Benefits of Migration Why do animals migrate? One obvious answer is to escape cold weather by moving to a warmer region. Each fall, millions of monarch butterflies migrate southw...

The Proto-Indo-European Language     Scholars have known for several centuries that most of the languages spoken in a broad swath from Britain to India are derived from ...

    The Collision Model of the Moon's Formation       The collection and analysis of rocks brought back from the Moon during the Apollo spaceflight prog...

Igloos   In the language spoken by the Inuit-an indigenous people inhabiting the Arctic regions of Canada, Greenland, and the United States-the word 'igloo' means 'house' or '...

Coal's Rise and Fall Changes in the use of coal over time are reflected in the environment. In the eighteenth century most peppered moths had black spots on white wings, but in th...

  Where Did the Carbon Go?     Over the last several hundred thousand years, atmospheric carbon dioxide (CO2) levels decreased when Earth's glacial ice sheets were ...

Early Photography in the United States     When photography first appeared in 1839 with the introduction of the daguerreotype, it was celebrated for revealing the truth ...

Creativity   A basic question about creativity is, what factors produce it? Several contrasting answers have been proposed. Cognitive psychologists, for example, have tended t...

Degradation and Erosion of Soil Land without soil can support only very small primitive plants such as lichens and mosses that can cling onto a rock surface. The rest of the worl...

  Sunspot Cycles   Dark regions on the Sun, called sunspots, were studied in 1610 by Galileo, who turned the newly invented telescope on objects in the sky. A lively deba...