Sciency Words: Supermoon

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:


I was recently part of a comment thread over on Scott’s Sky Watch.  We were talking about the term supermoon, along with other weird moon names like wolf moon, blood moon, harvest moon, corndog moon, flower power moon, gingivitis moon… you get the idea.  After that, I thought a Sciency Words post on “supermoon” was in order.

The term supermoon was coined by American astrologer (repeat: astrologer, not astronomer) Richard Nolle.  The term first appeared in an article Nolle wrote in 1979 for Horoscope magazine.  To quote Nolle himself from this 2011 webpage article, the term supermoon describes:

[…] a new or full moon which occurs with the Moon at or near (within 90% of) its closest approach to Earth in a given orbit.  In short, Earth, Moon and Sun are in a line, with Moon in its nearest approach to Earth.

This particular alignment of the Sun, Moon, and Earth is also known as a syzygy-perigee.  Perigee means the point when as object orbiting Earth comes closest to Earth, and syzygy refers to the straight line alignment of three celestial objects.

A syzygy-perigee has a marginal effect on Earth’s tides, and if the Sun and Moon are on opposite sides of the Earth (as depicted in the highly technical diagram below), then the Moon will appear to be slightly larger and slightly brighter than normal in our night sky.  Astrologers would have more to say about supermoons, but from an astronomy perspective we’re pretty much done here.

Personally, I don’t really have a problem with the term supermoon.  When the full moon or new moon happens to be 90% closer to Earth than usual, that’s kind of neat.  Sure, the term started as an astrology thing, but there’s a long history of astrology concepts and terminology being borrowed by astronomers.  Supermoon is no different.

And supermoons do tend to get a lot of attention in the popular press.  I’ve had a lot of awesome conversations with people about the Moon and space and science in general that started because of a news report about the latest supermoon.  I think that’s great.  Anything that gets people to take an interest in science is a positive thing in my book.

On the other hand, a few of those conversations have ended with people asking me about their horoscopes, which is a bit disappointing.

Next time on Planet Pailly, please don’t hate anybody, not even the people who deserve it.

10 thoughts on “Sciency Words: Supermoon

  1. It’s interesting to remember that astronomy was originally the mathematical arm of the “practical” field of astrology. (Consider the names.) Early modern astronomers such as Tycho Brahe and Galileo made money on the side doing astrological readings for the nobility. Of course, those mathematics eventually led to the fields diverging. Today, one is a respected science, and the other is…not.

    Liked by 3 people

    1. You know, I actually never did consider the names, but the names do tell the story of what happened, don’t they? I’ve often thought of the relationship between astrology and astronomy as similar to the relationship between alchemy and chemistry. You start off with some superstitious mumbo jumbo, and then an actual science managed to evolve out of it.

      Liked by 1 person

      1. I don’t know as much about alchemy, but that fits my understanding of how chemistry evolved. I guess the origins of both fields explains why neither has the traditional “ology” suffix.

        Liked by 1 person

  2. Supermoons look very nice where I live; they stand out among the trees really well. It’s a shame micromoons don’t get as much press.

    Liked by 1 person

    1. I’ve never really been able to tell the difference when it’s a supermoon. Or a micromoon. But I still think they’re both neat in the same way I think it’s neat in the same way that perihelion day and aphelion day are neat.

      Liked by 2 people

      1. After that last conversation I got thinking about why I get so exhausted by “supermoon”. I think I mentioned this in one of the comments, too, but it’s the breathlessness of it all. There was one article I saw a couple of weeks ago that said something like “Last of Three Rare Supermoons this Year…!” Right there in the one sentence, they say it’s rare, but then also say that a quarter of the ones this year alone are that type.

        But the real problem is when we focus on this type of coverage, adjective upon adjective, we’re in trouble for two reasons:

        First, it gets people convinced that the only time they should look up is when there’s a Super Worm/Rose/Sturgeon Moon. So, it,maybe inadvertently, discourages people from looking when it’s not one of those. They miss out on a gorgeous regular ol’ full Moon arcing high overhead on a January night. They miss that subtle difference between the night before and the night after first quarter. They miss Earthshine.

        Second, and probably more important, the difference between super and non-super is often hard to notice unless you have a side-by-side photo. If the idea is outreach and education, which, as you know I’m 10000% in favor of, this is risky. I’ve spoken with people who were disappointed because it just looked like a regular old Moon. No worms, no roses, no sturgeons. I’d hate to think that this backfires and causes people to never look again.

        The Moon’s amazing every night. I know most people won’t look that often, but limits like these are kind of self-defeating.

        It’s just like, deep down, you know that “Oven-roasted, tea-infused, free-range organic chicken” is going to be terrible… but you order it anyway. 🙂

        Liked by 1 person

      2. Well, I do prefer organic chicken. Silicon-based chicken just doesn’t sit well in my stomach. 😉

        Yeah, I get what you’re saying, and I’ve certainly had encounters with people who got the wrong idea. I remember one person who thought he’d missed his once-in-a-lifetime opportunity to see Mars, based on the way the news talked about Mars being in opposition the night before.

        But this is really a problem with the way the popular press covers astronomy news. Really, it’s a problem with science news in general. In my experience having worked in TV news for the last ten years, anything sciency is treated like a human interest story, not hard news. So supermoons and Mars oppositions are lumped in with kids selling T-shirts and swimming competitions for dogs and the local baseball team raising money for breast cancer research.

        These sorts of stories aren’t really held to the same standards as hard news, and reporters are encouraged to get creative and have some fun with the story.

        So I guess what I’m saying is that the word supermoon isn’t really the problem for me. I think supermoons are neat in the same way that Mars oppositions are neat, or the way perihelion and aphelion days are neat. The issue for me is the way the popular press covers science news. It’s misleading at best and it contributes to the public’s science illiteracy. And at worst, if we’re talking about something like medical science, this sort of sloppy science journalism can get people killed.

        Liked by 1 person

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