After the Winter Solstice - Why our mornings may still be a bit dark
22 December 2021
After the Winter Solstice
Why our mornings may still be a bit dark
It was an overcast Winter Solstice at Broughton near Milton Keynes for Rex Horwood.
Yesterday was the shortest day of the year, so things should start getting a little lighter from now on, but that isn't actually the case for the mornings.
In fact, while the days will indeed begin to lengthen, it is the afternoons that will gradually see more daylight, while the mornings continue to get a little darker until the New Year, but why is this?
The reason is that a day - or a Solar Day - is not always 24 hours in length. A day is actually at its shortest with 23 hours 59 minutes and 30 seconds in early September and at its longest of around 24 hours and 30 seconds in December.
Why does this happen?
The reason that a day varies is because of two factors. First is the 23.5 tilt of the Earth and second is the speed of the Earth that varies because of its elliptical orbit around the sun.
During its orbit, the speed of the Earth is faster when it is closer to the sun because of the sun's gravitational pull but slower when it is further away.
This means, that while our clocks and watches use 24 hour days, for some parts of the year, the sun actually lags behind them while at other times it is faster making solar days slightly longer or slightly shorter each day.
It is this cumulative shifting that explains why evenings also reach their earliest sunset a couple of weeks before the Winter Solstice and why our mornings continue to get a little darker until the New Year.
You can see the sunrise/sunset and moonrise/moonset on our Progressive Web App where you are to see when your sunrise starts a little earlier. This feature will also become available on your devices in the first half of the New Year.