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  1. 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. The Tilt-A-Whirl, for example, spins its passengers in one direction, then another, sometimes hesitating between forays and sometimes swinging abruptly from one motion to another. A rider never […]

    By Ivars Peterson
  2. Math

    Hiding in DNA

    Spies might have to start boning up on molecular biology to pass along and decipher secret messages. During World War II, German spies used microdots to hide information in plain view. Consisting of a greatly reduced photograph of a typed page, a microdot could be pasted on top of a printed period at the end […]

    By Ivars Peterson
  3. Math

    Hiding in DNA

    Spies might have to start boning up on molecular biology to pass along and decipher secret messages.