Nine hours and 10 minutes of daylight.
Thanks to the 23° 27 tilt of the earth, we have nine freaking hours of daylight. Burying myself in the science seems to help. So first, this tilt was calculated before satellites, even before telescopes — it’s been known of since the ancients. There is evidence that the ancient Egyptians traced the effects of the tilt to track seasons (US dept of energy, Ask A Scientist). Martin Gotz of the Physics Dept at Brown has this simple formula, probably employed by the unknown person(s) who first calculated this tilt:
“Figuring out the changing seasons, the tilt of the Earth’s axis, the date of the solstice, etc. is very simple. E.g. look at how the rising (or setting) point of the Sun changes during a year. When the Sun rises or sets the furthest to the south, it is winter solstice. If it’s furthest to the north, it’s summer solstice. Measuring the difference between the maximum altitude of the Sun reached on the days of the solstices gives twice the tilt of the Earth’s equator, and hence the tilt of the Earth’s axis of rotation, and so forth. You don’t need satellites or space travel for that.
Looking at nature with open eyes, observing the motion of the Sun across the sky will reveal these things very quickly. So it’s no surprise at all that this was known very early to humans.” (letters section from candlegrove.com)
There is this old, but really, really informative site on the rotation of the earth, Analemma
Back to solstice. There is the science, which is fascinating, and helps ease my Seasonal Affective Disorder, and then there is the mythology —which outside of the science of anthropology is just silly.
Recent scholarship on Neolithic cultures has shown that agriculture may date back to 15,000 years ago (in a paper by Aurenche, Galet, Reganon-Caroline and Evin they calibrate carbon-dating of ceramics that indicate agriculture and livestock raising to 12,500 BC). It is posited that careful observation of the natural world was key to the development of agriculture. The changing place of the sun, and the shortening and lengthening of the days, would logically be observed. I can accept neolithic farmers getting nervous about the shortening days and concocting rituals to bring back the sun. I have trouble with Glen Beck doing the same.
That’s another post.
Back to the science. Here is the article on carbon dating ceramics from 15,000 years ago: Proto-Neolithic and Neolithic Cultures. There is no direct correlation between pinpointing the solstice and the development of agriculture, and so far, the earliest evidence of calendars track the changes in the moon (not the sun), but people much more knowledgeable than I posit these ancient people observing all of nature quite keenly (see Prof Gotz, above).
So, this is the darkest day of the year. Enjoy?