The year will end on a seemingly ominous sign — a rare and menacing-sounding black moon will dominate Monday’s night sky.
However, there’s nothing mysterious about black moons. Like the more-common-than-you’d-think blue moon, it’s just a calendar quirk. The moon seems to almost disappear because it gets between the Earth and sun.
“The Farmer’s Almanac can throw around any words they want about celestial phenomena, but a black moon is just an artifact of timekeeping,” said Max Gilbraith, planetarium coordinator for the University of Wyoming Physics and Astronomy Department.
Black And Blue
Astronomy doesn’t recognize a black moon as anything because it isn’t anything. There isn’t even a consensus on what a black moon is.
A black moon could be the second new moon in a calendar month, according to the months laid out by the Gregorian calendar. But it could also be the third new moon in a season with four new moons.
That means a black moon happens roughly every 29 months, or every 33 months, depending on which arbitrary definition is used.
The last black moon (that was the second new moon in a month) happened Aug. 30, 2019.
Monday’s black moon would be the second new moon in December, the first was Dec. 1. Regardless, there’s nothing astronomically significant about a black moon other than what the imagination can glean from its name.
“If you believe in astrology, it might have some significance that you might get worried about,” Gilbraith said. “It sounds like something out of ‘The Witcher,’ but there’s nothing to see.”
The same dubious circumstances apply to the more commonly known blue moon, the second full moon in a Gregorian calendar month. Both moons are calendrical rather than astronomical.
And neither concept is very old. The standard definition of a blue moon appeared in 1946, while the earliest reference to a black moon appeared on the website Time and Date in 2016.
Impossible Moons
Black and blue moons are calendar quirks, but they’re unique to the Gregorian calendar, the universally used solar calendar established by Pope Gregory XIII in 1582. These color moons don’t happen on other calendars.
“A solar calendar has more days in a month than a lunar calendar,” Gilbraith said. “There wouldn’t be any black or blue moons on the Jewish, Muslim or Chinese traditional calendars because it’s impossible to have more than one full or new moon on lunar calendars.”
While the lunar cycle is consistent, it isn’t the best method for tracking the progression of years and seasons. The foundation of the modern solar calendar is the Julian calendar, established by Julius Caesar in 46 B.C. and slightly modified to become the Gregorian calendar.
Gilbraith explained that blue and black moons are only possible when either the full or new moon occurs on the first day of the month. That’s the only way a Gregorian calendar month will have enough days to encompass an entire lunar cycle.
Nothing To See Here
If this is all a bit confusing, it doesn’t need to be. Black and blue moons are intriguing, but meaningless outside of their status as calendar quirks.
“There's a lot of conspiracies about the different ways they tried to manipulate the calendar back in the day,” Gilbraith said. “December means ‘10th month” in Latin, and it was the 10th month of the year in the past. Now it’s the 12th month. There are a lot of artifacts of our calendar system.”
With a blue moon in August and a black moon in December 2024 has been a colorful year for the moon. However, because of those calendar quirks, there won’t be any black or blue moons in 2025,
“The next time we'll get a blue moon will be in 2026,” Gilbraith said, adding it’s “not sure that we'll get a black moon in any timely fashion.”
When Wyomingites step outside Monday, the moon will undoubtedly look black, but that’s because it’s a standard new moon. There won’t be any astronomically unique to observe that evening.
Nevertheless, a new moon is an excellent opportunity for stargazing — something Gilbraith encourages all Wyomingites to enjoy while it’s available.
Partridges And Pear Trees
In the spirit of the season, Gilbraith decided to point out another calendar quirk many people aren’t aware of. Anyone who’s heard “The 12 Days of Christmas” is probably putting them where they aren’t supposed to go.
“I feel like most Americans think the 12 days of Christmas are the 12 days before Dec. 25,” he said. “It’s actually from Dec. 25 to Jan. 6, so we’re still in the midst of them.”
Friday: Any Wyomingite who hasn’t received their three French hens, two turtle doves and partridge in a pear tree this day might want to call their true love. They might be holding out on you.
But don't worry. That only happens once in a black moon, right?
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
