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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


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

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.

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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

“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.