#day length

I wrote a silly little fic to mark the day:

The next equinox is coming up in just under seven hours at the time of this posting, at 2023-09-23 06:50 UTC

(See when the impending southward equinox will be in YOUR timezone!)

Many folks have the impression that the equinox is "when day or night are equal" but actually, an equinox is a moment in time! It's when the sun is directly above the Earth's equator, and happens twice a year.

Above image of the moment of equinox from wikipedia.

The day that day and night are equal is known as the equilux and happens in different places on different days (depending on latitude).

And, if you are close enough to the equator, you NEVER get a day less than 12 hours and a day is ALWAYS at least a few minutes longer than night! This is because of atmospheric refraction.

Speaking of atmospheric refraction, this also causes the sun to be above the horizon at BOTH the north and south poles for a short time before and after an equinox!

According to what I've been able to determine (with this sunrise and sunset calculator) at the south pole, the sun rose September 21 at 03:39 UTC, and the sun will set at the north pole on September 25 09:58 UTC!

A common lab plant that’s been poked and put under microscopes for decades may seem unlikely to keep secrets. But in widely studied Arabidopsis thaliana, scientists have identified the “cantil” — a newly reported plant organ named for its cantilever-like way of branching off of the main stem. The structure appears in only some A. thaliana and only under certain conditions, researchers report online June 15 in Development.

“If you told me of a new organ in a weird plant in Amazonia, I wouldn’t be surprised at all,” says François Parcy, a plant biologist at CNRS in Paris, who was not involved in the study. “What struck me is this happened in Arabidopsis. This is something that’s really surprising.”

Molecular biologist Timothy Gookin first suspected contamination or a mutation when he noticed some A. thaliana with odd stalks jutting out from the stem, like half-finished bridges. It took 12 years of experiments at Penn State to show that the rare stalks are a new type of plant part and to explain their trigger: delayed flowering.

Like many other plants, short days prompt A. thaliana, which is in the same family as cabbage and mustard greens, to shore up resources; long days tell it to churn out flowers. Cantils form when that transition from stockpiling to blooming is postponed, as the plant keeps growing while waiting for the flowering signal,

Day Length across Denmark on the Winter Solstice.

Today, we’ve gotten to 14 hours of daylight per day.  And 57 seconds if you are into that sort of precision.

Dawn is at 6:07am and sunset is at 8:08pm.