Perigee? Syzygy? Sure. But no supermoon

Keep those headlights on and those barbecues tucked away. Tomorrow's

Relax, the cow will have no trouble clearing this one.

Tomorrow night, if the moon looks a little bigger, it's not your imagination - and you've got amazing eyesight if you even notice. The moon should appear about 14 percent larger than it does when it's farthest away from Earth. That's not even the difference between a medium and a large pizza, and who can tell that from 221,463 miles away?

But for the past week, Americans have been making plans to hold winter barbecues, thanks to rumors that tomorrow's moonrise would be more like sunrise - thanks to a series of celestial coincidences. Well, the coincidences are real, say scientists whose patience has been tried by media frantic to report on the "supermoon," but tomorrow's sky will probably look very much like every other night.

So, despite newspaper accounts calling it the brightest thing since Stephen Hawking, if you get the urge to dance by the light of the moon tomorrow, bring a flashlight.

You probably won't be able to sit on the porch and read a book without a lamp - unless, of course, you live near that guy in Arkansas who puts up enough Christmas lights to land planes by.

And no matter what you may have read elsewhere, please, please don't drive with your car headlights off. It's a full moon, folks, not Times Square.

This, the last one of the 1900s, has sparked enough interest to make Artemis proud. It's the first time a full moon has landed on the winter solstice since Reconstruction, and the last time it occurred, according to an e-mail that's been circulating at the speed of light, Dec. 21, 1866, the Lakota Sioux staged an ambush on US soldiers in the Wyoming territory.

But while numerically interesting, experts say, it's hardly scientifically important. And it's not like one of those celestial special effects that made our ancestors cover their heads and schedule a sacrifice. Meteor showers and eclipses have got it all over this one, say scientists.

'Near-falsehood'

After his 17th phone call from moonstruck reporters, NASA spokesman Stephen Maran sounded about ready to send the lot of them up on the space shuttle so they could measure the blasted orb and be done with it. "My office ... has been bombarded all week with media queries on this near-falsehood," Mr. Maran responded, calling reports of a supermoon "nonsense."

Yes, the full moon is at perigee (the point in its orbit where the moon is closest to Earth). And yes, the light from the sun bouncing off the moon will appear 7 percent brighter. But professionals with high-powered telescopes will have trouble telling the difference, never mind the rest of us.

In Connecticut, Yale astronomer Brad Schaefer's wife had seen the e-mail. She sent him a copy to add to his collection of scientific rumors and oddities.

Still chuckling, Dr. Schaefer points out that a perigee and a full moon (or a new moon, for that matter) happens "a couple nights a year. It's not a big deal."

What is a big deal, he says, is the fact that tomorrow's perigee is happening while the earth, sun, and moon are lined up - a phenomenon called syzygy. (Remember those cool shots in "2001: A Space Odyssey"?)

When that happens, you get the very highest tides. Add a nasty weather pattern at just the wrong moment "and you could get mega-damage."

Historically, for example, the breach of the Dutch dikes - which killed as many as 400,000 people, occurred during a confluence of perigee and syzygy, Schaefer says. So, when the legendary Dutch boy stuck his finger in the dike to stop a breach, the sun, Earth, and moon could have been lined up very much as they will be tomorrow night.

Tool of war

During World War II, both sides used the combination of perigee and syzygy to score two naval victories. In 1939, the German U-47 used the high tides created during a new moon to creep past the blockade boats to the British naval base at Scapa Flow. And the HMS Campbeltown used the perigee and syzygy during a full moon to go over the mud flats of the Loire estuary and blow open a dry dock gate at St. Nazaire, France.

Today, if a typhoon happens during a confluence of perigee and syzygy, "one-third of Bangladesh goes under water," Schaefer says. "So, it does actually matter."

But it's the tides, not the light, people should be watching out for tomorrow night.

Oh, and the Sioux attack? It happened at noon.

(c) Copyright 1999. The Christian Science Publishing Society

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