Today, the 21st December is the Winter Solstice or Midwinter, Yule, the Shortest Day or the Longest Night, unless of course you are in the Southern Hemisphere (I'm trying not to think about my antipodean Steem pals sitting on a beach in Durban, Rio or Port Douglas when it's dark, raining and 10 degrees C outside). So what is the Winter Solstice?
It's all to do with the tilt of the earth relative to the sun. As you can see from the above image the southern half of the globe is tilted towards the sun and the top half away from the sun. It's not the distance away from the sun that matters it's the tilt of the earth to the sun.
If you are standing where the red androgynous stick person is, the sun is right overhead at midday. If you're standing where purple stick person is standing the sun is at a significant tilt - approximately 30 degrees at midday. There are a couple of factors that come into play here. Firstly the sun falling on red's head passes through very little atmosphere, for purple the sun is passing through much more atmosphere weakening its power as it goes. Also for red stickperson the sun goes from on the horizon at dawn to directly overhead and back to the horizon at sunset. For purple it goes from the horizon to about 30 degrees above the horizon and back to the horizon again. This takes less time, hence the shorter days. In reality what's happening is the sun is spending more of its time below the horizon. As you can see from the above image. If you're in the Arctic circle no matter how much the earth spins from day to night for the rest of us, it's always below the horizon - it's only the land of the midnight sun in the summertime.
We've kind of forgotten about how this all works in the modern world, but our ancient ancestors were obsessed with midsummer and mid winter. Famously structures like Stonehenge, the Hatshepsut temple and Newgrange all have mid winter alignments.
If you feeling the Winter blues at the minute in the Northern Hemisphere, just remember that for the next 6 months each day will get slightly longer. Tomorrow is going to be 3 seconds longer than today. Hurray!!
photos both courtesy of Wikimedia and are labelled for reuse