After Hours

Geek Trivia: A moon for all seasons

What three mass-media trivia sources are most responsible for the newest definition of a "blue moon"?

Test your command of useless knowledge by subscribing to TechRepublic's Geek Trivia e-newsletter. Automatically sign up today!

This week, the Trivia Geek sends a special shout-out to fellow GeekRepublicist Eric Brinley, who brought most of this marvelous minutia to my attention.

On July 31 of this year, those taking an evening stroll beneath a cloudless sky will have the opportunity to look up and see what modern folklore refers to as a "blue moon." Though the moon itself will not actually be blue—or likely even appear blue—it will be the second full moon in the same calendar month of July, which is what qualifies this Saturday's lunar view as a blue moon, at least by today's standards.

That's not to say that the moon has never appeared blue in color to the average, unaided, ground-bound observer. The moon can and has shone blue or even green in color whenever a sufficient quantity of micron-sized particulates is present in the atmosphere, usually after a volcanic eruption.

The micron-sized debris (specifically, any particles slightly larger than the wavelength of red light, about 0.7 microns) refracts the moonlight, turning it green or blue, based on certain atmospheric factors. For an example of this phenomenon, one need look no further than accounts of blue moons following the eruption of the island of Krakatau in 1883.

While instances of actual blue-tinted moons represent one of several documented meanings of the term, using blue moon to describe the second full moon in one calendar month is a fairly recent practice. This definition arose in the 20th century, and it didn't really become part of the widespread public consciousness until the 1980s.

We can attribute this sudden proliferation of a previously undocumented and unused definition for blue moon to three otherwise reputable sources of fine information and fun trivia, all of which were working off bad information.


What three reputable mass-media trivia resources are most responsible for the current popular definition of a "blue moon" to mean the second full moon in the same calendar month, and what is the likely origin of this "mistaken" definition?

The most recent and most widely known source of the "new" blue moon definition is none other than the king daddy of all trivia board games, Trivial Pursuit. Specifically, the Trivial Pursuit Genus II edition published in 1986 included this definition as a question in the Science and Nature category.

Given the popularity of the game, it's little wonder that folklorists witnessed this definition enter widespread usage in the 1980s. But where did the game makers get their information?

Trivial Pursuit archives (yes, they exist) cite The Kids' World Almanac of Records and Facts, published in 1985, as the source of the question. The book's authors, however, can't trace their own source for this "fact."

So where did the Almanac authors get it? Folklorist Philip Hiscock suggests it came from our second mass-media source.

In January 1980, the National Public Radio (NPR) program "Star Date" featured a piece by Deborah Byrd that noted the "second full moon in one calendar month" definition of blue moon. Byrd cited a 1946 article in Sky & Telescope magazine as her source. Hiscock considers the "Star Date" broadcast as the likely source of the Almanac entry, and thus NPR is the second mass-media source to get blue moon "wrong."

The third, obviously, is the usually reliable Sky & Telescope magazine. A March 1946 article by amateur astronomer James Hugh Pruett titled "Once in a Blue Moon" contains the modern definition of the term, but it cites the 1937 Maine Farmers' Almanac as its source. No edition of that Almanac, however, contains the modern definition of a blue moon.

Several editions of the Almanac do list a different definition of a blue moon—the third, extra full moon of an agricultural season. The Maine Farmers' Almanacs of that era used a convoluted planting calendar that followed the lunar cycle that included three "named" full moons, such as the Harvest Moon, per season.

When the lunar cycle added an extra, "nameless" full moon to a season, it called that moon a "blue moon." A 1943 issue of Sky & Telescope correctly cited this strange definition in an article by Laurence J. Lafleur.

Pruett's 1946 article quotes Lafleur's 1943 comments, but he misinterprets the definition to mean an "extra" full moon in one month, not one season. And so began a chain of citation that led to our current definition of a blue moon appearing in Trivial Pursuit, and thus cementing its status in the public consciousness—and Geek Trivia history.

Check out GeekRepublic v2.0

We've taken surveys, measured Web traffic data, and communed with our inner geeks to create an even better GeekRepublic beta than before. Check out the new home for Geek Trivia, and keep talking smack about the product. It's the only way we'll ever learn.

The Quibble of the Week

If you uncover a questionable fact or debatable aspect of this week's Geek Trivia, just post it in the discussion area of the article. Every week, yours truly will choose the best post from the assembled masses and discuss it in the next edition of Geek Trivia.

This week, we look once again to the June 7 edition of Geek Trivia, "Too cool for fuel," in which I mistakenly implied that liquid hydrogen and liquid oxygen rocket fuel reach super-cold temperatures when kept under extreme pressure. TechRepublic member Motorcycles_are_fun pointed out this gross violation of basic physics.

"The statement, 'require high-pressure storage to remain in liquid form, and are lethally cold when under such pressure,' is equally wrong. By the Ideal Gas Equation, high pressure and very cold are mutually exclusive. I've had liquid oxygen in a styrofoam coffee cup, and it'll last for quite a while before it boils away.

"Conversely, O2 can be liquid at room temp under very high pressure. A typical gas cylinder is [about] 2000 psi when full. [Liquid oxygen] boils at -183 Celsius. [Nitrous oxide] boils at -88 Celsius—hardly 'room temperature.'"

You're mostly right, dear reader: Gas pressure and gas temperature are inversely proportional, though not mutually exclusive. NASA refrigerates its liquid oxygen and hydrogen fuel sources to prevent them from heating when pressurized (or creating excess outward pressure when returning to ambient temperature), which is what the Ideal Gas Law says would otherwise happen.

The Trivia Geek, also known as Jay Garmon, is a former advertising copywriter and Web developer who's duped TechRepublic into underwriting his affinity for movies, sci-fi, comic books, technology, and all things geekish or subcultural.

About Jay Garmon

Jay Garmon has a vast and terrifying knowledge of all things obscure, obtuse, and irrelevant. One day, he hopes to write science fiction, but for now he'll settle for something stranger — amusing and abusing IT pros. Read his full profile. You can a...

Editor's Picks

Free Newsletters, In your Inbox