Science: New Tools

Last week Enrico Fermi had his picture taken holding a hollow globe of paraffin as big as a pumpkin, standing beside a piece of apparatus that looked like stovepipe put together with baling wire (see cut). Said Dr. Fermi: “The most obvious application of artificial radioactivity which can be foreseen is in the medicinal field. Radium, naturally radioactive, is used for the treatment of cancer. The completely new radioactive substances created in the laboratory should give medical men new tools, some of which may prove more efficient than radium.”

Dr. Fermi had arrived in the U. S. to take charge of summer work in physics at Columbia, and that University was eager to let the world know that it was harboring for a few weeks Italy’s foremost researcher on the physics of the atom. Since artificial radioactivity was discovered by the Curie-Joliots of Paris (TIME, Feb. 12, 1934), Dr. Fermi by bombardments with neutrons has induced radioactivity in more elements (about 40) than any other scientist.

Neutrons have about the same mass as the heart of a hydrogen atom, but they are much smaller. Dr. George Braxton Pegram and his associates at Columbia have set the neutron diameter at one ten-trillionth of an inch. Unlike electrons, positrons, protons and deuterons, neutrons have no electric charge. Hence they make splendid projectiles for bombardment since they are not repelled by the positive charges on the atomic nuclei. Alpha particles knock neutrons in quantity out of beryllium and other light elements at speeds up to 30,000 miles per second. When the neutron hits a nucleus it either bounces off, transforming the atom instantly into another element, or is captured, producing a swollen, unstable atom which spits out the awkward excess for seconds, hours, sometimes days in the form of radiation or particles. Dr. Fermi found that slow neutrons were more easily captured than fast ones, worked out the equation for the slowing effect of hydrogen nuclei. Since the hydrogen atom, having only one outside electron, consists almost entirely of nucleus, it is excellent for braking fast neutrons, and substances rich in hydrogen such as water, paraffin and oil are commonly used for this purpose.

Thus Dr. Fermi holding a ball of paraffin in his hand symbolizes a matter of immense importance to biology. Organic substances are rich in hydrogen. Professor Ernest Orlando Lawrence of the University of California, whose huge apparatus produces a beam of 10,000,000 neutrons a second, finds that on the white blood cells of rats neutrons exert ten times the destructive effect of X rays of equal intensity. As laid down last month in the American Journal of Roentgenology and Radium Therapy, the biologic neutron problems now confronting science are these:

1) Effect of neutrons on cancerous growths. 2) Use of neutrons to kill harmful bacteria. 3) Possibility that neutrons may produce _new mutations (sharp hereditary variations) in animals and plants.

Enrico Fermi was born in Rome 34 years ago, studied at the University of Pisa, has taught and researched at the University of Rome since 1927. Short, wiry, dapper, cheerful, he is married, has a 5-year-old daughter, likes to ski, play tennis. Some years ago he perceived that when a nuclear impact knocks a neutron and a positron out of an electron, there is a mysterious disappearance of energy. He surmised that the excess energy rode away on a little particle which, now generally accepted as theoretically necessary, still eludes observation. It is because of Fermi that this little particle, the neutrino, has an Italian name.