precisely when surely it just refers to a day on which day and night are of equal length, implying that it’s a day not a specific time?

The answer is that the equinox is defined by a specific event, the event in question being when the plane defined by Earth’s equator passes through the centre of the Sun’s disk (or, if you prefer, when the centre of the Sun passes through the plane defined by Earth’s equator). Day and night are not necessarily exactly equal on the equinox, but they’re the closest they get. From now until the Autumnal Equinox, days in the Northern hemisphere will be longer than nights, and they’ll get longer until the Summer Solstice before beginning to shorten again.

Loughcrew (County Meath), near Newgrange, an ancient burial site and a traditional place to observe the sunrise at the Equinox

There’s usually a lot of neo-Pagan nonsense going around at the Solstices and Equinoxes, which reminded me of the following clipping related to an even more significant astronomical event, a total eclipse. I found it in The Times, in 1999, just before the total eclipse that was visible from parts of the United Kingdom on August 11th of that year. It was a feature about the concerns raised by certain residents of Cornwall about the possible effects of the sudden influx of visitors on the local community. Here is a scan  of a big chunk of the story, which you probably can’t read…

.and here is a blow-up of the section shown in the red box, which places cosmologists such as myself in rather strange company:

In protest, I wrote a letter to the The Times saying that, as a cosmologist, I thought this piece was very insulting … to Druids. They didn’t publish it.