Syzygy: In astronomy, a straight-line configuration of three celestial bodies in a gravitational system – e.g., the Sun, the Moon, and the Earth. When the event occurs during lunar perigee (the point during its orbit when the moon is closest to Earth), it’s sometimes erroneously called a “supermoon.” Syzygy comes from Greek syzygein, “to yoke together,” via Latin; it’s pronounced SIZZ-ih-gee.
A syzygy occurred yesterday, June 23, causing the normal spring tide – the high-high and low-low tides that occur every new and full moon – to be about 5 percent stronger than normal. (Five percent may not seem like much, but those of us who swim and kayak in San Francisco Bay noticed the effect over the weekend, when a 7-foot difference between high and low tide created a significant current.)
Syzygy does not cause “earthquakes, volcanoes, bad weather, halitosis, dust bunnies, and hangnails,” according to Phil Plait, author of Discover magazine’s Bad Astronomy blog1. Writing just before the March 2011 syzygy, Plait noted acerbically:
We humans love to seek correlations, and will see them even when they aren’t there. That’s why astrologers are still in business, despite having no scientific evidence whatsoever that their predictions are any better than random guessing.2
In fact, this “supermoon” idea was started by an astrologer named Richard Nolle. On his website, he defines the term as a new or full Moon when the Moon is closer to Earth than usual. He goes and gives a more precise definition, but it’s rather arbitrary*. He says quite bluntly — and quite incorrectly — that lots of seismic events (plus bad weather) can be attributed to the Moon.
But I’ll add that the Moon will actually be a bit closer than usual, and while you might not notice the size or brightness difference by eye, the full Moon is always a lovely and compelling sight in the sky. So I urge everyone to go out and take a look. And while you’re looking think on this: a dozen men have walked on the Moon, dozens of probes have been sent there, and the Lunar Reconnaissance Orbiter is still snapping away, mapping our friendly satellite and taking dazzling images of its surface.
That’s real, that’s tangible, and that’s what we humans can do when we stick with science.
Syzygy is a legitimate and potentially high-scoring Scrabble word. Syzygy is also the name of another word game played with letter tiles (but no board).
1 Plait's column has since moved to Slate.com, where he published a column on Sunday about this year’s syzygy. Thanks to commenter Steve Hall for the update.
2 That link goes to Plait’s long and worthwhile post on astrology. Here’s his conclusion, which he places at the beginning so you won’t miss it: “Astrology is wrong.”