The Professionalization of the U.S. Labor Force
The increased number of college graduates in the U.S. has altered the composition of its work force. Professionals and managers now hold one out of four of the nation's jobs
Features
Apollo Objects
They are asteroidlike bodies whose orbits cross the orbit of the earth. Some 30 of them are now known. They may be nuclei of comets that have lost their volatile components
Cancer Metastasis
Metastasis, and not the primary tumor, is usually the threat in cancer. Apparently only certain very malignant cells possess characteristics that enable them to travel through the body and establish new tumors...
The Spectrum of Atomic Hydrogen
For almost a century light emitted by the simplest of atoms has been the chief experimental basis for theories of the structure of matter. Exploration of the hydrogen spectrum continues, now aided by lasers...
The Perception of Surface Blacks and Whites
What shade of gray a surface appears is related to the perceived distribution of light and shadow, which in turn depends on the perceived spatial relation between the surface and its neighbors...
Ion Channels in the Nerve-Cell Membrane
The nerve impulse is generated by the flow of sodium and potassium ions through molecular channels embedded in the nerve membrane. The operation of these ion channels is now being intensively studied...
Dolphins
These descendants of land mammals that took to sea have a large brain, learn quickly and exhibit a rich vocal repertory. Yet lack of evidence leaves open the question of how intelligent they are...
Ancient Catapults
Surviving Greek and Roman texts reveal the remarkable level of mathematical and engineering skill that went into the development of these early ballistic-missile launchers
Departments
50 and 100 Years Ago, March 1979
Science and the Citizen, March 1979
- Letters
Letters to the Editors, March 1979
- Recommended
Books, March 1979
- Mathematical Recreation
Mathematical Games, March 1979
- Amateur Scientist
The Amateur Scientist, March 1979
- Departments
The Authors, March 1979
Bibliography, March 1979
