A Full Moon? Easter? April Fool’s Day? Well, Kind Of.

Did you see that big old moon setting in the southwest this morning? Me too. And then I thought this is really cool, a full moon, Easter and April Fool’s Day, all at once.

Except that’s not possible. It’s not possible to have a full moon on Easter Sunday. Because the rule is, Easter is celebrated the first Sunday AFTER the first full moon after the Spring Equinox.

So the moon pulled an April Fool’s joke on us this morning. It only looked full. The full moon occurred at exactly 7:36 a.m. yesterday, March 31, (I don’t know if that’s Central Daylight Time, or Greenwich Mean Time–the Internet didn’t specify, but it definitely was yesterday), so today is the first Sunday after the first full moon after the Spring Equinox, which was March 20 this year—but don’t get me started about how the Spring Equinox is determined—that’s a subject for another day.

Full Moon on Easter? Not quite.

So the moon was actually 98.6 per cent full this morning, according to the Internet, a waning gibbous moon. Of note, it also happened to be a blue moon, the second full moon in the month of March.

I actually wrote a whole blog about this moon and Easter phenomenon a couple years ago, You can read it here. Oh, by the way, Lent is over. My sister-in-law Sarah can turn on her TV again this morning. And my other sister-in-law Beckie can have a glass of wine for breakfast. And I can eat my Peeps.

Happpy Easter, Everyone!

4 Responses

  1. John Burke

    The concept of “Blue Moon” is an opportunity to learn about one of the most arcane and useless distinctions of all. The original definition of a “blue moon” is the third Full Moon in an astronomical season with four Full Moons (versus the usual three). “Astronomical seasons” are Summer, Spring, Fall, and Winter, measured by equinoxes and solstices, as opposed to specific dates. A later definition of “Blue Moon” is the second full moon in a month with two full moons. The reason the second definition of Blue Moon exists is down to an error originally made by amateur astronomer James Hugh Pruett (1886–1955). He misunderstood the basis for calculating the seasonal Blue Moon and wrote that a Blue Moon was the second Full Moon in a month in an article published in Sky & Telescope magazine in 1946. This erroneous definition since spread, particularly after it was quoted in a popular radio program called StarDate in 1980 and then appeared as an answer in a 1986 version of the board game Trivial Pursuit. Today, it is considered a second definition rather than a mistake.

    The seasonal Blue Moon originally came about as a kind of placeholder name for a Full Moon which doesn’t have a proper Full Moon name, such as Harvest Moon or Paschal Moon. This way, when there are 13 Full Moons in a year instead of the usual 12, the other 12 can keep their rightful place in relation to the solstices and equinoxes.

    So, by the original definition of Blue Moon, there are no Blue Moons in 2018, as there are not four Full Moons in any season. Yet by the “second” definition, there are two (Jan 31 and Mar 31).

    SEASONAL FULL MOONS IN 2018
    Winter Solstice: Dec. 21, 2017 – 8:27 am PST
    Full Moon Jan 01, 2018
    Full Moon Jan 31, 2018
    Full Moon Mar 01, 2018
    Vernal Equinox: March 20, 2018 – 9:15 am PST
    Full Moon Mar 31, 2018
    Full Moon Apr 29, 2018
    Full Moon May 29, 2018
    Summer Solstice: June 21, 2018 – 3:07 am PDT
    Full Moon Jun 27, 2018
    Full Moon Jul 27, 2018
    Full Moon Aug 26, 2018
    Autumnal Equinox: Sep. 22, 2018 – 6:54 am PDT
    Full Moon Sep 24, 2018
    Full Moon Oct 24, 2018
    Full Moon Nov 22, 2018
    Winter Solstice: Dec. 21, 2018 – 2:22 pm PST
    Full Moon Dec 22, 2018

  2. Jim Fuglie

    Dammit, John, I knew that, and just spaced it out. I could have saved you a lot of typing if I hadn’t just casually thrown it in there before I had my second cup of coffee. Thanks.

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