Finding the Natural Neutrino

In the depths of a South African gold mine, scientists have snared some strange cosmic ghosts that could be the basic stuff of the universe. They are the first natural neutrinos ever detected.

A neutrino is the most elusive and mysterious of the some 30 known particles of energy scattered by the splitting of the atom. For more than two decades the neutrino was known only in theory. It has no electric charge or mass of its own. It travels at the speed of light, can penetrate matter equal to 100 million miles of lead without being stopped. Billions of neutrinos bombard each square centimeter of the earth's surface every second; but every one of them eluded scientists until 1956. Then physicists detected the first neutrinos in the debris from man-made nuclear reactions. But scientists still could not capture natural neutrinos.

Finally one of the co-detectors of man-made neutrinos, Dr. Frederick Reines of Cleveland's Case Institute of Technology, came up with a successful method. Near Johannesburg, he went to work in a 10,492-ft.-deep chamber, which he knew would shield out nearly all radiation from the surface except the deep-penetrating neutrinos. He lined the sides of the chamber with 36 containers of common mineral oil. Then he waited for an expected reaction of several stages: 1) the neutrinos hit atomic nuclei in the rock surrounding the chamber; 2) this interaction generated particles called mu-mesons; 3) the mu-mesons penetrated the mineral oil; 4) this caused tiny flashes of light called scintillations. On a 20-ton scintillation detector, Reines registered the scintillations, which he knew were caused originally by neutrinos.

In Physical Review Letters, Reines reported that he and a team of Case Institute and South African scientists detected seven natural neutrinos--not many, but a hopeful beginning. These neutrinos, each of which registered energies well in excess of 10 billion electron volts, presumably were produced by the interaction of primary cosmic rays with the earth's atmosphere. Except for their superhigh energies, the natural neutrinos appeared to be about the same as those created by man.

Now that physicists know how to detect neutrinos, they should be able to gain a deeper understanding of the complex nature of energy and matter. They are eager to test their many theories about neutrinos, especially the one that the tiny particles may be "ashes" left by the disintegration of ordinary matter--or possibly a basic component in the creation of all matter.

This file is automatically generated by a robot program, so reader's discretion is required.