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Cosmic rays.

One way to detect the presence of energetic radiation is by the use of a gold-leaf electroscope. This device consists of two pieces of gold leaf, joined at the upper end, and contained in a sealed jar. They can be electrically charged from the outside, and since both leaves have the same charge, they repel each other, forming an inverted V. Any energetic radiation entering the jar produces ions, which will carry off the electric charge and allow the gold leaves to come together slowly.

There seemed no way of keeping the leaves permantently apart, however, even in the absence of any known source of energetic radiation. Some radiation was apparently coming from an unknown source.

An Austrian physicist, Victor Franz Hess (1883-1964), felt that the source must be somewhere in the ground, so in 1911 he took electroscopes up on balloon flights to get them out of range of the ground radiation.

He made ten flights and observed quite to his astonishment that the gold leaves came together up to eight times as rapidly at considerable heights as they did at ground level. The radiation seemed to be coming from above, after all-to be coming from outer space, from the cosmos generally. Millikan (see above) suggested, therefore, that the radiation be called cosmic rays, a name that stuck.

For his discovery, Hess was awarded a share of the Nobel Prize in physics in 1936.

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Author:Asimov, Isaac
Publication:Asimov's Chronology of Science & Discovery, Updated ed.
Article Type:Reference Source
Date:Jan 1, 1994
Words:235
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