Uncategorized

  1. Math

    Testing for Divisibility

    The crisp new dollar bill that I have just taken from my wallet bears the serial number 24598176. It’s easy to tell that the number is exactly divisible by 2 but not by 5. Is it divisible by 3? by 4? by 11? In a 1962 Scientific American article, Martin Gardner noted that during the […]

    By Ivars Peterson
  2. Earth

    Nature’s Own: Ocean yields gases that had seemed humanmade

    Chemical analyses of seawater provide the first direct evidence that the ocean may be a significant source of certain atmospheric gases that scientists had previously assumed to be produced primarily by industrial activity.

    By Sid Perkins
  3. Astronomy

    X-Ray Chaos: Violence shows itself in a nearby galaxy

    New X-ray observations provide additional evidence that Centaurus A, the nearest radio-wave-emitting galaxy to Earth that has a supermassive black hole, is a maelstrom of violence.