Rain from Space

When Australia's Physicist Edward G. Bowen first proposed the startling theory that the earth's rainfall is strongly influenced by showers of space dust, most meteorologists howled him down. But Welsh-born Bowen is hard to discourage. For eight years, whenever he could take time from his job as chief of the Radiophysics Division of Australia's Commonwealth Scientific and Industrial Research Organization, he searched for evidence to buttress his argument. He found a hopeful amount, and by last week Physicist Bowen had become something of a meteorological hero. After hearing Bowen talk at the International Conference of Cloud Physics in Australia, Meteorologist Dwight B. Kline, of the U.S. Weather Bureau, announced bluntly: "Dr. Bowen's theory is one of the most stimulating hypotheses in meteorology that has come along in years."

Meteor Streams. Bowen's long study of space dust began back in 1953, when he noticed that certain days of each year had abnormally high rainfall. In his search for an explanation, Bowen quickly eliminated the high and low pressure areas that meteorologists generally blame for rainfall. They appear too irregularly, and they never affect the whole earth in the same way at the same time. Bowen was more intrigued by the streams of meteors that the earth passes through on regular schedule. When he looked up the dates of known meteor showers, he found that they seemed to precede every peak of heavy rainfall on his charts. The prominent rain peak on Jan. 12 came 30 days after the Geminid meteor shower of Dec. 13. Other rain peaks came at about the same interval after other meteor showers. The explanation, said Bowen, was clear: meteor showers seed the top of the atmosphere with microscopic dust particles that make clouds form droplets big enough to fall to the ground as rain. The 30-day lag between the meteor showers and the rain, said Bowen, is accounted for by the time it takes the dust to filter to cloud level from the top of the atmosphere.

At first, meteorologists raised many objections; they doubted the rainfall statistics on which the theory was based, and they were sure that any dust particles that cause rainfall must come from the earth's surface, not from outer space. Bowen met the first objection by analyzing more precipitation statistics--including Japanese snowfall records that have been kept for 330 years. Most of the records supported his theory; none directly opposed it.

Catching the meteoric dust particles on their way down from space was a far more difficult job. In 1958-59, Bowen got Australian air force jets to carry dust-collecting apparatus up as high as 45,000 ft. There they found plenty of dust, but higher flights were needed for rigid proof that the high-altitude dust had not merely been blown aloft from the surface of the earth.

In 1960, and early this year, the U.S. Air Force came to Bowen's rescue. A pair of U-2s visiting Australia carried his dust filters on 16 cruises to 70,000 ft. over the Antarctic Ocean, far from land. The filters came back containing dust that could hardly have come from the ground. Some U-2 nights carried a special camera that photographed what looked like a thin layer of dust far up in the upper atmosphere.

Nowhere but Space. Bowen believes that the dust collected by the U-2s at 70,000 ft. could have come from nowhere but space. During meteor showers, he feels sure, the smallest meteoric particles hit the atmosphere softly and sink slowly toward earth. Larger meteors burn up, their smoke-fine debris sinking with the rest. The particles take about 30 days to reach the lower atmosphere, where they then turn clouds into rain.

All meteorologists are not yet convinced by Bowen's revolutionary theory, but there are few who still deride it rudely. Many are reserving judgment until the particles collected by the U-2s have been positively analyzed and identified as space dust. Then will come the additional job of proving that the space dust can and does cause rain. But Bowen and a growing army of believers are sure that this final proof is not far ahead.

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