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"Blue Moon" Appears in Sky Saturday Night

Posted by Hemos on from the blue-moon-you-saw-me-standing-alone dept.

ArbiterOne writes "Tonight a rare spectacle can be seen: the second full moon in a month, which is sometimes called the "blue moon", according to CNN. Don't be disappointed if it isn't actually blue, though; the blueness is caused by increased density of smoke or ash in the air, such as after a volcanic eruption."

40 of 154 comments (clear)

  1. Not all that rare by PlazMatiC · · Score: 5, Interesting

    It's not that much of a rare occurrance .. Once every 2.7 years, even.

    1. Re:Not all that rare by Orinthe · · Score: 3, Interesting

      I don't know where this google calculator gets its numbers from, but blue moons are actually twice as common as it implies.

      There are approximately 13 lunar cycles in a year, and 12 months. Simple math should be able to tell you that there must be a blue moon on average at least once a year--rarely two, and rarely none. In fact, over the next 20 years, 17 will have blue moons.

      That's about every 1.2 years.

      --
      SELECT quote.text AS sig FROM quote NATURAL JOIN attribute WHERE attribute.description = 'witty';
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    2. Re:Not all that rare by swimboy · · Score: 4, Informative

      The moon's cycle is about 29.5 days, which makes about 12.4 full moons a year. That means a blue moon about every 3 years.

      The 17 blue moons in 20 years is due to two different definitions of what constitutes a blue moon. So, blue moons are twice as common, because there are two different ways to define what a blue moon is!

      --
      Ask me how the Heisenberg Principle may or may not have saved my life.
    3. Re:Not all that rare by kzinti · · Score: 2, Informative

      The lunar cycle is 29.5 days long on average, not 28. That gives about 12.4 full moons per year, on average.

      I don't know how infoplease.com counted blue moons to get 17 in the next twenty years, unless it was counting both the 2nd-in-a-month and the 4th-in-a-season varieties. Ask this blue moon calculator to list the blue moons between 2004 and 2024, and it lists nine of them (of the 2nd-in-a-month kind).

      That's about every 2.2 years.

    4. Re:Not all that rare by Peter_JS_Blue · · Score: 4, Funny

      Oh shit !! My friends say I only buy a round of drinks every blue moon - its going to be a very expensive night in my local pub this evening.

      --
      Art Makers Just an excuse to show photos of naked women !!
    5. Re:Not all that rare by LC+Gundo · · Score: 2, Informative

      According to the CNN article the original definition is the 3rd full moon in a quarter that has 4 full moons, so tonight meets both the original Maine Farmer's Almanac definition and the post-1980 Sky and Telescope magazine definition.

      --
      I'm time traveling, right now
  2. ARgh! by mfh · · Score: 4, Funny

    Now I have to do all that stuff I told everyone I would only do when the moon turns blue. *sigh*

    --
    The dangers of knowledge trigger emotional distress in human beings.
  3. Rare? by MaelstromX · · Score: 5, Interesting

    From TFA:

    The phrase "Once in a blue moon" was first noted in 1824 and refers to occurrences that are uncommon, perhaps even rare. Yet, to have two full Moons in the same month is not as uncommon as one might think. In fact, it occurs, on average, about every 32 months. And in the year 1999 it actually occurred twice in three months.

    --
    audioLibre - freedom of music
    1. Re:Rare? by severoon · · Score: 4, Informative

      I heard that the adoption of the term blue moon in modern usage actually stems from a misappropriation of the term from some Native American tribe (around the time frame you mention, early 19th C). The term, as far as my uninformed and caffeine-addled mind can conjure at the moment, originally referred to an occurrence of a particular full moon that occurred during the three-month harvest season; specifically, when four moons occurred during this three month season, the third of the sequence was called a "blue moon". (The Wikipedia entry seems to make reference to this--see the second entry--but I can't find anything specific on it. Also, it doesn't seem to mention the "harvest" season, just any season, which is not what I heard from my unreliable source.)

      This is why our concept of blue moon as the second in a month doesn't seem to make sense in terms of rarity...it's not that rare. It makes a bit more sense if we consider how often four moons occur during the three month harvest season. That was probably quite a bit more rare.

      --
      but have you considered the following argument: shut up.
    2. Re:Rare? by drang · · Score: 4, Interesting

      (treating the months as independent of each other which obviously isn't the case but shouldn't affect the outcome)

      It is not the case, it should affect the outcome, and it does. Using your figures and ignoring fractional days of a lunation, the day of the month on which a full moon occurs regresses 1-3 days each month, so if a "blue" moon occurs this month (in days 29-31) one can't occur next month (in days 26-28).

