In the Dark

Today is a very busy teaching day, so I just have time to post a quick note to say that the Autumnal Equinox (in the Northern Hemisphere) takes place in the early hours of tomorrow morning, Wednesday 23rd September 2026, at 01:05 Irish Time (00:05 UTC). I don’t intend to be awake then, so I’m posting this now. Of course the Equinox will be later today rather than tomorrow for some of you, depending on your time zone. Of course for those of you in the Southern Hemisphere it will be the Spring (or Vernal) Equinox.

Although  the term `equinox’  refers to a situation in which day and night are of equal length, which implies that it’s a day rather than a specific time, the astronomical equinox is more accurately defined by a specific event, i.e. 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 on days in the Northern hemisphere will be shorter than nights and they’ll get shorter still until the Winter Solstice on Monday 21st December 2026 at 11.50 pm Irish Time.

Many people take the autumnal equinox to be the end of summer. There is a saying in some quarters, however, that `Summer is Summer to Michaelmas Day’ (September 29th), which is not until next week. The weather has indeed been very nice in Maynooth for the first couple of days of term. The temperature reached 23°C yesterday!

This entry was posted on September 22, 2026 at 1:00 pm and is filed under Biographical, Education, Maynooth, The Universe and Stuff with tags Autumnal Equinox. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.