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  1. Paleontology

    Extinctions Tied to Impact from Space

    Evidence trapped in 250-million-year-old sediments may help researchers pin the ultimate blame for the massive extinctions that occurred then on the impact of an extraterrestrial object about 9 kilometers across.

    By Sid Perkins
  2. Math

    Appealing Numbers

    The ancient Greeks, especially the Pythagoreans, were fascinated by whole numbers. They defined as “perfect” numbers those equal to the sum of their parts (or proper divisors, including 1). For example, 6 is the smallest perfect number-the sum of its three proper divisors: 1, 2, and 3. The next perfect number is 28, which is […]

    By Ivars Peterson

  3. From the February 21, 1931, issue

    WHAT BABIES THINK ABOUT What are baby’s secret thoughts? Babies understand what is said long before they are able to speak, psychologists have discovered.