Geophysics: Toward a Longer Day

Russian Scientist Vladimir Kotelnikov checked and rechecked the calclations, but the answer remained essentially the same: between March 1963 and October 1965, the rotation of the earth slowed down so much that the average day lengthened by 1.6 milliseconds—or about one six-hundredth of a second. The result was "extremely unexpected," a surprised Kotelnikov told the Soviet Academy of Sciences. The length of a day had increased only one millisecond (one-thousandth of a second) during the previous 120 years.

Was something unusual happening? Not likely. While most scientists found no reason to doubt Kotelnikov's figures, they did not share his surprise. Records...