Big Bomb Waves

When the Soviet 50-megaton test-bomb exploded on Novaya Zemlya last October, it set the earth's whole atmosphere vibrating. Last week in London, Seismologists Eric Carpenter, George Harwood and Thomas Whiteside reported how the bomb waves looked when they were recorded on the microbarograph at Britain's Atomic Weapons Research Establishment.

The bomb exploded at 8:33 a.m. British time. By 11:44 a.m., the first air wave reached England, having taken 3 hr. 11 min. to travel from Novaya Zemlya at the speed of sound--about 700 m.p.h. At 4:40 p.m. on the next day, the barograph pen jiggled again, recording the air waves that had taken the long path and circled the earth in the opposite direction and approached England from the southwest. At ten minutes past midnight on Nov. 1, the first wave swept over England again, making almost as strong a record as on its first trip. At 12:40 p.m. on Nov. 2, it made its third appearance, three days after the explosion. Seismologist Carpenter is sure that special microbarographs, tuned up for the purpose, would have detected the persistent waves for several more days.

In 1883 the explosion of the Indonesian volcano Krakatoa sent out air waves that registered easily on the crude barographs of the period. Big as the Soviet bomb was, its waves were far weaker than the volcano's, but the time they took to circle the earth was almost exactly the same: 36 hr. 27 min. Small variations in their speed were due to varying winds and temperatures. Carpenter is now putting the Soviet bomb test to unexpected and peaceful use: he is asking the world's scientists to send him copies of their barograph records so that he can study atmospheric conditions revealed by the behavior of the bomb's waves.

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