Meteorologists consider the arrival of December as the start of winter, the beginning of the coldest three months of the year. Astronomically, the season starts a little after 10 a.m. on Sunday, Dec. 21, marking the winter solstice, an actual moment in time.
You’ve likely heard about this happening for years, learning about the winter solstice first in school and then continually thereafter. One of the biggest misconceptions about winter’s start is that the latest sunrise and earliest sunset of the year occur on the winter solstice. But actually, the earliest sunset here was 4:11 p.m. on Dec. 8, while the latest sunrise is roughly 7:13 a.m. around Jan. 4. In fact, on the winter solstice, the sunset is three minutes later than the earliest sunset.
The winter solstice does, however, mark the shortest gap between sunrise and sunset — meaning the shortest day and longest night — across the Northern Hemisphere.
The winter solstice occurs at 10:03 a.m. on Sunday, Dec. 21, when the Northern Hemisphere will be tilted the farthest away from the sun.Boston GlobeThe sun rises with a rainbow effect as people look on during the winter solstice at Newgrange in Ireland, on Dec. 21, 2023. Newgrange, a 5,200-year-old passage tomb, predates both Stonehenge and the Great Pyramids of Giza.Charles McQuillan/Getty
Math explains why sunrise and sunset extremes don’t occur on the solstice; the equation of time itself corrects for this seeming anomaly. Think of it as sundial time versus the actual clock we use. The sun sometimes moves slower and sometimes faster across the sky in a 24-hour day. Think of the sun like a runner on an elliptical track that is also slightly tilted. The clocks we all use assume that the runner, the sun, is moving at a steady pace every single day of the year. The reality is that sometimes the sun appears to be moving a little faster and sometimes it’s moving a little slower across the sky. Sundial time can be faster or slower than actual time by up to about 16 minutes twice a year.
The equation of time, with the pink line showing how many minutes fast or slow the sun is compared to our clocks and watches. A negative number means the sun is running slow; a positive number means it is running fast.timeanddate.com
Another interesting aspect of the sun this time of year is that it reaches its peak before noon. As a matter of fact, back in early November, when we switched the clocks back, the sun was at its maximum height before 11:30 in the morning, meaning by 12:30 p.m., it had already been going down for an hour.
The winter solstice itself is really more than just an astronomical event around the world; it’s inspired monuments, and led to celebrations and century-long rituals based on ancient traditions. One such gathering takes place each year when thousands gather at Stonehenge in Wiltshire, England, to mark the return of the sun and the lengthening of the days.
People watch the sunrise at the northern winter solstice celebration at Stonehenge in Wiltshire, England.Tim Ireland
You can celebrate the solstice locally at Mount Auburn Cemetery in Cambridge, where the “reflections on winter light is underway.” There may still be tickets before the actual solstice this weekend. This is a great opportunity to do some reflecting on the season and the year in a beautiful setting close to Boston.
A full moon and some manufactured fog give an eerie feel to the Mount Auburn Cemetery in Cambridge during the “Solstice: Reflections on Winter Light” event in 2024.Stan Grossfeld/Globe Staff
Other interesting winter solstice facts
• In a typical winter, the solstice also does not bring the coldest air of the season in spite of the long night. The third week in January is the actual minimum average for temperatures in our area. The saying “as the days lengthen, the cold strengthens” is definitely applicable, although we have had some cold air already this year, and it’s likely there’s even more extreme cold to come.
• You may also be surprised to know that the Earth is actually closer to the sun on the winter solstice than it is on the summer solstice. It’s just that the Northern Hemisphere is tilted the farthest away from the sun during the winter solstice.
• Earth will actually reach something called perihelion around Jan. 4 when we are about 3 million miles closer than we’re going to be in July. The reason why it’s colder in the winter is that the angle of the sun is so much lower, and that is a much bigger driver of temperature than proximity.
Stargazing time during the solstice
Clear skies this time of year will also afford a wonderful opportunity to see one of the most recognized constellations in the sky: Orion will rise in the early evening with its telltale belt and will remain a prominent feature in the winter sky.
Finally, if you’re feeling like the winter solstice just emphasizes the beginning of a not-so-pleasant time for you, there are some signs of spring to look forward to in the coming weeks. Solar spring begins the first week of February, marking the start of the fastest light gain of the year and you’ll start to hear bird song shortly thereafter in the morning. And that’s actually not that far away.
Happy solstice!
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