It wasn’t until a couple of years ago that I noticed that the mornings weren’t getting any lighter despite it being after 21st December, the Winter Solstice and the shortest day of the year. Naturally, worrying that the apocalypse was imminent and no-one else had noticed, I mentioned my concern to a good friend who was well versed in science and was a fellow dawn watcher, also with animals needing pre-daylight attention in Winter.
Naturally, my friend knew all about this. The answer wasn’t an obvious one, but the fact that I have since mentioned it to several people who were equally amazed made me feel better about this lifelong knowledge gap and inspired me to share this in case others were similarly in the dark.
Put very simply, one main factor causes this – the discrepancy between solar time for a day (the time it takes the earth to perform a rotation) and clock time which is calculated as the same 24 hours every day of the year using the Gregorian Calendar which has been universally adopted. The tilt of the earth’s axis means we are orbiting around the sun in an elliptical or oblong fashion rather than a purely round way.
As solar time and clock time are not exactly the same, this has the effect that in the mid-Northern hemisphere the earliest sunset will be in early December, before the Winter Solstice, and the latest sunrise will be early January. This depends on your latitude, but here in the Brecon Beacons this morning, January 2nd 2022, was the latest sunrise at 08.21am hoorah, so looking forwards to lighter mornings from now on!
Julia – Good Day Out