If you saw this morning’s sunrise, it was in a sense midwinter for you. It was the latest sunrise in the whole year, at any rate for a mid-US latitude of 40 degrees north, as we explain at perhaps laborious length on page 33 of Astronomical Calendar 2015.
We could call it the third of four midwinters. The first is the earliest sunset, around Dec. 8, when days seem shortest because they end soonest. The solstice of Dec. 21 is the second and most arithmetically solid midwinter, bringing the shortest day and lowest Sun. Then there’s this third midwinter, the day that begins latest for early risers. And the fourth and most tangible midwinter, the pit of cold, may come around the end of February! They say “The coldest hour is the hour before dawn,” and the coldest month may be the month before spring.
For my children at latitudes 38 and 36 the latest sunrise is yet to come, around Jan. 7. For me at latitude 51, it happened back on New Year’s Eve. I was probably out watching but forgot to be aware of this fact about it. I wasn’t out seeing it and sympathizing with you this morning because I won’t be riding again, or on clifftops to watch sunrises, till I know I’ve properly healed from my last fall off a cliff. In any case the difference between sunrise times is not a readily a noticeable phenomenon. Around such a date when something is reaching an extreme, it is changing most slowly, by only seconds.
This third midwinter may have been somewhat more real for cultures that were in the habit of watching for the Sun to rise, and for the stars to make their first “heliacal risings” before it; for instance, the priests of ancient Egypt. For them, at latitudes (between about 31 and 24) nearer to the equator, latest sunrise would have come some days later, about Jan. 11 or 12 (Gregorian) – further from the solstice. Still, one wonders whether they might have timed sunrises by means of sundials or water clocks and recognized the latest sunrise as the moment when the Sun began to return northward.
Really it would be feasible to discriminate sunrise times only on a flat horizon such as a sea or desert. Most sunrises are seen on elevated and irregular horizons.
I want to take the risk of adding something that will happen near the equator of our planet tomorrow, Tuesday. Some very brave people born into a minority (a sexual one) in Uganda will be risking their lives by handing out a free publication. http://www.independent.co.uk/news/media/press/gay-rights-activists-defy-ugandan-laws-by-publishing-new-lgbti-magazine-9955950.html