Science: Fallible Radar

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Under certain rare conditions, magic-eyed radar goes blind. This sad fact was brought out last week at a Halifax inquiry into the collision of Canada's destroyer Micmac with the freighter Yarmouth County (TIME, July 28). The Micmac's radar scopes, said her crewmen, did not show the freighter, hidden in a fog bank dead ahead.

Canadian radar expert Lieut. Commander Harold D. McCormick explained the radar failure as a case of "substandard propagation." This means, he said, that when the air becomes warmer and dryer as altitude increases (an unusual condition), "it is possible for the waves from the radar transmitter to skip over the target."

The experts did not see eye to eye on the McCormick explanation. One agreed, grudgingly: sometimes the air does have belts of varying density. On very rare occasions, these may act as "wave guides" and conduct the radar's waves up from the surface of the water and over an obstacle.

U.S. Navy radar men thought the McCormick explanation "possible but extremely unlikely." One expert went so far as to insist: "a close-in target is always seen, unless the radar is out of order."

What everyone agreed on: fog horns are still useful.