The visual proximity of the two giant planets offers a good reason to gaze skyward on the solstice. But if you miss the event (or clouds spoil the show), there’s still plenty to appreciate about the winter solstice in its own right.
What happens on the solstice?
On the December solstice, the sun appears directly over the Tropic of Capricorn, a line of latitude 23.5 degrees south of Earth’s equator. It’s as far south as the sun ever gets before starting its six-month journey northward again. Here in the Northern Hemisphere, we see the sun take its lowest and shortest path across the southern sky, which is why it’s dark for a good portion of the day.
The reason we have solstices, and seasons, is because the Earth doesn’t orbit the sun completely upright. Instead, our planet is tilted on its axis by about 23.5 degrees, which means one hemisphere receives more of the sun’s light and energy at different times of year.
On the winter solstice, the Northern Hemisphere leans away from the sun, and we receive much less direct sunlight. Meanwhile, the Southern Hemisphere is entering summer and people are enjoying their longest day of the year.
A common misconception is that Earth is farther from the sun during winter in the Northern Hemisphere. In fact, the opposite is true: We’re about 3 million miles closer to the sun in early January than in July, writes space.com.
The word “solstice” comes from the Latin word solstitium, which means “sun standing still.” On the December solstice, the sun’s daily southward movement in the sky appears to pause, and we see the sun rise and set at its southernmost points on the horizon. After the solstice, the position of sunrise and sunset slowly begin to shift northward again.
Daylight hours on the solstice
The Northern Hemisphere sees its shortest day of the year on Dec. 21, but the amount of daylight depends on how far you live from the equator. In the Lower 48, daylight on the winter solstice exceeds 10 hours in most of Texas, Louisiana and Florida, while much of the Upper Midwest and states near the Canadian border have under nine hours of sunlight.
Washington, D.C., has 9 hours and 26 minutes of daylight on Dec. 21, with sunrise at 7:23 a.m. and sunset at 4:49 p.m. At solar noon (12:06 p.m.), the sun climbs just 27.7 degrees above the horizon, our lowest midday sun angle of the year. The low sun angle is why you’ll cast your longest noontime shadow of the year on the winter solstice.
If these long winter nights are sapping your energy, it helps to put things in perspective. In Alaska, for example, the sun barely climbs above the horizon this time of year. Anchorage sees only 5 hours and 27 minutes of daylight on the winter solstice, while in Fairbanks, the sun is up for just 3 hours and 42 minutes.
North of the Arctic Circle (66.5 degrees north latitude), the sun doesn’t rise at all. Apart from a few hours of faint twilight, the entire day is shrouded in darkness.
Shortest day but not the earliest sunset
Though the winter solstice marks the shortest daylight period in the Northern Hemisphere, it’s never the day of the latest sunrise or earliest sunset. D.C.'s earliest sunset (4:45 p.m.) is usually around Dec. 7, while our latest sunrise (7:27 a.m.) isn’t until Jan. 5, according to timeanddate.com.
This misalignment happens for two reasons: the Earth is tilted on its axis and we orbit the sun in an ellipse, not a perfect circle. Together, these two factors cause our 24-hour clocks to get slightly out of sync with the length of the “solar day” — the amount of time it takes the sun to reach its highest point in the sky from one day to the next. While humans measure days in 24-hour increments, the “solar day” isn’t exactly 24 hours.
Near the December solstice, each solar day is about 24 hours and 30 seconds long. That means it takes a little longer than 24 hours for the sun to appear in the same place in the sky from one day to the next. The lag time adds up over the course of a few weeks, causing the time of both sunrise and sunset to shift slightly later each day, even as the days continue to get shorter until Dec. 21.
The exact dates of the earliest sunset and the latest sunrise depend on one’s latitude. In most of the Lower 48, the earliest sunset and the latest sunrise occur about two weeks before and after the solstice, respectively. Closer to the Arctic Circle, the earliest sunset and latest sunrise occur on or near the date of the winter solstice.
The upshot is that mornings will continue to get darker for another two weeks, even as we slowly tack on a few minutes of daylight in the evenings. By the end of December, sunset in the District will be at 4:56 p.m., a gain of 10 minutes since the start of the month. By Jan. 6, we’ll see our first sunset after 5 p.m.
Though the coldest days of winter don’t typically arrive until mid-January, the silver lining is that brighter days are just around the corner.