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Features

Marine Farming

Man gets food from the sea essentially by hunting and gathering. Yet the farming of fish and shellfish has been pursued for some 2,000 years, and its potentialities are far from being exhausted

By Gifford B. Pinchot

The Absorption Lines of Quasi-Stellar Objects

Emission lines in the spectra of these objects, sometimes called quasars, are enormously shifted toward the red. Absorption lines in some of the spectra, however, are shifted by different amounts

By E. Margaret Burbidge and C. Roger Lynds

Auditory Illusions and Confusions

These failures of perception are studied because they isolate and clarify some fundamental processes that normally lead to accuracy of perception and appropriate interpretation of ambiguous sounds

By Richard M. Warren and Roslyn P. Warren

Optical Interference Coatings

The same phenomenon that is responsible for the iridescence of various natural surfaces, including peacocks' tail feathers, is exploited to produce a host of modern optical components

By Philip Baumeister and Gerald Pincus

Rickets

Although it is still widely regarded as a dietary-deficiency disease resulting from a lack of "vitamin D," it results in fact from a lack of sunlight. In smoky cities it was the first air-pollution disease

By W. F. Loomis

Permanent Magnets

New alloys of cobalt with rare-earth elements have magnetic properties so superior to those of former materials that they constitute virtually a new class

By Joseph J. Becker

The Mule

This man-made animal is nearing extinction under the impact of mechanization. Its biology goes considerably beyond the mere fact that it is the result of a cross between a donkey and a horse

By Thcodore H. Savory

Departments

  • 50 and 100 Years Ago: December 1970

  • Science and the Citizen: December 1970

  • Human Embryos in the Laboratory

  • Books

  • Letters

    Letters to the Editors, December 1970

  • Mathematical Recreation

    Mathematical Games

  • Amateur Scientist

    The Amateur Scientist

  • Departments

    The Authors

  • Annual Index

  • Bibliography

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December 1970

See the World from a Different Perspective

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