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  1. Earth

    Clipping the Fin Trade

    New research and policy developments aim to curb the wasteful and gruesome practice of killing sharks solely for their fins.

    By Janet Raloff
  2. Math

    Tilt-A-Whirl Chaos (II)

    Tilt-A-Whirl in action. Sellner Manufacturing Co. The Tilt-A-Whirl amusement park ride serves as a wonderful example of a chaotic system. The unpredictable motion of the Tilt-A-Whirl’s cars occurs when the ride’s seven platforms travel at a speed of about 6.5 revolutions per minute along the undulating, circular track (see Tilt-A-Whirl Chaos (I), April 22, 2000). […]

    By Ivars Peterson
  3. Math

    Tilt-A-Whirl Chaos (I)

    Tilt-A-Whirl. Sellner Manufacturing Co. Schematic drawing (top view) showing the Tilt-A-Whirl’s geometry. Much of the fun of an amusement park ride results from its stomach-churning, mind-jangling unpredictability.