A CONVERSATION overheard in my local hardware store earlier this month is revealing. A customer was telling the clerk about the concern her relatives living in a Southern state felt about the prediction that a major earthquake would strike their area as the moon became full in early December. On Dec. 2, Earth, sun, and moon came into line with the moon at perigee, its closest approach to Earth. Business consultant Iben Browning predicted a 50 percent probability of a magnitude 6.5 to 7.5 quake in the New Madrid, Mo., region between Dec. 1 and Dec. 5 due to the tidal strain the celestial lineup would cause.
Piffle! Earthquake geologists generally dismissed the forecast. As the National Earthquake Prediction Evaluation Council explained, the tidal strain would be minuscule. It has occurred a number of times without triggering quakes. Also, as the council noted, no one can predict earthquakes that precisely, given the present state of geological knowledge.
But New Madrid was the focus of three major earthquakes from 1811 to 1812. So, fed by gullible media reporting, needless fear among the public outran reason. In some places, schools and factories reportedly closed down Dec. 3 and residents prepared for possible disaster. The overheard conversation was an individual confirmation of this reaction.
Nothing happened, of course. And the extra supplies this individual's relatives laid in will undoubtedly come in handy. But why should they have been subjected to needless anxiety in the first place?
It's tempting to blame the forecaster for being alarmist. Yet Mr. Browning has a right to call attention to a danger that he sincerely believes he foresees. You can blame news media for being lax where they failed to play up the weakness of that forecast. But, at bottom, isn't this a case where we should, individually, take responsibility for our thinking?
In an age when news media saturate us with alarms and warnings, discriminating between the silly and the serious is a necessary form of self-defense. That's not easy when the subject is as arcane as earthquake forecasting. But the old adage ``consider the source'' is a useful guide. Does the alarm come from reasonably authoritative assessment or is it beyond the fringe of credibility?
In the present case, the forecast was based on reasoning few geological scientists found credible. Furthermore, the forecaster's track record in quake prediction was no better than random guessing, according to the forecast review panel. That should have been enough to evoke the traditional Missouri skepticism.
We have a second chance to put this skepticism to the test. This is a month when whatever happens once in a blue moon may happen. A blue moon occurs when it is the second full moon in a month. The moon turns full on Dec. 31. Once again, it will be at perigee - close to Earth with maximum tide-raising force. For good measure, Uranus will also be in conjunction with the sun, for what that is worth to would-be prophets.
If there was a 50 percent chance of a New Madrid quake in early December, there should be a good probability for one New Year's Eve. But there's so little credibility to that kind of forecast, it's not worth foregoing New Year's Eve parties. It's not even worth wasting a store clerk's time.