Particle-Beam Weapons
It is said that missiles could be shot down by accelerator. Even if such a weapon could be built, which is questionable, it would be ineffective because it would be vulnerable to countermeasures
Features
A Timekeeping Enzyme in the Pineal Gland
The activity of the enzyme N-acetyltransferase in the pineal gland of some animals provides a natural timing mechanism: a biological clock that may regulate both physiological and behavioral processes
The Evolution of Disk Galaxies
A spiral galaxy can evolve into a smooth disk without spiral arms. Whether or not it does so depends on its environment: the galaxy most ilkely to evolve into a smooth disk belongs to a rich cluster
Clay
It has myriad uses principally because it consists of fine particles, which result from the nature of clay minerals. These minerals are created and destroyed and created again in a long geological cycle
Teratomas and Chimeras
Teratomas are tumors composed of a jumble of differentiated cells and tissues. Their malignant stem cells can differentiate normally in the mouse embryo and give rise to chimeras, or genetic mosaics
Chinese Oracle Bones
In the Shang dynasty of 3,000 years ago aristocrats liked to seek the advice of their ancestors. The questions, engraved on bone or on turtle shell, are clues to the origins of Chinese civilization
The Physics of Karate
A close examination of how the karate expert can break wood and concrete blocks with his bare hand reveals the remarkable capacity of the unaided human body for exerting physical force
Ink-Jet Printing
Minute drops of ink, squirted from a nozzle and steered in flight, can be made to form printed characters. The ink-jet technology is particularly well suited to printing at the command of a computer
Departments
50 and 100 Years Ago, April 1979
Science and the Citizen, April 1979
- Letters
Letters to the Editors, April 1979
- Recommended
Books, April 1979
- Mathematical Recreation
Mathematical Games, April 1979
- Amateur Scientist
The Amateur Scientist, April 1979
- Departments
The Authors, April 1979
Bibliography, April 1979