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Mermen and other optical trickery

Out of the mists of old Norse legends, mermen, and sea serpents have reemerged in the modern world, with the help of a computer. Programmed to stimulate mirages and other optical distortions in the atmosphere, it shows that the incredible creatures reported by medieval Norse mariners were very likely ordinary things seen under unusual circumstances. In other words, a kind of mirage.

Whales or walruses, poking their heads above the water, can loom in the distance like an elongated cylinder. Is it any wonder that Norse sailors took them for some kind of merman?

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W. H. Lehn of the University of Manitoba, in Winnipeg, and I. Schroeder, also of Winnipeg, have been studying these effects. they point out in a recent report in Nature that were made by men who had attained a "high level of sophistication" in observing natural phenomena.

The images produced by the computer correlate in detail with the descriptions of "mermen" from that era. There is little doubt, the scientists say, that "the merman described in the early sources . . . is, in fact, an accurate description of an unusual optical phenomenon." These phenomena involve refraction. The path a light ray takes is bent when the density of the air through which the light travels changes rapidly with height. This happens when warm air passes over a relatively cool sea.

Such atmospheric conditions often occur in the North Sea when a warm front brings relatively warm air into the region. Since storms often follow, it was natural for the old Norse sailors to take the appearance of mermen as a storm warning.

These sailors reported other, related effects. One was called hafgerdingar -- fences in the sea -- which has already been identified as a mirage. The other was the famous sea serpent, the Kraken, which the Norse called hafgufa.

In later periods, kraken were sighted all over the world. Marine biologists think many of these sightings involved giant squid. Lehn and Schroeder note, however, that some other natural phenomena may have caused the Norse reports. Since two of the effects described are now known to be optical tricks, it would be worth looking for some such explanation of the hafgufa, too, they suggest.

As Lehn and Schroeder note, modern scientists tend to avoid the study of such anomalous sightings, partly because they seem nonsoluble and partly because they seem superstitious. Now the two Canadian researchers have shown that there are things to be discovered in old legends. Furthermore, it's a humbling reminder that those rugged Norse sailors were just as sophisticated and intelligent as any modern computer ha cker.