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  1. Earth

    Solving one mystery of polar wander

    Long-term fluctuations in pressure at the ocean's bottom may be the driving force for the Chandler wobble, which causes the North Pole to wander about 20 feet every 14 months or so.

    By Sid Perkins
  2. Earth

    Early web-footed bird made impression

    Researchers have discovered the fossil tracks of an otherwise unknown bird in 110-million-year-old sediments, which pushes back evidence of web-footed birds by at least 25 million years.

    By Sid Perkins
  3. Earth

    Where’s Waldo . . . and 6 billion others?

    Scientists have combined satellite imagery and detailed census data to develop a worldwide database that can provide estimates of the number of people located in areas on a grid that has boxes with areas of 1 square kilometer or less.