UKH

The journey away from the warming rays of the sun has finally turned and from here the day light spills slowly back, minute by minute.

I can only imagine the relief in the past that spring and times of hope might be coming.

Strange to think that winter was in fact a time of plenty ... food supplies would dwindle during the summer, until replenished (or not) by the Autumn harvests.

However it was a world of darkness ... only the rich could afford candles, everyone else spent 5 - 6  months in perpetual gloom.

Thank you! I'm another year older today.

I always think about how much mud there would have been, everywhere

Happy solstice.

I was wondering, how did the ancients knew it was the solstice. So I did a quick search and found this, which is quite cool.

The solstice was determined by observing the shade of the gnomon (a vertical stick on a level ground). Indeed, this is difficult to observe with a good precision. However, if you do this for many years, you obtain a better and better result. For example, suppose that your error is E, and you observe for N years. This gives you the length of the year (the time interval between, say two summer solstices) with error E/N. This principle permitted to determine the length of the year (and other constants in astronomy) with high accuracy.

Ptolemy describes the following device for determining equinoxes. A flat metal ring was permanently installed in Alexandria in the plane parallel to the equator. (For this you have to determine the inclination of ecliptic first, then your latitude. All this is done by measuring the sun altitude at noon with a gnomon). At the moment of equinox, both surfaces of the ring will be illuminated by the Sun.

Determination of the moment of a solstice is more difficult and less accurate. But again you measure the altitude of the Sun with the gnomon or a similar device at noon, if the solstice happens at noon, say summer solstice, you will obtain the maximal possible altitude for this place. If the maximum this year is less than the maximum possible altitude, this means that the solstice did not happen at noon, and you interpolate.

All this information is contained in Ptolemy's Almagest. Modern calculations permit to verify the numerical data. They show that Hypparchus and Ptolemy could determine the time of an equinox with 7 hours accuracy and solstice to 12 hours.

Hypparchus and Ptolemy determined the length of the year as 365 days 5 hours 55 min 12 sec. They used observations spanned over 550 years.

Not a moment too soon! Thank Ra / Inti / Sol for that, etc.

This reminded me that the Winter Solstice is particularly significant at Maeshowe on Orkney. The sun shines down the entrance passage onto the back wall of the structure. This video shows it at about 34:00. youtube.com/watch?v=3IBIWm7Zoro&.

There is no live footage from today as the sun was obscured by clouds. Quite a spectacle nonetheless.

youtube.com/watch?v=fd2GHhnI4Ys& 

I invite you all to join me tomorrow morning in experiencing the solstice at Stonehenge virtually. 7:20 am on the above link.

Any day the sun shines down your entrance passage must be a big day up there?

I drove past Stonehenge today at around 1430, the sun low in sky shining on the sides of the stones. Very beautiful and mysterious.

The winter solsist is a double edged sword for me. The temperature is perfect at this time of year but I miss the sunlight. I love the long days of summer but I hate the temperature. 

This was a genuinely lively start to the day. I hope to get to go to the stones next year. Maybe it will be possible. 

I like both the long days and the temps. Today is a great day as I get 2 extra seconds daylight since yesterday and this gain gathers momentum as the days elapse.

One shouldn't wish one's life away but dark, long dreary days aren't for me.

Perhaps there isn't a constant answer to this but is the 21st always the shortest day? And is the night before it (20th/21st) or after it (21/22nd) the longest?

I picked last night to "celebrate" as Tuesday was the last day of term where I teach, so no massive rush to get up today. I drove into the Peak last night and leaving the car at about 10 pm walked up on to Alport Castles and camped on the top. Windy and mainly misty walking up - no electric lights visible from where I camped although I could see the moon at times through high thin cloud when breaks in the lower clouds allowed. Everything frozen this morning including ice on the inside and outside of my tent.

No, not always. Some info on the solstice here - https://in-the-sky.org/news.php?id=20211221_07_100&town=2643743

Dave

No, the 21st isn't always the shortest day. It's also the case that the changes in sunrise and sunset are not symmetrical. At my location, sunrise will continue to get later until the 31st, but sunset started getting later a week ago (both by such small amounts as to be unnoticeable)

You must be a king....