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The Science-Textbook Controversies

Over the past few years groups in various parts of the country have urged that special creation be given "equal time" with evolution. What accounts for these efforts and what are their future prospects?

By Dorothy Nelkin

The Sensing of Chemicals by Bacteria

Motile bacteria are capable of chemotaxis, or movement toward some chemicals and away from others. Chemosensors in the cell envelope can detect the chemicals and signal the flagella of the cell to respond

By Julius Adler

Subjective Contours

Certain combinations of incomplete figures give rise to clearly visilble contours even when the contours do not actually exist. It appears that such contours are supplied by the visual system

By Gaetano Kanizsa

Catastrophe Theory

Things that change suddenly, by fits and starts, have long resisted mathematical analysis. A method derived from topology describes these phenomena as examples of seven "elementary catastrophes"

By E. C. Zeeman

Opals

What makes these gems sparkle with flecks of pure spectral color when they are rotated in white light? The answer has been found in the optical behavior of regularly stacked tiny spheres of silica

By P. J. Darragh, A. J. Gaskin and J. V. Sanders

The Analysis of Materials by X-Ray Absorption

Tiny wiggles in the characteristic X-ray-absorption "signature" of an atom embedded in a solid can now be interpreted to provide clues to the exact spatial arrangement of the neighboring atoms

By Edward A. Stern

Galileo and the First Mechanical Computing Device

It was the sector, which could be employed to solve mechanically a number of mathematical problems. Galileo devised it to attack an insoluble problem and then perceived its value for simpler ones

By Stillman Drake

Departments

  • 50 and 100 Years Ago, April 1976

  • Science and the Citizen, April 1976

  • The Nile Crocodile

  • Letters

    Letters to the Editors, April 1976

  • Recommended

    Books, April 1976

  • Mathematical Recreation

    Mathematical Games, April 1976

  • Departments

    The Authors, April 1976

  • Bibliography, April 1976

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