There Is No Such Thing as a “Supermoon”

Pseudoscience is often amusing, sometimes irritating, and occasionally angering. Today’s example from the Daily Mail in the UK is in the latter category: Is the Japanese earthquake the latest natural disaster to have been caused by a ‘supermoon’? (Hat tip to Ben Goldacre.) To summarize, astrologers (yes, they’re citing astrologers) have predicted the Moon’s closest approach to Earth—called the perigee, which occurs several times yearly—will cause natural disasters. The particular astrologer they interview in the article is calling the event a “supermoon”, a term that is pretty absurd in itself, but suffice it to say there is zero science in his claim.

  1. The perigee (and therefore “supermoon”) occurs once per orbit of the Moon around Earth—in other words, about every 27 days. That’s a lot of “supermoons” to occur every year! Do we see natural disasters of this magnitude that many times? (I’ll give you one guess.)
  2. At perigee, the Moon is 363,000 kilometers away from Earth. At its farthest (known as apogee), the Moon is 406,000 km away. The difference may seem large, but it’s only about 11% total. The tidal force of the Moon on Earth is simply not going to be that radically different between perigee and apogee—about 28%. That’s large enough to be noticeable in things like the ocean, but not in the tectonic plates of Earth, which are the real cause of earthquakes. If the Moon’s tidal force caused earthquakes, we’d have earthquakes twice every day, when the tides go in and out.

It’s obvious the astrologer in question is exploiting a terrible tragedy in which many people are dying; the newspaper’s motives are a lot harder to parse, but it’s certain they shouldn’t be printing exploitative nonsense like this.

Update: Phil Plait has a far longer, more detailed take on this issue, so go read what he has to say.


4 responses to “There Is No Such Thing as a “Supermoon””

  1. To actually provide *help* to the tsunami and earthquake victims, text REDCROSS to 90999 to donate $10.

    1. Phil Plait says pretty much the same thing I did, but more eloquently and in greater detail:
      He also caught a crucial detail I missed in my outrage: we aren’t even at perigee!

    ok the moon being the closest on march 12 – 19 2011 curtain mountian ranges on the moon and earth at one time were both on earth when the earth was in its molding stage or a impact broke off a big chunk of earth and made our moon so the geologic molten forms and maby
    theres more than earths magnatic pull keeping the moon in perfict harmony with us hell it doesnt even spin think about it
    and electromagnetically could forms quartz crystal and can be exciteted mabe some kind of piezoelectric mother cristal on earth and
    a A T cut quartz crystal with a y axis being the moon tilt lineing up to charge the mother crystal can and will make strong frequencies thus
    makeing earth quakes thats my theroy frequencies do( vibrate) Wesley Grants think tank

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