By SCOTT ELNES
CENTRAL OREGON DAILY NEWS
This Halloween, look up to the skies and watch the moon turn blue.
Well, not literally. This Halloween we are going to be treated to something called a “Blue Moon”.
But Grant Tandy, the manager of the Worthy Hopservatory, points out that they may not be what you think they are.
“You’ve heard the phrase, “Once in a Blue Moon”, which is supposed to mean “rare”, yet if you strictly follow the science, it happens once every two to three years, which really isn’t all that “rare,'” Handy said.
Yet, Blue Moons on Halloween only happen once every 18-19 years, which one could argue, makes it kind of rare.
Ella Fitzgerald sang the song Blue Moon, which was a rare treat.
However, so did The Marcels and Frank Sinatra, which means it wasn’t all that rare.
Now Neil Young sang about the “Harvest Moon”, which occurs every year because it is the closest full moon to the fall equinox, which means it’s not rare.
“Yet this year the Harvest Moon fell on the first of October instead of in September,” Tandy says, “which makes it kind of rare…like a Blue Moon.”
So this year we’ve had a rare Harvest moon in October which led to a somewhat rare Blue Moon, which is made even more rare by the fact that it falls on Halloween.
Yet did you know that 100% of all Full Moons that fall on Halloween are Blue Moons?
Which once again…doesn’t make them all that rare.
Confused? Let’s crunch the numbers.
A Blue Moon does not actually mean the moon is turning blue, it means that it’s the second full moon in a single month.
The moon cycles to “full” every 29.5 days, and October is 31 days. Which if you do the math, results in every full moon on Halloween being a Blue Moon.
And yet, that same math excludes the month of February from ever having a Blue Moon.
Tandy lays out the math, “February, even on a leap year, is 29 days, not 29.5, so a Blue Moon can, by definition, never happen in the month of February.”
That’s not just rare, that’s mathematically impossible.
In a year with a pandemic, a supreme court judge dying, the most divisive election cycle in modern history and record wildfires, something like a Harvest Moon and a Blue Moon all in the month of October pretty much seem par for the course, don’t they?
But in truth, they are actually kind of rare.