    3. Re:Rare? by SoSueMe · · Score: 5, Informative
      Here is a really good explanation of the background on our current definition of a "Blue Moon" which seems to have been popularized by none other than Trivial Persuit.

      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 MASS-MEDIA TRIVIA SOURCES ARE MOST RESPONSIBLE FOR THE NEWEST DEFINITION OF A "BLUE MOON"?

      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 tha

    4. Re:Rare? by srleffler · · Score: 4, Informative

      Sky and Telescope has published an article more recently, explaining what happened and their role in it. It is available online.

    5. Re:Rare? by Nefarious+Wheel · · Score: 2, Interesting

      And of course, in very old trade calendars (1930's or thereabouts IIRC) phases of the moon were prominently displayed with the calendar dates. If a page spilled over to another month, and a full moon was shown, it was invariably printed in blue ink.

      --
      Do not mock my vision of impractical footwear
  4. Once in a Blue Moon by pipingguy · · Score: 4, Funny


    Neat! Maybe that means my askslashdot submission will be accepted!

  5. Rare? by Finuvir · · Score: 4, Interesting

    We see a full moon every 28 days. So a month with 31 days will have a blue moon if it has a full moon in the first three days. The chance of that is 3/28. The chance of a blue moon in a 30-day month is 2/28. There are 7 31-day months, 4 30-day months. So chance of no blue moon in a year (treating the months as independent of each other which obviously isn't the case but shouldn't affect the outcome) is (25/28)^7 * (26/28)^4 which is about 43.4%. So there's a 56.6% chance of a blue moon in any year.

    --
    Why is anything anything?
  6. Very very rare by Anonymous Coward · · Score: 5, Funny

    It occurs slightly less often than IE is patched.

  7. How rare? by lildogie · · Score: 4, Insightful

    "A rare spectacle" that happens more often than U.S. Presidential elections. I guess that makes the elections a rarer spectacle.

    1. Re:How rare? by Grey+Tomorrow · · Score: 3, Funny

      But still a spectable, eh?

  8. interesting article about it in sky & telescop by laejoh · · Score: 5, Informative
    see article

    From the article:
    According to Canadian folklorist Philip Hiscock, the term "blue Moon" has been around for more than 400 years, but its modern calendrical meaning has become widespread only in the last 25. And as discovered five years ago, it can be traced to a mistake published in Sky & Telescope in the 1940s!
  9. Black Moon is even more rare by cyber_rigger · · Score: 4, Interesting

    When no full moons occur in a month (usually February).

    1. Re:Black Moon is even more rare by gnu-generation-one · · Score: 4, Informative
      "Black Moon is even more rare: When no full moons occur in a month (usually February)"

      That would make it 2018 then?
      Blue moon: 31/Jan/2008, 9am
      Worm moon: 01/Mar/2008, 10pm
      b.t.w. I don't think it's "usually february", I think it is always february. Every month other than february is guaranteed to be longer than the synodic period (about 29.5 days), so is guaranteed to contain a full moon. (apart from the month in which you change from julian to gregorian calendars...)

    2. Re:Black Moon is even more rare by tootlemonde · · Score: 2, Informative

      The last time there was no full moon in a month was February, 1999. The event was related to there being a Blue Moon in both January and March of that year.

      Black Moon can also refer to two new moons in one month. The last time it happened was May, 2003. The next time will be December, 2005.

      And let us not forget the Cheshire Moon. This name refers to a new or crescent moon where the line of the crescent looks like a smile or bowl instead of the typical "C" shape.

      The explanation given here:

      So, when a Crescent Moon is about to set and the Sun has already set, the Moon points down to the departed Sun: West. The horns poke up and that setting Crescent Moon "grins." If the Moon sets before the Sun, the nearby Sun creates such a glare that we can't see the setting crescent. Then it "frowns, " unseen.

      Nearly the same is true of a rising Crescent Moon. If the rising Crescent rises before the Sun, the Moon points east, down towards the laggard Sun and its horns likewise stick up -- it, too grins. Otherwise, if the crescent rises after the Sun, the Moon frowns unseen.

    3. Re:Black Moon is even more rare by gnu-generation-one · · Score: 2, Informative

      "Black Moon is even more rare: When no full moons occur in a month (usually February)"

      Of course, as someone pointed out, a "back moon" would imply
      two blue moons in that year

      So are we supposed to give them different names, or is it not possible to uniquely identify each moon in 2018? January Blue Moon and March Blue Moon or something?

      And can you change when blue moons occur by selecting an appropriate timezone, or by changing to daylight-savings-time just before a full moon?

    4. Re:Black Moon is even more rare by no_space_in_time · · Score: 2, Funny

      It's just not right, February doesn't get it's props. I'm calling Al Sharpton to have a day of protest.

