Big Game

Six weeks ago a report reached the U. S. about an atomic explosion which took place in a Berlin laboratory--the most violent atomic explosion ever accomplished by human agency (TIME, Feb. 6). This news, known then only to a few insiders, streaked over the physical world like a meteor. By last week a half-dozen leading science journals were popping with reports confirming, extending or interpreting the original phenomenon.

Dr. Otto Hahn, 60, of Germany's Kaiser Wilhelm Institute, and his coworker, F. Strassmann, had bombarded uranium with neutrons. In the products of bombardment they found something which seemed to be atoms of barium. This barium was the clue to something terrific. For the huge uranium atom, heaviest of the 92 standard elements, weighs 238 units.* The barium atom weighs 137 units. Since the barium could have originated only as a fragment of the big uranium atom, it was logical to suppose that the latter had cracked asunder, in two nearly equal parts. The release of atomic energy was 200,000,000 electron-volts. Heavy atoms had been "chipped" before --that is, forced to throw off small particles like neutrons--but this was the first time they had been cracked in two.

This discovery has already brought into play new words, familiar in other fields of science but not so in atomic physics. The splitting of the uranium nucleus is described as a "fission," which, in biology, means division of an organism into two or more parts. The big nucleus has been compared to a "droplet." When a neutron of the right energy strikes it, the new energy is shared by all the components of the nucleus so that the "surface tension" fails to hold it together. Therefore it splits.

Dr. Hahn calls himself a radiologist and his previous record includes discovery of several radioactive elements. Some years ago he lectured at Cornell, is remembered there as an "outstanding scientist"--also as a good lecturer, an amiable and energetic man. Last week the "fission" of the uranium atom definitely looked like a find of Nobel Prize calibre. But present German law forbids Germans to accept Nobel Prizes. Meanwhile, physicists have unofficially distributed some of the credit to Liese Meitner in Stockholm (a woman physicist) and R. Frisch of Copenhagen, who presented a fine interpretation of what happened when the uranium atom cracked. Some credit also went to Nobel Laureate Irene Curie-Joliot (daughter of Marie Curie) and P. Savitch of Paris, who had done work which helped Hahn identify the all-important barium in his bombardment products.

Since the first explosion reverberated through the world's laboratories, the fission of thorium, as well as uranium, has been demonstrated. Atom-wranglers at Columbia University have shown that, under various conditions, the fission of uranium yields krypton, strontium, iodine, xenon, tellurium as disintegration products. The flood of reports made it appear that atomic physicists are off on the biggest big-game hunt since the discovery of artificial radioactivity was announced in 1934.

* The unit is approximately the weight of the hydrogen atom (or, precisely, 1/16 the weight of the oxygen atom).

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