Cosmic Obstacle Race

"Cosmic rays," said Professor H. V. Neher of Caltech, "have for years been regarded as a means of justifying travel to remote areas of the world." Dr. Neher's latest ray-hunting junket was to one of the world's least seductive places, the North Magnetic Pole in barren arctic Canada. Last week he told a Pasadena meeting of the American Physical Society about the results of the trip.

No one knows yet where cosmic ray particles come from. A few may originate in rare solar "flares," but most of them come from farther space. The fastest particles pack an enormous punch, up to 1016 ev (10 million billion electron volts) of energy. To accelerate a flea to this speed, said Neher, would require all the energy released by a hydrogen bomb.

Magnetic Chimney. The more powerful particles have their scientific uses, but they travel so fast that they pay scant attention to most forces acting upon them. Others are so easily influenced that the earth's magnetic field curves them away from their course and out into space again. The only place where the weak particles can reach the atmosphere unhampered is above the magnetic poles.

At this point the earth's field points directly downward and therefore has no deflecting effect on the incoming particles. In Canada last summer, Dr.

Neher's party launched balloons that counted the particles at 95,000 feet as they plunged down the polar "chimney." The same thing had been done before, in 1951, without notable findings. On this occasion, the scientists found in the chimney no particles with energy so low that it would not carry them safely through the stronger parts of the earth's field.

On the latest expedition, results were different. There were more cosmic rays, and among them were feeble particles with only 150 mev (150 million electron volts).

If they had not hit the magnetic chimney, they would never have been caught by balloon-borne instruments.

Solar Clouds. What had changed since 1951? For one thing, Professor Neher pointed out, the sun had decreased its "activity," shooting out less gaseous matter than it did a few years before. He believes that this thin stuff, mostly hydrogen, drifts in enormous, tenuous clouds through the solar system. Each cloud carries its own magnetic field, and when the clouds are numerous, they fill the solar system with magnetic obstacles in the path of the cosmic rays. The weak ones cannot make the grade. They curve off into space and never reach the inner region where the earth revolves.

This was what happened in 1951 when the sun was active. Last summer the sun was in a quiet mood. The clouds in space had dissipated, allowing the weak particles to approach the earth. Most of them were chased away by the earth's magnetic field, but a few hit the magnetic chimney and reached a close-in altitude where the scientist's instruments could catch and count them.

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