      --
      "save a cow, eat a vegetarian"
  10. Blue moon explained by hshana · · Score: 3, Informative

    The term blue moon actually comes from the fact that in old almanacs the second full moon in a month was colored blue on the calendar.

  11. I swear I'm not making this up by TrickFred · · Score: 5, Funny

    ...I read the article, and casually mentioned to the wife that tonight was a blue moon. She looked at me, and said with a straight face, "So, does that mean we have to have sex tonight?"

    1. Re:I swear I'm not making this up by Myopic · · Score: 2, Funny

      to which you looked back at her with a straight face and said "yes, with that neighbor lady".

    2. Re:I swear I'm not making this up by OldManAndTheC++ · · Score: 4, Funny

      That reminds me, in a roundabout way, of one of my favorite jokes. A college psychology professor decides to quiz his students on their sexual habits. He asks the class how many have had sex more than once in the past week? Several raise their hands. How about once in the past week? More hands go up. Once in the past two weeks? And so on ... after he has gotten to once every two months, he notices that everyone in the classroom has raised his or her hand, except for one guy sitting in the back. So he goes on:

      "Three months". Nothing.

      "Four months". Nope.

      "Six months". Still nothing.

      "One year?!".

      Finally the guy in the back practically leaps out of his chair, raising his hand up high and bouncing up and down enthusiatically. The prof acknowledges him, and asks, "Well if you only get it once a year, why are you so happy?". The geeky guy smiles and says:

      "'Cause tonight's the night!!"

      P.S. If your wife wears glasses, may I recommend blue filters? :)

      --
      Soylent Green is peoplicious!
  12. Ske & Telescope had an article about this... by MaxRahder · · Score: 2, Interesting

    See the Sky & Telescope article: "What's a Blue Moon? The trendy definition of "blue Moon" as the second full Moon in a month is a mistake." http://skyandtelescope.com/observing/objects/moon/ article_127_1.asp

  13. Science? by bokmann · · Score: 3, Insightful

    This falls under science? This is solely an artifact of our time measuring system. The moon is full every 28 days, but months are slightly longer than that. If a full moon is early enough in the month, it will be full twice.

  14. Mead moon and Nanci Griffith by wherley · · Score: 2, Informative

    Related:

    The first moon in July is known as the "Mead Moon".

    A real nice song about the rarity of a Blue Moon is by Nanci Griffith.

  15. Re:I wonder how it affects global tides? by Neophytus · · Score: 4, Informative

    None: The earth doesn't rely on a calendar so no pattern is changing.

  16. So what? by codexus · · Score: 4, Insightful

    This is just a calendar coincidence not any kind of astronomical event. And in fact it happens quite often. So really, there is nothing special to see here. Was that really worth mentioning on slashdot?

    --
    True warriors use the Klingon Google
  17. Once in a blue moon by shoemakc · · Score: 3, Funny


    "Sara, please cancel all my appointments; I'll be spending the day compiling E17 final and playing Duke Nukem Forever....."

    -Chris

    --
    --an unbreakable toy is useful for breaking other toys--
  18. Still a chance for a `true' blue moon ... by dougmc · · Score: 2, Informative
    This whole `second full moon in a month' thing is just stupid. Looks like there's already some interesting comments here about the original source of this idea.

    Fortunately, there is a chance of a real blue moon if you live near Anchorage, Alaska. Actually, it's not really a fortunate thing, because if this volcano does erupt and spew ash everywhere, it's a big mess. It mucks up your car, you don't want to breath it, it's almost caused airplanes to crash, etc. But it does have the possibility of causing the moon to appear truely blue.

  19. Woohoo by SlightOverdose · · Score: 4, Funny

    I'm gonna get laid!

  20. Admire it while it lasts.... by abram10 · · Score: 2, Funny

    This type of thing happens only once in a blue moon.

  21. Blue photo at Astronomy Picture of the Day by jks · · Score: 2, Informative

    See also a pretty photo, along with some explanations of the term "blue moon".

  22. Blue Moon by Anonymous Coward · · Score: 2, Funny

    Clearly this is "moon" you speak of is simply nothing more than IBM's newest supercomputer. The question is...can it play chess?

  23. Re:I wonder how it affects global tides? by kzinti · · Score: 2, Informative

    Factors that affect tides are the moon's distance from the earth, and its alignment relative to the sun. Tides are higher when the moon is at perigee (when its orbit brings it closest to the earth). Tides are also higher when the sun, moon, and earth align with the sun and moon on the same side of earth. The gravitational forces due to sun and moon add up to produce higher tides. The latter affect would occur at new moon; don't know if the former has any relationship to the lunar phases. Neither affect would have any relationship to "blue moons", which are an artifact of our calendar.